@article {6266, title = {Nothing lasts forever: Dominant species decline under rapid environmental change in global grasslandsAbstract}, journal = {Journal of Ecology}, year = {In Press}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.14198}, url = {https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.14198}, author = {Wilfahrt, Peter A. and Seabloom, Eric W. and Bakker, Jonathan D. and Biederman, Lori and Bugalho, Miguel N. and Cadotte, Marc W. and Caldeira, Maria C. and Catford, Jane A. and Chen, Qingqing and Donohue, Ian and Ebeling, Anne and Eisenhauer, Nico and Haider, Sylvia and Heckman, Robert W. and Jentsch, Anke and Koerner, S.E. and Komatsu, K.J. and Laungani, Ramesh and MacDougall, Andrew and Martina, Jason P. and Martinson, Holly and Moore, Joslin L. and Niu, Yujie and Ohlert, Timothy and Venterink, Harry Olde and Orr, Devyn and Peri, Pablo and Pos, Edwin and Price, Jodi and Raynaud, Xavier and Ren, Zhengwei and Roscher, Christiane and Smith, Nicholas G. and Stevens, Carly J. and Sullivan, Lauren L. and Tedder, Michelle and Tognetti, Pedro M. and Veen, Ciska and Wheeler, George and Young, Alyssa L. and Young, Hillary and Borer, Elizabeth T.} } @article {6322, title = {Save or spend? Diverging water-use strategies of grasses and encroaching clonal shrubs}, journal = {Journal of Ecology}, year = {In Press}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.14276}, url = {https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.14276}, author = {Keen, R. M. and Helliker, B. R. and McCulloh, K. A. and Jesse B. Nippert} } @article {6294, title = {Extreme drought impacts have been underestimated in grasslands and shrublands globally}, journal = {Proceedings of the National Academy of Sciences}, volume = {121}, year = {2024}, pages = {e230988112}, keywords = {LTER-KNZ}, doi = {10.1073/pnas.2309881120}, url = {https://pnas.org/doi/10.1073/pnas.2309881120}, author = {M. D. Smith and Wilkins, Kate D. and Holdrege, Martin C. and Wilfahrt, Peter and S.L Collins and Knapp, Alan K. and Sala, Osvaldo E. and Dukes, Jeffrey S. and Phillips, Richard P. and Yahdjian, Laura and Gherardi, Laureano A. and Ohlert, Timothy and Beier, Claus and Fraser, Lauchlan H. and Jentsch, Anke and Loik, Michael E. and Maestre, Fernando T. and Power, Sally A. and Yu, Qiang and Felton, Andrew J. and Munson, Seth M. and Luo, Yiqi and Abdoli, Hamed and Abedi, Mehdi and Alados, Concepci{\'o}n L. and Alberti, Juan and Alon, Moshe and An, Hui and Anacker, Brian and Anderson, Maggie and Auge, Harald and Bachle, Seton and Bahalkeh, Khadijeh and Bahn, Michael and Batbaatar, Amgaa and Bauerle, Taryn and Beard, Karen H. and Behn, Kai and Beil, Ilka and Biancari, Lucio and Blindow, Irmgard and Bondaruk, Viviana Florencia and Borer, Elizabeth T. and Bork, Edward W. and Bruschetti, Carlos Martin and Byrne, Kerry M. and Cahill Jr., James F. and Calvo, Dianela A. and Carbognani, Michele and Cardoni, Augusto and Carlyle, Cameron N. and Castillo-Garcia, Miguel and Chang, Scott X. and Chieppa, Jeff and Cianciaruso, Marcus V. and Cohen, Ofer and Cordeiro, Amanda L. and Cusack, Daniela F. and Dahlke, Sven and Daleo, Pedro and D{\textquoteright}Antonio, Carla M. and Dietterich, Lee H. and S. Doherty, Tim and Dubbert, Maren and Ebeling, Anne and Eisenhauer, Nico and Fischer, Fel{\'\i}cia M. and Forte, T{\textquoteright}ai G. W. and Gebauer, Tobias and Gozalo, Beatriz and Greenville, Aaron C. and Guidoni-Martins, Karlo G. and Hannusch, Heather J. and Vats{\o} Haugum, Siri and Hautier, Yann and Hefting, Mariet and Henry, Hugh A. L. and Hoss, Daniela and Ingrisch, Johannes and Iribarne, Oscar and Isbell, Forest and Johnson, Yari and Jordan, Samuel and Kelly, Eugene F. and Kimmel, Kaitlin and Kreyling, Juergen and Kr{\"o}el-Dulay, Gy{\"o}rgy and Kr{\"o}pfl, Alicia and K{\"u}bert, Angelika and Kulmatiski, Andrew and Lamb, Eric G. and Larsen, Klaus Steenberg and Larson, Julie and Lawson, Jason and Leder, Cintia V. and Linst{\"a}dter, Anja and Liu, Jielin and Liu, Shirong and Lodge, Alexandra G. and Longo, Grisel and Loydi, Alejandro and Luan, Junwei and Curtis Lubbe, Frederick and Macfarlane, Craig and Mackie-Haas, Kathleen and Malyshev, Andrey V. and Maturano-Ruiz, {\'a}n and Merchant, Thomas and Metcalfe, Daniel B. and Mori, Akira S. and Mudongo, Edwin and Newman, Gregory S. and Nielsen, Uffe N. and Nimmo, Dale and Niu, Yujie and Nobre, Paola and O{\textquoteright}Connor, Rory C. and Ogaya, Rom{\`a} and O{\~n}atibia, Gast{\'o}n R. and Orb{\'a}n, Ildik{\'o} and Osborne, Brooke and Otfinowski, Rafael and P{\"a}rtel, Meelis and Pe{\~n}uelas, Josep and Peri, Pablo L. and Peter, Guadalupe and Petraglia, Alessandro and Picon-Cochard, Catherine and Pillar, Val{\'e}rio D. and Pi{\~N}Eiro-Guerra, Juan Manuel and Ploughe, Laura W. and Plowes, Robert M. and Portales-Reyes, Cristy and Prober, Suzanne M. and Pueyo, Yolanda and Reed, Sasha C. and Ritchie, Euan G. and Rodr{\'\i}guez, Ayl{\'e}n and Rogers, William E. and Roscher, Christiane and S{\'a}nchez, Ana M. and Santos, Br{\'a}ulio A. and Scarf{\'o}, Mar{\'\i}a and Seabloom, Eric W. and Shi, Baoku and Souza, Lara and Stampfli, Andreas and Standish, Rachel J. and Sternberg, Marcelo and Sun, Wei and S{\"u}nnemann, Marie and Tedder, Michelle and Thorvaldsen, {\r a}l and Tian, Dashuan and Tielb{\"o}rger, Katja and Valdecantos, Alejandro and van den Brink, Liesbeth and Vandvik, Vigdis and Vankoughnett, Mathew R. and Guri Velle, Liv and Wang, Changhui and Wang, Yi and Wardle, Glenda M. and Werner, Christiane and Wei, Cunzheng and Wiehl, Georg and Williams, Jennifer L. and Wolf, Amelia A. and Zeiter, Michaela and Zhang, Fawei and Zhu, Juntao and Zong, Ning and Zuo, Xiaoan} } @article {6288, title = {Product-inhibition feedbacks, not microbial population level tradeoffs or soil pH, regulate decomposition potential under nutrient eutrophication}, journal = {Soil Biology and Biochemistry}, volume = {189}, year = {2024}, pages = {109247}, keywords = {LTER-KNZ}, doi = {10.1016/j.soilbio.2023.109247}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0038071723003097?via\%3Dihub}, author = {Nieland, Matthew A. and Carson, Christine M. and Floyd, Victoria and Zeglin, Lydia H.} } @article {6284, title = {Drier streams despite a wetter climate in woody-encroached grasslands}, journal = {Journal of Hydrology}, volume = {627}, year = {2023}, pages = {130388}, keywords = {LTER-KNZ}, doi = {10.1016/j.jhydrol.2023.130388}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0022169423013306}, author = {Sadayappan, Kayalvizhi and Keen, Rachel and Jarecke, Karla M. and Moreno, Victoria and Nippert, J.B. and Kirk, M. F. and Sullivan, P.L. and Li, Li} } @mastersthesis {6255, title = {Early detection of wildfire risk in the Great Plains: merging machine learning, landscape metrics, and rich data sources}, volume = {MS Thesis}, year = {2023}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/bitstream/handle/2097/43444/BrynnNoble2023.pdf?sequence=3}, author = {Noble, Brynn.} } @phdthesis {6217, title = {Ecohydrological implications of clonal shrub encroachment in tallgrass prairie}, volume = {PhD Dissertation}, year = {2023}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/handle/2097/43279}, author = {Keen, Rachel.} } @phdthesis {6218, title = {Ecosystem recovery from chronic fertilization: Biotic mechanisms underpinning soil nitrogen legacies in burned and unburned grasslands}, volume = {PhD Dissertation}, year = {2023}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/handle/2097/43281}, author = {Nieland, Matthew} } @article {6205, title = {Evolutionary lineage explains trait variation among 75 coexisting grass species}, journal = {New Phytologist}, volume = {239}, year = {2023}, pages = {887}, chapter = {875}, keywords = {LTER-KNZ}, doi = {10.1111/nph.18983}, url = {https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.18983}, author = {Donnelly, R, and Wedel, E.R. and Taylor, J.H. and Nippert, J.B. and Helliker, B.R. and Riley, W. and Still, C.J. and Griffith, D.} } @article {6144, title = {Intermittent streamflow generation in a merokarst headwater catchment}, journal = {Environmental Science: Advances}, volume = {2}, year = {2023}, pages = {115-131}, abstract = {

Intermittent headwater streams are highly vulnerable to environmental disturbances, but effective management of these water resources requires first understanding the mechanisms that generate streamflow. This study examined mechanisms governing streamflow generation in merokarst terrains, a type of carbonate terrain that covers much of the central United States yet has received relatively little attention in hydrological studies. We used high-frequency sampling of precipitation, stream water, and groundwater during summer 2021 to quantify the contributions to streamflow from different water sources and characterize their short-term dynamics in a 1.2 km2 merokarst catchment at the Konza Prairie Biological Station (Kansas, USA). Mixing calculations using stable water isotopes and dissolved ions indicate that streamflow is overwhelmingly contributed by groundwater discharge from thin (1\–2 m) limestone aquifers, even during wet periods, when soil water and surface runoff are generally expected to be more important. Relationships between hydraulic heads in the aquifers and their contributions to streamflow differed early in the study period compared to later, after a major storm occurred, suggesting there is a critical threshold of groundwater storage that the bedrock needs to attain before fully connecting to the stream. Furthermore, contributions from each limestone unit varied during the study period in response to differences in their hydrogeological properties and/or their stratigraphic position, which in turn impacted both the length of streamflow and its composition. Taken together, we interpret that the subsurface storage threshold and variation in aquifer properties are major controllers of flow intermittency in merokarst headwater catchments.

}, keywords = {LTER-KNZ}, doi = {10.1039/D2VA00191H}, url = {https://pubs.rsc.org/en/content/articlepdf/2023/VA/D2VA00191H}, author = {Hatley, Camden M. and Armijo, Brooklyn and Andrews, Katherine and Anhold, Christa and Nippert, J.B. and Kirk, Matthew F.} } @article {6204, title = {Remotely sensed soil moisture can capture dynamics relevant to plant water uptake}, journal = {Water Resources Research}, volume = {59}, year = {2023}, pages = {e2022WR033814}, keywords = {LTER-KNZ}, doi = {10.1029/2022WR033814}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022WR033814}, author = {Feldman, Andrew F. and Short Gianotti, Daniel J. and Dong, Jianzhi and Akbar, Ruzbeh and Crow, Wade T. and McColl, Kaighin A. and Konings, Alexandra G. and Nippert, J.B. and Tumber-D{\'a}vila, Shersingh Joseph and Holbrook, Noel M. and Rockwell, Fulton E. and Scott, Russell L. and Reichle, Rolf H. and Chatterjee, Abhishek and Joiner, Joanna and Poulter, Benjamin and Entekhabi, Dara} } @article {6177, title = {Trajectories and state changes of a grassland stream and riparian zone after a decade of woody vegetation removal}, journal = {Ecological Applications}, volume = {33}, year = {2023}, pages = {e2830}, keywords = {LTER-KNZ}, doi = {10.1002/eap.2830}, url = {https://onlinelibrary.wiley.com/doi/10.1002/eap.2830}, author = {Walter K. Dodds and Z. Ratajczak and Keen, Rachel M. and Nippert, J.B. and Grudzinski, Bartosz and Veach, Allison and Taylor, Jeffery H. and Kuhl, Amanda} } @mastersthesis {6140, title = {The amazing diversity of Poaceae: trait variation across space, time, and lineage}, volume = {MS Thesis}, year = {2022}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, author = {Donnelly, Ryan.} } @inbook {6053, title = {Climate change in grassland ecosystems: current impacts and potential actions for a sustainable future}, booktitle = {CLIMATE ACTIONS - LOCAL APPLICATIONS AND PRACTICAL SOLUTIONS}, year = {2022}, pages = {36}, publisher = {CRC}, organization = {CRC}, edition = {1}, abstract = {

Grasslands are a widespread and globally important biome providing key ecosystem services, including carbon storage, regulation of the water cycle and diverse assemblages of plant and animal species. Grasslands also provide many important benefits to humans, such as food and forage for livestock. Climate changes manifest as temperature fluctuations, increased intensity of drought and flood cycles and increased atmospheric CO2 concentrations. These changes are impacting species growth responses, plant composition and other key grassland processes. In addition to the direct consequences of climate change, secondary (or indirect) impacts of climate change threaten grassland ecosystems. These include changes in land-use and land-cover, agricultural conversion, woody encroachment, invasive species and atmospheric nitrogen deposition. In this chapter, we discuss the direct and indirect impacts of climate change on grasslands generally, while using case studies from specific global grassland types to illustrate key threats and climate change impacts. We specifically provide examples of how direct and indirect climate changes interact, increasing the vulnerability of grasslands. In the final section of this chapter, we outline a climate action plan for grassland ecosystems that includes efforts focused at multiple scales, including the individual, community and global levels. These climate actions can be used to influence policy, reduce the rate of climate change, conserve and restore grasslands and, most importantly, need to begin immediately. Collectively, we explain the general ecological processes in grasslands, illustrate the consequences of climate change on this ecosystem and identify potential solutions to maintain the viability and persistence of grassland ecosystems for the foreseeable future.

}, keywords = {LTER-KNZ}, isbn = {9780367478339}, author = {Jesse B. Nippert and Keen, R.M. and Bachle, Seton and Wedel, E.R. and B. Groskinsky} } @article {6021, title = {Climate variability supersedes grazing to determine the anatomy and physiology of a dominant grassland species}, journal = {Oecologia}, volume = {198}, year = {2022}, pages = {345{\textendash}355}, keywords = {LTER-KNZ}, issn = {0029-8549}, doi = {10.1007/s00442-022-05106-x}, url = {https://link.springer.com/10.1007/s00442-022-05106-x}, author = {Bachle, Seton. and Nippert, J.B.} } @article {6203, title = {Elevated CO2 counteracts effects of water stress on woody rangeland-encroaching species}, journal = {Tree Physiology}, year = {2022}, pages = {tpac150}, keywords = {LTER-KNZ}, doi = {10.1093/treephys/tpac150}, url = {https://academic.oup.com/treephys/advance-article/doi/10.1093/treephys/tpac150/6966044}, author = {O{\textquoteright}Connor, R.C. and Blumenthal, Dana M and Ocheltree, Troy W and Nippert, J.B.}, editor = {Adams, Henry} } @article {6087, title = {Embracing the dynamic nature of soil structure: A paradigm illuminating the role of life in critical zones of the Anthropocene}, journal = {Earth-Science Reviews}, volume = {225}, year = {2022}, pages = {103873}, keywords = {LTER-KNZ}, issn = {00128252}, doi = {10.1016/j.earscirev.2021.103873}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0012825221003743}, author = {Sullivan, P.L. and Billings, S.A. and Hirmas, D. and Li, L. and Zhang, X. and Ziegler, S. and Murenbeeld, K. and Ajami, H. and Guthrie, A. and Singha, K. and Gimenez, D. and Duro, A. and Moreno, V. and Flores, A. and Cueva, A. and Koop, A. and Aronson, E.L. and Barnard, H.R. and Banwart, S.A. and Keen, R.M. and Nemes, A. and Nikolaidis, N.P. and Nippert, J.B. and Richter, D. and Robinson, D.A. and Sadayappan, K. and de Souza, L.F.T. and Unruh, M. and Wen, H.} } @article {6049, title = {Impacts of riparian and non-riparian woody encroachment on tallgrass prairie ecohydrology}, journal = {Ecosystems}, year = {2022}, keywords = {LTER-KNZ}, doi = {10.1007/s10021-022-00756-7}, url = {https://link.springer.com/10.1007/s10021-022-00756-7}, author = {Keen, Rachel M. and Jesse B. Nippert and Sullivan, P.L. and Z. Ratajczak and Ritchey, Brynn and O{\textquoteright}Keefe, K. and W. K. Dodds} } @article {6082, title = {Intra-canopy leaf trait variation facilitates high leaf area index and compensatory growth in a clonal woody-encroaching shrub}, journal = {Tree Physiology}, volume = {42}, year = {2022}, pages = {2186{\textendash}2202}, keywords = {LTER-KNZ}, doi = {10.1093/treephys/tpac078}, url = {https://academic.oup.com/treephys/advance-article/doi/10.1093/treephys/tpac078/6647984}, author = {Tooley, E. G. and Jesse B. Nippert and Bachle, Seton. and Keen, R.M.} } @article {6083, title = {Kernel weight contribution to yield genetic gain of maize: a global review and US case studies}, journal = {Journal of Experimental Botany}, volume = {73}, year = {2022}, pages = {3597 - 3609}, keywords = {LTER-KNZ}, doi = {10.1093/jxb/erac103}, url = {https://academic.oup.com/jxb/article/73/11/3597/6547901}, author = {Fern{\'a}ndez, Javier A and Messina, Carlos D and Salinas, Andrea and Prasad, P V Vara and Jesse B. Nippert and Ciampitti, Ignacio A}, editor = {Dreisigacker, Susanne} } @article {6050, title = {N and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry}, journal = {Ecological Applications}, volume = {32}, year = {2022}, pages = {e2684}, keywords = {LTER-KNZ}, doi = {10.1002/eap.2684}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/eap.2684}, author = {Rastetter, E.B. and Kwiakowski, B.L. and Kicklighter, D.W. and Barker Plotkin, A. and Genet, H. and Jesse B. Nippert and O{\textquoteright}Keefe, K. and Perakis, S.R. and Porder, S. and Roley, S.S. and Reuss, R.W. and Thompson, J.R. and Wieder, W.R. and K.R. Wilcox and Yanai, R.D.} } @article {6052, title = {Poor relationships between NEON Airborne Observation Platform data and field-based vegetation traits at a mesic grassland}, journal = {Ecology}, volume = {103}, year = {2022}, pages = {e03590}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.v103.210.1002/ecy.3590}, url = {https://onlinelibrary.wiley.com/toc/19399170/103/2}, author = {Pau, Stephanie and Jesse B. Nippert and Slapikas, Ryan and Griffith, D. and Bachle, Seton and Helliker, Brent R. and O{\textquoteright}Connor, R.C. and Riley, William J. and Still, Christopher J. and Zaricor, Marissa} } @article {6086, title = {Post-silking 15N labelling reveals an enhanced nitrogen allocation to leaves in modern maize (Zea mays) genotypes}, journal = {Journal of Plant Physiology}, volume = {268}, year = {2022}, pages = {153577}, keywords = {LTER-KNZ}, doi = {10.1016/j.jplph.2021.153577}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0176161721002169}, author = {Fernandez, Javier A. and Jesse B. Nippert and Prasad, P.V. Vara and Messina, Carlos D. and Ciampitti, Ignacio A.} } @article {6081, title = {Reintroducing bison results in long-running and resilient increases in grassland diversity}, journal = {PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES}, volume = {119}, year = {2022}, pages = {e2210433119}, abstract = {

The widespread extirpation of megafauna may have destabilized ecosystems and altered biodiversity globally. Most megafauna extinctions occurred before the modern record, leaving it unclear how their loss impacts current biodiversity. We report the long-term effects of reintroducing plains bison (Bison bison) in a tallgrass prairie versus two land uses that commonly occur in many North American grasslands: 1) no grazing and 2) intensive growing-season grazing by domesticated cattle (Bos taurus). Compared to ungrazed areas, reintroducing bison increased native plant species richness by 103\% at local scales (10 m2) and 86\% at the catchment scale. Gains in richness continued for 29 y and were resilient to the most extreme drought in four decades. These gains are now among the largest recorded increases in species richness due to grazing in grasslands globally. Grazing by domestic cattle also increased native plant species richness, but by less than half as much as bison. This study indicates that some ecosystems maintain a latent potential for increased native plant species richness following the reintroduction of native herbivores, which was unmatched by domesticated grazers. Native-grazer gains in richness were resilient to an extreme drought, a pressure likely to become more common under future global environmental change.

}, keywords = {LTER-KNZ}, doi = {10.1073/pnas.2210433119}, url = {https://www.pnas.org/doi/10.1073/pnas.2210433119}, author = {Ratajczak, Z. and S.L Collins and J. M. Blair and Koerner, S.E. and Louthan, A.M. and M. D. Smith and Taylor, J.H. and Jesse B. Nippert} } @article {6051, title = {Root traits reveal safety and efficiency differences in grasses and shrubs exposed to different fire regimes}, journal = {Functional Ecology}, volume = {36}, year = {2022}, pages = {368 - 379}, keywords = {LTER-KNZ}, doi = {10.1111/fec.v36.210.1111/1365-2435.13972}, url = {https://onlinelibrary.wiley.com/toc/13652435/36/2}, author = {O{\textquoteright}Keefe, Kimberly and Bachle, Seton and Keen, Rachel and Tooley, E. Greg and Jesse B. Nippert} } @mastersthesis {6054, title = {The unique canopy structure, leaf morphology, and physiology of Cornus drummondii}, volume = {MS Thesis}, year = {2022}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/dspace/handle/2097/42162}, author = {Tooley, E. G} } @phdthesis {5999, title = {Anatomical constraints on grass physiological responses depend on water availability}, volume = {PhD Dissertation}, year = {2021}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/dspace/handle/2097/41354}, author = {Bachle, Seton} } @article {KNZ002047, title = {Consumer roles of small mammals within fragmented native tallgrass prairie}, journal = {Ecosphere}, volume = {12}, year = {2021}, pages = {e03441}, abstract = {

Grassland ecosystems globally are being negatively impacted by changes in climate, disturbance regimes, nutrient flux, and consumer guilds. Changes in the trophic ecology of consumers can substantially influence local resources, contributing to shifting diversity, community turnover, and other processes of ecosystem change. Small mammals are diverse and abundant within grasslands and yet the impact of changing ecosystems on small mammals and the role of these mammals as consumers are still both under-studied. We assessed small mammal resource use within grassland and woodland vegetation types that have resulted from landscape-scale experimental disturbance through fire treatments within the tallgrass prairie ecoregion of the North American Great Plains. We predicted that resource use would vary significantly among grassland vs. woodland communities, in turn reducing the role of small mammals in contributing to future maintenance of native prairies. We sampled five dominant species of rodents across three years and multiple habitats. Using stable isotope analysis, we investigated isotopic niche area and overlap to infer variation in diet, both within and among species. Resource use shifted in bivariate isotopic space seasonally but not across years when combining all species and habitats. Inferred spring diet (based on fur samples) was highly diverse and overlapping. Summer isotopic values (based on liver tissue) in woody habitat treatments were narrower and overlapped less than within grassland habitats. Consumers generally shifted from C4 herbivory to C3 herbivory, or greater omnivory, when analyzing grassland, shrubland, and woodland habitats respectively. Within the tallgrass prairie ecosystem, small mammal populations in herbaceous-dominated habitats use a broader variety of resources than small mammals in proximate woody-dominated habitats. As native grasslands experience woody encroachment, small mammal assemblages experience turnover of dominant species and associated changes in diet. Ecosystem changes such as cessation of frequent fire resulting in more woody habitats may include reduced roles by native small mammals as consumers/dispersers/propagators of native grassland plants.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecs2.3441}, url = {https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecs2.3441}, author = {Hope, A.G. and Gragg, S.F. and Nippert, J.B. and Combe, F.J.} } @article {KNZ002058, title = {Differential resilience of soil microbes and ecosystem functions following cessation of long-term fertilization}, journal = {Ecosystems}, volume = {24}, year = {2021}, pages = {2042{\textendash}2060}, abstract = {

Nitrogen (N) from anthropogenic sources has dramatically increased in terrestrial ecosystems globally. Although belowground microbial processes and events that release N into the atmosphere, such as fire, could support ecosystem resilience to eutrophication, little is known about how these factors might affect N loss following chronic fertilization, thus promoting ecosystem recovery. We studied how N pools, N-cycling potential rates and their affiliated microbial populations, and microbial community composition responded to the factorial effects of cessation of 30 years of chronic N fertilization and annual burning at a tallgrass prairie. Soil N availability in previously fertilized plots recovered by 86\% (using never-fertilized control plots as a 100\% recovery reference), while plant and microbial biomass did not change. Nitrification potential recovered (80\%), and denitrification potential partially recovered (50\%), in previously fertilized plots. There were differential responses among key groups of nitrifiers (archaea vs. bacteria) and denitrifiers (nosZ clade I vs. clade II from Anaeromyxobacter dehalogenans) to long-term N fertilization and cessation despite the whole microbial community composition not shifting significantly after fertilization ceased. Also, N-cycling potentials were consistently higher in unburned prairie. Together, results suggest that fire is a prominent mechanism for ecosystem N removal in annually burned prairie, while N-cycling microbes will have an important role in the absence of fire; however, the recovery to pre-fertilized condition, with or without fire, will take longer than 1 year. Overall, differential resilience of biotic populations and processes can potentially shape different outcomes of soil N loss and tallgrass prairie ecosystem recovery from long-term N fertilization.

}, keywords = {LTER-KNZ}, doi = {10.1007/s10021-021-00633-9}, url = {http://link.springer.com/10.1007/s10021-021-00633-9}, author = {Nieland, M.A. and P. Moley and J. Hanschu and L.H. Zeglin} } @article {5974, title = {Fire and browsing interact to alter intra-clonal stem dynamics of an encroaching shrub in tallgrass prairie}, journal = {Oecologia}, volume = {196}, year = {2021}, pages = {1039 - 1048}, abstract = {

The expansion of woody species into grasslands has altered community structure and ecosystem function of grasslands worldwide. In tallgrass prairie of the Central Great Plains, USA, decreased fire frequency and intensity have increased the cover and abundance of woody species. In particular, clonal shrub cover has increased at accelerated rates due to vegetative reproduction and resprouting after disturbance. We measured the intra-clonal stem demography and relative growth rates (estimated change in woody biomass) of the shrub Cornus drummondii in response to fire frequency (4 vs 20year burn intervals) and simulated browsing during the 2018 and 2019 growing seasons at Konza Prairie Biological Station (Manhattan, Kansas). Overall, infrequent fire (4year burn interval) increased intra-clonal stem relative growth rates and shrub relative growth rates. Intra-clonal stem relative growth rates were reduced in unbrowsed clones in 2018 due to drought and simu-lated browsing reduced intra-clonal stem relative growth rates in 2019. Additionally, simulated browsing nearly eliminated flower production within clones but did not affect intra-clonal stem mortality or recruitment within a growing season. Fire in conjunction with simulated browsing reduced estimated relative growth rates for entire shrub clones. Browsed shrubs that experienced prescribed fire in 2017 had reduced intra-clonal stem densities compared to unbrowsed shrubs and stem densities of browsed shrubs did not recover in 2018 or 2019. These results illustrate that infrequent fire alone promotes the expansion of clonal shrubs in tallgrass prairie and multiple interacting disturbances (e.g., fire and browsing) are required to control the spread of clonal shrubs into grasslands.

}, keywords = {LTER-KNZ}, doi = {10.1007/s00442-021-04980-1}, url = {https://link.springer.com/10.1007/s00442-021-04980-1}, author = {Wedel, E.R. and Nippert, J.B. and D.C. Hartnett} } @article {KNZ002043, title = {Fire frequency, state change and hysteresis in tallgrass prairie}, journal = {Ecology Letters}, volume = {24}, year = {2021}, pages = {636-647}, abstract = {

Hysteresis is a fundamental characteristic of alternative stable state theory, yet evidence of hysteresis is rare. In mesic grasslands, fire frequency regulates transition from grass- to shrub-dominated system states. It is uncertain, however, if increasing fire frequency can reverse shrub expansion, or if grass-shrub dynamics exhibit hysteresis. We implemented annual burning in two infrequently burned grasslands and ceased burning in two grasslands burned annually. With annual fires, grassland composition converged on that of long-term annually burned vegetation due to rapid recovery of grass cover, although shrubs persisted. When annual burning ceased, shrub cover increased, but community composition did not converge with a long-term infrequently burned reference site because of stochastic and lagged dispersal by shrubs, reflecting hysteresis. Our results demonstrated that annual burning can slow, but not reverse, shrub encroachment. In addition, reversing fire frequencies resulted in hysteresis because vegetation trajectories from grassland to shrubland differed from those of shrubland to grassland.

}, keywords = {LTER-KNZ}, doi = {10.1111/ele.13676}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.13676}, author = {Collins, Scott L. and Nippert, J.B. and Blair, J. M. and J. M. Briggs and Blackmore, P. and Ratajczak, Zak} } @article {5967, title = {Lateral bedrock erosion and valley formation in a heterogeneously layered landscape, Northeast Kansas}, journal = {Earth Surface Processes and Landforms}, year = {2021}, abstract = {

In this study, we present direct field measurements of modern lateral and vertical bedrock erosion during a 2-year study period, and optically stimulated luminescence (OSL) ages of fluvial material capping a flat bedrock surface at Kings Creek located in northeast Kansas, USA. These data provide insight into rates and mechanisms of bedrock erosion and valley-widening in a heterogeneously layered limestone-shale landscape. Lateral bedrock erosion outpaced vertical incision during our 2-year study period. Modern erosion rates, measured at erosion pins in limestone and shale bedrock reveal that shale erosion rate is a function of wetting and drying cycles, while limestone erosion rate is controlled by discharge and fracture spacing. Variability in fracture spacing amongst field sites controls the size of limestone block collapse into the stream, which either allowed continued lateral erosion following rapid detachment and transport of limestone blocks, or inhibited lateral erosion due to limestone blocks that protected the valley wall from further erosion. The OSL ages of fluvial material sourced from the strath terrace were older than any material previously dated at our study site and indicate that Kings Creek was actively aggrading and incising throughout the late Pleistocene. Coupling field measurements and observations with ages of fluvial terraces can be useful to investigate the timing and processes linked to how bedrock rivers erode laterally over time to form wide bedrock valleys.

}, keywords = {LTER-KNZ}, doi = {10.1002/esp.5172}, url = {https://onlinelibrary.wiley.com/doi/10.1002/esp.5172}, author = {Marcotte, A.L. and Neudorf, C.M. and Langston, A.L.} } @article {6002, title = {Precipitation manipulation and terrestrial carbon cycling: The roles of treatment magnitude, experimental duration and local climate}, journal = {Global Ecology and Biogeography}, volume = {30}, year = {2021}, pages = {1909 - 1921}, keywords = {LTER-KNZ}, doi = {10.1111/geb.13356}, url = {https://onlinelibrary.wiley.com/doi/10.1111/geb.13356?af=R}, author = {Wang, Jinsong and Tian, Dashuan and Alan K. Knapp and Chen, Han Y. H. and Luo, Yiqi and Li, Zhaolei and Hou, Enqing and Huang, Xinzhao and Jiang, Lifen and Niu, Shuli}, editor = {Michaletz, Sean} } @article {5969, title = {Is a prescribed fire sufficient to slow the spread of woody plants in an infrequently burned grassland? A case study in tallgrass prairie}, journal = {Rangeland Ecology \& Management}, volume = {78}, year = {2021}, pages = {79 - 89}, abstract = {

In many mesic grasslands, such as the central Great Plains in North America, frequent fire is a key regulator of ecological processes. Long periods of infrequent fire facilitate the conversion of herbaceous-dominated grassland to woody-dominated shrubland or woodland. At the Konza Prairie Biological Station in northeast Kansas, one infrequently burned portion of the landscape has undergone transformation from grassland to woodland after nearly 30 yr without fire. In Spring 2017, a prescribed burn was implemented to assess fire effectiveness on woody plant mortality. A postfire census of 3 000+ individual woody plants identified the distribution of species by size (height), topographic position, and slope on the landscape. Mortality and canopy fire damage were calculated for each individual. In lowland locations with near-continuous shrub cover (30.7\% of the landscape), woody plants were unaffected by fire. However, in upland and slope locations, where shrubs and trees were sparser, survival probability varied by topographic position and species. In these locations 68\% of all woody individuals experienced 90\% or greater fire damage to the canopy, with 56\% of these individuals exhibiting new canopy regrowth within 2 mo after the fire. The two most abundant woody shrubs, Cornus drummondii and Rhus aromatica, showed high survival at all height classes and landscape positions. The two abundant tree species, Gleditsia triacanthos and Juniperus virginiana, showed increased survival probability with tree height that varied by landscape position. Survival of J. virginiana also varied according to proximity and size of neighboring clonal shrubs, providing a mechanism for persistence of this fire-sensitive tree species even at small height classes. The probability survival curves developed here are useful for managers assessing when to prescribe fire to maximize mortality for J. virginiana and provide insight relevant for broader ecological understanding of woody encroachment within grasslands throughout the world.

}, keywords = {LTER-KNZ}, doi = {10.1016/j.rama.2021.05.007}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1550742421000609}, author = {Nippert, J.B. and Telleria, Lizeth and Blackmore, Pamela and Taylor, Jeffrey H. and O{\textquoteright}Connor, Rory C.} } @article {KNZ002060, title = {SoDaH: the SOils DAta Harmonization database, an open-source synthesis of soil data from research networks, version 1.0}, journal = {Earth System Science Data}, volume = {13}, year = {2021}, pages = {1843 - 1854}, keywords = {LTER-KNZ}, doi = {10.5194/essd-13-1843-2021}, url = {https://essd.copernicus.org/articles/13/1843/2021/essd-13-1843-2021.pdf}, author = {Wieder, William R. and Pierson, Derek and Earl, Stevan and Lajtha, Kate and S.G. Baer and Ballantyne, Ford and Berhe, Asmeret Asefaw and Billings, Sharon A. and Brigham, Laurel M. and Chacon, Stephany S. and Fraterrigo, Jennifer and Frey, Serita D. and Georgiou, Katerina and de Graaff, Marie-Anne and Grandy, A. Stuart and Hartman, Melannie D. and Hobbie, Sarah E. and Johnson, Chris and Kaye, Jason and Kyker-Snowman, Emily and Litvak, Marcy E. and Mack, Michelle C. and Malhotra, Avni and Moore, Jessica A. M. and Nadelhoffer, Knute and Rasmussen, Craig and Silver, Whendee L. and Sulman, Benjamin N. and Walker, Xanthe and Weintraub, Samantha} } @article {KNZ001922, title = {Soil fungal communities are compositionally resistant to drought manipulations {\textendash} Evidence from culture-dependent and culture-independent analyses}, journal = {Fungal Ecology}, volume = {51}, year = {2021}, pages = {101062}, abstract = {

Current environmental change predictions forecast intensified drought conditions. It is becoming increasingly evident that plant communities are sensitive to drought and that soil-inhabiting microbial communities vary along precipitation gradients. However, the drought sensitivity of microbial communities in general and that of soil fungi in particular remains unclear, even though understanding their responses to adverse environmental conditions is vital for better understanding of ecosystem service provisioning. We sampled soils at two sites with established experiments that imposed extreme, chronic drought to assess fungal community responses. We analyzed fungal communities using both culture-dependent and -independent tools and MiSeq-sequenced communities from colony forming units (CFU-PCR) on a drought simulating medium and from environmental DNA (ePCR), to compare the conclusions derived from these two methods. Our data from the two approaches consistently indicate that the composition of fungal communities is not affected by the drought treatment, whereas \– based on the CFU-PCR but not ePCR data \– their richness and diversity increased under drought conditions at the more mesic of the two sites. Further, based on the direct comparisons of CFU-PCR and ePCR, we estimate that more than 10\% of the fungal community and more than 20\% of the ascomycetes were culturable. We conclude that although recent research indicates that plant and bacterial communities respond to drought, fungal community responses are more variable, particularly in experiments that impose chronic drought under field conditions.

}, keywords = {LTER-KNZ}, doi = {10.1016/j.funeco.2021.101062}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1754504821000246}, author = {Narayanan, Achala and Ismert, K.J. and M.D. Smith and A. Jumpponen} } @article {KNZ002059, title = {Spatial variation in soil microbial processes as a result of woody encroachment depends on shrub size in tallgrass prairie}, journal = {Plant and Soil}, volume = {460}, year = {2021}, pages = {359 - 373}, keywords = {LTER-KNZ}, doi = {10.1007/s11104-020-04813-9}, url = {http://link.springer.com/10.1007/s11104-020-04813-9}, author = {Connell, R. K. and O{\textquoteright}Connor, Rory and Nippert, J.B. and Blair, J.M.} } @article {5995, title = {Spatio-temporal differences in leaf physiology are associated with fire, not drought, in a clonally integrated shrub}, journal = {AoB PLANTS}, volume = {13}, year = {2021}, pages = {plab037}, keywords = {LTER-KNZ}, doi = {10.1093/aobpla/plab037}, url = {https://academic.oup.com/aobpla/article/doi/10.1093/aobpla/plab037/6295325}, author = {Wedel, E.R. and O{\textquoteright}Keefe, K. and Jesse B. Nippert and Hoch, Braden and O{\textquoteright}Connor, R.C.}, editor = {Mitchell, Patrick} } @article {5992, title = {State changes: insights from the U.S. Long Term Ecological Research Network}, journal = {Ecosphere}, volume = {12}, year = {2021}, month = {e03433}, keywords = {LTER-KNZ}, doi = {10.1002/ecs2.v12.510.1002/ecs2.3433}, url = {https://onlinelibrary.wiley.com/toc/21508925/12/5}, author = {Zinnert, Julie C. and Nippert, J.B. and Rudgers, Jennifer A. and Pennings, Steven C. and Gonz{\'a}lez, Grizelle and Alber, Merryl and S.G. Baer and J. M. Blair and Burd, Adrian and S L Collins and Craft, Christopher and Di Iorio, Daniela and Dodds, Walter K. and Groffman, Peter M. and Herbert, Ellen and Hladik, Christine and Li, Fan and Litvak, Marcy E. and Newsome, Seth and O{\textquoteright}Donnell, John and Pockman, William T. and Schalles, John and Young, Donald R.} } @mastersthesis {5997, title = {A study of grass structure and function in response to drought and grazing}, volume = {MS Thesis}, year = {2021}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/dspace/handle/2097/41514}, author = {Zaricor, M.L.} } @article {KNZ002049, title = {Synergies among environmental science research and monitoring networks: A research agenda}, journal = {Earth{\textquoteright}s Future}, volume = {9}, year = {2021}, pages = {e2020EF001631}, abstract = {

Many research and monitoring networks in recent decades have provided publicly available data documenting environmental and ecological change, but little is known about the status of efforts to synthesize this information across networks. We convened a working group to assess ongoing and potential cross-network synthesis research and outline opportunities and challenges for the future, focusing on the US-based research network (the US Long-Term Ecological Research network, LTER) and monitoring network (the National Ecological Observatory Network, NEON). LTER-NEON cross-network research synergies arise from the potentials for LTER measurements, experiments, models, and observational studies to provide context and mechanisms for interpreting NEON data, and for NEON measurements to provide standardization and broad scale coverage that complement LTER studies. Initial cross-network syntheses at co-located sites in the LTER and NEON networks are addressing six broad topics: how long-term vegetation change influences C fluxes; how detailed remotely sensed data reveal vegetation structure and function; aquatic-terrestrial connections of nutrient cycling; ecosystem response to soil biogeochemistry and microbial processes; population and species responses to environmental change; and disturbance, stability and resilience. This initial study offers exciting potentials for expanded cross-network syntheses involving multiple long-term ecosystem processes at regional or continental scales. These potential syntheses could provide a pathway for the broader scientific community, beyond LTER and NEON, to engage in cross-network science. These examples also apply to many other research and monitoring networks in the US and globally, and can guide scientists and research administrators in promoting broad-scale research that supports resource management and environmental policy.

}, keywords = {LTER-KNZ}, doi = {10.1029/2020EF001631}, url = {https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020EF001631}, author = {Jones, J.A. and Groffman, P.M. and Blair, J.M. and Davis, F.W. and Dugan, H. and Euskirchen, E.E. and Frey, S.D. and Harms, T.K. and Hinckley, E. and Kosmala, M. and Loberg, S. and Malone, S. and Novick, K. and Record, S. and Rocha, A.V. and Ruddell, B.L. and Stanley, E.H. and Sturtevant, C. and Thorpe, A. and White, T. and Wieder, W.R. and Zhai, L. and Zhu, K.} } @article {KNZ001996, title = {Bridging the flux gap: Sap flow measurements reveal species-specific patterns of water use in a tallgrass prairie}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {125}, year = {2020}, pages = {e2019JG005446}, abstract = {

Predicting the hydrological consequences following changes in grassland vegetation type (i.e., woody encroachment) requires an understanding of water flux dynamics at high spatiotemporal resolution for predominant species within grassland communities. However, grassland fluxes are typically measured at the leaf or landscape scale, which inhibits our ability to predict how individual species contribute to changing ecosystem fluxes. We used external heat balance sap flow sensors and a hierarchical Bayesian state-space modeling approach to bridge this \“flux gap\” and estimate continuous species-level water flux in common tallgrass prairie species. Specifically, we asked the following: (1) How do diurnal and nocturnal water fluxes differ among woody and herbaceous plants? (2) How sensitive are woody and herbaceous species to environmental drivers of diurnal and nocturnal water flux? We highlight three results: (1) Cornus drummondii, the primary woody encroacher in this grassland, exhibited the greatest canopy-level water loss; (2) nocturnal transpiration was a large component of the water lost in this ecosystem and was driven primarily by C4 grasses and C. drummondii; and (3) the sensitivity of canopy transpiration to environmental drivers varies among plant functional types and throughout a 24-hr period. Our data reveal important insights regarding the water use strategies of woody versus herbaceous species in tallgrass prairies and about the potential hydrological consequences of ongoing woody encroachment. We suggest that the high, static flux rates observed in woody species will likely deplete deep water stores over time, potentially creating hydrological deficits in grasslands experiencing woody encroachment and concomitantly increasing the vulnerability of these ecosystems to drought.

}, keywords = {LTER-KNZ}, doi = {10.1029/2019JG005446}, url = {https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019JG005446}, author = {O{\textquoteright}Keefe, Kimberly and Bell, David M. and McCulloh, Katherine A. and Jesse B. Nippert} } @article {KNZ001997, title = {Browsing and fire decreases dominance of a resprouting shrub in woody encroached grassland}, journal = {Ecology}, volume = {101}, year = {2020}, pages = {e02935}, abstract = {

North American grasslands have experienced increased relative abundance of shrubs and trees over the last 150 years. Alterations in herbivore composition, abundance and grazing pressure along with changes in fire frequency are drivers that can regulate the transition from grassland to shrubland or woodland (a process known as woody encroachment). Historically, North American grasslands had a suite of large herbivores that grazed and/or browsed (i.e. bison, elk, pronghorn, deer), as well as frequent and intense fires. In the tallgrass prairie, many large native ungulates were extirpated by the 1860\’s corresponding with increased homesteading (which led to decreased fire frequencies and intensities). Changes in the frequency and intensity of these two drivers (browsing and fire) has coincided with woody encroachment in tallgrass prairie. Within tallgrass prairie, woody encroachment can be categorized in to two groups: non-resprouting species that can be killed with fire, and resprouting species that cannot be killed with fire. Resprouting species require additional active management strategies to decrease abundance and eventually be removed from the ecosystem. In this study we investigated plant cover, ramet density and physiological effects of continuous simulated browsing and prescribed fire on Cornus drummondii C.A. Mey, a resprouting clonal native shrub species. Browsing reduced C. drummondii canopy cover and increased grass cover. We also observed decreased ramet density that allowed for more infilling of grasses. Photosynthetic rates between browsed and unbrowsed control shrubs did not increase in 2015 or 2016. In 2017, photosynthetic rates for browsed shrubs were higher in the unburned site than the unbrowsed control shrubs at the end of the growing season. Additionally, after the prescribed fire, browsed shrubs had ~ 90\% decreased cover, ~50\% reduced ramet density, and grass cover increased by ~ 80\%. In the roots of browsed shrubs after the prescribed fire, non-structural carbohydrates (NSC) experienced a 2-fold reduction in glucose and a 3-fold reduction in both sucrose and starch. The combined effects of browsing and fire show strong potential as a successful management tool to decrease the abundance of clonal-resprouting woody plants in mesic grasslands and illustrate the potential significance of browsers as a key driver in this ecosystem.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.2935}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.2935}, author = {O{\textquoteright}Connor, R.C. and Taylor, J.H. and Jesse B. Nippert} } @article {KNZ002038, title = {Microanatomical traits track climate gradients for a dominant C4 grass species across the Great Plains, USA}, journal = {Annals of Botany}, volume = {mcaa146}, year = {2020}, keywords = {LTER-KNZ}, doi = {10.1093/aob/mcaa146}, url = {https://doi.org/10.1093/aob/mcaa146}, author = {Bachle, Seton and Nippert, J.B.} } @article {KNZ002014, title = {Rainfall-manipulation experiments as simulated by terrestrial biosphere models: where do we stand?}, journal = {Global Change Biology}, volume = {26}, year = {2020}, pages = {3336{\textendash}3355}, abstract = {

Changes in rainfall amounts and patterns have been observed and are expected to continue in the near future with potentially significant ecological and societal consequences. Modelling vegetation responses to changes in rainfall is thus crucial to project water and carbon cycles in the future. In this study, we present the results of a new model-data intercomparison project, where we tested the ability of ten terrestrial biosphere models to reproduce observed sensitivity of ecosystem productivity to rainfall changes at ten sites across the globe, in nine of which, rainfall exclusion and/or irrigation experiments had been performed.

The key results are:
(a) Inter-model variation is generally large and model agreement varies with time scales. In severely water limited sites, models only agree on the interannual variability of evapotranspiration and to a smaller extent gross primary productivity. In more mesic sites model agreement for both water and carbon fluxes is typically higher on fine (daily-monthly) time scales and reduces on longer (seasonal-annual) scales.
(b) Models on average overestimate the relationship between ecosystem productivity and mean rainfall amounts across sites (in space) and have a low capacity in reproducing the temporal (interannual) sensitivity of vegetation productivity to annual rainfall at a given site, even though observation uncertainty is comparable to inter-model variability.
(c) Most models reproduced the sign of the observed patterns in productivity changes in rainfall manipulation experiments but had a low capacity in reproducing the observed magnitude of productivity changes. Models better reproduced the observed productivity responses due to rainfall exclusion than addition.
(d) All models attribute ecosystem productivity changes to the intensity of vegetation stress and peak leaf area, whereas the impact of the change in growing season length is negligible. The relative contribution of the peak leaf area and vegetation stress intensity was highly variable among models.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.15024}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15024}, author = {Paschalis, Athanasios and Fatichi, Simone and Zscheischler, Jakob and Ciais, Philippe and Michael Bahn and Lena R. Boysen and Chang, Jinfeng and De Kauwe, Martin and Estiarte, Marc and Goll, Daniel and Hanson, Paul J. and Harper, Anna B. and Hou, Enqing and Kigel, Jaime and Alan K. Knapp and Larsen, Klaus Steenberg and Li, Wei and Lienert, Sebastian and Luo, Yiqi and Meir, Patrick and Nabel, Julia E.M.S. and Ogaya, Rom{\`a} and Parolari, Anthony J and Peng, Changhui and Pe{\~n}uelas, Josep and Pongratz, Julia and Rambal, Serge and Schmidt, Inger Kappel and Shi, Hao and Sternberg, Marcelo and Tian, Hanqin and Tschumi, Elisabeth and Ukkola, Anna and Vicca, Sara and Viovy, Nicolas and Wang, -Ping and Wang, Zhuonan and Williams, Karina and Wu, Donghai and Zhu, Qiuan} } @article {KNZ002037, title = {SoDaH: the SOils DAta Harmonization database, an open-source synthesis of soil data from research networks, version 1.0}, journal = {Earth System Science Data Discussion}, year = {2020}, keywords = {LTER-KNZ}, doi = {10.5194/essd-2020-195}, url = {https://essd.copernicus.org/preprints/essd-2020-195/}, author = {Wieder, W.R. and Pierson, D. and Earl, S.R. and Lajtha, K. and Baer, S. and Ballantyne, F. and Berhe, A.A. and Billings, S. and Brigham, L.M. and Chacon, S.S. and Fraterrigo, J. and Frey, S.D. and Georgiou, K. and de Graaff, M. and Grandy, A.S. and Hartman, M.D. and Hobbie, S.E. and Johnson, C. and Kaye, J. and Snowman, E. and Litvak, M.E. and Mack, M.C. and Malhotra, A. and Moore, J.A.M. and Nadelhoffer, K. and Rasmussen, C. and Silver, W.L. and Sulman, B.N. and Walker, X. and Weintraub. S.} } @article {KNZ002033, title = {Terabase metagenome sequencing of grassland soil microbiomes}, journal = {Microbiology Resource Announcements}, volume = {9}, year = {2020}, pages = {00718-20}, keywords = {LTER-KNZ}, doi = {10.1128/MRA.00718-20}, url = {https://mra.asm.org/content/9/32/e00718-20.abstract}, author = {Nelson, W. and Anderson, L. and Wu, R. and McDermott, J. and Bell, S. and A. Jumpponen and Fansler, S. and Tyrrell, K. and Farris, Y. and Hofmockel, K. and Jansson, J.} } @article {KNZ002027, title = {Three decades of divergent land use and plant community change alters soil C and N content in tallgrass prairie}, journal = {Journal of Geophysical Research: Biogeosciences}, volume = {125}, year = {2020}, pages = {e2020JG005723}, abstract = {

Frequent fire and grazing by megafauna are important determinants of tallgrass prairie plant community structure. However, fire suppression and removal of native grazers have altered these natural disturbance regimes and changed grassland plant communities with potential long-term consequences for soil carbon (C) and nitrogen (N) storage. We investigated multi-decade changes in soil C and N pools in response to contrasting long-term burning and grazing treatments. Fire suppression with or without grazers, and exclusion of grazers in annually-burned prairie increased soil C content and shifted the δ13C signature of soil C over time, concomitant with changes in plant community composition. Soil δ13C values indicated that increased soil C content was associated with an increased contribution from plants using a C3 photosynthetic pathway (i.e., woody shrubs) under fire suppression. Soil N content also increased when fire was suppressed, relative to frequently burned grassland, but the rate of increase was slower when grazers were present. Additionally, changes in δ15N values suggested that grazing increased the openness of the N cycle, presumably due to greater N losses. By coupling long-term fire and grazing treatments with plant community data and soil samples archived over three decades, we demonstrate that human-caused changes to natural disturbance regimes in a tallgrass prairie significantly alters soil C and N cycles through belowground changes associated with shifts in the plant community. Since natural disturbance regimes have been altered in grasslands across the world, our results are relevant for understanding the long-term biogeochemical consequences of these ongoing land-use changes.

}, keywords = {LTER-KNZ}, doi = {10.1029/2020JG005723}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2020JG005723}, author = {Connell, K.R. and J Nippert and J. M. Blair} } @article {KNZ001948, title = {Building an integrated infrastructure for exploring biodiversity: field collections and archives of mammals and parasites}, journal = {Journal of Mammalogy}, volume = {100}, year = {2019}, pages = {382 - 393}, abstract = {

Museum specimens play an increasingly important role in predicting the outcomes and revealing the consequences of anthropogenically driven disruption of the biosphere. As ecological communities respond to ongoing environmental change, host\–parasite interactions are also altered. This shifting landscape of host\–parasite associations creates opportunities for colonization of different hosts and emergence of new pathogens, with implications for wildlife conservation and management, public health, and other societal concerns. Integrated archives that document and preserve mammal specimens along with their communities of associated parasites and ancillary data provide a powerful resource for investigating, anticipating, and mitigating the epidemiological, ecological, and evolutionary impacts of environmental perturbation. Mammalogists who collect and archive mammal specimens have a unique opportunity to expand the scope and impact of their field work by collecting the parasites that are associated with their study organisms. We encourage mammalogists to embrace an integrated and holistic sampling paradigm and advocate for this to become standard practice for museum-based collecting. To this end, we provide a detailed, field-tested protocol to give mammalogists the tools to collect and preserve host and parasite materials that are of high quality and suitable for a range of potential downstream analyses (e.g., genetic, morphological). Finally, we also encourage increased global cooperation across taxonomic disciplines to build an integrated series of baselines and snapshots of the changing biosphere.

}, keywords = {LTER-KNZ}, doi = {10.1093/jmammal/gyz048}, url = {https://academic.oup.com/jmammal/article/100/2/382/5436909}, author = {Galbreath, Kurt E and Hoberg, Eric P and Cook, Joseph A and Armi{\'e}n, Blas and Bell, Kayce C and Campbell, Mariel L and Dunnum, Jonathan L and Dursahinhan, Altangerel T and Eckerlin, Ralph P and Gardner, Scott L and Greiman, Stephen E and Henttonen, Heikki and Jim{\'e}nez, Agust{\'\i}n and Koehler, Anson V A and Nyamsuren, Batsaikhan and Tkach, Vasyl V and Torres-P{\'e}rez, Fernando and Tsvetkova, Albina and Hope, Andrew G} } @phdthesis {KNZ001955, title = {Drivers, mechanisms, and thresholds of wood encroachment in mesic grasslands}, volume = {PhD Dissertation}, year = {2019}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS. }, keywords = {LTER-KNZ}, url = {https://krex.k-state.edu/dspace/handle/2097/40021}, author = {O{\textquoteright}Connor, Rory} } @article {KNZ001960, title = {Evaluating a Lagrangian inverse model for inferring isotope CO2 exchange in plant canopies}, journal = {Agricultural and Forest Meteorology}, volume = {276-277}, year = {2019}, pages = {107651}, abstract = {

Multi-layer Lagrangian models could be useful techniques for studying stable isotope exchange within and just above plant canopies. The main objective of this study was to evaluate the use of an analytical Lagrangian analysis (localized near-field theory, LNF), to study 13CO2 and C18OO isotope exchange in different plant canopies by comparing the LNF estimates with those provided by the eddy covariance (EC) technique and the isotope flux ratio method (IFR). Mixing ratios of stable isotopes of CO2 were measured within and above a temperate deciduous forest, tallgrass prairie and corn field using a multi-port sampling system and the tunable diode laser spectroscopy technique. Wind velocity data and the net CO2 ecosystem exchange (NEE) were measured above the plant canopies using an EC system. The wind velocity data and CO2 stable isotope mixing ratios were combined with the LNF theory to infer NEE and source/sinks of isotopes inside canopies. The LNF NEE estimates were likely affected by the flux decoupling in the forest canopy, resulting in a low correlation (R2 ranging from 0.03 to 0.35) between LNF and EC NEE estimates. On the other hand, LNF NEE estimates for corn and grassland canopies showed better correlation with EC NEE estimates (R2 ranging from 0.58 to 0.85), suggesting better coupling between in and above canopy air flows. Although, both LNF and IFR estimates showed large variability, our results show that the LNF approach reduced the uncertainties of the isotope compositions of NEE when compared to the IFR approach. These results suggest that LNF is a useful tool to study CO2 isotope exchange within short canopies where flux measurements are more challenging than inside tall canopies.

}, keywords = {LTER-KNZ}, doi = {10.1016/j.agrformet.2019.107651}, url = {https://linkinghub.elsevier.com/retrieve/pii/S016819231930259X}, author = {Santos, Marshall and Santos, Eduardo and Wagner-Riddle, Claudia and Brown, Shannon and Stropes, Kyle and Staebler, Ralf and Jesse B. Nippert} } @article {KNZ001933, title = {Global patterns and drivers of ecosystem functioning in rivers and riparian zones}, journal = {Science Advances}, volume = {5}, year = {2019}, pages = {eaav0486}, abstract = {

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth\’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented \“next-generation biomonitoring\” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.

}, keywords = {LTER-KNZ}, doi = {10.1126/sciadv.aav0486}, url = {http://advances.sciencemag.org/content/5/1/eaav0486}, author = {Tiegs, Scott D. and Costello, David M. and Isken, Mark W. and Woodward, Guy and McIntyre, Peter B. and Gessner, Mark O. and Chauvet, Eric and Griffiths, Natalie A. and Flecker, Alex S. and Acu{\~n}a, Vicenc and Albari{\~n}o, Ricardo and Allen, Daniel C. and Alonso, Cecilia and Andino, Patricio and Arango, Clay and Aroviita, Jukka and Barbosa, Marcus V. M. and Barmuta, Leon A. and Baxter, Colden V. and Bell, Thomas D. C. and Bellinger, Brent and Boyero, Luz and Brown, Lee E. and Bruder, Andreas and Bruesewitz, Denise A. and Burdon, Francis J. and Callisto, Marcos and Canhoto, Cristina and Capps, Krista A. and Castillo, Mar{\'\i}a M. and Clapcott, Joanne and Colas, Fanny and Col{\'o}n-Gaud, Checo and Cornut, Julien and Crespo-P{\'e}rez, Ver{\'o}nica and Cross, Wyatt F. and Culp, Joseph M. and Danger, Michael and Dangles, Olivier and de Eyto, Elvira and Derry, Alison M. and Villanueva, {\'\i}az and Douglas, Michael M. and Elosegi, Arturo and Encalada, Andrea C. and Entrekin, Sally and Espinosa, Rodrigo and Ethaiya, Diana and Ferreira, Ver{\'o}nica and Ferriol, Carmen and Flanagan, Kyla M. and Fleituch, Tadeusz and Follstad Shah, Jennifer J. and Frainer Barbosa, Andr{\'e} and Friberg, Nikolai and Frost, Paul C. and Garcia, Erica A. and Garc{\'\i}a Lago, Liliana and Garc{\'\i}a Soto, Pavel Ernesto and Ghate, Sudeep and Giling, Darren P. and Gilmer, Alan and {\c c}alves, Jos{\'e} Francisco and Gonzales, Rosario Karina and Graca, Manuel A. S. and Grace, Mike and Grossart, Hans-Peter and Guerrold, Francois and Gulis, Vlad and Hepp, Luiz U. and Higgins, Scott and Hishi, Takuo and Huddart, Joseph and Hudson, John and Imberger, Samantha and {\~n}iguez-Armijos, Carlos and Iwata, Tomoya and Janetski, David J. and Jennings, Eleanor and Kirkwood, Andrea E. and Koning, Aaron A. and Kosten, Sarian and Kuehn, Kevin A. and Laudon, Hjalmar and Leavitt, Peter R. and Lemes da Silva, Aurea L. and Leroux, Shawn J. and LeRoy, Carri J. and Lisi, Peter J. and MacKenzie, Richard and Marcarelli, Amy M. and Masese, Frank O. and McKie, Brendan G. and Oliveira Medeiros, Adriana and Meissner, Kristian and Mili{\v s}a, Marko and Mishra, Shailendra and Miyake, Yo and Moerke, Ashley and Mombrikotb, Shorok and Mooney, Rob and Moulton, Tim and Muotka, Timo and Negishi, Junjiro N. and Neres-Lima, Vinicius and Nieminen, Mika L. and Nimptsch, Jorge and Ondruch, Jakub and Paavola, Riku and Pardo, Isabel and Patrick, Christopher J. and Peeters, Edwin T. H. M. and Pozo, Jesus and Pringle, Catherine and Prussian, Aaron and Quenta, Estefania and Quesada, Antonio and Reid, Brian and Richardson, John S. and Rigosi, Anna and Rinc{\'o}n, Jos{\'e} and Risnoveanu, Geta and Robinson, Christopher T. and Rodr{\'\i}guez-Gallego, Lorena and Royer, Todd V. and Rusak, James A. and Santamans, Anna C. and Selmeczy, G{\'e}za B. and Simiyu, Gelas and Skuja, Agnija and Smykla, Jerzy and Sridhar, Kandikere R. and Sponseller, Ryan and Stoler, Aaron and Swan, Christopher M. and Szlag, David and Mello, Franco Teixeira-de and Tonkin, Jonathan D. and Uusheimo, Sari and Veach, Allison M. and Vilbaste, Sirje and Vought, Lena B. M. and Wang, Chiao-Ping and Webster, Jackson R. and Wilson, Paul B. and Woelfl, Stefan and Xenopoulos, Marguerite A. and Yates, Adam G. and Yoshimura, Chihiro and Yule, Catherine M. and Zhang, Yixin X. and Zwart, Jacob A.} } @article {KNZ001971, title = {Increasing groundwater CO2 in a midcontinent tallgrass prairie: Controlling factors}, journal = {E3S Web of Conferences}, volume = {98}, year = {2019}, pages = {06008}, abstract = {

Alkalinity and groundwater CO2 have increased linearly from 1991\–2017 at the Konza Prairie Biological Station (KPBS), a tallgrass prairie research site in northeastern Kansas. The projected increase in groundwater alkalinity (as HCO3-) and CO2 based on an earlier trend was confirmed in 2016, with predictions nearly equal to recent values (e.g., 408 ppm vs 410 ppm as HCO3-, respectively). Both the water balance and groundwater CO2 trends within the study watershed could be impacted by long-term changes in land use and climate: 1) encroachment of woody vegetation (1983\–2012) as a result of the 4-year fire return interval, 2) re-introduction of bison (phased in, 1994\–2006), 3) increases in air temperature, and 4) changes in precipitation patterns. If only linear processes are driving the observed water chemistry changes, then the linear increase in air temperature (1983\–2017) that stimulates soil respiration may be the most likely factor enhancing groundwater HCO3- and CO2, as air temperature has risen ~1 to 1.4\°C over 34 years. If groundwater chemistry is driven by more threshold behaviour, woody encroachment, which was linear but in three distinct phases, may drive groundwater chemistry. The ~2 to 3\‰ decrease in the discontinuous δ13C data in the groundwater-dominated stream suggests enhanced inputs of microbially-respired labile carbon, CO2 sourced from C3 (woody vegetation), or a combination of the two.

}, keywords = {LTER-KNZ}, doi = {10.1051/e3sconf/20199806008}, url = {https://www.e3s-conferences.org/10.1051/e3sconf/20199806008}, author = {G. L. Macpherson and Sullivan, P.L. and Stotler, R.L. and Norwood, B.S.}, editor = {Chudaev, O. and Kharaka, Y. and Harmon, R. and Millot, R. and Shouakar-Stash, O.} } @article {KNZ001910, title = {Restoring grassland in the context of climate change}, journal = {Grasslands and Climate Change}, year = {2019}, pages = {310 -322}, keywords = {LTER-KNZ}, doi = {10.1017/9781108163941.020}, url = {https://doi.org/10.1017/9781108163941.020}, author = {S.G. Baer and D.J. Gibson and Johnson, L.C.}, editor = {D.J. Gibson and Newman, J.A.} } @article {KNZ001986, title = {Soil organic carbon, aggregation, and microbial community Structure in annual and perennial biofuel crops}, journal = {Agronomy Journal}, volume = {111}, year = {2019}, pages = {128 - 142}, keywords = {LTER-KNZ}, doi = {10.2134/agronj2018.04.0284}, url = {http://doi.wiley.com/10.2134/agronj2018.04.0284}, author = {McGowan, Andrew R. and Nicoloso, Rodrigo S. and Diop, Habib E. and Roozeboom, Kraig L. and C. W. Rice} } @inbook {KNZ001941, title = {Will climate change push grasslands past critical thresholds?}, booktitle = {Grasslands and Climate Change}, year = {2019}, pages = {98 - 114}, publisher = {British Ecological Society and Cambridge University Press}, organization = {British Ecological Society and Cambridge University Press}, address = {Cambridge, UK.}, keywords = {LTER-KNZ}, url = {https://www.cambridge.org/core/books/grasslands-and-climate-change/will-climate-change-push-grasslands-past-critical-thresholds/368C9316D9C5A8A3C6B6881779BA5EB5}, author = {Z. Ratajczak and L. Ladwig}, editor = {Gibson, D. and Newman, J.} } @article {KNZ001898, title = {Ambient changes exceed treatment effects on plant species abundance in long-term global change experiments}, journal = {Glob Chang Biol}, volume = {24}, year = {2018}, pages = {5668 - 5679}, abstract = {

The responses of species to environmental changes will determine future community composition and ecosystem function. Many syntheses of global change experiments examine the magnitude of treatment effect sizes, but we lack an understanding of how plant responses to treatments compare to ongoing changes in the unmanipulated (ambient or background) system. We used a database of long-term global change studies manipulating CO2 , nutrients, water, and temperature to answer three questions: (a) How do changes in plant species abundance in ambient plots relate to those in treated plots? (b) How does the magnitude of ambient change in species-level abundance over time relate to responsiveness to global change treatments? (c) Does the direction of species-level responses to global change treatments differ from the direction of ambient change? We estimated temporal trends in plant abundance for 791 plant species in ambient and treated plots across 16 long-term global change experiments yielding 2,116 experiment-species-treatment combinations. Surprisingly, for most species (57\%) the magnitude of ambient change was greater than the magnitude of treatment effects. However, the direction of ambient change, whether a species was increasing or decreasing in abundance under ambient conditions, had no bearing on the direction of treatment effects. Although ambient communities are inherently dynamic, there is now widespread evidence that anthropogenic drivers are directionally altering plant communities in many ecosystems. Thus, global change treatment effects must be interpreted in the context of plant species trajectories that are likely driven by ongoing environmental changes.

}, keywords = {LTER-KNZ, elevated CO2, nitrogen, Phosphorus, plant community, Warming, water}, doi = {10.1111/gcb.14442}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14442}, author = {Langley, A. and Chapman, S.K. and Kimberly J. La Pierre and M.L. Avolio and W.D. Bowman and Johnson, D. and Isbell, F. and K.R. Wilcox and Foster, B. and Hovenden, M. and Alan K. Knapp and Koerner, S.E. and Lortie, C. and Megonigal, J. and Newton, P. and Reich, B. and M.D. Smith and Suttle, B.K. and Tilman, D.} } @article {KNZ001863, title = {Asymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites}, journal = {Biogeosciences}, volume = {15}, year = {2018}, pages = {3421 - 3437}, abstract = {

Field measurements of aboveground net primary productivity (ANPP) in temperate grasslands suggest that both positive and negative asymmetric responses to changes in precipitation (P) may occur. Under normal range of precipitation variability, wet years typically result in ANPP gains being larger than ANPP declines in dry years (positive asymmetry), whereas increases in ANPP are lower in magnitude in extreme wet years compared to reductions during extreme drought (negative asymmetry). Whether the current generation of ecosystem models with a coupled carbon\–water system in grasslands are capable of simulating these asymmetric ANPP responses is an unresolved question. In this study, we evaluated the simulated responses of temperate grassland primary productivity to scenarios of altered precipitation with 14 ecosystem models at three sites: Shortgrass steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a rainfall gradient from dry to moist. We found that (1)\ the spatial slopes derived from modeled primary productivity and precipitation across sites were steeper than the temporal slopes obtained from inter-annual variations, which was consistent with empirical data; (2)\ the asymmetry of the responses of modeled primary productivity under normal inter-annual precipitation variability differed among models, and the mean of the model ensemble suggested a negative asymmetry across the three sites, which was contrary to empirical evidence based on filed observations; (3)\ the mean sensitivity of modeled productivity to rainfall suggested greater negative response with reduced precipitation than positive response to an increased precipitation under extreme conditions at the three sites; and (4)\ gross primary productivity (GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground NPP (BNPP) all showed concave-down nonlinear responses to altered precipitation in all the models, but with different curvatures and mean values. Our results indicated that most models overestimate the negative drought effects and/or underestimate the positive effects of increased precipitation on primary productivity under normal climate conditions, highlighting the need for improving eco-hydrological processes in those models in the future.

}, keywords = {LTER-KNZ}, doi = {10.5194/bg-15-3421-2018}, url = {https://www.biogeosciences.net/15/3421/2018/}, author = {Wu, Donghai and Ciais, Philippe and Viovy, Nicolas and Alan K. Knapp and K.R. Wilcox and Michael Bahn and M.D. Smith and Vicca, Sara and Fatichi, Simone and Zscheischler, Jakob and He, Yue and Li, Xiangyi and Ito, Akihiko and Arneth, Almut and Harper, Anna and Ukkola, Anna and Paschalis, Athanasios and Poulter, Benjamin and Peng, Changhui and Ricciuto, Daniel and Reinthaler, David and Chen, Guangsheng and Tian, Hanqin and Genet, {\'e}l{\`e}ne and Mao, Jiafu and Ingrisch, Johannes and Nabel, Julia E. S. M. and Pongratz, Julia and Lena R. Boysen and Kautz, Markus and Schmitt, Michael and Meir, Patrick and Zhu, Qiuan and R. Hasibeder and Sippel, Sebastian and Dangal, Shree R. S. and Sitch, Stephen and Shi, Xiaoying and Wang, Yingping and Luo, Yiqi and Liu, Yongwen and Piao, Shilong} } @article {KNZ001888, title = {Change in dominance determines herbivore effects on plant biodiversity}, journal = {Nature Ecology and Evolution}, volume = {2}, year = {2018}, pages = {1925-1932}, abstract = {

Herbivores alter plant biodiversity (species richness) in many of the world\’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis\—that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.

}, keywords = {LTER-KNZ}, doi = {https://doi.org/10.1038/s41559-018-0696-y}, url = {https://www.nature.com/articles/s41559-018-0696-y$\#$article-info}, author = {Koerner, S.E. and M.D. Smith and Burkepile, D.E. and N.P. Hanan and M.L. Avolio and Scott. L. Collins and Alan K. Knapp and N.P. Lemoine and E.J. Forrestel and S. Eby and D.I. Thompson and G. Aguado-Santacruz and J.P. Anderson and Anderson, M. and A. Angassa and S. Bagchi and E.S. Bakker and Bastin, Gary and L.E. Baur and K.H. Beard and E.A. Beever and P.J. Bohlen and Elizabeth H. Boughton and Canestro, Don and Cesa, Ariela and Chaneton, Enrique and Cheng, Jimin and C.M. D{\textquoteright}Antonio and C. Deleglise and Fadiala. Demb{\'e}l{\'e} and Josh. Dorrough and David. J. Eldridge and Barbara. Fernandez-Going and Silvia. Fern{\'a}ndez-Lugo and Lauchlan. H. Fraser and Bill. Freedman and Gonzalo. Garc{\'\i}a-Salgado and Jacob. R. Goheen and Liang. Guo and Sean. Husheer and Moussa. Karemb{\'e} and Johannes. M. H. Knops and Tineke. Kraaij and Andrew. Kulmatiski and Minna-Maarit. Kyt{\"o}viita and Felipe. Lezama and Gregory. Loucougaray and Alejandro. Loydi, Dan G. Milchunas, and Dan.G. Milchunas, and Suzanne. J. Milton and J.W. Morgan and Claire. Moxham and Kyle. C. Nehring and Han. Olff and Todd. M. Palmer and Salvador. Rebollo and Corinna. Riginos and Anita. C. Risch and Marta Rueda and Mahesh. Sankaran and Takehiro. Sasaki and Kathryn. A. Schoenecker and Nick. L. Schultz and Martin. Sch{\"u}tz and Angelika. Schwabe and Frances. Siebert and Christian. Smit and Karen. A. Stahlheber and Christian. Storm and Dustin. J. Strong and Jishuai. Su and Yadugiri. V. Tiruvaimozhi and Claudia. Tyler and James. Val and Martijn. L. Vandegehuchte and Kari. E. Veblen and Lance. T. Vermeire and David. Ward and Jianshuang. Wu and Truman. P. Young and Qiang. Yu and Tamara. Jane. Zelikova} } @inbook {KNZ001908, title = {Chapter 5: Agriculture}, booktitle = {Second State of the Carbon Cycle Report (SOCCR2): A Sustained Assessment Report}, year = {2018}, pages = {229 - 263}, publisher = {U.S. Global Change Research Program}, organization = {U.S. Global Change Research Program}, keywords = {LTER-KNZ}, doi = {10.7930/SOCCR2.2018.Ch5}, url = {https://carbon2018.globalchange.gov/chapter/5/}, author = {Hristov, A. N. and Johnson, J. M. F. and C. W. Rice and Brown, M. E. and Conant, R. T. and Del Grosso, S. J. and Gurwick, N. P. and Rotz, C. A. and Sainju, U. M. and Skinner, R. H. and West, T. O. and Runkle, B. R. K. and Janzen, H. and Reed, S. and Cavallaro, N. and Shrestha, G. and Birdsey, R.}, editor = {Cavallaro, N. and Shrestha, G. and Mayes, M. A. and Najjar, R. and Reed, S. and Romero-Lankao, P. and Zhu, Z.} } @article {KNZ001821, title = {Developing a conceptual framework of landscape and hydrology on tallgrass prairie: A critical zone approach}, journal = {Vadose Zone Journal}, volume = {17}, year = {2018}, pages = {1 - 11}, abstract = {

Agricultural intensification and urbanization have greatly reduced the extent of tallgrass prairie across North America. To evaluate the impact of these changes, a reference ecosystem of unperturbed prairie is required. The Konza Prairie Biological Station in northeastern Kansas is a long-term research site at which a critical zone approach has been implemented. Integration of climatic, ecologic, and hydropedologic research to facilitate a comprehensive understanding of the complex environment provides the basis for predicting future aquifer and landscape evolution. We present a conceptual framework of the hydrology underpinning the area that integrates the extensive current and past research and provides a synthesis of the literature to date. The key factors in the hydrologic behavior of Konza Prairie are climate, ecology, vadose zone characteristics and management, and groundwater and bedrock. Significant interactions among these factors include bedrock dissolution driven by cool-season precipitation and hence a climatic control on the rate of karstification. Soil moisture dynamics are influenced at various timescales due to the short- and long-term effects of prescribed burning on vegetation and on soil physical characteristics. The frequency of burning regimes strongly influences the expansion of woody species in competition with native tallgrasses, with consequent effects on C and N dynamics within the vadose zone. Knowledge gaps exist pertaining to the future of Konza Prairie (a model for US tallgrass prairie)\—whether continued karstification will lead to increasingly flashy and dynamic hydrology and whether compositional changes in the vegetation will affect long-term changes in water balances.

}, keywords = {LTER-KNZ}, doi = {10.2136/vzj2017.03.0069}, url = {https://dl.sciencesocieties.org/publications/vzj/pdfs/17/1/170069}, author = {Vero, S. E. and G. L. Macpherson and Sullivan, P.L. and A.E. Brookfield and Jesse B. Nippert and Kirk, M. F. and Datta, S. and Kempton, P.} } @article {KNZ001876, title = {Drivers of nocturnal water flux in a tallgrass prairie}, journal = {Functional Ecology}, volume = {32}, year = {2018}, pages = {1155-1167}, abstract = {

Nocturnal transpiration can impact water balance from the local community to earth-atmosphere fluxes. However, the dynamics and drivers of nocturnal transpiration among coexisting plant functional groups in herbaceous ecosystems are unknown.
Here, we addressed the following questions: (1) How do nocturnal (Enight) and diurnal (Eday) transpiration vary among coexisting grasses, forbs, and shrubs in a tallgrass prairie? (2) What environmental variables drive Enight and do these differ from the drivers of Eday? (3) Is Enight associated with daytime physiological processes?
We measured diurnal and nocturnal leaf gas exchange on perennial grass, forb and woody species in a North American tallgrass prairie. Measurements were made periodically across two growing seasons (May\–August 2014\–2015) on three C4 grasses (Andropogon gerardii, Sorghastrum nutans and Panicum virgatum), two C3 forbs (Vernonia baldwinii and Solidago canadensis), one C3 sub-shrub (Amorpha canescens) and two C3 shrubs (Cornus drummondii and Rhus glabra).
By extending our study to multiple functional groups, we were able to make several key observations: (1) Enight was variable among co-occurring plant functional groups, with the highest rates occurring in C4 grasses, (2) Enight and Eday exhibited different responses to vapour pressure deficit and other environmental drivers, and (3) rates of Enight were strongly related to predawn leaf water potential for grasses and woody species, and were likely modulated by small-scale changes in soil moisture availability.
Our results provide novel insight into an often-overlooked portion of ecosystem water balance. Considering the high rates of Enight observed in C4 grasses, as well as the widespread global occurrence of C4 grasses, nocturnal water loss might constitute a greater proportion of global evapotranspiration than previously estimated. Additionally, future predictions of nocturnal water loss may be complicated by stomatal behaviour that differs between the day and at night. Finally, these data suggest a water-use strategy by C4 grasses wherein the high rates of Enight occurring during wet periods may confer a competitive advantage to maximize resource consumption during periods of greater availability.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2435.13072}, url = {https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.13072}, author = {O{\textquoteright}Keefe, K. and Jesse B. Nippert}, editor = {Sala, Anna} } @article {KNZ001931, title = {Intraspecific trait variability in Andropogon gerardii, a dominant grass species in the US Great Plains}, journal = {Frontiers in Ecology and Evolution}, year = {2018}, abstract = {

The climatic conditions in the North American Great Plains are highly variable, characteristic of an inter-continental climate. Antecedent climate history has impacted the flora of Great Plains grasslands, resulting in high species richness as well as dominance by only a few grass species, such as Andropogon gerardii. While the productivity of A. gerardii is well described, the individual physiological, and morphological characteristics that confer species dominance over wide spatial gradients are not clearly understood. We performed a literature search to assess intra-specific trait variability of A. gerardii from as many locations as possible. Ultimately, only 13 locations in the Great Plains have reported common plant functional traits (PFTs) for this species. To best represent site-specific climate conditions, plant functional trait data (8 PFTs) were collected from literature reporting ambient growing conditions, and excluded experimental manipulations. For most PFTs, we found insufficient data to fully quantify the range of variation across the geographical extent of A. gerardii dominance. This is surprising given that we focused on the most abundant grass in one of the most well-studied regions globally. Furthermore, trait data collected from our literature search showed a high degree of variability, but no strong relationships were observed between mean trait values and climate predictors. Our review of the literature on A. gerardii suggests a role for trait variability as a mechanism enabling the dominance of this species across large regions such as the Great Plains of North America.

}, keywords = {LTER-KNZ}, doi = {10.3389/fevo.2018.00217}, url = {https://www.frontiersin.org/articles/10.3389/fevo.2018.00217/full}, author = {Bachle, Seton. and Griffith, D.M. and Jesse B. Nippert} } @article {KNZ001822, title = {Partitioning assimilatory nitrogen uptake in streams: an analysis of stable isotope tracer additions across continents}, journal = {Ecological Monographs}, volume = {88}, year = {2018}, pages = {138}, chapter = {120}, abstract = {

Headwater streams remove, transform, and store inorganic nitrogen (N) delivered from surrounding watersheds, but excessive N inputs from human activity can saturate removal capacity. Most research has focused on quantifying N removal from the water column over short periods and in individual reaches, and these ecosystem-scale measurements suggest that assimilatory N uptake accounts for most N removal. However, cross-system comparisons addressing the relative role of particular biota responsible for incorporating inorganic N into biomass are lacking. Here we assess the importance of different primary uptake compartments on reach-scale ammonium (NH4+-N) uptake and storage across a wide range of streams varying in abundance of biota and local environmental factors. We analyzed data from 17\ 15N-NH4+tracer addition experiments globally, and found that assimilatory N uptake by autotrophic compartments (i.e., epilithic biofilm, filamentous algae, bryophytes/macrophytes) was higher but more variable than for heterotrophic microorganisms colonizing detrital organic matter (i.e., leaves, small wood, and fine particles). Autotrophic compartments played a disproportionate role in N uptake relative to their biomass, although uptake rates were similar when we rescaled heterotrophic assimilatory N uptake associated only with live microbial biomass. Assimilatory NH4+-N uptake, either estimated as removal from the water column or from the sum uptake of all individual compartments, was four times higher in open- than in closed-canopy streams. Using Bayesian Model Averaging, we found that canopy cover and gross primary production (GPP) controlled autotrophic assimilatory N uptake while ecosystem respiration (ER) was more important for the heterotrophic contribution. The ratio of autotrophic to heterotrophic N storage was positively correlated with metabolism (GPP: ER), which was also higher in open- than in closed-canopy streams. Our analysis shows riparian canopy cover influences the relative abundance of different biotic uptake compartments and thus GPP:ER. As such, the simple categorical variable of canopy cover explained differences in assimilatory N uptake among streams at the reach scale, as well as the relative roles of autotrophs and heterotrophs in N storage. Finally, this synthesis links cumulative N uptake by stream biota to reach-scale N demand and provides a mechanistic and predictive framework for estimating and modeling N cycling in other streams.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecm.1280}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecm.1280}, author = {Tank, J.L. and Marti, E. and Riis, T. and von Schiller, D. and Reisinger, A.J. and W. K. Dodds and M.R. Whiles and L.R. Ashkenas and W.B. Bowden and S. M. Collins and Crenshaw, C.L. and Crowl, T.A. and Griffiths, N.A. and Grimm, N.B. and Hamilton, S.K. and Johnson, S.L. and McDowell, W.H. and Norman, B.M. and Rosi, E.J. and Simon, K.S. and Thomas, S.A. and Webster, J.R.} } @article {KNZ001926, title = {Physiological and anatomical trait variability of dominant C4 grasses}, journal = {Acta Oecologica}, volume = {93}, year = {2018}, pages = {14 - 20}, abstract = {

Climate variability is a key driver of physiological responses in common grass species in grasslands of North America. Differences in microanatomical traits among coexisting species may influence physiological responses to climate variability over large geographic scales. The goal of this research was to determine leaf-level physiological and microanatomical trait variability among four dominant C4 grass species across a natural precipitation gradient. Physiological traits were observed to vary significantly across the gradient with greater variability than microanatomical traits. Microanatomical traits were shown to predict physiological responses in A. gerardii and P. virgatum, but the nature of the relationships varied between species. These results illustrate that microanatomical and physiological traits vary across a precipitation gradient, there are clear linkages between microanatomy and physiology in grass species, and this evidence underscores the need for further investigation using phylogenetically diverse assemblages.

}, keywords = {LTER-KNZ}, doi = {10.1016/j.actao.2018.10.007}, url = {https://linkinghub.elsevier.com/retrieve/pii/S1146609X17304587}, author = {Bachle, Seton. and Jesse B. Nippert} } @article {KNZ001820, title = {Assessing the roles of fire frequency and precipitation in determining woody plant expansion in central U.S. grasslands}, journal = {Journal of Geophysical Research - Biogeosciences}, volume = {122}, year = {2017}, pages = {2683{\textendash}2698}, abstract = {

Woody plant expansion into grasslands and savannas is occurring and accelerating worldwide and often impacts ecosystem processes. Understanding and predicting the environmental and ecological impacts of encroachment has led to a variety of methodologies for assessing its onset, transition, and stability, generally relying on dynamical systems approaches. Here we continue this general line of investigation to facilitate the understanding of the roles of precipitation frequency and intensity and fire frequency on the conversion of grasslands to woody-dominated systems focusing on the central United States. A low-dimensional model with stochastic precipitation and fire disturbance is introduced to examine the complex interactions between precipitation and fire as mechanisms that may suppress or facilitate increases in woody cover. By using Lyapunov exponents, we are able to ascertain the relative control exerted on woody encroachment through these mechanisms. Our results indicate that precipitation frequency is a more important control on woody encroachment than the intensity of individual precipitation events. Fire, however, exerts a much more dominant impact on the limitation of encroachment over the range of precipitation variability considered here. These results indicate that fire management may be an effective strategy to slow the onset of woody species into grasslands. While climate change might predict a reduced potential for woody encroachment in the near future, these results indicate a reduction in woody fraction may be unlikely when considering anthropogenic fire suppression.

}, keywords = {LTER-KNZ}, doi = {10.1002/2017JG004046}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JG004046}, author = {N. Brunsell and van Vleck, E.S. and Nosshi, M. and Z. Ratajczak and Jesse B. Nippert} } @article {KNZ001804, title = {An assessment of diurnal water uptake in a mesic prairie: evidence for hydraulic lift?}, journal = {Oecologia}, volume = {183}, year = {2017}, month = {Feb-02-2017}, pages = {963{\textendash}975}, abstract = {Hydraulic lift, the passive movement of water through plant roots from wet to dry soil, is an important ecohydrological process in a wide range of water-limited ecosystems. This phenomenon may also alter plant functioning, growth, and survival in mesic grasslands, where soil moisture is spatially and temporally variable. Here, we monitored diurnal changes in the isotopic signature of soil and plant xylem water to assess (1) whether hydraulic lift occurs in woody and herbaceous tallgrass prairie species (Rhus glabra, Amorpha canescens, Vernonia baldwinii, and Andropogon gerardii), (2) if nocturnal transpiration or grazing by large ungulates limits hydraulic lift, and (3) if a dominant grass, A. gerardii, utilizes water lifted by other tallgrass prairie species. Broadly, the results shown here suggest that hydraulic lift does not appear to be widespread or common in this system, but isolated instances suggest that this process does occur within tallgrass prairie. The isolated instance of hydraulic lift did not vary by grazing treatment, nor did they result in facilitation for neighboring grasses. We suggest that the topographic complexity of this tallgrass prairie and the high rates of nocturnal transpiration observed in this study likely limit the frequency and occurrence of hydraulic lift. These results suggest that hydraulic lift can be a patchy process, particularly in heterogeneous landscapes.}, keywords = {LTER-KNZ, Hydraulic lift, Stable, tallgrass prairie, Transpiration, Water potential}, doi = {10.1007/s00442-017-3827-2}, url = {https://link.springer.com/article/10.1007\%2Fs00442-017-3827-2}, author = {O{\textquoteright}Keefe, K. and Jesse B. Nippert} } @article {KNZ001857, title = {Below-ground biological responses to pyrogenic organic matter and litter inputs in grasslands}, journal = {Functional Ecology}, volume = {31}, year = {2017}, pages = {260 - 269}, abstract = {

1. Terrestrial ecosystems are often burned by both managed and wildfires. During a fire, the above-ground biomass that would typically accumulate and be decomposed as litter on the soil surface is combusted. Pyrogenic organic matter (PyOM) remaining after a fire is a considerably more recalcitrant organic input to the soil than fresh litter. The activity and community composition of soil organisms responsible for decomposition of organic matter and nutrient recycling in the soil could thus be affected by altered resource availability caused by frequent fires.

2. We examined the effect of PyOM vs. fresh litter inputs to soil biota at both an annually burned and an infrequently burned tallgrass prairie site by tracing (13) C-and N-15-labelled litter and PyOM into growing plant roots, microbial phospholipid fatty acids (PLFAs) and soil nematodes for 1 year.

3. Litter-derived C or N was incorporated into microbes, nematodes and roots, while PyOM contributed minimally to soil microbes and plant roots and was not detectable in nematodes. Soil microbial and nematode abundances in the PyOM amended plots did not significantly differ from the bare soil plots, but nematodes were more abundant and microbial PLFAs less abundant in litter-amended plots. The annually burned site had less predator and omnivore nematodes, with increased abundance of microbial feeders and greater microbial uptake of litter C.

4. An alteration of the soil food web structure caused by burning and the removal of the litter layer, along with the accumulation of non-microbially decomposed PyOM in the soil, contributes to the limitation of N cycling in frequently burned ecosystems.

}, keywords = {LTER-KNZ, fire, litter decomposition, Nematodes, phospholipid fatty acid, pyrogenic organic matter, Stable isotopes, tallgrass prairie}, doi = {10.1111/fec.2017.31.issue-110.1111/1365-2435.12693}, author = {Soong, Jennifer L. and Dam, Marie and Wall, Diana H. and Cotrufo, M. Francesca}, editor = {Nicolson, Susan W. and Wright, Geraldine A. and Sala, Anna} } @article {KNZ001794, title = {Changes in spatial variance during a grassland to shrubland state transition}, journal = {Journal Ecology}, volume = {105}, year = {2017}, pages = {750-760}, abstract = {
  1. State transitions are changes in ecosystem structure and self-reinforcing feedbacks that are initiated when an exogenous driver variable crosses a threshold. Reversing state transitions is difficult and costly. While some state transitions are relatively rapid, many take years to decades. Outside of theoretical models, very little is known about slower state transitions and how they unfold in time and space.
  2. We quantified changes in spatial variance as a mesic grassland ecosystem shifts to a shrub-dominated state, using long-term experiments and simulations that maintain grasslands with annual fires or initiate a state transition to shrub dominance by decreasing fire frequency.
  3. In the experiments, the susceptibility to state transitions varied substantially in space. In the less frequent fire treatment, some plots became shrub-dominated around year 20 and grass extirpations began in year 25, but a third of the plots were still grass-dominated in year 37. Variable rates of state transition resulted in increasing spatial variance of grass cover over time, whereas shrub cover variance decreased. In the annually burned treatment, grasses remained dominant and the spatial variance of grass cover declined.
  4. In a separate experiment, less frequent fires were maintained for 23\ years and then switched to annual fires. The switch to annual fires occurred shortly after grass variance started to increase and a majority of these plots quickly returned to a grass dominated state.
  5. In simulations, spatial variance remained low and average grass cover was high under frequent fires. If fire frequency decreased below a threshold, the ecosystem transitioned to shrubland, with a transient increase in the spatial variance of grass cover during the transition between states.
  6. Synthesis. Spatial variability in the rate and susceptibility to state transitions is indicative of a system with a patchy spatial structure, high spatial heterogeneity and low connectivity between patches. Increases in spatial variance can serve as an indication that some patches have begun a state transition and that management interventions are needed to avoid widespread transitions. This is one of the first empirical examples where altering management after an increase in spatial variance prevented state transitions.

}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2745.12696}, url = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.12696}, author = {Z. Ratajczak and D{\textquoteright}Odorico, P.D. and Jesse B. Nippert and Scott. L. Collins and N. Brunsell and Ravi, S.} } @article {KNZ001824, title = {Drivers of nitrogen transfer in stream food webs across continents}, journal = {Ecology}, volume = {98}, year = {2017}, pages = {3055}, chapter = {3044}, abstract = {

Studies of trophic-level material and energy transfers are central to ecology.\ The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs.\ We analyzed data from thirteen\ 15N-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean 11.5\%, range \<1\% to 43\%) than N transfer efficiencies from primary consumers to predators (mean 80\%, range 5\% to \>100\%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and percent canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.2009}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.2009}, author = {Norman, B. C. and Whiles, M. R. and S. M. Collins and Flecker, A. S. and Hamilton, S. K. and Johnson, S. L. and Rosi-Marshall, E. J. and L.R. Ashkenas and W.B. Bowden and Crenshaw, C. L. and Crowl, T. and W. K. Dodds and Hall, R. O. and El-Sabaawi, R. and Griffiths, N. A. and Marti, E. and McDowell, W. H. and Peterson, S. D. and Rantala, H. M. and Riis, T. and Simon, K. S. and Tank, J. L. and Thomas, S. A. and von Schiller, D. and Webster, J. R.} } @article {KNZ001758, title = {Grazing by bison is a stronger driver of plant ecohydrology in tallgrass prairie than fire history}, journal = {Plant and Soil}, volume = {411}, year = {2017}, pages = {423-436}, abstract = {

Background and Aims: Fire and grazing are important disturbances in grasslands, yet we know little about how they impact a variety of plant physiological processes such as plant ecohydrology. Here, we assessed the impact of fire history and grazing by Bison bison on the source of water uptake and niche overlap in common grassland species at the Konza Prairie Biological Station, a temperate mesic grassland located in northeastern Kansas, USA. Methods: We used the stable isotopic signature of soil and xylem water to evaluate water uptake in Andropogo n gerardii, Vernonia baldwinii, Amorpha canescens,and Rhus glabra within varying grazing (grazed, ungrazed), fire (0,1,2 or 3 years since last burn), topography (upland, lowland), and month (July, August) contrasts over 3 years (2013\–2015). Results: The presence of grazers, not fire history, altered water uptake patterns in these common grassland species. Particularly, grazing increased the proportion of shallow water utilized by A. gerardii and R. glabra, reducing niche overlap with other co-occurring species. However, these responses varied intra-annually and were often modulated by topography. Conclusions: These results suggest that grazing can alter aspects of grassland ecohydrology at small scales, which may extend to impact community and ecosystem processes at larger spatial scales.

}, keywords = {LTER-KNZ, fire, Herbivory, Mesic grassland, Niche overlap, Source water, Stable isotopes}, doi = {10.1007/s11104-016-3048-1}, url = {https://link.springer.com/article/10.1007\%2Fs11104-016-3048-1}, author = {O{\textquoteright}Keefe, K. and Jesse B. Nippert} } @article {KNZ001808, title = {The interactive effects of press/pulse intensity and duration on regime shifts at multiple scales}, journal = {Ecological Monographs}, volume = {87}, year = {2017}, pages = {198-218}, abstract = {

Regime shifts are difficult to reverse transitions that occur when an ecosystem reorganizes around a new set of self-reinforcing feedbacks. Regime shifts are predicted to occur when the intensity of some exogenous driver variable\—such as temperature, annual harvest rate or nutrient addition rate\—gradually approaches and crosses a threshold value, initiating a transition to an alternative state. However, many driver variables now change rapidly as presses or pulses, not gradually, requiring new conceptual frameworks for understanding and predicting regime shifts. We argue that identifying and controlling regime shifts in response to presses and pulses will require a greater focus on the duration, not just intensity, of changes in driver variables. In ecosystems with slower dynamics, transitions to an alternative state can take years to decades and as a result, a driver press with an intensity capable of resulting in a regime shift over long time-spans may fail to cause a regime shift when applied for shorter durations. We illustrate these ideas using simulations of local-scale alternative stable state models and preliminary evidence from long-term grazing and eutrophication experiments. The simulations also suggest that small changes in the duration of driver presses or pulses can determine whether an ecosystem recovers to its original state. These insights may extend to larger scales. In spatially extended simulations that included patchiness, spatial heterogeneity, and spatial connectivity, all patches recovered to their original state after shorter presses. However, once press duration exceeded a threshold, growing proportions of the landscape shifted to an alternative state as press duration increased. We observed similar patchy transitions in a catchment-scale experiment that reinstated frequent fires approximately halfway through a regime shift from grassland to shrubland, initiated by fire suppression. In both the local- and larger-scale models, the threshold duration needed to elicit regime shifts decreased as press intensity increased or when factors counteracting regime shifts weakened. These multiple lines of evidence suggest that conceptualizing regime shifts as an interactive function of the intensity and duration of driver changes will increase understanding of the varying effects of driver presses, pulses, and cycles on ecosystem dynamics.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecm.1249}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecm.1249}, author = {Z. Ratajczak and D{\textquoteright}Odorico, Paolo and Scott. L. Collins and B.T. Bestelmeyer and Isbell, F.L. and Jesse B. Nippert} } @mastersthesis {KNZ001871, title = {Physiological and morphological responses of grass species to drought}, volume = {MS Thesis}, year = {2017}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, abstract = {

The impacts of climate change over the next 100 years on North American grasslands are unknown. Climate change is projected to increase rainfall and seasonal temperature variability, leading to increased frequency of drought and decreased rainfall amounts for many grassland locations in the central Great Plains of North America. To increase our ability to predict the effects of a changing climate, I measured multiple morphological and physiological responses from a diverse suite of C3 and C4 grasses. Due to varying characteristics associated with the different photosynthetic pathways, these grass species respond differently to altered temperature and precipitation. I monitored grass physiology and microanatomy in conjunction with varying watered availability to replicate drought. In the second chapter, I observed leaf-level physiology and root level morphology of C3 and C4 grasses when exposed to 100\% water reduction. Results indicated that response to water reduction are not always dependent on the photosynthetic pathway. Root-level morphological measurements were found to vary significantly between species in the same genus; F. ovina had the highest specific root length (SRL), which is an indicator of tolerance to environmental variability. Results also indicated that grasses of interest have thresholds that when passed result in a photosynthetically inactive plant; however it was shown that they are able to recover to near pre-drought gas exchange rates when water is re-applied. The third chapter investigated both leaf-level physiology and morphology in dominant C4\¬ grasses across Kansas\’ rainfall gradient over the growing season. I hypothesized that variation within a species\’ physiology would be greater than its\’ morphology. I also hypothesized that morphology would predict variability in a species physiological response to changes in climate. This research discovered within a location and species, leaf morphology is fixed across the growing season. Strong correlations between leaf physiology and morphology were observed, however, the strength and relationship changed among the species compared. A. gerardii and P. virgatum exhibited opposing relationships when comparing their photosynthetic rates to the amount of bundle sheath cells. This result highlights strong species-specific relationship between physiology and morphology. My results illustrate the importance of utilizing plant physiology and morphology to understand how grasses may respond to future climate change scenarios.

}, keywords = {LTER-KNZ, Climate change, Drought; Great Plains, Ecophysiology, Grasslands, tallgrass prairie}, url = {http://krex.k-state.edu/dspace/handle/2097/36188}, author = {Bachle, Seton} } @article {KNZ001721, title = {Assessing the potential for transitions from tallgrass prairie to woodlands: are we operating beyond critical transitions?}, journal = {Rangeland Ecology \& Management}, volume = {69}, year = {2016}, pages = {280{\textendash}287}, abstract = {

A growing body of evidence suggests humans are pushing ecosystems near or beyond key ecological thresholds, resulting in transitions to new, sometimes undesirable phases or states that are costly to reverse. We used remotely sensed fire data to assess if the Flint Hills\—a landscape of tallgrass prairie in the Central Great Plains, United States\—is operating beyond fire frequency thresholds. Long-term fire experiments and observational evidence suggests that applying prescribed fire at return intervals \> 3 yr can lead to transitions from grassland to shrubland. Fire return intervals \> 10 yr and complete fire suppression, in particular, can result in transitions to woodlands over 30 \− 50 yr. Once shrublands and woodlands are established, restoration back to grassland is difficult with prescribed fires. We applied these fire frequency cutoffs to remotely sensed fire data from 2000 to 2010 in the Flint Hills, identifying the extent of tallgrass prairie susceptible to shrub and tree expansion. We found that 56\% (15 620 km2) of grasslands in this region are burned less than every 3 yr and are therefore susceptible to conversion to shrub or tree dominance. The potential effects of this large-scale shift are greater risk for evergreen (Juniperus virginiana) woodland fires, reduced grazing potential, and increased abundance of woodland adapted species at the expense of the native grassland biota. Of the 12 127-km2 area likely to remain grassland, 43\% is burned approximately annually, contributing to vegetative homogenization and potential air-quality issues. While this synthesis forecasts a precarious future for tallgrass prairie conservation and their ecosystem services, increases in shrub or tree dominances are usually reversible until fire frequency has been reduced for more than 20 yr. This delay leaves a small window of opportunity to return fire to the landscape and avoid large-scale transformation of tallgrass prairie.

}, keywords = {LTER-KNZ, catastrophic shifts, forecasting, mesic grasslands, regime shifts, resilience, tipping points}, doi = {http://dx.doi.org/10.1016/j.rama.2016.03.004}, url = {https://www.sciencedirect.com/science/article/pii/S1550742416300021?via\%3Dihub}, author = {Z. Ratajczak and J. M. Briggs and Goodin, D.G. and Mohler, R. and Jesse B. Nippert and Obermeyer, B.K.} } @article {KNZ001720, title = {Comparative ecohydrology between Cornus drummondii and Solidago canadensis in upland tallgrass prairie}, journal = {Plant Ecology}, volume = {217}, year = {2016}, pages = {267-276}, abstract = {

Woody species expansion threatens to transform mesic North American grasslands. In many tallgrass prairies of the central Great Plains with deep soil, Cornus drummondii develops large shrub islands that exhibit non-linear increases in cover through time. Reliance on soil moisture from deeper soil depths facilitates constant gas exchange rates and minimizes competition with coexisting herbaceous species. Conversely, C. drummondii growth and expansion in thin-soil locations is stochastic and these locations are typically free of large shrub islands. At the Konza Prairie in northeast Kansas, USA, we compared the ecohydrology of C. drummondii individuals to a similar-sized forb (Solidago canadensis) in thin-soil locations with varying fire frequency (4-, 20-year) and grazer abundance (bison present or absent). Gas exchange rates were relatively constant for C. drummondii, while S. canadensis declined across the growing season. For S. canadensis, maximum photosynthesis (Amax), daytime transpiration (E), and stomatal conductance (gs) were higher on ungrazed than grazed treatments. Nighttime E rates were higher in C. drummondii, accounting for over 10 \% of the daytime E rates. The water source used did not vary among contrasts, with the majority of water uptake occurring from 30 cm depth for both species. These results highlight a unique ecohydrology of C. drummondii (static water flux, and high rates of nighttime E) compared to a similar-sized, co-occurring forb. Whereas C. drummondii is infrequent in thin-soil locations, the climate conditions occurring during measurements were not a likely filter restricting persistence. Rather, drier conditions or interactions with other grassland disturbances are likely required to restrict C. drummondii encroachment in the thins-soil locations of tallgrass prairie.

}, keywords = {LTER-KNZ, Konza Prairie, Mesic grassland, photosynthesis, Stable water isotopes, Transpiration, woody encroachment}, doi = {10.1007/s11258-016-0567-z}, url = {https://link.springer.com/article/10.1007\%2Fs11258-016-0567-z}, author = {Muench, A. and O{\textquoteright}Keefe, K. and Jesse B. Nippert} } @article {KNZ001753, title = {Foraging decisions underlying restricted space use: effects of fire and forage maturation on large herbivore nutrient uptake}, journal = {Ecology and Evolution}, volume = {6}, year = {2016}, pages = {5843{\textendash}5853 }, type = {Journal Articles}, abstract = {

Recent models suggest that herbivores optimize nutrient intake by selecting patches of low to intermediate vegetation biomass. We assessed the application of this hypothesis to plains bison (Bison bison) in an experimental grassland managed with fire by estimating daily rates of nutrient intake in relation to grass biomass and by measuring patch selection in experimental watersheds in which grass biomass was manipulated by prescribed burning. Digestible crude protein content of grass declined linearly with increasing biomass, and the mean digestible protein content relative to grass biomass was greater in burned watersheds than watersheds not burned that spring (intercept; F1,251 = 50.57, P \< 0.0001). Linking these values to published functional response parameters, ad libitum protein intake, and protein expenditure parameters, Fryxell\&$\#$39;s (Am. Nat., 1991, 138, 478) model predicted that the daily rate of protein intake should be highest when bison feed in grasslands with 400\–600 kg/ha. In burned grassland sites, where bison spend most of their time, availability of grass biomass ranged between 40 and 3650 kg/ha, bison selected foraging areas of roughly 690 kg/ha, close to the value for protein intake maximization predicted by the model. The seasonal net protein intake predicted for large grazers in this study suggest feeding in burned grassland can be more beneficial for nutrient uptake relative to unburned grassland as long as grass regrowth is possible. Foraging site selection for grass patches of low to intermediate biomass help explain patterns of uniform space use reported previously for large grazers in fire-prone systems.

}, keywords = {LTER-KNZ}, doi = {10.1002/ece3.2304}, url = {https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.2304}, author = {Raynor, E.J. and Anthony Joern and Jesse B. Nippert and J. M. Briggs} } @phdthesis {KNZ001835, title = {Patterns and ecological consequences of water uptake, redistribution, and loss in tallgrass prairie}, volume = {PhD Dissertation}, year = {2016}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, abstract = {

Water availability is a key driver of many plant and ecosystem processes in tallgrass prairies, yet we have a limited understanding of how grassland plants utilize water through space and time. Considering that tallgrass prairies experience tremendous heterogeneity in soil resources, identifying spatiotemporal variation in plant ecohydrology is critical for understanding current drivers of plant responses to water and for predicting ecosystem responses to future changes in climate. Here, I investigated the patterns, drivers, and ecological consequences of plant water use (e.g., water uptake, water redistribution, and water loss) in a native tallgrass prairie located in northeastern Kansas, USA. Using a combination of leaf gas exchange, sap flow, and isotopic techniques, I addressed four main questions: 1) How does fire and grazing by bison impact use of water from different sources and niche overlap for common grasses, forbs, and shrubs? 2) Does hydraulic lift occur in grazed and ungrazed tallgrass prairie, and does this impact facilitation for water within grassland communities? 3) What are the patterns and drivers of nocturnal transpiration in common grassland species? 4) How does diel stem sap flow and canopy transpiration vary among common grassland species?

I found that bison grazing increased the depth of water uptake by Andropogon gerardii and Rhus glabra, reducing niche overlap with co-occurring species. Conversely, grazing did not affect hydraulic lift, which was generally uncommon and likely limited by nocturnal transpiration. Further, leaf gas exchange measurements indicated that nocturnal transpiration occurred commonly in tallgrass prairie plants and was greatest among grasses and early in the growing season. Nocturnal transpiration was not driven by vapor pressure deficit or soil moisture, as commonly observed in other systems, but was regulated by nocturnal stomatal conductance in most species. Finally, I found that daytime sap flow rates were variable among species and functional types, with larger flux rates among woody species. Nocturnal sap flow rates were more consistent across species, which caused nighttime sap flow and transpiration to account for a larger proportion of daily flux rates in grasses than in forbs or shrubs. These results show that water uptake, water redistribution, and water loss are all influenced by different biotic and abiotic drivers and have varying ecological impacts across a heterogeneous landscape. Additionally, extensive differences in water flux exist among co-occurring species and plant functional groups, which likely reflect varying strategies to tolerate water limitation. These results suggest that shifts in the abundance of these species with future climate changes, or with ecosystem state changes, will likely impact ecosystem-level water balance.

}, keywords = {LTER-KNZ, Grasslands, Isotopes, Plant physiology, Sap flow, Transpiration}, url = {http://krex.k-state.edu/dspace/handle/2097/34514}, author = {O{\textquoteright}Keefe, Kimberly} } @article {KNZ001798, title = {Quantifying global soil carbon losses in response to warming}, journal = {Nature}, volume = {540}, year = {2016}, pages = {104 - 108}, abstract = {

The majority of the Earth\’s terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming, Despite evidence that warming enhances carbon fluxes to and from the soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30\ \±\ 30 petagrams of carbon to 203\ \±\ 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55\ \±\ 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12\–17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon\–climate feedback that could accelerate climate change.

}, keywords = {LTER-KNZ, Biogeochemistry, carbon cycle}, doi = {10.1038/nature20150}, url = {https://www.nature.com/articles/nature20150}, author = {Crowther, T. W. and Todd-Brown, K. E. O. and Rowe, C. W. and Wieder, W. R. and Carey, J. C. and Machmuller, M. B. and Snoek, B. L. and Fang, S. and Zhou, G. and Allison, S. D. and John M. Blair and Bridgham, S. D. and Burton, A. J. and Carrillo, Y. and Reich, P. B. and Clark, J. S. and Classen, A. T. and Dijkstra, F. A. and Elberling, B. and Emmett, B. A. and Estiarte, M. and Frey, S. D. and Guo, J. and Harte, J. and Jiang, L. and Johnson, B. R. and Kr{\"o}el-Dulay, G. and Larsen, K. S. and Laudon, H. and Lavallee, J. M. and Luo, Y. and Lupascu, M. and Ma, L. N. and Marhan, S. and Michelsen, A. and Mohan, J. and Niu, S. and Pendall, E. and {\~n}uelas, J. and Pfeifer-Meister, L. and Poll, C. and Reinsch, S. and Reynolds, L. L. and Schmidt, I. K. and Sistla, S. and Sokol, N. W. and Templer, P. H. and Treseder, K. K. and Welker, J. M. and Bradford, M. A.} } @article {KNZ001823, title = {A safety vs efficiency trade-off identified in the hydraulic pathway of grass leaves is decoupled from photosynthesis, stomatal conductance and precipitation}, journal = {New Phytologist}, volume = {210}, year = {2016}, pages = {97-107}, abstract = {

A common theme in plant physiological research is the trade-off between stress tolerance and growth; an example of this trade-off at the tissue level is the safety vs efficiency hypothesis, which suggests that plants with the greatest resistance to hydraulic failure should have low maximum hydraulic conductance. Here, we quantified the leaf-level drought tolerance of nine C4 grasses as the leaf water potential at which plants lost 50\% (P50 \× RR ) of maximum leaf hydraulic conductance (Ksat ), and compared this trait with other leaf-level and whole-plant functions. We found a clear trade-off between Ksat and P50 \× RR when Ksat was normalized by leaf area and mass (P = 0.05 and 0.01, respectively). However, no trade-off existed between P50 \× RR and gas-exchange rates; rather, there was a positive relationship between P50 \× RR and photosynthesis (P = 0.08). P50 \× RR was not correlated with species distributions based on precipitation (P = 0.70), but was correlated with temperature during the wettest quarter of the year (P \< 0.01). These results suggest a trade-off between safety and efficiency in the hydraulic system of grass leaves, which can be decoupled from other leaf-level functions. The unique physiology of C4 plants and adaptations to pulse-driven systems may provide mechanisms that could decouple hydraulic conductance from other plant functions.

}, keywords = {LTER-KNZ}, doi = {http://dx.doi.org/10.1111/nph.13781}, url = {https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.13781}, author = {Ocheltree, Troy W. and Jesse B. Nippert and Prasad, P. V. Vara} } @article {KNZ001756, title = {Tight coupling of leaf area index to canopy nitrogen and phosphorus across heterogeneous tallgrass prairie communities}, journal = {Oecologia}, volume = {182}, year = {2016}, pages = {889 - 898}, abstract = {

Nitrogen (N) and phosphorus (P) are limiting nutrients for many plant communities worldwide. Foliar N and P along with leaf area are among the most important controls on photosynthesis and hence productivity. However, foliar N and P are typically assessed as species level traits, whereas productivity is often measured at the community scale. Here, we compared the community-level traits of leaf area index (LAI) to total foliar nitrogen (TFN) and total foliar phosphorus (TFP) across nearly three orders of magnitude LAI in grazed and ungrazed tallgrass prairie in north-eastern Kansas, USA. LAI was strongly correlated with both TFN and TFP across communities, and also within plant functional types (grass, forb, woody, and sedge) and grazing treatments (bison or cattle, and ungrazed). Across almost the entire range of LAI values and contrasting communities, TFN:TFP ratios indicated co-limitation by N and P in almost all communities; this may further indicate a community scale trend of an optimal N and P allocation per unit leaf area for growth. Previously, results from the arctic showed similar tight relationships between LAI:TFN, suggesting N is supplied to canopies to maximize photosynthesis per unit leaf area. This tight coupling between LAI, N, and P in tallgrass prairie suggests a process of optimal allocation of N and P, wherein LAI remains similarly constrained by N and P despite differences in species composition, grazing, and canopy density.

}, keywords = {LTER-KNZ, Co-limitation, fire, grassland, grazers, nutrients}, issn = {0029-8549}, doi = {10.1007/s00442-016-3713-3}, url = {https://link.springer.com/article/10.1007\%2Fs00442-016-3713-3}, author = {Klodd, A.E. and Jesse B. Nippert and Z. Ratajczak and Waring, H. and Phoenix, G.K.} } @article {KNZ001700, title = {Breeding system and sex ratio variation in mulberries}, journal = {Journal of the Botanical Research Institute of Texas}, volume = {9}, year = {2015}, pages = {383-395}, abstract = {Flowering plants exhibit a diverse array of sex expression patterns that become of particular interest when considered in the context of coexisting native-invasive congeners. This study presents findings on sex expression and sex ratio variation in two congeneric tree species, the native Morus rubra and the exotic M. alba, in the Flint Hills region of the Great Plains in the United States. Both species exhibited a subdioecious breeding system (with male, female and hermaphrodite individuals co-occurring within populations), and significantly male-biased sex ratios (i.e., males are more numerous than females). Cumulative sex ratio deviation was higher in the native M. rubra populations than in the exotic M. alba. Within-species sex ratio did not vary significantly among populations. In one focus study area surveyed over three years, most individuals were consistent in sex expression, but approximately 10\% switched their sex at least once; the vast majority of these changes were between unisexual and hermaphrodite morphs. There was no size dependence of sex expression based on current sampling. Our results document subdioecy as the breeding system in these Morus species, and advance the group as an interesting study system for its reproductive biology. }, keywords = {LTER-KNZ, Breeding system, Moraceae, Morus, sex ratio, sex switch, subdioecy}, issn = {1934-5259}, author = {Nepal, M.P. and Ferguson, C.J. and Mayfield, M.H.} } @article {KNZ001722, title = {Challenging the maximum rooting depth paradigm in grasslands and savannas}, journal = {Functional Ecology}, volume = {29}, year = {2015}, pages = {739 - 745}, abstract = {
  1. For many grassland and savanna ecosystems, water limitation is a key regulator of individual plant, community and ecosystem processes. Maximum rooting depth is commonly used to characterize the susceptibility of plant species to drought. This rests on the assumption that deep-rooted plant species would have a greater total volume of soil water to exploit and should be less susceptible to episodic changes in water availability.
  2. Independent of maximum rooting depth, rooting strategies based on differences in biomass allocation with depth, uptake plasticity in relation to water availability and variation in water transport capability may all influence growth responses and susceptibility to drought. Many examples from grasslands and savannas reflect these rooting strategies among coexisting grass, forb and woody species.
  3. Here, we use a dynamic model of plant water uptake and growth to show how changes in root distribution, functional plasticity and root hydraulic conductivity have the potential to influence aboveground biomass and competitive outcomes, even when maximum rooting depth remains constant. We also show theoretically that shifts in root distribution to surface soils without changes in maximum depth can potentially outweigh the benefits of increased maximum rooting depth.
  4. Combining our current reliance on biogeographic descriptions of maximum rooting depth with insights about other, more subtle aspects of root structure and function are likely to improve our understanding of ecosystem responses to dynamic water limitation.
}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2435.12390}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.12390}, author = {Jesse B. Nippert and Holdo, R. M.}, editor = {Sayer, E.} } @article {KNZ001776, title = {Long-term changes in structure and function of a tropical headwater stream following a disease-driven amphibian decline}, journal = {Freshwater Biology}, volume = {60}, year = {2015}, pages = {575 - 589}, abstract = {

1. Taxonomic and functional diversity in freshwater habitats is rapidly declining, but we know little about how such declines will ultimately affect ecosystems. Neotropical streams are currently experiencing massive losses of amphibians, with many losses linked to the chytrid fungus, Batrachochytrium dendrobatidis (Bd). 2. We examined the ecological consequences of the disease-driven loss of amphibians from a Panamanian stream. We quantified basal resources, macroinvertebrates, N uptake and fluxes through food-web components and ecosystem metabolism in 2012 and 2014 and compared them to pre-decline (2006) and 2 year post-decline (2008) values from a prior study. 3. Epilithon biomass accrued after the decline, more than doubling between 2006 and 2012, but then decreased fivefold from 2012 to 2014. In contrast, suspended particulate organic matter (SPOM) concentrations declined continuously after the amphibian decline through 2014. 4. Biomass of filter-feeding, grazing and shredding macroinvertebrates decreased from 2006 to 2014, while collector\–gatherers increased during the same time period. Macroinvertebrate taxa richness decreased from 2006 (52 taxa) to 2012 (30 taxa), with a subsequent increase to 51 taxa in 2014. 5. Community respiration, which initially decreased after the amphibian decline, remained lower than pre-decline in 2012 but was greater than pre-decline values in 2014. Gross primary production remained low and similar among years, while inline image uptake length in both 2012 and 2014 was longer than pre-decline. Nitrogen flux to epilithon increased after the decline and continued to do so through 2014, but N fluxes to fine particulate organic matter and SPOM decreased and remained low. 6. Our findings underscore the importance of studying the ecological consequences of declining biodiversity in natural systems over relatively long time periods. There was no evidence of functional redundancy or compensation by other taxa after the loss of amphibians, even after 8 years.

}, keywords = {LTER-KNZ}, doi = {10.1111/fwb.12505}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.12505}, author = {Rantala, H.M. and Nelson, A.M. and Fulgoni, J.N. and M.R. Whiles and Hall, R.O. and W. K. Dodds and Verburg, P. and Huryn, A. and Pringle, C.. and Kilham, S.S. and Lips, K.R. and Colon-Gaud, C. and Rugenski, A.T. and Peterson, S.D. and Fritz, K. and McLeran, K.E. and Connelly, S.} } @article {KNZ001612, title = {Abrupt transition of mesic grassland to shrubland: evidence for thresholds, alternative attractors, and regime shifts}, journal = {Ecology}, volume = {95}, year = {2014}, pages = {2633 -2645}, abstract = {

Ecosystems with alternative attractors are susceptible to abrupt regime shifts that are often difficult to predict and reverse. In this study, we quantify multiple system dynamics to determine whether the transition of mesic grassland to shrubland, a widespread phenomenon, represents a linear reversible process, a nonlinear but reversible threshold process, or a transition between alternative attractors that is nonlinear and prone to hysteresis. Using a 28-yr data set with annual resolution and extensive spatial replication, we found that shrub cover is correlated with distinct thresholds of fire and C4 grass cover, resulting in temporal bimodality of shrub cover and abrupt shifts of shrub cover despite gradual changes in grass cover. These abrupt increases in shrub cover are the most rapid ever reported in grasslands, and illustrate internal thresholds that separate grasslands and shrublands. Nonlinear transitions from low to high shrub cover were also closely associated with positive feedback mechanisms that alter fire and competition (r2 = 0.65), suggesting that grasslands and shrublands could show hysteresis, and by definition exist as alternative attractors. Thus, the response of this ecosystem to anthropogenic activity should tend to be rapid, nonlinear, and perhaps difficult to reverse. Regime shifts in this mesic grassland were predictable: we found that grassland and shrubland attractors were differentiated by critical thresholds of \∼50\–70\% grass cover, 5\–10\% shrub cover, and a fire return interval of \∼3 yr. These thresholds may provide adaptive potential for managing nonlinear behavior in socio-ecological systems in a changing environment.

}, keywords = {LTER-KNZ}, doi = {10.1890/13-1369.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/13-1369.1}, author = {Z. Ratajczak and Jesse B. Nippert and Ocheltree, T.W.} } @article {KNZ001568, title = {Cessation of burning dries soils long-term in a tallgrass prairie}, journal = {Ecosystems}, volume = {17}, year = {2014}, pages = {54 -65}, abstract = {

Soil moisture is a critical variable in grassland function, yet how fire regimes influence ecohydrology is poorly understood. By altering productivity, species composition, and litter accumulation, fire can indirectly increase or decrease soil water depletion on a range of time scales and depths in the soil profile. To better understand how fire influences soil moisture in grasslands, we analyzed 28 years of soil moisture data from two watersheds in a central North American grassland which differ in their long-term fire frequency. Across 28 years, cessation of prescribed burning initially led to wetter soils, likely as litter accumulated and both transpiration and evaporation were suppressed. Long-term, cessation of burning led to soils drying more, especially at depths greater than 75 cm. The long-term drying of deep soils is consistent with the increase in woody species in the infrequently burned grassland as woody species likely have a greater reliance on soil water from deeper soil layers compared to co-occurring herbaceous species. Despite the ecohydrological changes associated with the cessation of prescribed burning, watersheds with different burn regimes responded similarly to short-term variation in climate variation. In both watersheds, low precipitation and high temperatures led to drier soils with greater responses in soil moisture to climate variation later in the season than earlier. There is no current evidence that the cessation of burning in this ecosystem will qualitatively alter how evapotranspiration responds to climate variation, but the use of deeper soil water by woody plants has the potential for greater transpiration during dry times. In all, modeling the depth-specific responses of soil moisture and associated ecosystem processes to changes in burn regimes will likely require including responses of plant community composition over short and long time scales.

}, keywords = {LTER-KNZ, critical climate period, ecohydrology, Evapotranspiration, fire, Konza Prairie, soil moisture, woody species}, doi = {10.1007/s10021-013-9706-8}, url = {https://link.springer.com/article/10.1007\%2Fs10021-013-9706-8}, author = {Craine, J.M. and Jesse B. Nippert} } @phdthesis {KNZ001628, title = {Ecological thresholds and abrupt transitions of tallgrass prairie to shrublands and woodlands}, volume = { PhD. Dissertation}, year = {2014}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, abstract = {

Ecological thresholds are breakpoints where small increases in external pressure can generate rapid and difficult to reverse ecological transitions. Often, ecological thresholds are not recognized until they are crossed at a large-scale, leading to unintended and lasting externalities. In tallgrass prairie, we identified ecological thresholds of 3-year fire returns and ~60\% grass cover, based on mechanistic field studies and long-term fire and grazing experiments. When tallgrass prairie is pushed passed these thresholds, it makes an abrupt transition to a self-reinforcing shrubland state. Demographic bottlenecks, niche partitioning, and altered fire feedback mechanisms account for both the non-linear nature of grassland-shrubland transitions and the resistance of established shrublands to fire and drought. In the last decade, only ~27\% of Central Great Plains tallgrass prairie was burned every 1-2 years, and therefore ~73\% of this region is susceptible to shrubland and woodland transitions in the next two to three decades. If transitions to shrublands and woodlands do occur, we expect a multi-trophic loss of grassland biodiversity, decreased cattle production, and the potential for damaging woodland fires in close proximity to human development. However, knowledge of fire thresholds, adaptive management tools, and bottom-up citizen action campaigns are creating a rare window of opportunity to avoid transformation of the remaining tallgrass prairies.

}, keywords = {LTER-KNZ}, url = {http://hdl.handle.net/2097/17661}, author = {Z. Ratajczak} } @article {KNZ001627, title = {Fire dynamics distinguish grasslands, shrublands, and woodlands as alternative attractors in the Central Great Plains of North America}, journal = {Journal of Ecology}, volume = {102}, year = {2014}, pages = {1374 -1385}, abstract = {

Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1\–2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1\–2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency.

}, keywords = {LTER-KNZ, bison, Ecosystems, Forests, Grasslands, Grazing, Linear regression analysis, Trees, Watersheds}, doi = {10.1111/1365-2745.12311}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2745.12311}, author = {Z. Ratajczak and Jesse B. Nippert and J. M. Briggs and John M. Blair} } @inbook {KNZ001656, title = {Grassland Ecology}, booktitle = {Plant Sciences - Ecology and the Environment}, volume = {8}, number = {Springer Reference Series}, year = {2014}, pages = {389-423}, publisher = {Springer-Verlag Berlin Heidelberg}, organization = {Springer-Verlag Berlin Heidelberg}, keywords = {LTER-KNZ}, author = {John M. Blair and Jesse B. Nippert and J. M. Briggs}, editor = {Monson, R} } @article {KNZ001608, title = {Impacts of seasonality and surface heterogeneity on water-use efficiency in mesic grasslands}, journal = {Ecohydrology}, volume = {7}, year = {2014}, pages = {1223 -1233}, abstract = {

Woody encroachment is occurring in grasslands worldwide, with largely unknown effects on local carbon and water fluxes and the energy balance. Water-use efficiency (λ) is a measure of carbon assimilation per evapotranspiration. Here, a was compared among three different grassland ecosystems in eastern KS, USA, by using the eddy covariance technique. Variation in λ was examined at multiple timescales and across different burning regimes. Site-specific variations in λ were more readily observed at seasonal and inter-annual timescales rather than daily and monthly averages. Annually burned grassland with homogeneous C4 grass cover had less negative values of λ [lower water-use efficiency (WUE)] than infrequently burned grassland that is presently undergoing woody encroachment and a transition to a shrub-dominated ecosystem. The most likely explanation for differences in λ are differences in rooting depth and source-water acquisition between encroaching woody plants and the native grass community. Reliance on a deeper water source by the woody community may buffer the negative consequences of forecasted climate variability and drought, resulting in greater landscape WUE and reduced susceptibility to water stress when compared with the coexisting grass species. Copyright \© 2013 John Wiley \& Sons, Ltd.

}, keywords = {LTER-KNZ}, doi = {10.1002/eco.1455}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/eco.1455}, author = {N. Brunsell and Jesse B. Nippert and Buck, T.L.} } @article {KNZ001607, title = {Lack of eutrophication in a tallgrass prairie ecosystem over 27 years}, journal = {Ecology}, volume = {95}, year = {2014}, pages = {1225 -1235}, abstract = {

Many North American grasslands are receiving atmospheric nitrogen (N) deposition at rates above what are considered critical eutrophication thresholds. Yet, potential changes in grassland function due to anthropogenic N deposition are poorly resolved, especially considering that other dynamic factors such as land use and precipitation can also affect N availability. To better understand whether elevated N deposition has altered ecosystem structure or function in North American grasslands, we analyzed a 27-year record of ecophysiological, community, and ecosystem metrics for an annually burned Kansas tallgrass prairie. Over this time, despite increasing rates of N deposition that are within the range of critical loads for grasslands, there was no evidence of eutrophication. Plant N concentrations did not increase, soil moisture did not decline, forb diversity did not decline, and the relative abundance of dominant grasses did not shift toward more eutrophic species. Neither aboveground primary productivity nor N availability to plants increased. The fates of deposited N in grasslands are still uncertain, and could include management losses through burning and grazing. However, evidence from this grassland indicates that eutrophication of North American grassland ecosystems is not an inevitable consequence of current levels of N deposition.

}, keywords = {LTER-KNZ}, doi = {10.1890/13-1068.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/13-1068.1}, author = {McLauchlan, K.K. and Craine, J.M. and Jesse B. Nippert and Ocheltree, T.W.} } @article {KNZ001605, title = {Naphthalene addition to soil surfaces: A feasible method to reduce soil micro-arthropods with negligible direct effects on soil C dynamics}, journal = {Applied Soil Ecology}, volume = {74}, year = {2014}, pages = {21 -29}, abstract = {

Soil fauna are a key component of soil biodiversity and a driver of soil functioning. While the importance of soil fauna is well recognized, quantitative estimates of the role of soil fauna on soil biogeochemical processes, such as plant litter decomposition, are limited by methodological constraints. The addition of naphthalene, a polycyclic aromatic hydrocarbon (C10H8), to suppress soil fauna has been used for decades in decomposition experiments, but its efficacy remains questioned. In fact, we lack a rigorous field assessment of the efficacy of naphthalene additions for soil fauna suppression and potential non-target effects on the soil microbial community and carbon cycling. We added naphthalene at a high rate (477 g m\−2) monthly for 23 months on the bare soil surface of a tallgrass prairie. We determined the effect of such additions on the abundance of nematodes and micro-arthropods along the soil profile to a depth of 20 cm at 11, 16 and 23 months after initiating naphthalene application. We used the variation in the natural 13C abundance of the naphthalene (δ13C \– 25.5\‰) as compared to the native soil (δ13C \∼ \−17\‰) to quantify naphthalene contribution to soil CO2 efflux and microbial biomarkers (PLFA). Naphthalene addition significantly reduced the abundance of oribatid mites (\−45\%), predatory mites (\−52\%) and springtails (\−49\%), but did not affect nematode abundance. The 13C abundance of a few Gram-negative (cy17:0, 18:1ω7c, 16:1ω7c), Gram-positive (a15:0, i15:0) and Actinobacteria (10Me-16:0, 10Me-18:0) PLFA markers decreased significantly in naphthalene treated plots, indicating bacterial utilization of naphthalene-derived C. Mixing models showed this contribution to be highly variable, with the highest naphthalene-C incorporation for Gram negative bacteria. Naphthalene-C was not incorporated in fungal PLFAs. This microbial utilization did not affect overall microbial abundance, community structure or activity, estimated as soil respiration. This experiment proves that naphthalene addition is a feasible method to reduce soil micro-arthropods in the field, with negligible direct effects on soil nematodes, microbial abundance and C dynamics.

}, keywords = {LTER-KNZ, Fauna manipulation methods, Mites, Nematodes, PLFA, Springtails, Stable C isotopes}, doi = {10.1016/j.apsoil.2013.09.008}, url = {https://www.sciencedirect.com/science/article/pii/S0929139313002400?via\%3Dihub}, author = {Cotrufo, M.F. and Soong, J. and Vandegehuchte, M.L. and Ngryen, T. and Denef, K. and Shaw, E.A. and Sylvain, Z.A. and Tomasel, C.M.D. and Nielsen, U.N. and Wall, D.H.} } @article {KNZ001556, title = {Stomatal responses to changes in vapor pressure deficit reflect tissue-specific differences in hydraulic conductance}, journal = {Plant, Cell and Environment}, volume = {37}, year = {2014}, pages = {132 -139}, abstract = {

The vapor pressure deficit (D) of the atmosphere can negatively affect plant growth as plants reduce stomatal conductance to water vapor (gwv) in response to increasing D, limiting the ability of plants to assimilate carbon. The sensitivity of gwv to changes in D varies among species and has been correlated with the hydraulic conductance of leaves (Kleaf), but the hydraulic conductance of other tissues has also been implicated in plant responses to changing D. Among the 19 grass species, we found that Kleaf was correlated with the hydraulic conductance of large longitudinal veins (Klv, r2\ =\ 0.81), but was not related to Kroot (r2\ =\ 0.01). Stomatal sensitivity to D was correlated with Kleaf relative to total leaf area (r2\ =\ 0.50), and did not differ between C3 and C4 species. Transpiration (E) increased in response to D, but 8 of the 19 plants showed a decline in E at high D, indicative of an \‘apparent feedforward\’ response. For these individuals, E began to decline at lower values of D in plants with low Kroot (r2\ =\ 0.72). These results show the significance of both leaf and root hydraulic conductance as drivers of plant responses to evaporative demand.

}, keywords = {LTER-KNZ}, doi = {10.1111/pce.12137}, url = {https://onlinelibrary.wiley.com/doi/full/10.1111/pce.12137}, author = {Ocheltree, T.W. and Jesse B. Nippert and Prasad, P.V.V.} } @article {KNZ001740, title = {EO-1 Hyperion reflectance time series at calibration and validation sites: stability and sensitivity to seasonal dynamics}, journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing}, volume = {6}, year = {2013}, month = {Jan-04-2013}, pages = {276 - 290}, abstract = {

This study evaluated Earth Observing 1 (EO-1) Hyperion reflectance time series at established calibration sites to assess the instrument stability and suitability for monitoring vegetation functional parameters. Our analysis using three pseudo-invariant calibration sites in North America indicated that the reflectance time series are devoid of apparent spectral trends and their stability consistently is within 2.5-5 percent throughout most of the spectral range spanning the 12+ year data record. Using three vegetated sites instrumented with eddy covariance towers, the Hyperion reflectance time series were evaluated for their ability to determine important variables of ecosystem function. A number of narrowband and derivative vegetation indices (VI) closely described the seasonal profiles in vegetation function and ecosystem carbon exchange (e.g., net and gross ecosystem productivity) in three very different ecosystems, including a hardwood forest and tallgrass prairie in North America, and a Miombo woodland in Africa. Our results demonstrate the potential for scaling the carbon flux tower measurements to local and regional landscape levels. The VIs with stronger relationships to the CO2 parameters were derived using continuous reflectance spectra and included wavelengths associated with chlorophyll content and/or chlorophyll fluorescence. Since these indices cannot be calculated from broadband multispectral instrument data, the opportunity to exploit these spectrometer-based VIs in the future will depend on the launch of satellites such as EnMAP and HyspIRI. This study highlights the practical utility of space-borne spectrometers for characterization of the spectral stability and uniformity of the calibration sites in support of sensor cross-comparisons, and demonstrates the potential of narrowband VIs to track and spatially extend ecosystem functional status as well as carbon processes measured at flux towers.

}, keywords = {LTER-KNZ, calibration, geophysical techniques, remote sensing, vegetation}, issn = {1939-1404}, doi = {10.1109/JSTARS.2013.2246139}, url = {https://ieeexplore.ieee.org/document/6507569}, author = {Campbell, P.P.K. and Middleton, E.M. and Thome, K.J. and Kokaly, R.F. and Huemmrich, K.F. and Lagomasino, D. and Novick, K.A. and N. Brunsell} } @article {KNZ001606, title = {Evidence of physiological decoupling from grassland ecosystem drivers by an encroaching woody shrub}, journal = {PLoS ONE}, volume = {8}, year = {2013}, pages = {81630 -}, abstract = {

Shrub encroachment of grasslands is a transformative ecological process by which native woody species increase in cover and frequency and replace the herbaceous community. Mechanisms of encroachment are typically assessed using temporal data or experimental manipulations, with few large spatial assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra-annual variability in leaf δ13C in Cornus drummondii across a grassland landscape with varying fire frequency, presence of large grazers and topographic variability. This assessment of changes in individual shrub physiology is the largest spatial and temporal assessment recorded to date. Despite a doubling of annual rainfall (in 2008 versus 2011), leaf δ13C was statistically similar among and within years from 2008-11 (range of \−28 to \−27\‰). A topography*grazing interaction was present, with higher leaf δ13C in locations that typically have more bare soil and higher sensible heat in the growing season (upland topographic positions and grazed grasslands). Leaf δ13C from slopes varied among grazing contrasts, with upland and slope leaf δ13C more similar in ungrazed locations, while slopes and lowlands were more similar in grazed locations. In 2011, canopy greenness (normalized difference vegetation index \– NDVI) was assessed at the centroid of individual shrubs using high-resolution hyperspectral imagery. Canopy greenness was highest mid-summer, likely reflecting temporal periods when C assimilation rates were highest. Similar to patterns seen in leaf δ13C, NDVI was highest in locations that typically experience lowest sensible heat (lowlands and ungrazed). The ability of Cornus drummondii to decouple leaf physiological responses from climate variability and fire frequency is a likely contributor to the increase in cover and frequency of this shrub species in mesic grassland and may be generalizable to other grasslands undergoing woody encroachment.

}, keywords = {LTER-KNZ, Ecosystems, Grasslands, Grazing, Leaves, Plant physiology, Seasons, Shrubs, Water resources}, doi = {10.1371/journal.pone.0081630}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081630}, author = {Jesse B. Nippert and Ocheltree, T.W. and Orozco, G.L. and Z. Ratajczak and Ling, B. and Skibbe, A.M.} } @article {KNZ001488, title = {Global diversity of drought tolerance and grassland climate-change resilience}, journal = {Nature Climate Change}, volume = {3}, year = {2013}, pages = {63 -67}, abstract = {

Drought reduces plant productivity, induces widespread plant mortality and limits the geographic distribution of plant species1, 2, 3, 4, 5, 6, 7. As climates warm and precipitation patterns shift in the future8, 9, understanding the distribution of the diversity of plant drought tolerance is central to predicting future ecosystem function and resilience to climate change10, 11, 12. These questions are especially pressing for the world\’s 11,000 grass species13, which dominate a large fraction of the terrestrial biosphere14, yet are poorly characterized with respect to responses to drought. Here, we show that physiological drought tolerance, which varied tenfold among 426 grass species, is well distributed both climatically and phylogenetically, suggesting most native grasslands are likely to contain a high diversity of drought tolerance. Consequently, local species may help maintain ecosystem functioning in response to changing drought regimes without requiring long-distance migrations of grass species. Furthermore, physiologically drought-tolerant species had higher rates of water and carbon dioxide exchange than intolerant species, indicating that severe droughts may generate legacies for ecosystem functioning. In all, our findings suggest that diverse grasslands throughout the globe have the potential to be resilient to drought in the face of climate change through the local expansion of drought-tolerant species.

}, keywords = {LTER-KNZ, Climate-change ecology, Drought, Grassland ecology}, doi = {10.1038/nclimate1634}, url = {https://www.nature.com/articles/nclimate1634}, author = {Craine, J.M. and Ocheltree, T.W. and Jesse B. Nippert and Towne, E.G. and Skibbe, A.M. and Kembel, S.W. and Fargione, J.E.} } @article {KNZ001554, title = {Identifying the water sources consumed by bison: implications for large mammalian grazers worldwide}, journal = {Ecosphere}, volume = {4}, year = {2013}, pages = {23 -}, abstract = {

The sources of drinking water consumed by grazers vary over time and may be highly selective, similar to choices in diet. Water sources consumed by large grazers in natural populations are not typically measured directly. Instead, consumption is inferred based on animal proximity to water sources. Here, we analysed the stable isotopic signature of water (δ18O and δD) extracted from fecal samples from a herd of bison in mesic grassland as a direct estimation of the water sources consumed over time. Bison at this site have their choice of a range of habitats and drinking water sources. Potential source-water samples measured had a large range of isotopic signatures, allowing the isotopic composition of water from bison fecal samples to be proportionally estimated based on varying sources. Results indicate bison have low reliance on multiple streams on site; rather, the majority of water consumed was from rainfall-fed sources (puddles and wallows) and from forage. Our research suggests that source-water analysis from fecal samples is a robust technique when samples from large grazers can be collected soon after production. These results have implications for analyses of the foraging patterns and landscape utilization by this and other large grazers, because hotter and drier future conditions are likely to reduce the frequency and amount of rainfall-fed puddles available for consumption in many grassland systems worldwide.

}, keywords = {LTER-KNZ}, doi = {10.1890/ES12-00359.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES12-00359.1}, author = {Jesse B. Nippert and Culbertson, T.S.F. and Orozco, G.L. and Ocheltree, T.W. and Helliker, B.R.} } @article {KNZ001619, title = {Invertebrates, ecosystem services and climate change}, journal = {Biological Reviews}, volume = {88}, year = {2013}, pages = {327 -348}, abstract = {

The sustainability of ecosystem services depends on a firm understanding of both how organisms provide these services to humans and how these organisms will be altered with a changing climate. Unquestionably a dominant feature of most ecosystems, invertebrates affect many ecosystem services and are also highly responsive to climate change. However, there is still a basic lack of understanding of the direct and indirect paths by which invertebrates influence ecosystem services, as well as how climate change will affect those ecosystem services by altering invertebrate populations. This indicates a lack of communication and collaboration among scientists researching ecosystem services and climate change effects on invertebrates, and land managers and researchers from other disciplines, which becomes obvious when systematically reviewing the literature relevant to invertebrates, ecosystem services, and climate change. To address this issue, we review how invertebrates respond to climate change. We then review how invertebrates both positively and negatively influence ecosystem services. Lastly, we provide some critical future directions for research needs, and suggest ways in which managers, scientists and other researchers may collaborate to tackle the complex issue of sustaining invertebrate-mediated services under a changing climate.

}, keywords = {LTER-KNZ, Biodiversity, bioindicator species, Climate change, ecosystem engineers, ecosystem services, insects, invertebrates, sustainability}, doi = {10.1111/brv.12002}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/brv.12002}, author = {Prather, C.M. and Pelini, S. and Laws, A. and Rivest, E. and Woltz, M. and Bloch, C.P. and Del Toro, I. and Ho, Chuan-Kai. and Kominoski, J. and Newbold, T.A.S. and Parsons, S. and Anthony Joern} } @article {KNZ001499, title = {Physiological and growth responses of switchgrass (Panicum virgatum L.) in native stands under passive air temperature manipulation}, journal = {Global Change Biology-Bioenergy}, volume = {5}, year = {2013}, pages = {683 -692}, abstract = {

In the central Great Plains of North America, climate change predictions include increases in mean annual temperature of 1.5\–5.5 \°C by 2100. Ecosystem responses to increased temperatures are likely to be regulated by dominant plant species, such as the potential biofuel species Panicum virgatum (switchgrass) in the tallgrass prairie. To describe the potential physiological and whole-plant responses of this species to future changes in air temperatures, we used louvered open-sided chambers (louvered OSC; 1 \× 1 m, adjustable height) to passively alter canopy temperature in native stands of P. virgatum growing in tallgrass prairie at varying topographic positions (upland/lowland). The altered temperature treatment decreased daily mean temperatures by 1 \°C and maximum temperatures by 4 \°C in May and June, lowered daytime stomatal conductance and transpiration, decreased tiller density, increased specific leaf area, and delayed flowering. Among topographic contrasts, aboveground biomass, flowering tiller density, and tiller weight were greater in lowland sites compared to upland sites, with no temperature treatment interactions. Differences in biomass production responded more to topography than the altered temperature treatment, as soil water status varied considerably between topographic positions. These results indicate that while water availability as a function of topography was a strong driver of plant biomass, many leaf-level physiological processes were responsive to the small decreases in daily mean and maximum temperature, irrespective of landscape position. The varying responses of leaf-level gas exchange and whole-plant growth of P. virgatum in native stands to altered air temperature or topographic position illustrate that accurately forecasting yields for P. virgatum in mixed communities will require greater integration of physiological responses to simulated climate change (increased temperature) and resource availability over natural environmental gradients (soil moisture).

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1757-1707.2012.01204.x}, url = {https://onlinelibrary.wiley.com/doi/full/10.1111/j.1757-1707.2012.01204.x}, author = {Hartman, J.C. and Jesse B. Nippert} } @article {KNZ001555, title = {Population origin and genome size do not impact Panicum virgatum (switchgrass) responses to variable precipitation}, journal = {Ecosphere}, volume = {4}, year = {2013}, pages = {37 -}, abstract = {

Population-level adaptation to broad-scale regional climates or within-population variation in genome size of the genetically and phenotypically diverse C4 grass, Panicum virgatum (switchgrass), may influence the responses of this species to future precipitation variability associated with climate change. Therefore, we investigated P. virgatum responses to water variability between natural populations collected across a latitudinal gradient and among individuals spanning a range of genomes sizes within these populations. P. virgatum plants from natural populations originating from Kansas, Oklahoma, and Texas, U.S.A, received frequent, small precipitation events (\“ambient\”) or infrequent, large precipitation events (\“altered\”) to simulate contrasting rainfall variability expected for this region. We measured leaf-level physiology, aboveground biomass and genome size for each individual. Gas exchange rates and aboveground biomass varied significantly by population origin but did not differ by genome size. Altered precipitation treatments reduced leaf-level physiological rates; however this result did not vary by population or genome size. Our results suggest that trait variation in P. virgatum is primarily attributed to population-level adaptation across a latitudinal gradient, not genome size, and that neither population-level adaptation nor genome size may be important predictors of P. virgatum responses to future climatic conditions.

}, keywords = {LTER-KNZ}, doi = {10.1890/ES12-00339.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES12-00339.1}, author = {O{\textquoteright}Keefe, K. and Tomeo, N. and Jesse B. Nippert and Springer, C.J.} } @article {KNZ001474, title = {Precipitation timing and grazer performance in a tallgrass prairie}, journal = {Oikos}, volume = {122}, year = {2013}, pages = {191 -198}, abstract = {

Changes in precipitation amount and variability have the potential to alter the structure and function of grasslands, but we know little about how changes in the timing of precipitation might affect grasslands. Here, we analyze long-term records from a tallgrass prairie to show that shifts in the timing of precipitation during the growing season have little effect on primary productivity or grass reproduction, but can greatly affect grazer performance. While greater late-season precipitation increases the weight gain of adult and young bison, greater mid-season precipitation decreases their weight gain. In addition, calving rates are lower after years with greater mid-season precipitation and higher after years with greater late-season precipitation. As well-timed drought can actually increase grazer weight gain and reproduction, it will be necessary to generate predictions of within-season distribution of precipitation to successfully forecast future grazer performance.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1600-0706.2012.20400.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0706.2012.20400.x}, author = {Craine, J.M. and Towne, E.G. and Tolleson, D. and Jesse B. Nippert} } @article {KNZ001502, title = {Changes in stomatal conductance along grass blades reflect changes in leaf structure}, journal = {Plant Cell and Environment}, volume = {35}, year = {2012}, pages = {1040 -1049}, abstract = {

Identifying the consequences of grass blade morphology (long, narrow leaves) on the heterogeneity of gas exchange is fundamental to an understanding of the physiology of this growth form. We examined acropetal changes in anatomy, hydraulic conductivity and rates of gas exchange in five grass species (including C3 and C4 functional types). Both stomatal conductance and photosynthesis increased along all grass blades despite constant light availability. Hydraulic efficiency within the xylem remained constant along the leaf, but structural changes outside the xylem changed in concert with stomatal conductance. Stomatal density and stomatal pore index remained constant along grass blades but interveinal distance decreased acropetally resulting in a decreased path length for water movement from vascular bundle to stomate. The increase in stomatal conductance was correlated with the decreased path length through the leaf mesophyll. A strong correlation between the distance from vascular bundles to stomatal pores and stomatal conductance has been identified across species; our results suggest this relationship also exists within individual leaves.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-3040.2011.02470.x}, url = {https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3040.2011.02470.x}, author = {Ocheltree, T.W. and Jesse B. Nippert and Prasad, P.V.V.} } @article {KNZ001440, title = {Climate change alters growing season flux dynamics in mesic grasslands}, journal = {Theoretical and Applied Climatology}, volume = {107}, year = {2012}, pages = {427 -440}, abstract = {

Changing climate could affect the functioning of grassland ecosystems through variation in climate forcings and by altering the interactions of forcings with ecological processes. Both the short and long-term effects of changing forcings and ecosystem interactions are a critical part of future impacts to ecosystem ecology and hydrology. To explore these interactions and identify possible characteristics of climate change impacts to mesic grasslands, we employ a low-dimensional modeling framework to assess the IPCC A1B scenario projections for the Central Plains of the United States; forcings include increased precipitation variability, increased potential evaporation, and earlier growing season onset. These forcings are also evaluated by simulations of vegetation photosynthetic capacity to explore the seasonal characteristics of the vegetation carbon assimilation response for species at the Konza Prairie in North Central Kansas, USA. The climate change simulations show decreases in mean annual soil moisture and and carbon assimilation and increased variation in water and carbon fluxes during the growing season. Simulations of the vegetation response show increased variation at the species-level instead of at a larger class scale, with important heterogeneity in how individual species respond to climate forcings. Understanding the drivers and relationships behind these ecosystem responses is important for understanding the likely scale of climate change impacts and for exploring the mechanisms shaping growing season dynamics in grassland ecosystems.

}, keywords = {LTER-KNZ, ecohydrology, Konza Prairie, Low-dimensional modeling, Nonlinear interactions, Soil moisture feedback}, doi = {10.1007/s00704-011-0484-y}, url = {https://link.springer.com/article/10.1007\%2Fs00704-011-0484-y}, author = {Petrie, M.D. and N. Brunsell and Jesse B. Nippert} } @article {KNZ001468, title = {Comment on "Global Resilience of Tropical Forest and Savanna to Critical Transitions"}, journal = {Science}, volume = {336}, year = {2012}, pages = {541 -}, abstract = {

Hirota et al. (Reports, 14 October 2011, p. 232) used spatial data to show that grasslands, savannas, and forests represent opposing stable states. Reanalyzing their data and drawing from temporal studies, we argue that spatial analyses underestimate the bistability of grasslands and savannas due to limitations of substituting space for time. We propose that temporal and spatial data are needed to predict critical transitions between grasslands and savannas.

}, keywords = {LTER-KNZ}, doi = {10.1126/science.1219346}, url = {http://science.sciencemag.org/content/336/6081/541.3}, author = {Z. Ratajczak and Jesse B. Nippert} } @article {KNZ001462, title = {Community traitscape of foliar nitrogen isotopes reveals N availabiity patterns in a tallgrass prairie}, journal = {Plant and Soil}, volume = {356}, year = {2012}, pages = {395 -403}, abstract = {

Background and aims Nutrients are important determinants of community assembly, yet the roles they play in structuring plant communities are still poorly understood. One inferential approach to understanding how environmental factors structure plant communities is examining the distribution of key functional traits among species of a community\—a community traitscape. Methods To better understand how nitrogen (N) and water availability structure grasslands, we measured N concentrations and isotope ratios for 366 herbaceous species in a mesic N-limited temperate grassland, Konza Prairie. We also compared foliar N concentrations and N isotopes between Konza species and a global dataset. Results Species that had either high foliar N concentrations or high δ15NL were not necessarily more or less abundant on the landscape nor more or less likely to be found in uplands, grazed areas, or burned areas. Apparently there are unique hot spots of high N availability at Konza and the typical non-Fabaceae Konza species occupies sites with greater N availability than found globally. Conclusions Although nascent, the Konza traitscapes suggest that plant diversity in nutrient-limited communities might be strongly dependent on high-nutrient availability sites that enable high-fertility species to persist in a matrix of low nutrient availability.

}, keywords = {LTER-KNZ, Community assembly, disturbance, Grasslands, Isotopes, Konza Prairie, Resource limitation}, doi = {10.1007/s11104-012-1141-7}, url = {https://link.springer.com/article/10.1007\%2Fs11104-012-1141-7}, author = {Craine, J.M. and Towne, E.G. and Ocheltree, T.W. and Jesse B. Nippert} } @article {KNZ001500, title = {Ecotypic responses of switchgrass to altered precipitation}, journal = {Functional Plant Biology}, volume = {39}, year = {2012}, pages = {126 -136}, abstract = {

Anthropogenic climate change is projected to alter precipitation patterns, resulting in novel environments for plants. The responses of dominant plant species (e.g. Panicum virgatum L. (switchgrass)) to climate changes can drive broader ecosystem processes such as primary productivity. Using a rainfall mesocosm facility, three ecotypes of P. virgatum (collected from Kansas, Oklahoma and Texas, USA) were subjected to three precipitation regimes (average, \–25\%, +25\%) to determine the physiological and growth responses to altered precipitation in a common garden setting. Results showed mean maximum photosynthetic rates, stomatal conductance, transpiration, midday water potential and dark-adapted chlorophyll fluorescence were lowest in the Kansas ecotypes. Increased precipitation treatments raised the mean midday water potentials and lowered water-use efficiency. Aboveground biomass responded positively to changes in precipitation, but flowering initiation was later and rates were lower for Texas ecotypes. In general, ecotype origin was a better predictor of differences in physiological responses and flowering, whereas the precipitation treatments had greater control over biomass production. Depending on the growth variable measured, these results show responses for P. virgatum are under varying ecotypic or environmental control with few interactions, suggesting that future predictions to climate change need not inherently consider localised adaptations in this economically important and widely distributed species.

}, keywords = {LTER-KNZ}, doi = {10.1071/FP11229}, url = {http://www.publish.csiro.au/fp/FP11229}, author = {Hartman, J.C. and Jesse B. Nippert and Springer, C.J.} } @mastersthesis {KNZ001558, title = {Influences of local adaptation and genome size on Panicum virgatum (switchgrass) responses to variable precipitation timing}, volume = {MS Thesis}, year = {2012}, school = {St. Joseph{\textquoteright}s University}, type = {M.S. Thesis}, address = {Philadelphia, PA}, keywords = {LTER-KNZ}, author = {O{\textquoteright}Keefe, K.} } @mastersthesis {KNZ001494, title = {An iPhone application of Konza Prairie LTER}, volume = {MS Thesis}, year = {2012}, pages = {1 -47}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, url = {http://krex.k-state.edu/dspace/handle/2097/13960}, author = {Nukala, L.A.} } @article {KNZ001457, title = {Phylogenetics of Morus (Moraceae) inferred from ITS and trnL-trnF sequence data}, journal = {Systematic Botany}, volume = {37}, year = {2012}, pages = {442 -450}, abstract = {

Morus (Tribe Moreae, Moraceae) consists of ca. 13 species of trees distributed in Asia, Africa, Europe, and North, Central, and South America. The broad geographical distribution of the genus, overlapping ranges of many taxa, and documented hybridization between some species present interesting questions of taxonomy, phylogeny, and biogeography. Phylogenetic data for Morus also contribute to higher level taxonomic work in the family. We used sequence data from ITS of the nrDNA and the chloroplast trnL-trnF intergenic spacer to study phylogenetic relationships of Morus. Phylogenies based on separate data sets were not statistically incongruent, and the combined tree reveals that Morus, as currently circumscribed, is non-monophyletic. Subgenus Morus (sensu Leroy) is resolved as a clade and consists of two well-supported clades: one of Asian taxa and one of North American taxa. Sampled members of the genus Trophis (two, including the type) form a clade sister to subgenus Morus. Morus mesozygia (Africa; subgenus Afromorus) and M. insignis (Neotropics; subgenus Gomphomorus), which have not been included to date in other phylogenetic studies of the family, are placed outside the subgenus Morus-Trophis clade. This work is an important step in elucidating relationships of Morus and along with other recent phylogenetic studies in Moraceae, underscores the need for further work within Tribe Moreae to clarify natural generic relationships.

}, keywords = {LTER-KNZ, ITS, Moraceae, Moreae, Morus, phylogeny, trnL-trnF}, doi = {https://doi.org/10.1600/036364412X635485}, url = {https://bioone.org/journals/Systematic-Botany/volume-37/issue-2/036364412X635485/Phylogenetics-of-iMorus-i-Moraceae-Inferred-from-ITS-and-itrnL/10.1600/036364412X635485.full}, author = {Nepal, M.P. and Ferguson, C.J.} } @article {KNZ001501, title = {Root characteristics of C-4 grasses limit reliance on deep soil water in tallgrass prairie}, journal = {Plant and Soil}, volume = {355}, year = {2012}, pages = {385 -394}, abstract = {

Background C4 grass species in the mesic tallgrass prairie of central North America can exhibit both high root production and deep rooting in the soil profile (\>2 m). Differences in root growth and the types of roots produced vary according to local environmental gradients and management practices. The production of deep roots in tallgrass prairie has been historically presumed as a mechanism for water uptake when surface soils are dry. Methods We examined changes in root biomass, total root length, root width, and theoretical hydraulic conductivity using roots collected from deep soil cores in upland and lowland topographic positions in grazed and ungrazed watersheds of the Konza Prairie Biological Station in north-eastern Kansas, USA. Results Root biomass, total root length, and theoretical hydraulic conductivity were highest in roots found in the top 20 cm of the soil profile, and then declined exponentially with increasing soil depth. Compared to grazed areas, ungrazed locations had more root biomass and total root length of roots in the most superficial soil layers. No differences in rooting profiles were present among topographic contrasts. Theoretical hydraulic conductivity of axial root xylem did not vary by topographic position or grazing contrasts, and declines in conductivity by depth were driven by changes in the number of vessels per stele, rather than changes in vessel size. Conclusions Irrespective of differences by grazing treatment or topographic position, significant reductions in root biomass, total root length, and theoretical hydraulic conductivity of grass roots at soil depths greater than 1 m suggest deep roots in this grassland have limited functional significance for water uptake.

}, keywords = {LTER-KNZ, Andropogon gerardii, C4 grass, Mesic grassland, Root biomass, Theoretical hydraulic conductivity, Total root length}, doi = {10.1007/s11104-011-1112-4}, url = {https://link.springer.com/article/10.1007\%2Fs11104-011-1112-4}, author = {Jesse B. Nippert and Wieme, R.A. and Ocheltree, T.W. and Craine, J.M.} } @article {KNZ001473, title = {Stability of tallgrass prairie during a 19-year increase in growing season precipitation}, journal = {Functional Ecology}, volume = {26}, year = {2012}, pages = {1450 - 1459}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2435.2012.01995.x}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2435.2012.01995.x}, author = {Scott. L. Collins and Koerner, S.E. and Plaut, J.A. and Okie, J.G. and Brese, D. and Calabrese, L.B. and Carvajal, A. and Evanse, R.J. and Nonaka, E.} } @article {KNZ001464, title = {The timing of climate variability and grassland productivity}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {109}, year = {2012}, pages = {3401 -3405}, abstract = {

Changes in precipitation amount and variability have the potential to alter the structure and function of grasslands, but we know little about how changes in the timing of precipitation might affect grasslands. Here, we analyze long-term records from a tallgrass prairie to show that shifts in the timing of precipitation during the growing season have little effect on primary productivity or grass reproduction, but can greatly affect grazer performance. While greater late-season precipitation increases the weight gain of adult and young bison, greater mid-season precipitation decreases their weight gain. In addition, calving rates are lower after years with greater mid-season precipitation and higher after years with greater late-season precipitation. As well-timed drought can actually increase grazer weight gain and reproduction, it will be necessary to generate predictions of within-season distribution of precipitation to successfully forecast future grazer performance.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1600-0706.2012.20400.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0706.2012.20400.x}, author = {Craine, J.M. and Jesse B. Nippert and Elmore, A.J. and Skibbe, A.M. and Hutchinson, S.L. and N. Brunsell} } @article {KNZ001460, title = {Woody encroachment decreases diversity across North American grasslands and savannas}, journal = {Ecology}, volume = {93}, year = {2012}, pages = {697 -703}, abstract = {

Woody encroachment is a widespread and acute phenomenon affecting grasslands and savannas worldwide. We performed a meta-analysis of 29 studies from 13 different grassland/savanna communities in North America to determine the consequences of woody encroachment on plant species richness. In all 13 communities, species richness declined with woody plant encroachment (average decline = 45\%). Species richness declined more in communities with higher precipitation (r2 = 0.81) and where encroachment was associated with a greater change in annual net primary productivity (ANPP; r2 = 0.69). Based on the strong positive correlation between precipitation and ANPP following encroachment (r2 = 0.87), we hypothesize that these relationships occur because water-limited woody plants experience a greater physiological and demographic release as precipitation increases. The observed relationship between species richness and ANPP provides support for the theoretical expectation that a trade-off occurs between richness and productivity in herbaceous communities. We conclude that woody plant encroachment leads to significant declines in species richness in North American grassland/savanna communities.

}, keywords = {LTER-KNZ}, doi = {10.1890/11-1199.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/11-1199.1}, author = {Z. Ratajczak and Jesse B. Nippert and Scott. L. Collins} } @article {KNZ001363, title = {Differential responses to defoliation frequency in Little Bluestem (Schizachyrium scoparium) in tallgrass prairie: Implications for herbivory tolerance and avoidance}, journal = {Plant Ecology}, volume = {212}, year = {2011}, pages = {1275 -1285}, abstract = {

Plant responses to herbivory are complex. In grasses, relative growth rate (RGR), seed, and vegetative reproduction, resource allocation, and architecture vary differentially and often nonlinearly with grazing intensity. High grazing tolerance may be achieved through compensatory photosynthesis and leaf growth, or through demographic mechanisms such as activation of a belowground dormant bud bank. This study assessed the relationship between grazing frequency and responses of Schizachyrium scoparium (little bluestem) in a tallgrass prairie, and examined the roles of tiller growth, reproduction, and bud (meristem) populations in its persistence under grazing. Genets were subjected to varying simulated grazing frequencies for a period of 2 years. Strong differential responses were observed among plant traits. RGR, biomass, and flowering showed strong nonlinear reductions in response to increasing clipping frequency, with no evidence of threshold effects. However, meristem density was unaffected, and plants maintained a large bud bank across all clipping treatments. Tiller natality decreased initially, but increased with \>4 clippings, suggesting that declines in tiller RGR are partially offset by increasing tiller natality, and that variation in genet size is driven more by demography than by variation in individual tiller growth. Increased grazing frequency also resulted in differential activation of buds at different positions (emerging within vs. outside the subtending leaf sheath), explaining the shift to a more prostrate growth form observed in many caespitose grasses under persistent grazing. Thus, although this grass species lacks the capacity for compensatory foliage re-growth, the maintenance of a large dormant bud bank and the differential activation of buds in different positions contribute to its grazing tolerance and avoidance, respectively, and its long-term persistence in grazed grasslands.

}, keywords = {LTER-KNZ, bud banks, Compensation, demography, Grasses, Grazing, Herbivory}, doi = {10.1007/s11258-011-9904-4}, url = {https://link.springer.com/article/10.1007\%2Fs11258-011-9904-4}, author = {N{\textquoteright}Guessan, M. and D.C. Hartnett} } @article {KNZ001367, title = {Functional consequences of climate-change induced plant species loss in a tallgrass prairie}, journal = {Oecologia}, volume = {165}, year = {2011}, pages = {1109 -1117}, abstract = {

Future climate change is likely to reduce the floristic diversity of grasslands. Yet the potential consequences of climate-induced plant species losses for the functioning of these ecosystems are poorly understood. We investigated how climate change might alter the functional composition of grasslands for Konza Prairie, a diverse tallgrass prairie in central North America. With species-specific climate envelopes, we show that a reduction in mean annual precipitation would preferentially remove species that are more abundant in the more productive lowland positions at Konza. As such, decreases in precipitation could reduce productivity not only by reducing water availability but by also removing species that inhabit the most productive areas and respond the most to climate variability. In support of this prediction, data on species abundance at Konza over 16 years show that species that are more abundant in lowlands than uplands are preferentially reduced in years with low precipitation. Climate change is likely to also preferentially remove species from particular functional groups and clades. For example, warming is forecast to preferentially remove perennials over annuals as well as Cyperaceae species. Despite these predictions, climate change is unlikely to unilaterally alter the functional composition of the tallgrass prairie flora, as many functional traits such as physiological drought tolerance and maximum photosynthetic rates showed little relationship with climate envelope parameters. In all, although climatic drying would indirectly alter grassland productivity through species loss patterns, the insurance afforded by biodiversity to ecosystem function is likely to be sustained in the face of climate change.

}, keywords = {LTER-KNZ, biogeography, Climate change, Functional traits, Grasslands, Konza Prairie}, doi = {10.1007/s00442-011-1938-8}, url = {https://link.springer.com/article/10.1007\%2Fs00442-011-1938-8}, author = {Craine, J.M. and Jesse B. Nippert and Towne, E.G. and Tucker, S. and Kembel, S.W. and Skibbe, A.M. and McLauchlan, K.K.} } @article {KNZ001437, title = {Land fragmentation under rapid urbanization: A cross-site analysis of Southwestern cities}, journal = {Urban Ecosystems}, volume = {14}, year = {2011}, pages = {429 -455}, abstract = {

Explosive population growth and increasing demand for rural homes and lifestyles fueled exurbanization and urbanization in the western USA over the past decades. Using National Land Cover Data we analyzed land fragmentation trends from 1992 to 2001 in five southwestern cities associated with Long Term Ecological Research (LTER) sites. We observed two general fragmentation trends: expansion of the urbanized area leading to fragmentation in the exurban and peri-urban regions and decreased fragmentation associated with infill in the previously developed urban areas. We identified three fragmentation patterns, riparian, polycentric, and monocentric, that reflect the recent western experience with growth and urbanization. From the literature and local expert opinion, we identified five relevant drivers \– water provisioning, population dynamics, transportation, topography, and institutions \– that shape land use decision-making and fragmentation in the southwest. In order to assess the relative importance of each driver on urbanization, we linked historical site-specific driver information obtained through literature reviews and archival analyses to the observed fragmentation patterns. Our work highlights the importance of understanding land use decision-making drivers in concert and throughout time, as historic decisions leave legacies on landscapes that continue to affect land form and function, a process often forgotten in a region and era of blinding change.

}, keywords = {LTER-KNZ, Exurbanization, Land fragmentation, The US Southwest, Urban ecology}, doi = {10.1007/s11252-011-0157-8}, url = {https://link.springer.com/article/10.1007\%2Fs11252-011-0157-8}, author = {York, A.M. and Shrestha, M. and Boone, C.G. and Zhang, S. and J. A. Harrington and Prebyl, T.J. and Swann, A. and Agar, M. and Antolin, M.F. and Nolen, B. and Wright, J.B. and Skaggs, R.} } @article {KNZ001387, title = {Linking plant growth responses across topographic gradients in tallgrass prairie}, journal = {Oecologia}, volume = {166}, year = {2011}, pages = {1131 -1142}, abstract = {

Aboveground biomass in grasslands varies according to landscape gradients in resource availability and seasonal patterns of growth. Using a transect spanning a topographic gradient in annually burned ungrazed tallgrass prairie, we measured changes in the height of four abundant C4 grass species, LAI, biomass, and cumulative carbon flux using two closely located eddy flux towers. We hypothesized that seasonal patterns of plant growth would be similar across the gradient, but the magnitude of growth and biomass accumulation would vary by topographic position, reflecting spatial differences in microclimate, slope, elevation, and soil depth. Thus, identifying and measuring local growth responses according to topographic variability should significantly improve landscape predictions of aboveground biomass. For most of the growth variables measured, classifying topography into four positions best captured the inherent spatial variability. Biomass produced, seasonal LAI and species height increased from the upland and break positions to the slope and lowland. Similarly, cumulative carbon flux in 2008 was greater in lowland versus upland tower locations (difference of 64 g m\−2 by DOY 272). Differences in growth by topographic position reflected increased production of flowering culms by Andropogon gerardii and Sorghastrum nutans in lowland. Varying growth responses by these species may be a significant driver of biomass and carbon flux differences by topographic position, at least for wet years. Using a digital elevation model to classify the watershed into topographic positions, we performed a geographically weighted regression to predict landscape biomass. The minimum and maximum predictions of aboveground biomass for this watershed had a large range (86\–393 t per 40.4 ha), illustrating the drastic spatial variability in growth within this annually-burned grassland.

}, keywords = {LTER-KNZ, ANPP, Eddy covariance, Flux footprint, LAI, Mesic grassland, topography}, doi = {10.1007/s00442-011-1948-6}, url = {https://link.springer.com/article/10.1007\%2Fs00442-011-1948-6}, author = {Jesse B. Nippert and Ocheltree, T.W. and Skibbe, A.M. and Kangas, L.C. and J.M. Ham and Shonkwiler-Arnold, K.B. and N. Brunsell} } @article {KNZ001389, title = {Physiological drought tolerance and the structuring of tallgrass assemblages}, journal = {Ecosphere}, volume = {2}, year = {2011}, pages = {48 -}, abstract = {

Drought is a defining characteristic of many grasslands worldwide. Yet we have little understanding of how drought structures grassland communities and the degree to which physiological drought tolerance advantages plants in grasslands. We characterized physiological drought tolerance (Ψcrit) for a large number of species in a mesic grassland community (Konza Prairie, KS, USA). We then examined the relationships between Ψcrit and a number of other key functional traits, and tested whether physiological tolerance of drought underlay success across a number of ecological contrasts\—topographic position, burn frequency, and grazing\—with 17 years of abundance data. Physiological drought tolerance of Konza species covered almost the full range known to plants globally. Consistently, physiologically drought-tolerant species had thin roots, while associations with other traits were inconsistent across functional groups. In this mesic grassland, physiological drought tolerance appears to increase the abundance of plants in xeric uplands, but does not in the mesic lowlands. Physiological drought tolerance did not alter species responses to changes in burning or grazing. In contrast to Ψcrit, species with high root tissue density were more abundant in uplands and lowlands than species with low root tissue density largely irrespective of grazing or burning regimes. In all, drought appears to have a limited role in structuring the Konza plant community. As such, more severe or frequent droughts in the region would likely restructure the Konza plant community in ways that are currently not observable.

}, keywords = {LTER-KNZ}, doi = {10.1890/ES11-00023.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES11-00023.1}, author = {Tucker, S.S. and Craine, J.M. and Jesse B. Nippert} } @article {KNZ001450, title = {Positive feedbacks amplify rates of woody encroachment in mesic tallgrass prairie}, journal = {Ecosphere}, volume = {2}, year = {2011}, pages = {121 -}, abstract = {

Over the last century, many grasslands worldwide have transitioned from a graminoid to a tree/shrub-dominated state in a short period of time, a phenomenon referred to as woody encroachment. Positive feedbacks and bi-stability are thought to be important drivers of woody encroachment, but there is little empirical evidence to suggest that positive feedbacks accelerate the woody encroachment of mesic grasslands. In mesic tallgrass prairie, shrub establishment does not directly facilitate seedling establishment. Yet, shrub establishment may facilitate the clonal spread of existing shrubs into nearby patches, because clonal reproduction might circumvent barriers that typically limit woody seedlings. Our results show that when Cornus drummondii (the predominate encroacher of mesic tallgrass prairie) extends rhizomatous stems into open grasslands, these stems use the same deep soil water sources as mature stems\—thereby avoiding competition with grasses and gaining access to a reliable water source. In addition, herbaceous fuel concentrations are lower at the shrub/grass interface than in open grasslands, reducing the potential impacts of subsequent grassland fires. We propose that the release from resource and fire limitation results in a positive feedback loop as clonal stems are able to extend into surrounding patches, circumvent demographic barriers, mature, and spread by developing their own clonal stems. Long-term data on site (26 years) corroborates this interpretation: the size of deep-rooted clonal shrub species has increased 16-fold and their cover has increased from 0 to 27\%, whereas the cover of shallow-rooted species (both clonal and non-clonal) has only increased marginally. Together, these results suggest that (1) positive feedbacks can facilitate mesic woody encroachment and (2) bi-stability exists in mesic tallgrass prairie.

}, keywords = {LTER-KNZ}, doi = {10.1890/ES11-00212.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/ES11-00212.1}, author = {Z. Ratajczak and Jesse B. Nippert and Hartman, J.C. and Ocheltree, T.W.} } @article {KNZ001503, title = {Potential ecological impacts of switchgrass (Panicum virgatum L.) biofuel cultivation in the Central Great Plains, USA}, journal = {Biomass and Bioenergy}, volume = {35}, year = {2011}, pages = {3415 -3421}, abstract = {

Switchgrass (Panicum virgatum L.) is a broadly adapted warm-season grass species native to most of the central and eastern United States. Switchgrass has been identified as a potential biofuel species because it is a native species that requires minimal management, and has a large potential to sequester carbon underground. Since the 1990\’s, switchgrass has been bred to produce cultivars with increased biomass and feedstock quality. This review addresses potential ecological consequences of widespread switchgrass cultivation for biofuel production in the central United States. Specifically, this review address the ecological implications of changing use of marginal and CRP land, impacts on wildlife, potentials for disease and invasions, and changes in soil quality through reductions in erosion, decomposition rates, and carbon sequestrations. A central theme of the review is the utility of maintaining landscape heterogeneity during switchgrass biofuel production. This includes implementing harvest rotations, no till farming, and mixed species composition. If negative ecological consequences of switchgrass cultivation are minimized, biofuel production using this species has economical and environmental benefits.

}, keywords = {LTER-KNZ, Carbon sequestration, Crop rotation, CRP land, Landscape heterogeneity, Marginal land, SOC}, doi = {10.1016/j.biombioe.2011.04.055}, url = {https://www.sciencedirect.com/science/article/pii/S0961953411002935?via\%3Dihub}, author = {Hartman, J.C. and Jesse B. Nippert and Orozco, R.A. and Springer, C.J.} } @article {KNZ001449, title = {Relative effects of precipitation variability and warming on tallgrass prairie ecosystem function}, journal = {Biogeosciences}, volume = {8}, year = {2011}, pages = {3053 -3068}, abstract = {

Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenarios predict increasing precipitation variability and temperature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual) rainfall variability, and warming. We present results from an experiment applying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ~50\–200\% interannual variability in plant growth and aboveground net primary productivity (ANPP), leaf carbon assimilation (ACO2), and soil CO2 efflux (JCO2) despite only ~40\% variation in mean volumetric soil water content (0\–15 cm, Θ15). Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Differences between years in Θ15 explained the greatest portion (14\–52\%) of the variation in these processes. Experimentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture variation and reduced Θ15 by 15\%, causing most ecosystem processes to decrease 8\–40\% in some or all years with increased rainfall variability compared to ambient rainfall timing, suggesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, particularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter JCO2, and reduced summer JCO2 and forb ANPP, suggesting that the effects of warming differed in cooler versus warmer parts of the year. We conclude that (1) major ecosystem processes in this grassland may be substantially altered by predicted changes in interannual climate variability, intra-annual rainfall variability, and temperature, (2) interannual climate variation was a larger source of variation in ecosystem function than intra-annual rainfall variability and warming, and (3) effects of increased growing season rainfall variability and warming were small, but ecologically important. The relative effects of these climate drivers are likely to vary for different ecosystem processes and in wetter or drier ecosystems.

}, keywords = {LTER-KNZ}, doi = {10.5194/bg-8-3053-2011}, url = {https://www.biogeosciences.net/8/3053/2011/}, author = {Fay, P.A. and John M. Blair and M.D. Smith and Jesse B. Nippert and Carlisle, J.D. and Alan K. Knapp} } @mastersthesis {KNZ001429, title = {Responses of switchgrass (Panicum virgatum L.) to precipitation amount and temperature}, volume = {MS Thesis}, year = {2011}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, abstract = {

Anthropogenic climate change is likely to alter the function and composition of ecosystems worldwide through increased precipitation variability and temperatures. To predict ecosystem responses, a greater understanding of the physiological and growth responses of plants is required. Dominant species drive ecosystem responses, and it is essential to understand how they respond to understand potential ecosystem changes. Dominant species, such as switchgrass (Panicum virgatum L.), posses large genotypic and phenotypic variability, which will impact the degree of responses to projected climate changes. I studied the physiological and growth responses of switchgrass, a common perennial warm-season C4 grass that is native to the tallgrass prairie, to alterations in precipitation amount and temperature. The first experiment I conducted focused on the responses of three ecotypes of P. virgatum to three precipitation regimes (average, 25\% below, 25\% above). I concluded that the physiological responses of photosynthesis, stomatal conductance, transpiration, dark-adapted fluorescence, and mid-day water potential in P. virgatum were explained by ecotypic differences. Robust responses to altered precipitation were seen in the water use efficiency, mid-day water potential, and aboveground biomass. Ecotypic differences were also seen in several aboveground biomass variables, and most strikingly in flowering times and rates. There were few interactions between ecotype and precipitation, suggesting precipitation is a strong driver of biomass production, whereas adaption of ecotypes to their local environment affects physiological processes. A second experiment studied the response of local populations of P. virgatum to nocturnal warming. Results showed significant differences in daytime E, daytime gs, and flowering phenology between treatments. Differences in aboveground biomass were between topographic positions. I concluded that water availability, based on topographic position, is a strong driver of P. virgatum aboveground biomass production, but nocturnal warming has the potential to impact flowering phenology, physiological responses, and exacerbate plant water stress. I also reviewed the literature on the ecological effects of implementing switchgrass cultivation for biofuel. From the literature review, I concluded that large-scale switchgrass cultivation will have widespread ecological impacts. If landscape heterogeneity is maintained through harvest rotations, no till farming, and mixed species composition, ecosystem services can be maintained while providing economic value.

}, keywords = {LTER-KNZ, Aboveground biomass, Biofuel, Climate change, Ecophysiology, grassland}, url = {http://hdl.handle.net/2097/10720}, author = {Hartman, J.C.} } @article {KNZ001276, title = {Climate controls on grass culm production over a quarter century in a tallgrass prairie}, journal = {Ecology}, volume = {91}, year = {2010}, pages = {2132 -2140}, abstract = {

The flowering of grasses is a process critical to plant population dynamics and genetics, herbivore performance, and human health. To better understand the climate factors governing grass flowering, we analyzed the patterns of culm production over 25 years for three perennial tallgrass prairie species at Konza Prairie in Kansas, USA. The three species (Andropogon gerardii, Sorghastrum nutans, and Schizachyrium scoparium) all utilize the C4 photosynthetic pathway and were measured annually at the same locations for the past 25 years in an annually burned watershed. Culm production of all three species increased with higher growing-season soil moisture and precipitation but differed in their responses to water availability at different times during the growing season. Relative to Andropogon, Sorghastrum responded more to precipitation early in the growing season, and Schizachyrium responded more to precipitation late in the growing season. Flowering by each species also revealed a threshold relationship with late-season soil moisture at ~1 m depth, which likely is a proxy for season-long water balance. Although flowering can be influenced by conditions antecedent to the current growing season, neither soil moisture nor precipitation during the previous year influenced flowering over the 25-year period. Flowering culm production averaged 9\% and 7\% of total graminoid aboveground net primary production (ANPP) in the uplands and lowlands, respectively. Interannual variation in ANPP correlated only with Sorghastrum flowering, suggesting a predominant role of the species in ANPP responses to climate.

}, keywords = {LTER-KNZ}, doi = {10.1890/09-1242.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/09-1242.1}, author = {Craine, J.M. and Towne, E.G. and Jesse B. Nippert} } @article {KNZ001347, title = {Inter-regional comparison of land-use effects on stream metabolism}, journal = {Freshwater Biology}, volume = {55}, year = {2010}, pages = {1874 -1890}, abstract = {1. Rates of whole-system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first-order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban-influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike{\textquoteright}s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land-use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land-use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land-use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land-use categories showed reduced inter-regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2427.2010.02422.x}, author = {Bernot, M.J. and Sobota, D.J. and Hall, R.O. and Mulholland, P.J. and W. K. Dodds and Webster, J.R. and Tank, J.L. and L.R. Ashkenas and Cooper, L.W. and Dahm, C.N. and Gregory, S.V. and Grimm, N.B. and Hamilton, S.K. and Johnson, S.L. and W.H. McDowell and Meyer, J.L. and Peterson, B. and Poole, G.C. and Valett, H.M. and Arango, C.P. and Beaulieu, J.J. and Burgin, A.J. and Crenshaw, C. and Helton, A.M. and Johnson, L. and Merriam, J. and Niederlehner, B.R. and O{\textquoteright}Brien, J.M. and Potter, J.D. and Sheibley, R.W. and Thomas, S.M. and Wilson, K.} } @mastersthesis {KNZ001342, title = {Morphological and physiological traits as indicators of drought tolerance in tallgrass prairie plants}, volume = {MS Thesis}, year = {2010}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, abstract = {

The Konza Prairie in northern Kansas, USA contains over 550 vascular plant species; of which, few have been closely studied. These species are adapted to environmental stress as imposed by variable temperature, precipitation, fire, and grazing. Understanding which plant traits relate to drought responses will allow us to both predict drought tolerance and potential future shifts in plant community composition from changes in local climate. Morphological and physiological measurements were taken on 121 species of herbaceous tallgrass prairie plants grown from seed in a growth chamber. Gas exchange measurements including maximum photosynthetic rate, stomatal conductance to water vapor, and intercellular CO[subscript]2 concentration were measured. All plants were exposed to a drought treatment and were monitored daily until stomatal conductance was zero. At this point, critical leaf water potential (Ψ[subscript]crit), an indicator of physiological drought tolerance was assessed. Other measurements include root length, diameter, volume, and mass, leaf area, leaf tissue density, root tissue density, and root to shoot ratio. Traits were compared using pair-wise bivariate analysis and principal component analysis (PCA). A dichotomy was found between dry-adapted plants with thin, dense leaves and roots, high leaf angle, and highly negative Ψ[subscript]crit and hydrophiles which have the opposite profile. A second axis offers more separation based on high photosynthetic rate, high conductance rate, and leaf angle, but fails to provide a distinction between C[subscript]3 and C[subscript]4 species. When tested independently, grasses and forbs both showed drought tolerance strategies similar to the primary analysis. Matching up these axes with long term abundance data suggests that species with drought tolerance traits have increased abundance on Konza, especially in upland habitats. However, traits that relate to drought tolerance mirror relationships with nutrient stress, confounding separation of low water versus low nutrient strategies. My results not only illustrate the utility of morphological and physiological plant traits in classifying drought responses across a range of species, but as functional traits in predicting both drought tolerance in individual species and relative abundance across environmental gradients of water availability.

}, keywords = {LTER-KNZ, Abundance; Konza, Drought Tolerance, Plant traits, tallgrass prairie}, url = {http://krex.k-state.edu/dspace/handle/2097/4628}, author = {Tucker, S.} } @article {KNZ001418, title = {Shifting fungal endophyte communities colonize Bouteloua gracilis: effect of host tissue and geographical distribution}, journal = {Mycologia}, volume = {102}, year = {2010}, pages = {1012 -1026}, abstract = {

Communities of root-associated fungi (RAF) commonly have been studied under the auspices of arbuscular mycorrhizal fungi (AMF) or ectomycorrhizal fungi. However many studies now indicate that other groups of endophytic RAF, including dark septate endophytes (DSE) are more abundant in some plants and environments. The common forage grass, Bouteloua gracilis, was used as a model to examine whether RAF also colonize different organs within the same plant and to compare RAF communities from sites across North America, spanning the latitudinal range of B. gracilis (from Canada to Mexico). We compared the RAF communities of organs within individual plants at one site and within plant roots among six sites. With the possible exception of one group related to genus Paraphaeosphaeria there was little evidence that RAF colonized vertically beyond the crowns. Furthermore, although there was some variation in the constitution of rare members of the RAF communities, several taxonomically related groups dominated the RAF community at all sites. These dominant taxa included members in the Pleosporales (related to the DSE, Paraphaeosphaeria spp.), Agaricales (related to Moniliophthora spp., or Campanella spp.) and Hypocreales (related to Fusarium spp.). AMF were notable by their near absence. Similar phylotypes from the dominant groups clustered around adjacent sites so that similarity of the RAF communities was negatively correlated to site inter-distance and the RAF communities appeared to group by country. These results increase the possibility that at least some of these common and widely distributed core members of the RAF community form important, intimate and long lasting relationships with grasses.

}, keywords = {LTER-KNZ, Bouteloua gracilis, dark septate endophytes, endophytic fungi, grassland fungi, Grasslands National Park, Janos, Konza Prairie, Llanos de Ojuelos, Sevilleta, Wind Cave National Park}, doi = {10.3852/09-264}, url = {https://www.tandfonline.com/doi/abs/10.3852/09-264?journalCode=umyc20}, author = {Herrera, J. and Khidir, H.H. and Eudy, D.M. and Porras-Alfaro, A. and Natvig, D.O. and Sinsabaugh, R.L.} } @article {KNZ001293, title = {Variation in gene expression of Andropogon gerardii in response to altered environmental conditions associated with climate change}, journal = {Journal of Ecology}, volume = {98}, year = {2010}, pages = {374 -383}, abstract = {

1.\ If we are to understand the mechanisms underlying species responses to climate change in natural systems, studies are needed that focus on responses of non-model species under field conditions. We measured transcriptional profiles of individuals of Andropogon gerardii, a C4 grass native to North American grasslands, in a field experiment in which both temperature and precipitation were manipulated to simulate key aspects of forecasted climate change. 2.\ By using microarrays developed for a closely related model species, Zea mays, we were able to compare the relative influence of warming versus altered soil moisture availability on expression levels of over 7000 genes, identify responsive functional groups of genes and correlate changes in gene transcription with physiological responses. 3.\ We observed more statistically significant shifts in transcription levels of genes in response to thermal stress than in response to water stress. We also identified candidate genes that demonstrated transcription levels closely associated with physiological variables, in particular chlorophyll fluorescence. 4.Synthesis. These results suggest that an ecologically important species responds differently to different environmental aspects of forecast climate change. These translational changes have the potential to influence phenotypic characters and ultimately adaptive responses.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2745.2009.01618.x}, url = {https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2745.2009.01618.x}, author = {Travers, S.E. and Tang, Z. and Caragea, D. and Garrett, K.A. and Hulbert, S.H. and Leach, J.E. and Bai, J. and Saleh, A. and Alan K. Knapp and Fay, P.A. and Jesse B. Nippert and Schnable, P.S. and M.D. Smith} } @inbook {KNZ001204, title = {Approaches to predicting broad-scale regime shifts using changing pattern-process relationships across scales}, booktitle = {Real World Ecology: Design and Analyses of Large-Scale and Long-Term Research}, year = {2009}, publisher = {Springer-Verlag, NY}, organization = {Springer-Verlag, NY}, abstract = {Understanding and predicting the occurrence of alternative ecosystem states (i.e., regime shifts) at broad scales is a pressing challenge for ecologists given the scope and nature of global change. In many cases, regime shifts at broad-scales are affected by pattern-process relationships across a range of finer scales. However, experimental and analytical methods to examine state changes, such as from perennial grasslands to woodlands, have not been fully developed. We first define and describe the expansion of woody plants into perennial grasslands. Woody plant encroachment has well-documented consequences for local, regional, and global ecology, and takes several forms, from shrub invasion in arid/semiarid grasslands and arctic ecosystems to tree invasion in mesic and alpine grasslands. We then outline a multi-scale experimental approach to examining the key processes influencing woody plant encroachment from fine to broad scales, and describe the application of this approach to the Jornada Basin Agricultural Research Service-Long Term Ecological Research site as a case study. Several questions can be addressed with this approach, such as: how and under what conditions do dynamics and decisions made at fine scales influence dynamics at broader scales? How and under what conditions do broad-scale dynamics overwhelm fine-scale processes to influence landscape patterns? Finally, we discuss analytical techniques for predicting regime shifts and their associated thresholds.}, keywords = {LTER-KNZ, broad-scale regime, pattern-process}, url = {http://www.springer.com/us/book/9780387779416}, author = {Peters, D.P.C. and B.T. Bestelmeyer and Alan K. Knapp and Herrick, J.E. and Monger, H.C. and Havstad, K.M.}, editor = {Miao, S. and Carstenn, S. and Nungesser, M.} } @article {KNZ001238, title = {Ecophysiological responses of two dominant grasses to altered temperature and precipitation regimes}, journal = {Acta Oecologia}, volume = {35}, year = {2009}, pages = {400 -408}, abstract = {

Ecosystem responses to climate change will largely be driven by responses of the dominant species. However, if co-dominant species have traits that lead them to differential responses, then predicting how ecosystem structure and function will be altered is more challenging. We assessed differences in response to climate change factors for the two dominant C4 grass species in tallgrass prairie, Andropogon gerardii and Sorghastrum nutans, by measuring changes in a suite of plant ecophysiological traits in response to experimentally elevated air temperatures and increased precipitation variability over two growing seasons. Maximum photosynthetic rates, stomatal conductance, water-use efficiency, chlorophyll fluorescence, and leaf water potential varied with leaf and canopy temperature as well as with volumetric soil water content (0\–15 cm). Both species had similar responses to imposed changes in temperature and water availability, but when differences occurred, responses by A. gerardii were more closely linked with changes in air temperature whereas S. nutans was more sensitive to changes in water availability. Moreover, S. nutans was more responsive overall than A. gerardii to climate alterations. These results indicate both grass species are responsive to forecast changes in temperature and precipitation, but their differential sensitivity to temperature and water availability suggest that future population and community structure may vary based on the magnitude and scope of an altered climate.

}, keywords = {LTER-KNZ, Andropogon gerardii, Climate variability, Leaf gas exchange, RaMPs, Sensitivity, Sorghastrum nutans}, doi = {10.1016/j.actao.2009.01.010}, url = {https://www.sciencedirect.com/science/article/pii/S1146609X09000204?via\%3Dihub}, author = {Jesse B. Nippert and Fay, P.A. and Carlisle, J.D. and Alan K. Knapp and M.D. Smith} } @article {KNZ001251, title = {Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification}, journal = {Limnology and Oceanography}, volume = {54}, year = {2009}, pages = {666 -680}, abstract = {

We measured denitrification rates using a field 15NO3\− tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (SWdenn) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO3\− removal from water due to denitrification ranged from 0.5\% to 100\% among streams (median of 16\%), and was related to NH4+ concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling SWden were specific discharge (discharge / width) and NO3\− concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO3\− concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO3\− concentration, the efficiency of NO3\− removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO3\− load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO3\− concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO3\− concentration.

}, keywords = {LTER-KNZ}, doi = {10.4319/lo.2009.54.3.0666}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.4319/lo.2009.54.3.0666}, author = {Mulholland, P.J. and Hall, R.O. and Sobota, D.J. and W. K. Dodds and Findlay, S.E.G. and Grimm, N.B. and Hamilton, S.K. and W.H. McDowell and O{\textquoteright}Brien, J.M. and Tank, J.L. and L.R. Ashkenas and Cooper, L.W. and Dahm, C.N. and Gregory, S.V. and Johnson, S.L. and Meyer, J.L. and Peterson, B.J. and Poole, G.C. and Valett, H.M. and Webster, J.R. and Arango, C.P. and Beaulieu, J.J. and Bernot, M.J. and Burgin, A.J. and Crenshaw, C.L. and Helton, A.M. and Johnson, L.T. and Niederlehner, B.R. and Potter, J.D. and Sheibley, R.W. and Thomas, S.M.} } @article {KNZ001250, title = {Nitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake}, journal = {Limnology and Oceanography}, volume = {54}, year = {2009}, pages = {653 -665}, abstract = {

We measured uptake length of 15NO3\− in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO3\− uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban-urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO3\− concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO3\− uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79\% of the variation in log uptake length (SWtot). Uptake length increased with specific discharge (Q/w) and increasing NO3\− concentrations, showing a loss in removal efficiency in streams with high NO3\− concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO3\− removal. The fraction of catchment area as agriculture and suburban-urban land use weakly predicted NO3\− uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO3\− uptake lengths via directly increasing both gross primary production and NO3\− concentration. Gross primary production shortened SWtot, while increasing NO3\− lengthened SWtot resulting in no net effect of land use on NO3\− removal.

}, keywords = {LTER-KNZ}, doi = {10.4319/lo.2009.54.3.0653}, url = {https://aslopubs.onlinelibrary.wiley.com/doi/abs/10.4319/lo.2009.54.3.0653}, author = {Hall, R.O. Jr. and Tank, J.L. and Sobota, D.J. and Mulholland, P.J. and O{\textquoteright}Brien, J.M. and W. K. Dodds and Webster, J.R. and Valett, H.M. and Poole, G.C. and Peterson, B.J. and Meyer, J.L. and W.H. McDowell and Johnson, S.L. and Hamilton, S.K. and Grimm, N.B. and Gregory, S.V. and Dahm, C.N. and Cooper, L.W. and L.R. Ashkenas and Thomas, S.M. and Sheibley, R.W. and Potter, J.D. and Niederlehner, B.R. and Johnson, L.T. and Helton, A.M. and Crenshaw, C.M. and Burgin, A.J. and Bernot, M.J. and Beaulieu, J.J. and Arango, C.P.} } @inbook {KNZ001257, title = {Plant pathogens as indicators of climate change}, booktitle = {Climate and Global Change: Observed Impacts on Planet Earth}, year = {2009}, pages = {425 -437}, publisher = {Elsevier}, organization = {Elsevier}, keywords = {LTER-KNZ}, url = {http://pdf.usaid.gov/pdf_docs/PNADU515.pdf}, author = {Garrett, K.A. and Nita, M. and De Wolf, E.D. and Gomez, L. and Sparks, A.H.}, editor = {Letcher, T.} } @inbook {KNZ001113, title = {Biogeochemical changes associated with Juniperus virginia encroachment into grasslands}, booktitle = {Ecological Studies Vol. 196, Western North American Juniperus communities: A dynamic vegetation type}, year = {2008}, pages = {170 -187}, publisher = {Springer-Verlag, NY}, organization = {Springer-Verlag, NY}, keywords = {LTER-KNZ}, author = {McKinley, D.C. and Norris, M.D. and Johnson, L.C. and John M. Blair}, editor = {Van Auken, O.W.} } @article {KNZ001174, title = {Changes in grassland ecosystem function due to extreme rainfall events: implications for responses to climate change}, journal = {Global Change Biology}, volume = {14}, year = {2008}, pages = {1600 -1608}, abstract = {

Climate change is causing measurable changes in rainfall patterns, and will likely cause increases in extreme rainfall events, with uncertain implications for key processes in ecosystem function and carbon cycling. We examined how variation in rainfall total quantity (Q), the interval between rainfall events (I), and individual event size (SE) affected soil water content (SWC) and three aspects of ecosystem function: leaf photosynthetic carbon gain (inline image), aboveground net primary productivity (ANPP), and soil respiration (inline image). We utilized rainout shelter-covered mesocosms (2.6 m3) containing assemblages of tallgrass prairie grasses and forbs. These were hand watered with 16 I\×Q treatment combinations, using event sizes from 4 to 53 mm. Increasing Q by 250\% (400\–1000 mm yr\−1) increased mean soil moisture and all three processes as expected, but only by 20\–55\% (P\≤0.004), suggesting diminishing returns in ecosystem function as Q increased. Increasing I (from 3 to 15 days between rainfall inputs) caused both positive (inline image) and negative (inline image) changes in ecosystem processes (20\–70\%, P\≤0.01), within and across levels of Q, indicating that I strongly influenced the effects of Q, and shifted the system towards increased net carbon uptake. Variation in SE at shorter I produced greater response in soil moisture and ecosystem processes than did variation in SE at longer I, suggesting greater stability in ecosystem function at longer I and a priming effect at shorter I. Significant differences in ANPP and inline image between treatments differing in I and Q but sharing the same SE showed that the prevailing pattern of rainfall influenced the responses to a given event size. Grassland ecosystem responses to extreme rainfall patterns expected with climate change are, therefore, likely to be variable, depending on how I, Q, and SE combine, but will likely result in changes in ecosystem carbon cycling.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2486.2008.01605.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01605.x}, author = {Fay, P.A. and Kaufman, D.M. and Jesse B. Nippert and Carlisle, J.D. and Harper, C.W.} } @article {KNZ001184, title = {Modeled interactive effects of precipitation, temperature, and CO2 on ecosystem carbon and water dynamics in different climatic zones}, journal = {Global Change Biology}, volume = {14}, year = {2008}, pages = {1986 -1999}, abstract = {

Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive effects of climate warming (T), altered precipitation amounts [doubled (DP) and halved (HP)] and seasonality (SP, moving precipitation in July and August to January and February to create summer drought), and elevated [CO2] (C) on net primary production (NPP), heterotrophic respiration (Rh), net ecosystem production (NEP), transpiration, and runoff. We examined those responses in seven ecosystems, including forests, grasslands, and heathlands in different climate zones. The modeling analysis showed that none of the three-way interactions among T, C, and altered precipitation was substantial for either carbon or water processes, nor consistent among the seven ecosystems. However, two-way interactive effects on NPP, Rh, and NEP were generally positive (i.e. amplification of one factor\&$\#$39;s effect by the other factor) between T and C or between T and DP. A negative interaction (i.e. depression of one factor\&$\#$39;s effect by the other factor) occurred for simulated NPP between T and HP. The interactive effects on runoff were positive between T and HP. Four pairs of two-way interactive effects on plant transpiration were positive and two pairs negative. In addition, wet sites generally had smaller relative changes in NPP, Rh, runoff, and transpiration but larger absolute changes in NEP than dry sites in response to the treatments. The modeling results suggest new hypotheses to be tested in multifactor global change experiments. Likewise, more experimental evidence is needed for the further improvement of ecosystem models in order to adequately simulate complex interactive processes.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2486.2008.01629.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01629.x}, author = {Luo, Y. and Gerten, D. and Le Maire, G. and Parton, W.J. and Weng, E. and Zhou, X. and Keough, C. and Beier, C. and Ciais, P. and Cramer, W. and Dukes, J.S. and Emmett, B. and Hanson, P.J. and Alan K. Knapp and Linder, S. and Nepstad, D. and Rustad, L.} } @article {KNZ001183, title = {Modelled effects of precipitation on ecosystem carbon and water dynamics in different climatic zones}, journal = {Global Change Biology}, volume = {14}, year = {2008}, pages = {1 -15}, abstract = {

The ongoing changes in the global climate expose the world\&$\#$39;s ecosystems not only to increasing CO2 concentrations and temperatures but also to altered precipitation (P) regimes. Using four well-established process-based ecosystem models (LPJ, DayCent, ORCHIDEE, TECO), we explored effects of potential P changes on water limitation and net primary production (NPP) in seven terrestrial ecosystems with distinctive vegetation types in different hydroclimatic zones. We found that NPP responses to P changes differed not only among sites but also within a year at a given site. The magnitudes of NPP change were basically determined by the degree of ecosystem water limitation, which was quantified here using the ratio between atmospheric transpirational demand and soil water supply. Humid sites and/or periods were least responsive to any change in P as compared with moderately humid or dry sites/periods. We also found that NPP responded more strongly to doubling or halving of P amount and a seasonal shift in P occurrence than that to altered P frequency and intensity at constant annual amounts. The findings were highly robust across the four models especially in terms of the direction of changes and largely consistent with earlier P manipulation experiments and modelling results. Overall, this study underscores the widespread importance of P as a driver of change in ecosystems, although the ultimate response of a particular site will depend on the detailed nature and seasonal timing of P change.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2486.2008.01651.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2008.01651.x}, author = {Gerten, D. and Luo, Y. and Le Maire, G. and Parton, W.J. and Keough, C. and Weng, E. and Beier, C. and Ciais, P. and Cramer, W. and Dukes, J.S. and Emmett, B. and Hanson, P.J. and Alan K. Knapp and Linder, S. and Nepstad, D. and Rustad, L. and Sowerby, A.} } @article {KNZ001177, title = {Phenotypic correlates and survival consequences of male mating success in lek-mating Greater Prairie-chickens (Tympanuchus cupido)}, journal = {Behavioral Ecology and Sociobiology}, volume = {62}, year = {2008}, pages = {1377 -1388}, abstract = {

Female choice and male\–male aggression are two modes of sexual selection that can lead to elaboration of male morphological and behavioral traits. In lek-mating species, male mating success is often strongly skewed, and it is puzzling why variation in male traits is still observed given directional female choice. If male traits correlated with reproductive success are honest signals of male quality, there may be survival costs associated with the expression of those traits. In this study, we examined whether morphological, behavioral, and territorial traits are correlated with male mating success and survival in the lek-mating greater prairie-chicken (Tympanuchus cupido). We introduce a novel application of multinomial discrete choice models for analysis of female mate choice behavior. We found that behavioral and territorial attributes showed 6.5 times more variability among males than morphological traits. Both display and aggressive behaviors were strong predictors of male mating success, suggesting that both female choice and male\–male aggression were important in determining mating success among male greater prairie-chickens. Moreover, annual survival of male prairie-chickens was independent of mating success and male traits. Females appear to be choosing males based on behavioral traits where large variation exists between males (coefficient of variation \>30\%). Behavioral traits were the most important factor in determining mating success of male prairie-chickens, but the mechanism underlying this relationship is unknown. In the future, experimental manipulations of male hormones or parasite loads could bridge the proximate mechanisms and ultimate consequences of factors mediating male mating success in lek-mating grouse.

}, keywords = {LTER-KNZ, Galliformes, Life history trade-off, mate choice, reproduction, Sexual selection}, doi = {10.1007/s00265-008-0566-8}, url = {https://link.springer.com/article/10.1007\%2Fs00265-008-0566-8}, author = {Nooker, J.K. and Sandercock, B.K.} } @article {KNZ001164, title = {Stream denitrification across biomes and its response to anthropogenic nitrate loading}, journal = {Nature}, volume = {452}, year = {2008}, pages = {202 -207}, abstract = {

Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing1, 2 and terrestrial ecosystems are becoming increasingly nitrogen-saturated3, causing more bioavailable nitrogen to enter groundwater and surface waters4, 5, 6. Large-scale nitrogen budgets show that an average of about 20\–25 per cent of the nitrogen added to the biosphere is exported from rivers to the ocean or inland basins7, 8, indicating that substantial sinks for nitrogen must exist in the landscape9. Streams and rivers may themselves be important sinks for bioavailable nitrogen owing to their hydrological connections with terrestrial systems, high rates of biological activity, and streambed sediment environments that favour microbial denitrification6, 10, 11. Here we present data from nitrogen stable isotope tracer experiments across 72 streams and 8 regions representing several biomes. We show that total biotic uptake and denitrification of nitrate increase with stream nitrate concentration, but that the efficiency of biotic uptake and denitrification declines as concentration increases, reducing the proportion of in-stream nitrate that is removed from transport. Our data suggest that the total uptake of nitrate is related to ecosystem photosynthesis and that denitrification is related to ecosystem respiration. In addition, we use a stream network model to demonstrate that excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate that is exported to receiving waters and reduces the relative role of small versus large streams as nitrate sinks.

}, keywords = {LTER-KNZ}, doi = {10.1038/nature06686}, url = {https://www.nature.com/articles/nature06686}, author = {Mulholland, P.J. and Helton, A.M. and Poole, G.C. and Hall, R.O. Jr. and Hamilton, S.K. and Peterson, B.J. and Tank, J.L. and L.R. Ashkenas and Cooper, L.W. and Dahm, C.N. and W. K. Dodds and Findlay, S.E.G. and Gregory, S.V. and Grimm, N.B. and Johnson, S.L. and W.H. McDowell and Meyer, J.L. and Valett, H.M. and Webster, J.R. and Arango, C.P. and Beaulieu, J.J. and Bernot, M.J. and Burgin, A.J. and Crenshaw, C. and Johnson, L. and Niederlehner, B.R. and O{\textquoteright}Brien, J.M. and Potter, J.D. and Sheibley, R.W. and Sobota, D.J. and Thomas, S.M.} } @phdthesis {KNZ001214, title = {Systematics and reproductive biology of Morus L. (Moraceae)}, volume = {PhD Dissertation}, year = {2008}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, abstract = {

Morus L. (Moraceae) is a temperate and subtropical genus of ten to 15 species distributed in Asia, Africa, Europe, North, Central and South America. Despite its broad distribution and economic importance, it has received little attention from systematic botanists. Two species of this genus, the native M. rubra and the exotic M. alba, co-occur in eastern North America including the Flint Hills region of the Central Plains. In my dissertation research, I have conducted both species level and population level studies to obtain insights into the diversification of Morus. At the species level, my objectives were to re-evaluate the taxonomy and reconstruct the phylogeny of Morus. Based on herbarium and literature study as well as some field study, I recognize 13 species: eight species occurring in Asia, one in Africa and four in the New World. I used sequence data from the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA and the trnL-trnF region of the chloroplast DNA to reconstruct the evolutionary history of Morus. The phylogenies were congruent and indicate a) a monophyletic core group of Morus with two well-supported geographical clades (one containing Asian taxa and one of New World taxa); and b) that Morus, as currently circumscribed, is non-monophyletic. At the population level, I studied sex expression pattern variation between the Morus native-exotic pair in the Flint Hills region, and assessed hybridization between these species at Konza Prairie Biological Station (KPBS). Both species are subdioecious, and Flint Hills populations exhibit significantly male-biased sex ratios, with sex expression being size independent. Approximately 10\% of individuals of each species changed sex annually. In the population study at KPBS, I applied randomly amplified polymorphic DNA (RAPD) markers and microsatellites. The Morus species were moderately ([Theta]II = 0.079; RAPD data) to highly differentiated genetically (F[subscript]ST = 0.233; microsatellite data). Analysis of genetic structure suggested interspecific gene flow and indicated the presence of later generation hybrids. The presence of the exotic congener may affect the existence and genetic integrity of the native species. Overall, these studies contribute to our understanding of diversity in this interesting plant study system.

}, keywords = {LTER-KNZ, Interspecific hybridization, Microsatellites, Moraceae, Morus taxonomy, phylogeny, subdioecy}, url = {http://hdl.handle.net/2097/937}, author = {Nepal, M.P.} } @article {KNZ001095, title = {Altered ecosystem nitrogen dynamics as a consequence of land cover change in tallgrass prairie}, journal = {American Midland Naturalist}, volume = {158}, year = {2007}, pages = {432 -445}, abstract = {In recent decades, substantial areas of North American tallgrass prairie have been lost to the establishment and expansion of woodlands and forests, including those dominated by eastern redcedar (Juniperus virginiana). This shift in dominant plant life form, from C4 grasses to coniferous trees, may be accompanied by changes in productivity, standing stocks of biomass and nutrients and biogeochemical cycles. The goal of this study was to quantify and compare major pools and fluxes of nitrogen in recently established (<= 80 y) redcedar forests and adjacent native grasslands. Three former grassland sites in the Flint Hills region of Kansas that developed closed-canopy redcedar forests in the recent past were paired with adjacent grassland sites on similar soil type and topographic position (n  =  3 sites/land cover type), and selected soil and plant nitrogen pools and fluxes were measured in replicate plots (n  =  6/site) along transects in each forest or grassland site over a 20-mo period. We found few significant differences in median soil inorganic N pools or net N mineralization rates between the forest and grassland sites, though there was a trend for greater concentrations of inorganic N in grassland sites on most sample dates, and cumulative growing season net N mineralization averaged 15\% less in forest sites (14.3 kg N{\textperiodcentered}ha-1{\textperiodcentered}yr-1) than in grassland sites (16.9 kg N{\textperiodcentered}ha-1{\textperiodcentered}yr-1). Mean aboveground plant productivity of forest sites (9162 kg ha-1 yr-1) was about 2.5{\texttimes} greater than that of comparable grasslands (similar soils and topographic position), in spite of similar levels of soil N availability. This resulted in an ecosystem-level nitrogen use efficiency (ANPP:litterfall N) in forests that was more than double that of the grasslands they replaced. Additional changes in N cycling associated with redcedar forest development included large accumulations of N in aboveground biomass and transfer to the forest floor via litterfall; redcedar aboveground biomass contained 617 kg N/ha, forest floor litter N was 253 kg N/ha, and litterfall N flux was 41 kg ha-1{\textperiodcentered}yr-1. These are substantial increases in aboveground biomass N accumulation, surface litter N inputs, and surface litter N accumulation compared to the native grasslands characteristic of this region. These fundamental shifts in ecosystem patterns and processes have the potential to alter regional biogeochemistry and both nitrogen and carbon storage throughout areas of the eastern Central Plains where coverage of redcedars is increasing.}, keywords = {LTER-KNZ}, doi = {10.1674/0003-0031(2007)158[432:AENDAA]2.0.CO;2}, author = {Norris, M.D. and John M. Blair and Johnson, L.C.} } @article {KNZ001090, title = {Compensatory dynamics are rare in naturalecological communities}, journal = {Proceedings of the National Academy of Sciences}, volume = {104}, year = {2007}, pages = {3273 -3277}, abstract = {In population ecology, there has been a fundamental controversy about the relative importance of competition-driven (density-dependent) population regulation vs. abiotic influences such as temperature and precipitation. The same issue arises at the community level; are population sizes driven primarily by changes in the abundances of cooccurring competitors (i.e., compensatory dynamics), or do most species have a common response to environmental factors? Competitive interactions have had a central place in ecological theory, dating back to Gleason, Volterra, Hutchison and MacArthur, and, more recently, Hubbell{\textquoteright}s influential unified neutral theory of biodiversity and biogeography. If competitive interactions are important in driving year-to-year fluctuations in abundance, then changes in the abundance of one species should generally be accompanied by compensatory changes in the abundances of others. Thus, one necessary consequence of strong compensatory forces is that, on average, species within communities will covary negatively. Here we use measures of community covariance to assess the prevalence of negative covariance in 41 natural communities comprising different taxa at a range of spatial scales. We found that species in natural communities tended to covary positively rather than negatively, the opposite of what would be expected if compensatory dynamics were important. These findings suggest that abiotic factors such as temperature and precipitation are more important than competitive interactions in driving year-to-year fluctuations in species abundance within communities.}, keywords = {LTER-KNZ, biological interactions, Community dynamics, negative covariance, neutral models, zero-sum}, doi = {10.1073/pnas.0603798104}, author = {Houlahan, J.E. and Currie, D.J. and Cottenie, K. and Cumming, G.S. and Ernest, S.K.M. and Findlay, C.S. and Fuhlendorf, S.D. and Gaedke, U. and Legendre, P. and Magnuson, J.J. and McArdle, B.H. and Muldavin, E.H. and Noble, D. and Russell, R. and Stevens, R.D. and Willis, T.J. and Woiwod, I.P. and Wondzell, S.M.} } @mastersthesis {KNZ001343, title = {Effects of grazing on growth and morphology of rhizomatous and caespitose grasses in tallgrass prairie}, volume = {MS Thesis}, year = {2007}, pages = {1-65}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, abstract = {

Herbivory is one of the major biotic interactions shaping the structure and dynamics of grassland plant populations and community structure. The two major grass growth forms, rhizomatous and caespitose species, may show different grazing tolerance and short-term overcompensation may offset long-term reductions in plant performance and fitness. The objectives of this study were to assess 1) the effects of long-term ungulate grazing on plant architecture, population structure, and life history traits of the caespitose perennial grass, Schizachyrium scoparium (little bluestem), and the rhizomatous Bouteloua curtipendula (sideoats grama) in tallgrass prairie, and 2) the effects of grazing intensity (frequency of defoliation) on growth responses of little bluestem. Long-term bison grazing decreased the cover, frequency, tiller height, and proportion of tillers producing seed in little bluestem, but caused no changes in tiller density and total genet size. Grazed little bluestem plants maintained a significantly larger below ground bud bank. Bison grazing had no long-term effect on the abundance, bud bank densities, or rhizome growth of the rhizomatous side-oats grama grass. Biomass, tiller density, relative growth rates, and proportion of tillers flowering in little bluestem all decreased with increasing frequency of defoliation. However, even an intense grazing regime (9 defoliations over a 12 month period) caused no plant mortality and no changes in new tiller emergence rates, or bud bank densities. Increasing defoliation frequency did result in shifts in plant architecture, as an increasing proportion of extravaginal tillers led to a more lateral, decumbent growth form. These results show that the rhizomatous side-oats grama grass has a significantly higher grazing tolerance than does little bluestem, and/or that bison selectively graze little bluestem. Results from responses to the experimental defoliation regimes suggest that little bluestem shows lower tolerance to high frequency of defoliation, and its maintenance of a reserve below ground bud bank may be its primary tolerance mechanism, allowing tiller populations to recover following severe defoliation.

}, keywords = {LTER-KNZ, caespitose, Grazing, growth, morphology, rhizomatous, tallgrass}, url = {http://hdl.handle.net/2097/398 }, author = {N{\textquoteright}Guessan, M.} } @phdthesis {KNZ001111, title = {Factors affecting reproductive success in a lek-matingbird: the Greater Prairie-chicken}, volume = {PhD Dissertation}, year = {2007}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, abstract = {

Sexual selection via female choice and male-male aggression leads to elaboration of male traits. If male traits correlated with reproductive success are honest signals of male quality, survival costs may be associated with the expression of those traits. Testosterone (hereafter \‘T\’) may enhance male breeding success, but T can also reduce immunocompetence and survival. Socially monogamous male birds with higher circulating T experience reproductive advantages, but the role of T in lek mating systems is largely unknown. To address these issues, I individually marked and conducted focal behavioral observations of greater prairie-chickens (Tympanuchus cupido) at five lek sites over a 5-year period. Females were fitted with radio-telemetry to monitor nesting success and survival. I examined the relationship between male traits and mating success using multinomial discrete choice models, a statistical method not previously applied to studies of sexual selection. Male mating success was highly skewed at greater prairie-chicken leks with 18.5\% of males obtaining 87.2\% of all successful copulations (n = 108 males; 85 copulations). Mating success was influenced most by male behavior, followed by several morphological attributes. The role of T was quantified using blood samples and by experimentally implanting a subset of males with T. T did not consistently affect mating success. Non-territorial males had lower T levels than territorial males. Among territory holders, T was unexpectedly negatively correlated with mating success. However, the odds of receiving a copulation were 4.3 times (0.42 to 45.3) greater for T-implanted males than males with sham implants. Future work should explore the interactions among the immune system, parasite load, and mating success of prairie-chickens. Annual survival of male prairie-chickens was not related to mating success, behavior, age or T level, suggesting there is no cost of increased male mating success. Like males, reproductive success of females was also highly skewed because \< 10\% of nests successfully hatched young. Comparisons of seasonal and annual survival rates indicate that females experience increased mortality during the breeding season relative to the nonbreeding season. Synthesis of field estimates of demographic parameters indicates prairie-chicken populations will decline without changes in rangeland management to reduce predator numbers or provide more nesting cover.

}, keywords = {LTER-KNZ, Female mate choice, Grouse, Nest success, Reproductive success, Sexual selection, survival, Testosterone}, url = {http://hdl.handle.net/2097/375}, author = {Nooker, J.K.} } @article {KNZ001120, title = {Linking water uptake with rooting patterns in grassland species}, journal = {Oecologia}, volume = {153}, year = {2007}, pages = {261 -272}, abstract = {Water availability strongly governs grassland primary productivity, yet this resource varies dramatically in time (seasonally) and space (with soil depth and topography). It has long been assumed that co-occurring species differ in their partitioning of water use by depth, but direct evidence is lacking. We report data from two growing seasons (2004{\textendash}2005) in which we measured the isotopic signature of plant xylem water from seven species (including C3 forbs and shrubs and C4 grasses) growing along a topographic gradient at the Konza Prairie Biological Station. Plant xylem stable oxygen isotope ratio (δ18O) values were compared to soil water δ18O profiles, recent rainfall events, and groundwater. Species varied in both their temporal patterns of water use and their responses to seasonal droughts in both years. During wet periods, species differences in water use were minimal, with common dependency on recent rainfall events stored in the upper soil layers. However, during dry periods, most C3 species used proportionally more water from deeper portions of the soil profile relative to the C4 grasses. Plants in uplands used more shallow soil water compared to those in lowlands, with the greatest differences across the topographic gradient occurring during dry periods. While the documented vertical root distribution varies by species and growth form in this grassland, each of the species we measured appeared to compete for the same surface layer soil moisture when water was not limiting. Thus, our results suggest that variation in precipitation history and landscape positions are greater determinants of water-use patterns than would be expected based on absolute rooting depth.}, keywords = {LTER-KNZ, C3 plants, C4 plants, Mixing model, Stable oxygen isotope ratio, tallgrass prairie}, doi = {10.1007/s00442-007-0745-8}, author = {Jesse B. Nippert and Alan K. Knapp} } @article {KNZ001119, title = {Photosynthetic traits in C3 and C4 grassland species in mesocosm and field environments}, journal = {Environmental and Experimental Botany}, volume = {60}, year = {2007}, pages = {412 -420}, abstract = {The North American tallgrass prairie is composed of a diverse mix of C3 and C4 plant species that are subject to multiple resource limitations. C4 grasses dominate this ecosystem, purportedly due to greater photosynthetic capacity and resource-use efficiency associated with C4 photosynthesis. We tested the hypothesis that intrinsic physiological differences between C3 and C4 species are consistent with C4 grass dominance by comparing leaf gas exchange and chlorophyll fluorescence variables for seven C4 and C3 herbaceous species (legumes and non-legumes) in two different settings: experimental mesocosms and natural grassland sites. In the mesocosms, C4 grasses had higher photosynthetic rates, water potentials and water-use efficiency than the C3 species. These differences were absent in the field, where photosynthetic rates declined similarly among non-leguminous species. Thus, intrinsic photosynthetic advantages for C4 species measured in resource-rich mesocosms could not explain the dominance of C4 species in the field. Instead, C4 dominance in this ecosystem may depend more on the ability of the grasses to grow rapidly when resources are plentiful and to tolerate multiple limitations when resources are scarce.}, keywords = {LTER-KNZ, A:Ci curves, C3, C4, Chlorophyll fluorescence, gas exchange, Konza, tallgrass prairie}, doi = {10.1016/j.envexpbot.2006.12.012}, author = {Jesse B. Nippert and Fay, P.A. and Alan K. Knapp} } @article {KNZ001118, title = {Soil water partitioning contributes to species coexistence in tallgrass prairie}, journal = {Oikos}, volume = {116}, year = {2007}, pages = {1017 -1029}, abstract = {The majority of tallgrass prairie root biomass is located in the upper soil layers (0{\textendash}25 cm), but species differences exist in reliance on soil water at varying depths. These differences have led to the hypothesis that resource partitioning belowground facilitates species co-existence in this mesic grassland. To determine if plant water relations can be linked to soil water partitioning as a potential mechanism allowing C3 species to persist among the more dominant C4 grasses, we measured differences in the source of water-use using the isotopic signature of xylem water, volumetric soil water content at 4 depths, and leaf water potentials. Data were collected for seven species representing C4 grasses, C3 forbs and C3 shrubs over three growing seasons at the Konza Prairie (Kansas, USA) to encompass a range of natural climatic conditions. C4 grasses relied on shallow soil water (5 cm) across the growing season and had midday leaf water potentials that were highly correlated with shallow soil water regardless of soil water availability at other portions of the soil profile (20, 40 and 90 cm). In contrast, C3 species only used shallow soil water when plentiful at this depth; these species increased their dependence on soil water from greater depths as the upper soil layers dried. Structural equation models describing plant water relations were very similar for the three C4 species, whereas a unique set of models and drivers were identified for each of the C3 species. These results support soil water partitioning as a mechanism for species coexistence, as C4 species in this grassland have relatively consistent dependence on water in shallow soil layers, whereas C3 species show niche differentiation in water use strategies to avoid competition with C4 grasses for water in shallow soil layers when this resource is limiting and leaf water stress is high.}, keywords = {LTER-KNZ}, doi = {10.1111/j.0030-1299.2007.15630.x}, author = {Jesse B. Nippert and Alan K. Knapp} } @article {KNZ00993, title = {Intra-annual rainfallvariability and grassland productivity: can the past predictthe future}, journal = {Plant Ecology}, volume = {184}, year = {2006}, pages = {65 -74}, abstract = {Precipitation quantity has been shown to influence grassland aboveground net primary productivity (ANPP) positively whereas experimental increases in of temporal variability in water availability commonly exhibit a negative relationship with ANPP. We evaluated long term ANPP datasets from the Konza Prairie Long Term Ecological Research (LTER) program (1984{\textendash}1999) to determine if similar relationships could be identified based on patterns of natural variability (magnitude and timing) in precipitation. ANPP data were analyzed from annually burned sites in native mesic grassland and productivity was partitioned into graminoid (principally C4 grasses) and forb (C3 herbaceous) components. Although growing season precipitation amount was the best single predictor of total and grass ANPP (r 2=0.62), several measures of precipitation variability were also significantly and positively correlated with productivity, independent of precipitation amount. These included soil moisture variability, expressed as CV, for June (r 2=0.45) and the mean change in soil moisture between weekly sampling periods in June and August (\%wv) (r 2=0.27 and 0.32). In contrast, no significant relationships were found between forb productivity and any of the precipitation variables (p>0.05). A multiple regression model combining precipitation amount and both measures of soil moisture variability substantially increased the fit with productivity (r 2=0.82). These results were not entirely consistent with those of short-term manipulative experiments in the same grassland, however, because soil moisture variability was often positively, not negatively related to ANPP. Differences in results between long and short term experiments may be due to low variability in the historic precipitation record compared to that imposed experimentally as experimental levels of variability exceeded the natural variability of this dataset by a factor of two. Thus, forecasts of ecosystem responses to climate change (i.e. increased climatic variability), based on data constrained by natural and recent historical rainfall patterns may be inadequate for assessing climate change scenarios if precipitation variability in the future is expected to exceed current levels.}, keywords = {LTER-KNZ, ANPP, Climate change, grassland, Precipitation variability, soil moisture, tallgrass prairie}, doi = {10.1007/s11258-005-9052-9}, author = {Jesse B. Nippert and Alan K. Knapp and J. M. Briggs} } @phdthesis {KNZ001055, title = {Life by the drop: Water as a physiological driver of the tallgrass prairie plant community}, volume = {PhD Dissertation}, year = {2006}, pages = {1 -148}, school = {Colorado State University}, type = {Ph.D. Thesis}, address = {Fort Collins, CO}, keywords = {LTER-KNZ}, url = {https://search.proquest.com/docview/305354527/?pq-origsite=primo}, author = {Jesse B. Nippert} } @article {KNZ001026, title = {Redefining the community:a species-based approach}, journal = {Oikos}, volume = {112}, year = {2006}, pages = {464 -472}, abstract = {We propose that effective community size can be defined on the basis of the web of indirect interactions experienced on average by each individual species. Indirect interaction chains are composed of links provided by direct interactions. We analyzed previously published data on 20 assemblages of species. Chain strengths were estimated by the weakest link and by the product of link strength. The average strength of the interaction chain decreased with increasing numbers of links with both models. Positive indirect interactions in chains with an even number of links offset negative direct interactions. We set the community size by the chain length where 95\% of the indirect interactions are weaker than 10\% of the mean of the absolute value of direct interaction strength. Using the multiplicative model, seven assemblages had a community size (web of interaction length) of three links, one of four links, and the remainder of communities were too small to set community size. The analysis suggests that effective communities of size are rarely investigated in ecological experiments.}, keywords = {LTER-KNZ}, doi = {10.1111/j.0030-1299.2006.13558.x}, author = {W. K. Dodds and Nelson, J.A.} } @proceedings {KNZ00979, title = {Comparing the influence of precipitation, fire, and topography on plant productivity in the tallgrass prairie}, volume = {3}, year = {2005}, keywords = {LTER-KNZ}, url = {http://tiee.ecoed.net/vol/v3/issues/data_sets/konza/abstract.html}, author = {Jesse B. Nippert and John M. Blair} } @article {KNZ001062, title = {Introduced species in Kansas: floristic changes and patterns of collection based onan historical herbarium}, journal = {Sida}, volume = {21}, year = {2005}, pages = {1695 -1725}, keywords = {LTER-KNZ}, author = {Woods, T.M. and Strakosh, S.C. and Nepal, M.P. and Chakrabarti, S. and Simpson, N.B. and Mayfield, M.H. and Ferguson, C.J.} } @article {KNZ00893, title = {Regional patterns in carbon cycling across the Great Plains of North America}, journal = {Ecosystems}, volume = {8}, year = {2005}, pages = {106 -121}, abstract = {The large organic carbon (C) pools found in noncultivated grassland soils suggest that historically these ecosystems have had high rates of C sequestration. Changes in the soil C pool over time are a function of alterations in C input and output rates. Across the Great Plains and at individual sites through time, inputs of C (via aboveground production) are correlated with precipitation; however, regional trends in C outputs and the sensitivity of these C fluxes to annual variability in precipitation are less well known. To address the role of precipitation in controlling grassland C fluxes, and thereby soil C sequestration rates, we measured aboveground and belowground net primary production (ANPP-C and BNPP-C), soil respiration (SR-C), and litter decomposition rates for 2 years, a relatively dry year followed by a year of average precipitation, at five sites spanning a precipitation gradient in the Great Plains. ANPP-C, SR-C, and litter decomposition increased from shortgrass steppe (36, 454, and 24 g C m-2 y-1) to tallgrass prairie (180, 1221, and 208 g C m-2 y-1 for ANPP-C, SR-C, and litter decomposition, respectively). No significant regional trend in BNPP-C was found. Increasing precipitation between years increased rates of ANPP-C, BNPP-C, SR-C, and litter decomposition at most sites. However, regional patterns of the sensitivity of ANPP-C, BNPP-C, SR-C, and litter decomposition to between-year differences in precipitation varied. BNPP-C was more sensitive to between-year differences in precipitation than were the other C fluxes, and shortgrass steppe was more responsive than were mixed grass and tallgrass prairie.}, keywords = {LTER-KNZ, grassland, Great Plains, litter decomposition, Net primary production, Precipitation, Regional trends, soil respiration}, doi = {10.1007/s10021-004-0117-8}, author = {McCulley, R.L. and Burke, I.C. and Nelson, J.A. and Lauenroth, W.K. and Alan K. Knapp and Kelly, E.F.} } @article {KNZ001091, title = {Using local seed in prairie restoration}, journal = {Native Plants Journal}, year = {2005}, pages = {22 -28}, abstract = {Choice among local, non-local, and cultivar seeds for restoring native ecosystems is not purely an academic question{\textemdash}it also has practical consequences.In this article we summarize a series of genetic and competition studies of big bluestem (Andropogon gerardii Vitman. [Poaceae]), Indian grass (Sorghastrum nutans (L.) Nash. [Poaceae]), and purple prairie clover (Dalea purpurea Vent.[Fabaceae]) from remnant and restored Illinois (local) prairies, non-local remnant prairies, and 6 grass cultivars. We found genetic differences between local and non-local seed sources, that large populations do not necessarily have higher genetic diversity relative to small populations, and differences in plant performance could be related to seed source. Although obtaining large quantities of non-local and cultivar grass seeds may be affordable, available, and desirable given the amount of seeds required for prairie restoration, our research indicates genetic and plant performance differences between local and non-local seed sources in all 3 species. Such differences can affect both the short- and long-term success of restoration activities.}, keywords = {LTER-KNZ, Andropogon gerardii, cultivars, Dalea purpurea, Ecotype, Fabaceae, Poaceae, remnant and restored grasslands, Sorghastrum nutans}, doi = {10.2979/NPJ.2005.6.1.25}, author = {Gustafson, D.J. and D.J. Gibson and Nickrent, D.L.} } @article {KNZ00919, title = {Competitive relationships of Andropogon gerardii (big bluestem) from remnant and restored native populations and select cultivated varieties}, journal = {Functional Ecology}, volume = {18}, year = {2004}, pages = {451 -457}, abstract = {1Although genetic differentiation among plant populations is well known, its relevance for preserving the integrity of native ecosystems has received little attention. In a series of competition experiments with Andropogon gerardii Vitman, a dominant species of the North American Tallgrass Prairie, plant performance was related to seed provenance and restoration activities. 2Glasshouse experiments showed plant performance to be a function of seed source. Differential target plant performance relative to competitor identity was observed when plant performance was assessed across a range of competitor densities. Local and non-local plants were larger when competing against non-local plants relative to the local and cultivar plants, while cultivar plants were consistently larger than local and non-local plants regardless of competitor identity or density. The consistency of cultivar performance could reflect directional selection during cultivar development for consistently high fecundity, vigorous vegetative growth and resistance to pathogens. 3In a field experiment, non-local plants were half the size of local and cultivar plants, supporting recognition of seed provenances of A. gerardii based on differences in plant performance among source populations observed in the glasshouse study, and previous genetic analyses of the same populations. 4This study establishes that seed provenance and restoration activities influence the competitive ability of a dominant species which, in turn, may affect plant community structure and potential ecosystem function.}, keywords = {LTER-KNZ}, doi = {10.1111/j.0269-8463.2004.00850.x}, author = {Gustafson, D.J. and D.J. Gibson and Nickrent, D.L.} } @article {KNZ00918, title = {Conservation genetics of two co-dominant species in the endangered tallgrass prairie ecosystem}, journal = {Journal of Applied Ecology}, volume = {41}, year = {2004}, pages = {389 -397}, abstract = {

1. Global habitat fragmentation and loss of undisturbed grasslands has led to the use of non-local seed and cultivars in restoration. There is concern that these sources may be genetically depauperate and their introduction may lead to loss of unique local genotypes. Within this context we considered the issue with regard to the once widespread but now highly fragmented North American tallgrass prairie. 2. We characterized the genetic diversity and genetic relationships of the co-dominant species in this system, big bluestem Andropogon gerardii and Indian grass Sorghastrum nutans, from seven remnant and six restored local tallgrass prairies, a non-local remnant prairie, and five cultivated varieties. 3. Randomly amplified polymorphic DNA (RAPD) analysis of these grasses showed that genetic diversity was mostly retained within rather than among populations, and did not differ among restored or remnant populations or cultivars. 4. Genetic diversity estimates were not correlated with the area of the grassland, nor was there a clear association between diversity and species abundance. All of the restored grasslands in this study were established with seed from at least two local populations and were as genetically diverse as remnant sites. 5. Principal components analysis of RAPD band frequencies showed that the local remnant and restored populations were genetically different from the non-local remnant grasslands and were consistently different to the cultivars. The genetic relationships among local remnant and restored populations reflected biogeography and human activities. 6. Synthesis and applications. Restoration practitioners have often assumed that small populations are genetically depauperate and therefore the need for multiple seed sources to increase genetic diversity outweighs concerns over potential genetic differences among widespread species. Our research, however, indicates that genetic diversity is much less of an issue in these perennial outcrossing autopolyploid grasses than genetic differences among local and non-local or cultivar seed sources. Combining these results with our previous research, indicating differences in plant performance as a function of the source population, suggests that genetic differences and ecological performance among local and non-local seed sources are more of a concern than genetic diversity. Translocating non-local seed in order to increase diversity, or using cultivars, is likely to alter the genetic structure of remnant populations and potentially influence the associated community and affect ecosystem structure and function in unforeseen ways.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.0021-8901.2004.00904.x}, author = {Gustafson, D.J. and D.J. Gibson and Nickrent, D.L.} } @article {KNZ00920, title = {Water relations in grassland and desert ecosystems exposed to elevated atmospheric CO2}, journal = {Oecologia}, volume = {140}, year = {2004}, pages = {11 -25}, abstract = {

Atmospheric CO2 enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO2 enrichment, with an emphasis on water relations. Increasing CO2 led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO2 enrichment were relatively greater in dry years. In contrast, CO2-induced aboveground biomass increases in the Texas C3/C4 grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO2 in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO2-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO2 were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO2 on plant and soil water relations may contribute substantially to experimentally induced CO2-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO2 effects on photosynthesis and those indirect CO2 effects via soil moisture as documented here.

}, keywords = {LTER-KNZ, biomass, Carbon dioxide enrichment, Landscape predictions, soil water, Stomata}, doi = {10.1007/s00442-004-1550-2}, author = {Morgan, J.A. and Pataki, D.E. and Korner, C. and Clark, H. and Del Grosso, S.J. and Grunzweig, J.M. and Alan K. Knapp and Mosier, A.R. and Newton, P.C.D. and Niklaus, P.A. and Jesse B. Nippert and Nowak, R.S. and Parton, W.J. and Polley, H.W. and Shaw, M.R.} } @article {KNZ00823, title = {Genetic diversity and competitive abilities of Dalea purpurea (Fabaceae) from remnant and restored grasslands}, journal = {International Journal of Plant Science}, volume = {163}, year = {2002}, pages = {979 -990}, abstract = {Allozyme and randomly amplified polymorphic DNA (RAPD) analyses were used to characterize the genetic relationships of Dalea purpurea from remnant and restored Illinois tallgrass prairies and a large remnant tallgrass prairie in Kansas. The remnant Illinois populations were less genetically diverse than the restored Illinois populations and the Kansas population. These restored Illinois populations were established with at least two seed sources that were locally collected. There was little population divergence ( ), which is consistent with other perennial forbs, while the genetic relationships among populations reflected geographic proximity. In a greenhouse competition experiment, differences in performance between seedlings was not related to the remnant or restored status of Illinois populations, but plants from Kansas were significantly smaller than Illinois plants. Genetic diversity and competitive ability were not associated with the size of the original source population. Our data indicate that using multiple local seed sources for restoration projects will maintain the local gene pool while enhancing the regional genetic diversity of this species.}, keywords = {LTER-KNZ, conservation genetics, local seed source, restoration ecology, tallgrass prairie}, doi = {10.1086/342709}, author = {Gustafson, D.J. and D.J. Gibson and Nickert, D.L.} } @article {KNZ00781, title = {Assessing changes in biomass, productivity, and C and N stores following Juniperus virginiana forest expansion into tallgrass prairie}, journal = {Canadian Journal of Forest Research}, volume = {31}, year = {2001}, pages = {1940 -1946}, abstract = {An increase in woody plant abundance in regions historically dominated by grasses is a recent land cover change in grasslands worldwide. In tallgrass prairies of North America, this increase in woody plant cover includes the development of dense stands of eastern redcedar (Juniperus virginiana L.). To evaluate the consequences of this ongoing land cover change for ecosystem functioning, we developed allometric equations, using data from Kansas and Oklahoma, to estimate aboveground biomass and productivity in closed-canopy redcedar stands. We then applied these equations to three closed-canopy redcedar stands, 35–80 years old, which developed on sites formerly dominated by tallgrass prairie in eastern Kansas. Aboveground plant biomass for these redcedar-dominated sites ranged from 114 100 kg/ha for the youngest stand to 210 700 kg/ha for the oldest. Annual aboveground net primary productivity (ANPP) ranged from 7250 to 10 440 kg{\textperiodcentered}ha–1{\textperiodcentered}year–1 for the oldest and younger redcedar stands, respectively. Estimates of ANPP in comparable tallgrass prairie sites in this region average 3690 kg{\textperiodcentered}ha–1{\textperiodcentered}year–1 indicating a large increase in C uptake and aboveground storage as a result of the change from prairie to redcedar forests. Therefore, the widespread occurrence of redcedars across the woodland–prairie ecotone suggests that this land-cover change may have important consequences for regional net C storage.}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1139/x01-132}, author = {Norris, M.D. and John M. Blair and Johnson, L.C. and McKane, R.B.} } @article {KNZ00782, title = {Land cover change in eastern Kansas: litter dynamics of closed-canopy eastern redcedar forests in tallgrass prairie}, journal = {Canadian Journal of Botany}, volume = {79}, year = {2001}, pages = {214 -222}, abstract = {In the Great Plains region, eastern redcedar (Juniperus virginiana L.) abundance has increased dramatically in areas historically occupied by tallgrass prairie. This shift in dominant vegetation is likely to be accompanied by changes in ecosystem structure and function, including quantity, quality, and location (above- vs. below-ground) of litter inputs and subsequent effects on decomposition dynamics. The purpose of this study was to quantify and compare patterns of litterfall and decomposition in mature redcedar forests and adjacent prairie. Annual redcedar litterfall was 500 g{\textperiodcentered}m-2{\textperiodcentered}year-1, a large increase in foliar litter inputs compared with annually burned grassland (52 g{\textperiodcentered}m-2{\textperiodcentered}year-1). Using a reciprocal transplant decomposition study with four substrates, redcedar leaves and roots, and big bluestem (Andropogon gerardii Vitman) foliage and roots, we found marginal habitat effects, but greater differences between species, presumably owing to litter quality (including both C:N and lignin content). Decay rates were significantly higher in the prairie relative to the forest for each substrate. Additionally, within any particular habitat, grass litter had significantly faster decay rates than forest litter. These results suggest a shift in patterns of litter input and decomposition processes with afforestation of tallgrass prairie, which may result in long-term changes in C sequestration and storage.Key words: litter dynamics, eastern redcedar (Juniperus virginiana), big bluestem (Andropogon gerardii), decomposition, tallgrass prairie, nitrogen immobilization.}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1139/b00-159}, author = {Norris, M.D. and John M. Blair and Johnson, L.C.} } @phdthesis {KNZ00854, title = {Regional diversity of braconid wasps (Braconidae: Hymenoptera) collected from sites in Arkansas, Oklahoma and Kansas}, volume = {PhD Dissertation}, year = {2001}, pages = {1 -219}, school = {University of Arkansas}, type = {Ph.D. Thesis}, address = {Fayetteville, AR}, keywords = {LTER-KNZ}, url = {https://library.uark.edu/search~S14?/X\%28braconid+wasps+\%29\&SORT=D\&searchscope=14/X\%28braconid+wasps+\%29\&SORT=D\&searchscope=14\&SUBKEY=(braconid+wasps+)/1\%2C2\%2C2\%2CB/frameset\&FF=X\%28braconid+wasps+\%29\&SORT=D\&searchscope=14\&1\%2C1\%2C}, author = {Newcomb, L.C.} } @mastersthesis {KNZ00744, title = {Biogeochemical consequences of landcover change in eastern Kansas}, volume = {MS Thesis}, year = {2000}, pages = {1 -118}, school = {Kansas State University}, type = {M.S. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ}, author = {Norris, M.} } @phdthesis {KNZ00702, title = {The comparative floral ecology of seven species of Onagraceae in native tallgrass prairie (pollination)}, volume = {PhD Dissertation}, year = {1999}, school = {Saint Louis University}, type = {Ph.D. Thesis}, address = {Saint Louis, MO}, abstract = {

Seven species of Onagraceae, Tribe Onagreae, occur at sites in Konza Prairie Research Natural Area and Tuttle Creek Reservoir Dam area, controlled by the Kansas Army Corp of Engineers. Three species bloom in the Spring and four species bloom from mid-Summer into Fall. The Spring group displays flowers in an unstratified pattern with fewer, but larger, flowers per stem per day, while the mid-Summer group displays several smaller flowers per day on numerous inflorescences in a stratified, three dimensional pattern on tall plants. Both groups demonstrate high fruit set in three breeding systems. Self-pollinating and self-compatible \<italic\>Calylophus serrulatus\</italic\> (Nutt.) Raven attracts a diverse forager assemblage, but only small bees less than 10mm. carry adequate pollen loads. Outcrossing vernal species include \<italic\>Oenothera macrocarpa \</italic\> Nutt., and \<italic\>O. speciosa\</italic\> Nutt. Both species open at night and attract night-flying moths, but \<italic\>O. macrocarpa\</italic\> is the preferred nectar reward source for Sphingidae, of which six species foraged in a three tiered, niche-partitioning group. Samples of pre and post-forager levels of nectar reserves indicate that in 1995 and 1996, shorter tongued sphingids were the major or foragers. \<italic\>O. biennis\</italic\> L., was weedy and cleistogamous, \<italic\>Gaura longiflora\</italic\> Spach, was weedy but outcrossing, and attracted small to medium sized bees in the morning. \<italic\> G. parviflora\</italic\> Dougl., was a self-pollinating and self-compatible weed, and \<italic\>Stenosiphon linifolius\</italic\> (Nutt.) Heynh. was an outcrosser pollinated mostly by small bees less than 6mm long

}, keywords = {LTER-KNZ, tallgrass prairie}, author = {Nonnenmacher, H.F.} } @article {KNZ00718, title = {Demodicosis in an American Bison}, journal = {Canadian Veterinary Journal}, volume = {40}, year = {1999}, pages = {417 -418}, abstract = {An 18-month-old, male American bison (Bison bison) was presented with 7- to 9-mm size nodules periorbital, perineal, and on the ventral surface of the tail. Demodex spp. were identified from the exudate by microscopic examination. Examination 6 mo later revealed that the infestation had nearly cleared without treatment.}, keywords = {LTER-KNZ}, url = {http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1539720/}, author = {Vestweber, J.G. and Ridley, R.K. and Nietfeld, J.C. and Wilkerson, M.J.} } @inbook {KNZ00691, title = {Measuring decomposition, nutrient turnover and stores in plant litter}, booktitle = {Standard Soil Methods for Long Term Ecological Research}, year = {1999}, pages = {202 -240}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ}, author = {Harmon, M.E. and Naddlehoffer, K.J. and John M. Blair}, editor = {Robertson, G.P. and Bledsoe, C.S. and Coleman, D.C. and Sollins, P.S.} } @inbook {KNZ00706, title = {Soil Carbon and nitrogen availability: Nitrogen mineralization, nitrification, soil respiration potentials}, booktitle = {Standard Soil Methods for Long Term Ecological Research}, year = {1999}, pages = {258 -271}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ}, author = {Robertson, G.P. and Wedin, D. and Groffman, P.M. and John M. Blair and Holland, E. and Nadelhoffer, K.J. and Harris, D.}, editor = {Robertson, G.P. and Bledsoe, C.S. and Coleman, D.C. and Sollins, P.S.} } @inbook {KNZ00626, title = {A landscape perspective of patterns and processes in tallgrass prairie}, booktitle = {Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie}, year = {1998}, pages = {265 -279}, publisher = {Oxford University Press}, organization = {Oxford University Press}, address = {New York}, keywords = {LTER-KNZ, tallgrass prairie}, author = {J. M. Briggs and Nellis, M.D. and Turner, C.L. and Henebry, G.M. and Su, H.}, editor = {Alan K. Knapp and J. M. Briggs and D.C. Hartnett and Scott. L. Collins} } @article {KNZ00627, title = {Permutation of two-term local quadrat variance analysis: general concepts for interpretation of peaks}, journal = {Journal of Vegetation Science}, volume = {9}, year = {1998}, pages = {41 -44}, abstract = {Many ecological studies use Two-Term Local Quadrat Variance Analysis (TTLQV) and its derivatives for spatial pattern analysis. Currently, rules for determining variance peak significance are arbitrary. Variance peaks found at block size 1 and at > 50 \% of the transect length are the only peaks whose use is explicitly prohibited. Although the use of variance peaks found at block sizes > 10 \% of the transect length have also been warned against, many researchers interpret them regardless. We show in this paper that variance peaks derived from TTLQV are subject to additional {\textquoteleft}rules of thumb{\textquoteright}. Through the use of randomization and permutation analyses on real and simulated data of species abundance in contiguous plots along a single transect, we show that variance peaks found at block sizes 1, 2 and 3 occur frequently by chance and thus likely do not indicate biologically meaningful patterns. The use of multiple replicate transects decreases the probability of Type II error.}, keywords = {LTER-KNZ, Permutation analysis, Spatial pattern, Variance peak}, doi = {10.2307/3237221}, author = {Campbell, J.E. and Franklin, D.J.G. and Newman, J.A.} } @article {KNZ00606, title = {Evolutionary implications of meiotic chromosome behavior, reproductive biology, and hybridization in 6X and 9X cytotypes of Andropogon gerardii (Poaceae )}, journal = {American Journal of Botany}, volume = {84}, year = {1997}, pages = {201 -207}, abstract = {Andropogon gerardii, big bluestem, has 60 and 90 chromosome cytotypes. Meiosis in the hexaploid was shown to be regular, although some secondary associations of bivalents form. Meiosis in the enneaploid (2n = 9z = 90) is irregular, leading to most gametes having unbalanced chromosome complements. Both cytotypes show considerable self-incompatibility. Cytotypes crossed freely, forming a variety of fertile euploids and aneuploids. Indistinguishable exomorphology, intermixing in natural populations, and compatibility suggest that A. gerardii is best understood as a cytotypically complex single species.}, keywords = {LTER-KNZ}, url = {http://www.amjbot.org/content/84/2/201.short}, author = {Norrmann, G.A. and Quarin, C.L. and Keeler, K.H.} } @article {KNZ00605, title = {Modelling impact of bison on tallgrass prairie}, journal = {Transactions Kansas Academy of Science}, volume = {100}, year = {1997}, pages = {3 -9}, keywords = {LTER-KNZ, tallgrass prairie}, author = {Nellis, M.D. and J. M. Briggs} } @article {KNZ00612, title = {Soil N and plant responses to fire, topography and supplemental N in tallgrass prairie}, journal = {Ecology}, volume = {78}, year = {1997}, pages = {1832 -1843}, abstract = {Tallgrass prairie in the Flint Hills region of Kansas is characterized by considerable topographic relief coupled with variation in soil properties. These topoedaphic gradients, together with variation in fire regimes, result in temporal and landscape-level variability in soil resource availability and plant responses. Nitrogen usually is considered to be the nutrient most limiting to primary productivity in tallgrass prairie, but few studies have addressed how N availability varies seasonally, or across the landscape and with fire frequency. We measured soil inorganic N, in situ net N mineralization, aboveground net primary productivity (ANPP), and N mass on plots either fertilized with N in 1993 or in 1994, or unfertilized, in uplands and lowlands of two annually burned and two long-term unburned sites during the 1994 growing season. In addition, our study was conducted in the year following record rainfall, allowing us to assess the potential for high precipitation amounts to affect subsequent N cycling and plant production. Both fire treatment and topography affected soil N availability. In general, N mineralization was greater on unburned than on burned sites and was up to five times greater on uplands than lowlands. Total extractable soil N was highest early in the season and least at midseason, and it also tended to be higher in unburned sites than burned sites on unfertilized plots. Added N increased ANPP, but there were no differences between plots fertilized in 1994 and those fertilized in 1993. In general, patterns of ANPP on control plots were consistent with known production responses to topography and burning (higher in annually burned sites and in lowland sites) but were inversely related or unrelated to patterns of N availability (higher in unburned sites and at upland topographic positions). Potential loss of N by volatilization during spring burning was greater than in years with normal rainfall amounts and represented a significant portion of aboveground plant N mass. Potential N losses did not appear to limit ANPP or N availability in the current growing season. Our results suggest that different factors control soil N mineralization and plant productivity, which explains, in part, why patterns of ANPP are not well correlated with patterns of N availability in tallgrass prairie ecosystems.}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1890/0012-9658(1997)078[1832:SNAPRT]2.0.CO;2}, author = {Turner, C.L. and John M. Blair and Schartz, R.J. and Neel, J.C.} } @article {KNZ00581, title = {Spatial and temporal patterns of vegetation in the Flint Hills}, journal = {Transactions Kansas Academy of Science}, volume = {100}, year = {1997}, pages = {10 -20}, abstract = {In tallgrass prairie, complex interactions among multiple limiting resources in combination with a variety of land use practices can lead to a heterogeneous landscape. Remote-sensing data (AVHRR) were coupled with abiotic factors to explore spatial and temporal vegetation patterns of the Flint Hills in Kansas and Oklahoma. This information should enable the detection of both natural (e.g., interannual variation in precipitation and temperature) and anthropogenic (e.g., climate change, over-grazing, land-use practices) stresses on this grassland ecosystem. Shifts in the spatial and temporal patterns of vegetation (as measured from NDVI by AVHRR) have been correlated with meteorological data (from 117 weather stations) to identify key abiotic variables that determined vegetation patterns across this region. In 4 years, the combination of annual precipitation and growing degree days was useful to detect spatial and temporal vegetation patterns of the Flint Hills. However, it is imperative that land-use patterns are known in order to assess adequately spatial and temporal patterns of vegetation in this area.}, keywords = {LTER-KNZ}, doi = {10.2307/3628435}, author = {J. M. Briggs and Rieck, D.R. and Turner, C.L. and Henebry, G.M. and Goodin, D.G. and Nellis, M.D.} } @article {KNZ00457, title = {Expansion of gallery forest on Konza Prairie Research Natural Area, Kansas}, journal = {Landscape Ecology}, volume = {9}, year = {1994}, pages = {117 -125}, abstract = {To determine the dynamics of the spatial extent of gallery forest on Konza Prairie Research Natural Area (KPRNA), aerial photographs taken over a 46 year time frame were digitized into an ARC-INFO Geographic Information System (GIS). A Global Positioning System (GPS) was used to collect ground control points to co-register the photographs for each year. Gallery forest areas for the three major drainage boundaries (Kings Creek, Shane Creek, and White Pasture) were analyzed to assess the uniformity of change in the landscape system. Results indicated that the total gallery forest area on KPRNA has increased in area from 157 ha in 1939 to over 241 ha in 1985. During this time, there was an increase in the total number of patches and a decrease in the mean size of forest patches. However, the rate of increase was not consistent over this time period, nor was it uniform from one drainage basin or stream order to another. Detailed spatial analysis of the forested area with a geomorphology and digital elevation model of Konza Prairie showed that in 1985, 58\% of the forest was on alluvial/colluvial soil, yet only 15\% of that soil type was forested. In addition, over 70\% of the forest was on the 0{\textendash}15\% slope interval, but only 15{\textendash}20\% of that slope interval was forested. These results may be attributed to a variety of factors such as changing management practices (i.e., frequency of fires and herbicide spraying) and the temporal constraints on extent to which the gallery forest can expand across the landscape.}, keywords = {LTER-KNZ, burning, gallery forest, GIS, historical landuse, tallgrass prairie}, doi = {10.1007/BF00124378}, url = {http://link.springer.com/article/10.1007/BF00124378}, author = {Knight, C.L. and J. M. Briggs and Nellis, M.D.} } @proceedings {KNZ00463, title = {Space shuttle photography for monitoring global change}, year = {1994}, pages = {532 -534}, keywords = {LTER-KNZ}, author = {Nellis, M.D. and Lulla, K. and J. M. Briggs} } @proceedings {KNZ00471, title = {Micromorphology of polygenetic soils in a small watershed, north central Kansas, U.S.A}, journal = {Developments in Soil Science}, volume = {22}, year = {1993}, pages = {247 -255}, publisher = {Elsevier Science Publisher}, address = {Townsville, Australia}, keywords = {LTER-KNZ}, doi = {10.1016/S0166-2481(08)70413-6}, author = {Wehmueller, W.A. and Ransom, M.D. and Nettleton, W.D.}, editor = {Ringrose-Vaose, A.J. and Humphreys, G.S.} } @booklet {KNZ00379, title = {Collected data of the first ISLSCP field experiment: Volume 2: Satellite Imagery 1987-1989}, year = {1992}, keywords = {LTER-KNZ, ISLSCP}, author = {Strebel, D.E. and Landis, D.R. and Newcomer, J.A. and Elburg-Obler, D. and Meeson, B.W. and Agbu, P.A.} } @booklet {KNZ00381, title = {Collected data of the first ISLSCP field experiment: Volume 3: NS001 Imagery 1987 to 1989}, year = {1992}, keywords = {LTER-KNZ, ISLSCP}, author = {Strebel, D.E. and Landis, D.R. and Newcomer, J.A. and Goetz, S.J. and Meeson, B.W. and Agbu, P.A. and McManus, J.M.P.} } @booklet {KNZ00380, title = {Collected data of the first ISLSCP field experiment: Volume 4: ASAS; PBMR Imagery 1987-1989}, year = {1992}, keywords = {LTER-KNZ, ISLSCP}, author = {Strebel, D.E. and Landis, D.R. and Newcomer, J.A. and Meeson, B.W. and Agbu, P.A. and McManus, J.M.P.} } @article {KNZ00372, title = {Geographic information systems for modeling bison impact on Konza Prairie, Kansas}, journal = {GIS/LIS Proceedings}, volume = {2}, year = {1992}, pages = {618 -623}, keywords = {LTER-KNZ, Information Systems}, author = {Nellis, M.D. and J.D. Bathgate and J. M. Briggs} } @article {KNZ00373, title = {Growth and transition: Remote sensing and geographic information systems at Kansas State University}, journal = {Photogrammetric Engineering and Remote Sensing}, volume = {58}, year = {1992}, pages = {1159 -1161}, abstract = {

Remote sensing and geographic information systems education and research at Kansas State University have grown tremendously in the past decade. Dramatic improvements in hardware and software have enhanced offerings in a wide range of spatial analysis (including remote sensing) courses. Success in extramural funding through such agencies as the U.S. Agency for International Development and the National Science Foundation have created a major research thrust in Kansas State University\&$\#$39;s Geography and Biology programs relative to the application of remote sensing and geographic information systems for natural resource assessment and landscape ecology. The State of Kansas initatives have also enhanced Kansas State University\&$\#$39;s role in providing a significant contribution in remote sensing/geographic information systems research and education

}, keywords = {LTER-KNZ, Information Systems}, author = {Nellis, M.D. and J. M. Briggs and Seyler, H.L.} } @article {KNZ00371, title = {Transformed vegetation index for measuring spatial variation in drought impacted biomass on Konza Prairie, Kansas}, journal = {Transactions of the Kansas Academy of Science}, volume = {95}, year = {1992}, pages = {93 -99}, keywords = {LTER-KNZ}, doi = {10.2307/3628024}, author = {Nellis, M.D. and J. M. Briggs} } @proceedings {KNZ00302, title = {Effects of fire exclusion on tallgrass prairie and gallery forest communities in eastern Kansas}, year = {1991}, pages = {3 -10}, publisher = {Southeastern Forest Experiment Station}, abstract = {

The purpose of this review is to synthesize a long-term body of research dealing with fire exclusion effects on tallgrass prairie and gallery forest communities on Konza Prairie in eastern Kansas. Upland and lowland prairie communities burned in spring at intervals ranging from 1-11 years were consistently dominated (79-90 percent cover) by Andropogon gerardii. With this increasing interval between fires other dominant warm-season grasses, A. scoparius and Sorghastrum nutans, had decreased cover, whereas forbs and woody species had increased cover. Aboveground biomass was higher on an annual burned versus unburned lowland prairie, due to stimulated graminoid production. Sites unburned for 10 or more years were converting to woodlands dominated by Juniperus, Ulmus, Gleditsia and Celtis. Older gallery forests occurred in stream channels and ravines and were comprised of overstory Quercus and Celtis and understory Celtis, Cercis and Ulmus. The extent of gallery forests on Konza Prairie dramatically increased from the time of European settlement (1850) to present; this has been attributed to decreased fire frequency and intensity in the region. With continued fire exclusion this century further succession in these forests has caused oak replacement by more shade tolerant species

}, keywords = {LTER-KNZ, tallgrass prairie}, author = {Abrams, M.D. and D.J. Gibson}, editor = {Nodvin, S.C. and Waldrop, T.A.} } @article {KNZ00308, title = {Seasonal variation of heterogeneity in tallgrass prairie: a quantitative measure using remote sensing}, journal = {Photogrammetric Engineering and Remote Sensing}, volume = {57}, year = {1991}, pages = {407 -411}, abstract = {

Remote sensing may be a tool to quantitatively measure the change in heterogeneity that takes place in a landscape over a growing season. Seven different SPOT satellite scenes of the Konza Prairie Research Natural Area were analyzed to assess the potential of using textural algorithms as a quantitative measure of seasonal variation in heterogeneity. Unburned watersheds usually have greater heterogeneity than annually burned watersheds. However, the greatest amount of heterogeneity as measured by textural analysis occurs in those area with a mixture of forest and upland tallgrass prairie. Results suggest that remote sensing textural algorithms, in combination with normalized vegetation difference indices, can provide insight regarding both temporal changes that occur seasonally and the influences of periodic spring fires and management practices on the tallgrass prairie ecosystem

}, keywords = {LTER-KNZ, tallgrass prairie}, author = {J. M. Briggs and Nellis, M.D.} } @article {KNZ00332, title = {Stochastic analysis of the dynamics of nitrogen concentration in a stream ecosystem}, journal = {Ecological Modeling}, volume = {56}, year = {1991}, pages = {33 -45}, keywords = {LTER-KNZ}, doi = {10.1016/0304-3800(91)90191-3}, author = {Nassar, R. and Stewart, R. and Tate, C.M.} } @phdthesis {KNZ00292, title = {The effect of slope on the surface energy balance in a tallgrass prairie}, volume = {PhD Dissertation}, year = {1990}, pages = {1 -166}, school = {Kansas State University}, type = {Ph.D. Thesis}, address = {Manhattan, KS}, keywords = {LTER-KNZ, tallgrass prairie}, author = {Nie, D.} } @article {KNZ00294, title = {Field bioassessment for selecting test systems to evaluate military training lands in tallgrass prairie}, journal = {Ecosystem Health.V.1 Environmental Management}, volume = {14}, year = {1990}, pages = {81 -93}, abstract = {

Ecosystems responses to physical or chemical stress may vary from changes in single organisms to alteration of the structure and function of the ecosystem. These responses to stress cannot be predicted exactly. Ecosystems repeatedly exposed to physical and/or chemical stress can be used to study the separate and combined environmental effects of stress. Such studies also allow the development of procedures to select test systems for the analysis of stress in ecosystems. A preliminary field survey of six military training sites at Fort Riley, Kansas, USA, was conducted to identify and verify ecological test systems for evaluating ecosystem responses to physical and/or chemical stress. Comparisons of these data with data collected concurrently from Konza Prairie Research Natural Area reference sites showed that soil microarthropods, some species of macroarthropods, small mammals, and native earthworm species were negatively affected by stress. In contrast, plant species diversity, plant foliage biomass, soil mycorrhizae, and many soil characteristics were within the boundaries of nominal variations observed on \"pristine\" Konza Prairie. Introduced European earthworms appeared to be positively affected by training activities. This study provided a test of systematic procedures to support impact analysis, ecological toxicology, and ecosystem risk assessment

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1007/BF02394022}, author = {Schaeffer, D.J. and Seastedt, T.R. and D.J. Gibson and D.C. Hartnett and Hetrick, B.A.D. and James, S.W. and D.W. Kaufman and Schwab, A.P. and Herricks, E.E. and Novak, E.W.} } @inbook {KNZ00249, title = {Canopy photosynthesis}, booktitle = {Photosynthesis}, year = {1989}, note = {Published}, pages = {227 -241}, publisher = {Alan R. Liss, Inc}, organization = {Alan R. Liss, Inc}, address = {New York, N.Y}, keywords = {LTER-KNZ}, author = {Norman, J.M. and Polley, W.}, editor = {Briggs, W.R.} } @proceedings {KNZ00255, title = {Data management in the FIFE information system}, year = {1989}, pages = {42 -45}, address = {Vancouver, BC}, abstract = {

The First ISLSCP Field Experiment (FIFE) was conducted during 1987 on a 15 X 15 km area in central Kansas, including the Konza Prairie Natural Research Area. The experiment goal of understanding and modeling the effects of vegetation on the heat an mass fluxes in the atmosphere/land surface boundary layer required a flexible and responsive information system with georeferenced data to permit the necessary coordinated analyses. The FIFE Information Syseem (FIS) met this goal in a variety of ways, depending on the type of data and the type of scientific investigation involved. The FIS has served the FIFE investigatiors as a tool for experiment design, as well as for organizing and manipulating the complex data set. Two specific requirements were rapid and simple access to specialized user specified data sets and quick evolution as the science needs changed. As a result, the FIS differs in several important ways from \"classical\" data systems, covering the spectrum of conceptual, managerial, and organizational issues. Our experience indcates that the design, development, and operation of an information system supporting such an experiment must be flexible and under direct day-to-day control of scientist/users. This experience has also led to a number of observations (both technological and organizational) for designing and building both future experiment support data bases and long term data systems supporting scientific research. Key words: FIFE, Information Systems, ISLSCP

}, keywords = {LTER-KNZ, ISLSCP}, author = {Strebel, D.E. and Newcomer, J.A. and Ormsby, J.P. and Hall, F.G. and Sellers, P.J.} } @article {KNZ00247, title = {The effects of spatial scale on Konza landscape classification using textural analysis}, journal = {Landscape Ecology}, volume = {2}, year = {1989}, pages = {93 -100}, abstract = {

Spatial scale is inherent in the definition of landscape hererogeneity and diversity. For example, a landscape may appear heterogenous at one scale but not quite homogeneous at another scale. In assessing the impact of burning and grazing on the Konza Prairie Research Natural Area (a tallgrass prairie), spatial scale is extremely important. Textural contrast algorithms were applied to various scales of remote sensing data and related to landscape units for assessment of heterogeneity under a variety of burning treatments. Acquired data sets included Landsat multispectral scanner (MSS), with 80 m resolution, Landsat thematic mapper (TM), with 30 m resolution, and high resolution density sliced aerial photography (with a 5 m resolution). Results suggest that heterogeneous areas of dense patchiness (e.g., unburned areas) must be analyzed at a finer scale than more homogeneous areas which are burned at least every four years. Key words: spatial scale, textural analysis, tallgrass prairie, remote sensing, landscape ecology, Kansas

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1007/BF00137153}, author = {Nellis, M.D. and J. M. Briggs} } @inbook {KNZ00248, title = {Intergrating field experiences with remote sensing for understanding vegetation indices}, booktitle = {Current Trends in Remote Sensing Education}, year = {1989}, pages = {93 -100}, publisher = {Geocarto International Centre}, organization = {Geocarto International Centre}, address = {Hong Kong}, abstract = {

Students of the geographic field research techniques course at Kansas State University were presented with the problem of integrating data collected from field experiences with Landsat MSS digital data to better understand the influence of physical and cultural factors on the condition of vegetation. As part of a National Science Foundation sponsored program, Konza Prairie Natural Area in the Kansas Flint Hills, has developed a diversity of rangeland management strategies based on watershed units. During the summer of 1987, students were asked to gather information at the Konza site on field conditions along transects for selected watersheds. Students noted dominant vegetation types, density of vegatitive cover, and relative vegetetive greenness. Landsat MSS digital data sets for a date similat to the field data were then analyzed by the students using a microcomputer-based digital image processing system. Mean brightness values for each MSS band by selected watersheds were calculated and entered into two algorithms that estimated soil brightness and green vegetation index. Students then compared field data with the derived soil brightness and green vegetation indices, and determined reasons for variation in indices between watersheds

}, keywords = {LTER-KNZ}, author = {Nellis, M.D.}, editor = {Nellis, M.D. and Lougeay, R. and Lulla, K.} } @proceedings {KNZ00217, title = {Landsat thematic mapper digital data for predicting aboveground biomass in a tallgrass prairie ecosystem}, year = {1989}, pages = {53 -55}, publisher = {University of Nebraska Press}, address = {Lincoln, NE}, abstract = {

Landstat thematic mapper digital data was found to offer an excellent potential for regular monitoring of the tallgrass prairie ecosystem by providing estimates of aboveground biomass production. Data from several channels of a May thematic mapper scene were analyzed individually and in various combinations using stepwise regression in Statistical Analysis System (SAS). These procedures were used to determine the most appropriate multiple regression equation for estimating production of 1) total live aboveground biomass, 2) grasses, 3) forbs, 4) previous years dead, and 5) current years dead. Regression equations were based on satellite-derived estimates relative to ground level biomass values for watersheds on Konza Prairie Research Natural Area under a variety of burning treatments. Results suggest that multiple channel equations were most appropriate for measuring production of forbs and total live aboveground biomass. Channel one (0.45 to 0.52 {\ae}meters) and channel four (0.76 to 0.90 {\ae}meters) were applicable to estimate production of grass and levels of previous years litter, respectively. However, none of the channels were accurate in predicting current years dead. Further plans involve using thematic mapper data to estimate aboveground biomass over an entire growing season on Konza and exploring the potential of using satellite data to monitor grassland production across the Great Plains. Key Words: tallgrass prairie, remote sensing, aboveground biomass, Landstat, thematic mapper, monitoring, Konza Prairie, Kansas

}, keywords = {LTER-KNZ, tallgrass prairie}, author = {J. M. Briggs and Nellis, M.D.}, editor = {Bragg, T.B. and Stubbendieck, J.} } @proceedings {KNZ00153, title = {Simulating the long-term impact of burning on C, N, and P cycling in a tallgrass prairie}, year = {1988}, pages = {353 -370}, publisher = {Via Nizza}, address = {Roma, Italy}, abstract = {

A model has been developed to simulate the long-term dynamics of soil organic matter and plant production in response to different management practices. The model simulates the flow of C, N, and P in soil-plant systems and deals primarily with the cycling of nutrients in various soil organic matter pools. The model was used to simulate the long- term effects of different fire frequency and timing of the burning on soil organic matter levels, nutrient cycling and plant production. The model results are compared to nutrient cycling data, soil organic matter data and plant production data from a site in Kansas which was established in 1928 to study the impact of annual burning on a tallgrass prairie. The model results compare very favorably with the observed data and show that maximum production is achieved by annual burning in the late spring (April 20). The annual burning also causes the soil organic matter levels and N mineralization potential to decrease. Burning tends to increase the inorganic P levels at the soil surface, which results in increased N fixation

}, keywords = {LTER-KNZ, tallgrass prairie}, author = {Ojima, D.S. and Parton, W.J. and Schimell, D.S. and Owensby, C.E.}, editor = {Giovannozzi-Sermanni, G. and Nannipieri, P.} } @article {KNZ00199, title = {SPOT satellite data for pattern recognition on the North American tall-grass prairie Long-term Ecological Research Site}, journal = {Geocarto International}, volume = {3}, year = {1988}, pages = {37 -40}, abstract = {

The cluster routine uses a two-pass sequential clustering algorithm. In the first pass, the program reads through the entire data set, and sequentially builds clusters (groups of points in spectral space) based on parameters selected by the user, and computes the mean value for each cluster. These clusters become the signatures used to assign classes in the output GIS file. The second pass classifies each pixel in the data set according to a minimum distance classifier. The algorithm calculates the spectral distance between the candidate pixel and the mean value for every cluster, using the mean values that were computed in the first pass

}, keywords = {LTER-KNZ, tallgrass prairie}, doi = {10.1080/10106048809354174}, author = {Nellis, D.M. and J. M. Briggs} } @article {KNZ00152, title = {Micro-based Landsat TM data processing for tallgrass prairie monitoring in the Konza Prairie Research Natural Area, Kansas}, journal = {Papers and Proceedings of the Applied Geography Conference}, volume = {10}, year = {1987}, pages = {76 -80}, abstract = {

Despite the large amount of evidence supporting the important role that burning and frequency of burning have on grassland resources, information on the spatial extent of burning in the Flint Hills of Kansas has not been developed. This is primarily due to the massive data requirements needed to access burning on a regional scale. This study assesses the regional potential for monitoring burning practices in the Flint Hills of Kansas using satellite data. The specific objective of this study was to ascertain the utility of Landsat thematic mapper digital data for delineating the spatial characteristics of burning in the Konza Prairie Research Natural Area. The Konza Prairie is an area exceeding 8,000 acres owned by Nature Conservancy and leased to Kansas State University for long-term ecological research. The management objectives of the research area are based on the efforts of periodic fire and grazing on a tall grass prairie ecosystem

}, keywords = {LTER-KNZ, tallgrass prairie}, author = {Nellis, M.D. and J. M. Briggs} } @article {KNZ00124, title = {Remote sensing for monitoring rangeland management strategies in the Kansas Flint Hills}, journal = {International Archives of Photogrammetry and Remote Sensing}, volume = {26}, year = {1986}, pages = {370 -375}, abstract = {

The Konza Prairie Research Natural Area represents an effort by the Nature Conservancy to preserve natural diversity in the Flint Hills of Kansas. The management objectives within the Konza Prairie are based on a comparison of the natural prairie ecosystem with manipulated systems. The effects of fire and grazing on the prairie ecosystem are of particular concern. Qualitative examiniations using color infrared photography and digital enhanced photography of study zones within the Konza Prairie yielded positive results for delineation of varying mangement strategies. The study illustrates the utility of using color infrared for regular monitoring of the Flint Hills Region

}, keywords = {LTER-KNZ, rangeland, remote sensing}, author = {Nellis, M.D.} }