@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 {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 {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} } @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.} }