@article {KNZ001965, title = {Global change effects on plant communities are magnified by time and the number of global change factors imposed}, journal = {Proceedings of the National Academy of Sciences}, volume = {116}, year = {2019}, pages = {17867-17873}, abstract = {

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (\<10 y). In contrast, long-term (\≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity\–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.

}, keywords = {LTER-KNZ}, doi = {10.1073/pnas.1819027116}, url = {https://www.pnas.org/content/early/2019/08/14/1819027116}, author = {Kimberly J. Komatsu and M.L. Avolio and Lemoine, Nathan P. and Isbell, Forest and Grman, Emily and Houseman, Gregory R. and Koerner, Sally E. and Johnson, D.S. and K.R. Wilcox and Juha M. Alatalo and Anderson, J.P. and Aerts, R. and S.G. Baer and Baldwin, Andrew H. and Bates, J. and Beierkuhnlein, C. and Belote, R.T. and John M. Blair and Bloor, J.M.G. and Bohlen, P.J. and Edward W. Bork and Elizabeth H. Boughton and W.D. Bowman and Britton, Andrea J. and Cahill, James F. and Chaneton, Enrique J. and Chiariello, N.R. and Cheng, Jimin. and Scott. L. Collins and Cornelissen, J.H.C. and G. Du and Eskelinen, Anu and Firn, Jennifer and Foster, B. and Gough, L. and Gross, K. and Hallett, L.M. and Han, X. and Harmens, H. and Hovenden, M.J. and Jagerbrand, A. and Jentsch, A. and Kern, Christel and Klanderud, Kari and Alan K. Knapp and Kreyling, Juergen and Li, W. and Luo, Yiqi and McCulley, R.L. and McLaren, Jennie R. and Megonigal, Patrick and J.W. Morgan and Onipchenko, Vladimir and Pennings, S.C. and Prev{\'e}y, J.S. and Price, Jodi N. and P.B. Reich and Robinson, Clare H. and Russell, L.F. and Sala, O.E. and Seabloom, E.W. and M.D. Smith and Soudzilovskaia, Nadejda A. and Souza, Lara and K.N. Suding and Suttle, B.K. and Svejcar, T. and Tilman, David and Tognetti, P. and Turkington, R. and White, S. and Xu, Zhuwen and Yahdjian, L. and Yu, Q. and Zhang, Pengfei and Zhang, Yunhai} } @article {KNZ001927, title = {Mean annual precipitation predicts primary production resistance and resilience to extreme drought}, journal = {Science of The Total Environment}, volume = {636}, year = {2018}, pages = {360 - 366}, abstract = {

Extreme drought is increasing in frequency and intensity in many regions globally, with uncertain consequences for the resistance and resilience of ecosystem functions, including primary production. Primary production resistance, the capacity to withstand change during extreme drought, and resilience, the degree to which production recovers, vary among and within ecosystem types, obscuring generalized patterns of ecological stability. Theory and many observations suggest forest production is more resistant but less resilient than grassland production to extreme drought; however, studies of production sensitivity to precipitation variability indicate that the processes controlling resistance and resilience may be influenced more by mean annual precipitation (MAP) than ecosystem type. Here, we conducted a global meta-analysis to investigate primary production resistance and resilience to extreme drought in 64 forests and grasslands across a broad MAP gradient. We found resistance to extreme drought was predicted by MAP; however, grasslands (positive) and forests (negative) exhibited opposing resilience relationships with MAP. Our findings indicate that common plant physiological mechanisms may determine grassland and forest resistance to extreme drought, whereas differences among plant residents in turnover time, plant architecture, and drought adaptive strategies likely underlie divergent resilience patterns. The low resistance and resilience of dry grasslands suggests that these ecosystems are the most vulnerable to extreme drought \– a vulnerability that is expected to compound as extreme drought frequency increases in the future.

}, keywords = {LTER-KNZ}, doi = {10.1016/j.scitotenv.2018.04.290}, url = {https://www.sciencedirect.com/science/article/abs/pii/S0048969718314670}, author = {Ha{\"e}ntjens, Ellen and De Boeck, Hans J. and Lemoine, Nathan P. and M{\"a}nd, Pille and Dulay, K.G. and Schmidt, Inger K. and Jentsch, Anke and Stampfli, Andreas and Anderegg, William R.L. and Michael Bahn and Kreyling, Juergen and Wohlgemuth, Thomas and Lloret, Francisco and Classen, T.Aim{\'e}e. and Gough, Christopher M. and M.D. Smith} } @article {KNZ001811, title = {Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments}, journal = {Global Change Biology}, volume = {23}, year = {2017}, month = {4376-4385}, abstract = {

Climatic changes are altering Earth\&$\#$39;s hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.13706}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13706}, author = {K.R. Wilcox and Shi, Zheng and Gherardi, Laureano A. and Lemoine, Nathan P. and Koerner, Sally E. and Hoover, David L. and Bork, Edward and Byrne, Kerry M. and Cahill, James and Scott. L. Collins and Evans, Sarah and Gilgen, Anna K. and Holub, Petr and Jiang, Lifen and Alan K. Knapp and LeCain, Daniel and Liang, Junyi and Garcia-Palacios, Pablo and Pe{\~n}uelas, Josep and Pockman, William T. and M.D. Smith and Sun, Shanghua and White, Shannon R. and Yahdjian, Laura and Zhu, Kai and Luo, Yiqi} } @article {KNZ001834, title = {Precipitation and environmental constraints on three aspects of flowering in three dominant tallgrass species}, journal = {Functional Ecology}, year = {2017}, month = {Mar-05-2018}, abstract = {
  1. Flower production can comprise up to 70\% of aboveground primary production in grasslands. Yet we know relatively little about how the environment and timing of rainfall determine flower productivity. Evidence suggests that deficits or additions of rainfall during phenlologically relevant periods (i.e. growth, storage, initiation of flowering, and reproduction) can determine flower production in grasslands.
  2. We used long-term data from the Konza Prairie LTER to test how fire, soil topography, and precipitation amounts during four phenologically relevant periods of the growing season constrain three aspects of flowering in three dominant C4 grass species. Specifically, we examined the probability of flowering, flowering stalk density, and individual flowering stalk biomass for Andropogon gerardii, Schizachyrium scoparium and Sorghastrum nutans.
  3. We found that each of the three species responded to the amount of precipitation during phenologically relevant periods in unique ways. All aspects of A. gerardii flowering were sensitive to precipitation during the flowering stalk elongation period (June 20 \– Aug 3). The probability of S. nutans flowering was partly determined by precipitation during the rapid growth phase (April 21 \– June 4), whereas flowering stalk density of this species depended on rainfall during flowering stalk elongation (June 20 \– Aug 3). In contrast, all aspects of flowering of S. scoparium were relatively independent of rainfall during any period.
  4. Our results demonstrate that three functionally similar, codominant C4 grass species respond differently to phenologically relevant precipitation periods. As a result, drought during any phenological window during the growing season can adversely impact biomass and flowering production of grasslands via species-specific reductions in flowering stalk density and biomass.
}, keywords = {LTER-KNZ}, doi = {10.1111/1365-2435.12904}, url = {https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2435.12904}, author = {Lemoine, Nathan P. and Dietrich, J.D. and M.D. Smith} }