@article {6023, title = {Precipitation effects on nematode diversity and carbon footprint across grasslands}, journal = {Global Change Biology}, volume = {28}, year = {2022}, pages = {2124-2132}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.16055}, url = {https://onlinelibrary.wiley.com/doi/10.1111/gcb.16055}, author = {Franco, Andr{\'e} L.C. and Guan, Pingting and Cui, Shuyan and Tomasel, Cecilia M. and Gherardi, Laureano A. and Sala, O.E. and Wall, Diana H.} } @article {KNZ002040, title = {Ecto- and endoparasitic nematodes respond differently across sites to changes in precipitation}, journal = {Oecologia}, volume = {193}, year = {2020}, pages = {761 - 771}, keywords = {LTER-KNZ}, doi = {10.1007/s00442-020-04708-7}, url = {http://link.springer.com/10.1007/s00442-020-04708-7}, author = {Ankrom, K.E. and Franco, andr{\'e} and Fonte, S.J. and Gherardi, L.A. and de Tomasel, C.M. and Andriuzzi, W.S. and Shaw, E. A. and Sala, O.E. and Wall, D.H.} } @article {KNZ002039, title = {Drought suppresses soil predators and promotes root herbivores in mesic, but not in xeric grasslands}, journal = {Proceedings of the National Academy of Sciences}, volume = {116}, year = {2019}, pages = {12883 - 12888}, keywords = {LTER-KNZ}, doi = {10.1073/pnas.1900572116}, url = {http://www.pnas.org/lookup/doi/10.1073/pnas.1900572116}, author = {Franco, andr{\'e} and Gherardi, L.A. and de Tomasel, C.M. and Andriuzzi, W.S. and Ankrom, K.E. and Shaw, E. A. and Bach, E.M. and Sala, O.E. and Wall, D.H.} } @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 {KNZ001783, title = {Pushing precipitation to the extremes in distributed experiments: recommendations for simulating wet and dry years}, journal = {Global Change Biology}, volume = {23}, year = {2017}, pages = {1774-1782}, abstract = {

Intensification of the global hydrological cycle, ranging from larger individual precipitation events to more extreme multiyear droughts, has the potential to cause widespread alterations in ecosystem structure and function. With evidence that the incidence of extreme precipitation years (defined statistically from historical precipitation records) is increasing, there is a clear need to identify ecosystems that are most vulnerable to these changes and understand why some ecosystems are more sensitive to extremes than others. To date, opportunistic studies of naturally occurring extreme precipitation years, combined with results from a relatively small number of experiments, have provided limited mechanistic understanding of differences in ecosystem sensitivity, suggesting that new approaches are needed. Coordinated distributed experiments (CDEs) arrayed across multiple ecosystem types and focused on water can enhance our understanding of differential ecosystem sensitivity to precipitation extremes, but there are many design challenges to overcome (e.g., cost, comparability, standardization). Here, we evaluate contemporary experimental approaches for manipulating precipitation under field conditions to inform the design of \‘Drought-Net\’, a relatively low-cost CDE that simulates extreme precipitation years. A common method for imposing both dry and wet years is to alter each ambient precipitation event. We endorse this approach for imposing extreme precipitation years because it simultaneously alters other precipitation characteristics (i.e., event size) consistent with natural precipitation patterns. However, we do not advocate applying identical treatment levels at all sites \– a common approach to standardization in CDEs. This is because precipitation variability varies \>fivefold globally resulting in a wide range of ecosystem-specific thresholds for defining extreme precipitation years. For CDEs focused on precipitation extremes, treatments should be based on each site\&$\#$39;s past climatic characteristics. This approach, though not often used by ecologists, allows ecological responses to be directly compared across disparate ecosystems and climates, facilitating process-level understanding of ecosystem sensitivity to precipitation extremes.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.13504}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13504}, author = {Alan K. Knapp and M.L. Avolio and Beier, C. and Carroll, C.J.W. and Scott. L. Collins and Dukes, J.S. and Fraser, L.H. and Griffin-Nolan, R.J. and Hoover, D.L. and Jentsch, A. and Loik, M.E. and Phillips, R.P. and Post, A.K. and Sala, O.E. and Slette, I.J. and Yahdjian, L. and M.D. Smith} } @article {KNZ001730, title = {Few multiyear precipitation{\textendash}reduction experiments find a shift in the productivity{\textendash}precipitation relationship}, journal = {Global Change Biology}, volume = {22}, year = {2016}, pages = {2570-2581}, abstract = {

Well-defined productivity\–precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity\–precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation\–reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation\–manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity\–precipitation relationship downward the spatial fit. The majority of experiments (72\%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation\–reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with multiple, including more extreme, dry treatments, to identify the precipitation boundaries within which the current temporal fits remain valid.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.13269}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13269}, author = {Estiarte, M. and Vicca, S. and Pe{\~n}uelas, J. and Michael Bahn and Beier, C. and Emmett, B.A. and Fay, P.A. and Hanson, P.J. and R. Hasibeder and Kigel, J. and Kr{\"o}el-Dulay, G. and Larsen, K.S. and Lellei-Kov{\'a}cs, E. and Limousin, J-M. and Ogaya, R. and Ourcival, J-M. and Reinsch, S. and Sala, O.E. and Schmidt, I.K. and Sternberg, M. and Tielb{\"o}rger, K. and Tietema, A. and Janssens, I.A.} } @article {KNZ001684, title = {Characterizing differences in precipitation regimes of extreme wet and dry years: Implications for climate change experiments}, journal = {Global Change Biology}, volume = {21}, year = {2015}, pages = {2624 -2633}, abstract = {

Climate change is intensifying the hydrologic cycle and is expected to increase the frequency of extreme wet and dry years. Beyond precipitation amount, extreme wet and dry years may differ in other ways, such as the number of precipitation events, event size, and the time between events. We assessed 1614 long-term (100 year) precipitation records from around the world to identify key attributes of precipitation regimes, besides amount, that distinguish statistically extreme wet from extreme dry years. In general, in regions where mean annual precipitation (MAP) exceeded 1000 mm, precipitation amounts in extreme wet and dry years differed from average years by ~40\% and 30\%, respectively. The magnitude of these deviations increased to \>60\% for dry years and to \>150\% for wet years in arid regions (MAP\<500 mm). Extreme wet years were primarily distinguished from average and extreme dry years by the presence of multiple extreme (large) daily precipitation events (events \>99th percentile of all events); these occurred twice as often in extreme wet years compared to average years. In contrast, these large precipitation events were rare in extreme dry years. Less important for distinguishing extreme wet from dry years were mean event size and frequency, or the number of dry days between events. However, extreme dry years were distinguished from average years by an increase in the number of dry days between events. These precipitation regime attributes consistently differed between extreme wet and dry years across 12 major terrestrial ecoregions from around the world, from deserts to the tropics. Thus, we recommend that climate change experiments and model simulations incorporate these differences in key precipitation regime attributes, as well as amount into treatments. This will allow experiments to more realistically simulate extreme precipitation years and more accurately assess the ecological consequences.

}, keywords = {LTER-KNZ, rainfall patterns}, doi = {10.1111/gcb.12888}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.12888}, author = {Alan K. Knapp and D.L. Hoover and K.R. Wilcox and M.L. Avolio and Koerner, S.E. and Kimberly J. La Pierre and Loik, M.E. and Luo, Y. and Sala, O.E. and M.D. Smith} } @article {KNZ001614, title = {Soil animal responses to moisture availability are largely scale, not ecosystem dependent: Insight from a cross-site study}, journal = {Global Change Biology}, volume = {20}, year = {2014}, pages = {2631 -2643}, abstract = {

Climate change will result in reduced soil water availability in much of the world either due to changes in precipitation or increased temperature and evapotranspiration. How communities of mites and nematodes may respond to changes in moisture availability is not well known, yet these organisms play important roles in decomposition and nutrient cycling processes. We determined how communities of these organisms respond to changes in moisture availability and whether common patterns occur along fine-scale gradients of soil moisture within four individual ecosystem types (mesic, xeric and arid grasslands and a polar desert) located in the western United States and Antarctica, as well as across a cross-ecosystem moisture gradient (CEMG) of all four ecosystems considered together. An elevation transect of three sampling plots was monitored within each ecosystem and soil samples were collected from these plots and from existing experimental precipitation manipulations within each ecosystem once in fall of 2009 and three times each in 2010 and 2011. Mites and nematodes were sorted to trophic groups and analyzed to determine community responses to changes in soil moisture availability. We found that while both mites and nematodes increased with available soil moisture across the CEMG, within individual ecosystems, increases in soil moisture resulted in decreases to nematode communities at all but the arid grassland ecosystem; mites showed no responses at any ecosystem. In addition, we found changes in proportional abundances of mite and nematode trophic groups as soil moisture increased within individual ecosystems, which may result in shifts within soil food webs with important consequences for ecosystem functioning. We suggest that communities of soil animals at local scales may respond predictably to changes in moisture availability regardless of ecosystem type but that additional factors, such as climate variability, vegetation composition, and soil properties may influence this relationship over larger scales.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.12522}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.12522}, author = {Sylvain, Z.A. and Wall, D.H and Cherwin, K.L and Peters, D.P.C and Reichmann, L.G and Sala, O.E.} } @inbook {KNZ001125, title = {Estimating aboveground net primary production in grassland and herbaceous dominated ecosystems}, booktitle = {Principles and Standards for Measuring Net Primary Production}, year = {2007}, pages = {27 -48}, publisher = {Oxford University Press, NY}, organization = {Oxford University Press, NY}, abstract = {This paper reviews past and currently accepted methods of estimating aboveground net primary production (NPP) in grass and herb-dominated ecosystems, provides some guiding principles and recommendations to facilitate accurate determination of aboveground NPP, and discusses biases and errors and sampling adequacy. }, keywords = {LTER-KNZ}, author = {Alan K. Knapp and J. M. Briggs and Childers, D.L. and Sala, O.E.} } @article {KNZ00917, title = {Convergence across biomes to a common rain-use efficiency}, journal = {Nature}, volume = {429}, year = {2004}, pages = {651 -654}, keywords = {LTER-KNZ}, doi = {10.1038/nature02561}, author = {Huxman, T.E. and M.D. Smith and Fay, P.A. and Alan K. Knapp and Shaw, M.R. and Loik, M.E. and Smith, S.D. and Tissue, D.T. and Zak, J.C. and Weltzin, J.F. and Pockman, W.T. and Sala, O.E. and Haddad, B.M. and Harte, J. and Koch, G.W. and Schwinning, S. and Small, E.E. and Williams, D.G.} } @inbook {KNZ00563, title = {Impact of climate and atmospheric carbon dioxide changes on grasslands of the world}, booktitle = {Global Change: Effects on Coniferous Forests and Grasslands}, year = {1996}, pages = {271 -312}, publisher = {Wiley and Sons}, organization = {Wiley and Sons}, address = {Chichester}, keywords = {LTER-KNZ}, author = {Ojima, D.S. and Parton, W.J. and Coughenour, M.B. and Scurlock, J.M.O. and Kirchener, T.B. and Kittel, T.G.F. and Hall, D.O. and Schimel, D.S. and Moya, E.G. and Gilmanov, T.G. and Seastedt, T.R. and Kamnalrut, A. and Kinyamario, J.I. and Long, S.P. and Menaut, J.C. and Sala, O.E. and Scholes, R.J. and van Veen, J.A.}, editor = {Breymeyer, A.I. and Hall, D.O. and Melillo, J.M. and Agren, G.I.} } @article {KNZ0014, title = {Regional climatic similarities in the temperate zones of North and South America}, journal = {Journal of Biogeography}, volume = {22}, year = {1995}, pages = {915 -925}, abstract = {

An analysis of the climatic patterns of the temperate zones in North and South America using a global database of monthly precipitation and temperature was performed. Three synthetic variables, identified by a principal component analysis of the monthly data, were used: mean annual precipitation, mean annual temperature and the proportion of the precipitation falling during summer. The spatial gradient of the 3 variables was displayed by constructing a composite colour raster image. A parallelepiped classification algorithm was used to locate areas in both continents that are climatically similar to 5 North American long term ecological research (LTER) sites and to 2 South American LTER sites. The same algorithm was used to identify areas in South America which are climatically similar to some of the major grassland and shrubland types of North America. There was substantial overlap between the climates of North and South America. Most of the climatic patterns found in South America are well represented in North America but there are certain climates in North America that are not found in South America. An example is a climate with relatively low mean annual temperature and high summer precipitation. The climatic signatures of 3 North American LTER sites (Cedar Creek, CPER and Sevilleta) were not found in South America. The climatic signatures of two LTER sites (Konza and Jornada) had some representation in South America. Two South American research sites (Rio Mayo and Las Chilcas) were well represented climatically in North America. The climates of 6 out of 7 selected North American grassland and shrubland types were represented in South America. The northern mixed prairie type was not represented climatically in South America. It is suggested that comparisons of North and South America may provide a powerful test of climatic control over vegetation

}, keywords = {LTER-KNZ, climate}, url = {http://www.jstor.org/stable/2845992}, author = {Paruelo, J.M. and Lauenroth, W.K. and Epstein, H.E. and Burke, I.C. and Aguiar, M.R. and Sala, O.E.} }