@article {6165, title = {Stronger fertilization effects on aboveground versus belowground plant properties across nine U.S. grasslands}, journal = {Ecology}, volume = {104}, year = {2023}, pages = {e3891}, abstract = {

Increased nutrient inputs due to anthropogenic activity are expected to increase primary productivity across terrestrial ecosystems, but changes in allocation aboveground versus belowground with nutrient addition have different implications for soil carbon (C) storage. Thus, given that roots are major contributors to soil C storage, understanding belowground net primary productivity (BNPP) and biomass responses to changes in nutrient availability is essential to predicting carbon\–climate feedbacks in the context of interacting global environmental changes. To address this knowledge gap, we tested whether a decade of nitrogen (N) and phosphorus (P) fertilization consistently influenced aboveground and belowground biomass and productivity at nine grassland sites spanning a wide range of climatic and edaphic conditions in the continental United States. Fertilization effects were strong aboveground, with both N and P addition stimulating aboveground biomass at nearly all sites (by 30\% and 36\%, respectively, on average). P addition consistently increased root production (by 15\% on average), whereas other belowground responses to fertilization were more variable, ranging from positive to negative across sites. Site-specific responses to P were not predicted by the measured covariates. Atmospheric N deposition mediated the effect of N fertilization on root biomass and turnover. Specifically, atmospheric N deposition was positively correlated with root turnover rates, and this relationship was amplified with N addition. Nitrogen addition increased root biomass at sites with low N deposition but decreased it at sites with high N deposition. Overall, these results suggest that the effects of nutrient supply on belowground plant properties are context dependent, particularly with regard to background N supply rates, demonstrating that site conditions must be considered when predicting how grassland ecosystems will respond to increased nutrient loading from anthropogenic activity.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecy.3891}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.3891}, author = {Keller, Adrienne B. and Walter, Christopher A. and Blumenthal, Dana M. and Borer, Elizabeth T. and Collins, Scott L. and DeLancey, Lang C. and Fay, Philip A. and Hofmockel, Kirsten S. and Knops, Johannes M. H. and Leakey, Andrew D. B. and Mayes, Melanie A. and Seabloom, Eric W. and Hobbie, Sarah E.} } @article {6114, title = {Soil carbon stocks in temperate grasslands differ strongly across sites but are insensitive to decade-long fertilization}, journal = {Global Change Biology}, volume = {28}, year = {2022}, pages = {1659 - 1677}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.15988}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.15988}, author = {Keller, Adrienne B. and Borer, Elizabeth T. and S L Collins and DeLancey, Lang C. and Fay, Philip A. and Hofmockel, Kirsten S. and Leakey, Andrew D.B. and Mayes, Melanie A. and Seabloom, Eric W. and Walter, Christopher A. and Wang, Yong and Zhao, Qian and Hobbie, Sarah E.} } @article {5981, title = {Patterns and trends of organic matter processing and transport: Insights from the US Long-Term Ecological Research network}, journal = {Climate Change Ecology}, volume = {2}, year = {2021}, pages = {100025}, keywords = {LTER-KNZ}, doi = {10.1016/j.ecochg.2021.100025}, url = {https://linkinghub.elsevier.com/retrieve/pii/S2666900521000253}, author = {Harms, Tamara K. and Groffman, Peter M. and Aluwihare, Lihini and Craft, Chris and Wieder, William R and Hobbie, Sarah E. and S.G. Baer and J. M. Blair and Frey, Serita and Remucal, Christina K. and Rudgers, Jennifer A. and S L Collins} } @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 {KNZ002015, title = {Repeated fire shifts carbon and nitrogen cycling by changing plant inputs and soil decomposition across ecosystems}, journal = {Ecological Monographs}, volume = {90}, year = {2020}, pages = {e01409}, abstract = {

Fires shape the biogeochemistry and functioning of many ecosystems, and fire frequencies are changing across much of the globe. Frequent fires can change soil carbon (C) and nitrogen (N) storage by altering the quantity and chemistry of plant inputs through changes in plant biomass and composition as well as altering decomposition of soil organic matter. How decomposition rates change with shifting inputs remains uncertain because most studies focus on the effects of single fires, where transient changes may not reflect responses to decadal changes in burning frequencies. Here, we sampled seven sites exposed to different fire frequencies. In four of the sites, we intensively sampled both soils and plant communities across four ecosystems in North America and Africa spanning tropical savanna, temperate coniferous savanna, temperate broadleaf savanna, and temperate coniferous forest ecosystems. Each site contained multiple plots burned frequently for 33-61 years and nearby plots that had remained unburned over the same period replicated at the landscape scale. Across all sites, repeatedly burned plots had 25-185\% lower bulk soil C and N concentrations but also 2-10-fold lower potential decomposition of organic matter compared to unburned sites. Soil C and N concentrations and extracellular enzyme activities declined with frequent fire because fire reduced both plant biomass inputs into soils and dampened the localized enrichment effect of tree canopies. Examination of soil extracellular enzyme activities revealed that fire decreased the potential turnover of organic matter in the forms of cellulose, starch, and chitin (p\<0.0001) but not polyphenol and lignin (p=0.09), suggesting a shift in soil C and N cycling. Inclusion of δ13C data from three additional savanna sites (19-60 years of altered fire frequencies) showed that soil C losses were largest in sites where estimated tree inputs into soils declined the most (r2=0.91, p\<0.01). In conclusion, repeated burning reduced C and N storage, consistent with previous studies, but fire also reduced potential decomposition, likely contributing to slower C and N cycling. Trees were important in shaping soil carbon responses across sites, but the magnitude of tree effects differed and depended on how tree biomass inputs into soil responded to fire.

}, keywords = {LTER-KNZ}, doi = {10.1002/ecm.1409}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ecm.1409}, author = {Pellegrini, Adam.F.A. and Hobbie, Sarah E. and Reich, Peter B. and A. Jumpponen and Brookshire, E.N. Jack and Caprio, Anthony C. and Coetsee, Corli and Jackson, Robert B.} } @article {KNZ001945, title = {Belowground biomass response to nutrient enrichment depends on light limitation across globally distributed grasslands}, journal = {Ecosystems}, volume = {22}, year = {2019}, pages = {1466{\textendash}1477}, abstract = {

Anthropogenic activities are increasing nutrient inputs to ecosystems worldwide, with consequences for global carbon and nutrient cycles. Recent meta-analyses show that aboveground primary production is often co-limited by multiple nutrients; however, little is known about how root production responds to changes in nutrient availability. At twenty-nine grassland sites on four continents, we quantified shallow root biomass responses to nitrogen (N), phosphorus (P) and potassium plus micronutrient enrichment and compared below- and aboveground responses. We hypothesized that optimal allocation theory would predict context dependence in root biomass responses to nutrient enrichment, given variation among sites in the resources limiting to plant growth (specifically light versus nutrients). Consistent with the predictions of optimal allocation theory, the proportion of total biomass belowground declined with N or P addition, due to increased biomass aboveground (for N and P) and decreased biomass belowground (N, particularly in sites with low canopy light penetration). Absolute root biomass increased with N addition where light was abundant at the soil surface, but declined in sites where the grassland canopy intercepted a large proportion of incoming light. These results demonstrate that belowground responses to changes in resource supply can differ strongly from aboveground responses, which could significantly modify predictions of future rates of nutrient cycling and carbon sequestration. Our results also highlight how optimal allocation theory developed for individual plants may help predict belowground biomass responses to nutrient enrichment at the ecosystem scale across wide climatic and environmental gradients.

}, keywords = {LTER-KNZ, belowground biomass, Fertilization, nitrogen, Nutrient Network, optimal allocation, phosphorus roots}, doi = {10.1007/s10021-019-00350-4}, url = {https://link.springer.com/article/10.1007\%2Fs10021-019-00350-4}, author = {Cleland, Elsa E. and Lind, Eric M. and DeCrappeo, Nicole M. and DeLorenze, Elizabeth and Wilkins, Rachel Abbott and P. Adler and Bakker, Jonathan D. and Brown, Cynthia S. and Davies, Kendi F. and Esch, Ellen and Firn, Jennifer and Gressard, Scott and Gruner, Daniel S. and Hagenah, Nicole and Harpole, W. Stanley and Hautier, Yann and Hobbie, Sarah E. and Hofmockel, Kirsten S. and Kirkman, Kevin and Knops, Johannes and Kopp, Christopher W. and Kimberly J. La Pierre and MacDougall, Andrew and McCulley, Rebecca L. and Melbourne, Brett A. and Joslin L. Moore and Prober, Suzanne M. and Riggs, Charlotte and Risch, Anita C. and Schuetz, Martin and Stevens, Carly and Wragg, Peter D. and Wright, Justin and E.T. Borer and Seabloom, Eric W.} }