@article {KNZ001755, title = {Addition of multiple limiting resources reduces grassland diversity}, journal = {Nature}, volume = {537}, year = {2016}, pages = {93-96}, abstract = {

Niche dimensionality provides a general theoretical explanation for biodiversity\—more niches, defined by more limiting factors, allow for more ways that species can coexist1. Because plant species compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number of species that can coexist2. Multiple nutrient limitation of plant production is common and therefore fertilization may reduce diversity by reducing the number or dimensionality of belowground limiting factors. At the same time, nutrient addition, by increasing biomass, should ultimately shift competition from belowground nutrients towards a one-dimensional competitive trade-off for light3. Here we show that plant species diversity decreased when a greater number of limiting nutrients were added across 45 grassland sites from a multi-continent experimental network4. The number of added nutrients predicted diversity loss, even after controlling for effects of plant biomass, and even where biomass production was not nutrient-limited. We found that elevated resource supply reduced niche dimensionality and diversity and increased both productivity5 and compositional turnover. Our results point to the importance of understanding dimensionality in ecological systems that are undergoing diversity loss in response to multiple global change factors.

}, keywords = {LTER-KNZ}, doi = {10.1038/nature19324}, url = {https://www.nature.com/articles/nature19324}, author = {Harpole, W. S. and L.L. Sullivan and Lind, E.M. and Firn, J. and P. Adler and E.T. Borer and Chase, J. and Fay, P.A. and Hautier, Y. and Hillebrand, H. and MacDougall, A.S. and Seabloom, E.W. and Williams, R. and J.D. Bakker and Cadotte, M.W. and Chaneton, E.J. and Chu, C. and Cleland, E.E. and Antonio, C. and Davies, K.F. and Gruner, D.S. and Hagenah, N. and Kirkman, K. and Knops, J.M.H. and Kimberly J. La Pierre and McCulley, R.L. and Joslin L. Moore and J.W. Morgan and Prober, S.M. and A. Risch and Schuetz, M. and Stevens, C.J. and Wragg, P.D.} } @article {KNZ001788, title = {Grassland productivity limited by multiple nutrients}, journal = {Nature Plants}, volume = {1}, year = {2015}, pages = {15080}, abstract = {

Terrestrial ecosystem productivity is widely accepted to be nutrient limited1. Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)2,3, the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized4,​5,​6,​7,​8. However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.

}, keywords = {LTER-KNZ}, doi = {10.1038/nplants.2015.80}, url = {https://www.nature.com/articles/nplants201580}, author = {Fay, P.A. and Prober, S.M. and Harpole, W.S. and Knops, J.M.H. and J.D. Bakker and E.T. Borer and Lind, E.M. and MacDougall, A.S. and Seabloom, E.W. and Wragg, P.D. and P. Adler and D.M. Blumenthal and Buckley, Y.M. and Chu, C. and Cleland, E.E. and Scott. L. Collins and Davies, K.F. and G. Du and Feng, X. and Firn, J. and Gruner, D.S. and Hagenah, N. and Hautier, Y. and Heckman, R.W. and Jin, V.L. and Kirkman, K.P. and Klein, J. and L. Ladwig and Li, Q. and McCulley, R.L. and Melbourne, B.A. and Mitchell, C.E. and Joslin L. Moore and J.W. Morgan and A. Risch and sch{\"u}tz, M. and Stevens, C.J. and Wedin, D.A. and Yang, L.H.} } @article {KNZ001678, title = {Plant diversity predicts beta but not alpha diversity of soil microbes across grasslands worldwide}, journal = {Ecology Letters}, volume = {18}, year = {2015}, pages = {85 -95}, abstract = {

Aboveground\–belowground interactions exert critical controls on the composition and function of terrestrial ecosystems, yet the fundamental relationships between plant diversity and soil microbial diversity remain elusive. Theory predicts predominantly positive associations but tests within single sites have shown variable relationships, and associations between plant and microbial diversity across broad spatial scales remain largely unexplored. We compared the diversity of plant, bacterial, archaeal and fungal communities in one hundred and forty-five 1 m2 plots across 25 temperate grassland sites from four continents. Across sites, the plant alpha diversity patterns were poorly related to those observed for any soil microbial group. However, plant beta diversity (compositional dissimilarity between sites) was significantly correlated with the beta diversity of bacterial and fungal communities, even after controlling for environmental factors. Thus, across a global range of temperate grasslands, plant diversity can predict patterns in the composition of soil microbial communities, but not patterns in alpha diversity.

}, keywords = {LTER-KNZ}, doi = {10.1111/ele.12381}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.12381}, author = {Prober, S.M. and Leff, J.W. and Bates, S.T. and E.T. Borer and Firn, J. and Harpole, W.S. and Lind, E.M. and Seabloom, E.W. and P. Adler and J.D. Bakker and E.E Cleland and DeCrappeo, N.M. and DeLorenze, E. and Hagenah, N. and Hautier, Y. and Hofmockel, K.S. and Kirkman, K.P. and Knops, J.M.H. and Kimberly J. La Pierre and MacDougall, A.S. and McCulley, R.L. and Mitchell, C.E. and A. Risch and Schuetz, M. and Stevens, C.J. and Williams, R.J. and Fierer, N.} } @article {KNZ001697, title = {Plant species{\textquoteright} origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands}, journal = {Nature Communications}, volume = {6}, year = {2015}, pages = {7710 -}, abstract = {

Exotic species dominate many communities; however the functional significance of species\’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands.

}, keywords = {LTER-KNZ, Biological sciences, ecology, Plant sciences}, doi = {10.1038/ncomms8710}, url = {https://www.nature.com/articles/ncomms8710}, author = {Seabloom, E.W. and E.T. Borer and Buckley, Y. and Cleland, E.E. and Davies, K.F. and Firn, J. and Harpole, W.S. and Hautier, Y. and Lind, E. and MacDougall, A.S. and Orrock, J.L. and Prober, S.M. and P. Adler and Anderson, T.M. and J.D. Bakker and L.A. Biederman and D.M. Blumenthal and C.S. Brown and Brudvig, L.A. and Cadotte, M. and Chu, C. and Cottingham, K.L. and Crawley, M.J. and Damschen, E.I. and D{\textquoteright}Antonio, C.M. and CeCrappeo, N.M. and G. Du and Fay, P.A. and Frater, P. and Gruner, D.S. and Hagenah, N. and Hector, A. and Hillebrand, H. and Hofmockel, K.S. and Humphries, H.C. and Jin, V.L. and Kay, A.D. and Kirkman, K.P. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and L. Ladwig and Lambrinos, J.G. and Li, Q. and Li, W. and Marushia, R.} } @article {KNZ001589, title = {Biotic mechanisms of community stability shift along a precipitation gradient}, journal = {Ecology}, volume = {95}, year = {2014}, pages = {1693 -1700}, abstract = {

Understanding how biotic mechanisms confer stability in variable environments is a fundamental quest in ecology, and one that is becoming increasingly urgent with global change. Several mechanisms, notably a portfolio effect associated with species richness, compensatory dynamics generated by negative species covariance and selection for stable dominant species populations can increase the stability of the overall community. While the importance of these mechanisms is debated, few studies have contrasted their importance in an environmental context. We analyzed nine long-term data sets of grassland species composition to investigate how two key environmental factors, precipitation amount and variability, may directly influence community stability and how they may indirectly influence stability via biotic mechanisms. We found that the importance of stability mechanisms varied along the environmental gradient: strong negative species covariance occurred in sites characterized by high precipitation variability, whereas portfolio effects increased in sites with high mean annual precipitation. Instead of questioning whether compensatory dynamics are important in nature, our findings suggest that debate should widen to include several stability mechanisms and how these mechanisms vary in importance across environmental gradients.

}, keywords = {LTER-KNZ}, doi = {10.1890/13-0895.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/13-0895.1}, author = {Hallett, L.M. and Hsu, J.S. and Cleland, E.E. and Scott. L. Collins and Dickson, T.L. and Farrer, E.C. and Gherardi, L.A. and Gross, K.L. and Hobbs, R.J. and Turnbull, L. and K.N. Suding} } @article {KNZ001793, title = {Herbivores and nutrients control grassland plant diversity via light limitation}, journal = {Nature}, volume = {508}, year = {2014}, pages = {517 - 520}, keywords = {LTER-KNZ}, doi = {10.1038/nature13144}, url = {https://www.nature.com/articles/nature13144}, author = {E.T. Borer and Seabloom, E.W. and Gruner, D.S. and Harpole, W.S and Hillebrand, H. and Lind, E.M. and P. Adler and J. Alberti and Anderson, T.M. and J.D. Bakker and L.A. Biederman and D.M. Blumenthal and C.S. Brown and Brudvig, L.A. and Buckley, Y.M. and Cadotte, M. and Chu, C. and Cleland, E.E. and Crawley, M.J. and Daleo, P. and Damschen, E.I. and Davies, K.F. and DeCrappeo, N.M. and G. Du and Firn, J. and Hautier, Y. and Heckman, R.W. and Hector, A. and HilleRisLambers, J. and Iribarne, Oscar and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and Leakey, A.D.B. and Li, W. and MacDougall, A.S. and McCulley, R.L. and Melbourne, B.A. and Mitchell, C.E. and Joslin L. Moore and Mortensen, B. and O{\textquoteright}Halloran, L.R. and Orrock, J.L. and Pascual, J. and Prober, S.M. and Pyke, D.A. and A. Risch and Schuetz, M. and M.D. Smith and Stevens, C.J. and L.L. Sullivan and Williams, R.J. and Wragg, P.D. and Wright, J.P. and Yang, L.H.} } @article {KNZ001538, title = {Coordinated distributed experiments: an emerging tool for testing global hypotheses in ecology and environmental science}, journal = {Frontiers in Ecology and the Environment}, volume = {11}, year = {2013}, pages = {147 -155}, abstract = {

There is a growing realization among scientists and policy makers that an increased understanding of today\&$\#$39;s environmental issues requires international collaboration and data synthesis. Meta-analyses have served this role in ecology for more than a decade, but the different experimental methodologies researchers use can limit the strength of the meta-analytic approach. Considering the global nature of many environmental issues, a new collaborative approach, which we call coordinated distributed experiments (CDEs), is needed that will control for both spatial and temporal scale, and that encompasses large geographic ranges. Ecological CDEs, involving standardized, controlled protocols, have the potential to advance our understanding of general principles in ecology and environmental science.

}, keywords = {LTER-KNZ}, doi = {10.1890/110279}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/110279}, author = {Fraser, L.H. and Henry, H.A. and Carlyle, C.N. and White, S.R. and Beierkuhnlein, C. and Cahill, J.F. and Casper, B.B. and Cleland, E.E. and Scott. L. Collins and Dukes, J.S. and Alan K. Knapp and Lind, E. and Long, R. and Luo, Y. and P.B. Reich and M.D. Smith and Sternberg, M. and Turkington, R.} } @article {KNZ001790, title = {Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?}, journal = {Global Change Biology}, volume = {19}, year = {2013}, pages = {3677 - 3687}, abstract = {

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species\&$\#$39; relative abundance will more rapidly advance our understanding of invasions.

}, keywords = {LTER-KNZ}, doi = {10.1111/gcb.12370}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.12370}, author = {Seabloom, E.W. and E.T. Borer and Buckley, Y. and Cleland, E.E. and Davies, K. and Firn, J. and Harpole, W.S. and Hautier, Y. and Lind, E. and MacDougall, A. and Orrock, J.L. and Prober, S.M. and P. Adler and J. Alberti and Anderson, M.T. and J.D. Bakker and L.A. Biederman and D.M. Blumenthal and C.S. Brown and Brudvig, L.A. and Caldeira, M. and Chu, C. and Crawley, M.J. and Daleo, P. and Damschen, E.I. and D{\textquoteright}Antonio, C.M. and DeCrappeo, N.M. and Dickman, C.R. and G. Du and Fay, P.A. and Frater, P. and Gruner, D.S. and Hagenah, N. and Hector, A. and Helm, A. and Hillebrand, H. and Hofmockel, K.S. and Humphries, H.C. and Iribarne, O. and Jin, V.L. and Kay, A. and Kirkman, K.P. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and L. Ladwig and Lambrinos, J.G. and Leakey, A.D.B. and Li, Q. and Li, W. and McCulley, R. and Melbourne, B. and Mitchell, C.E. and Joslin L. Moore and J.W. Morgan and Mortensen, B. and O{\textquoteright}Halloran, L.R. and P{\"a}rtel, M. and Pascual, J and Pyke, D.A. and A. Risch and Salguero-Gomez, R. and Sankaran, M. and Schuetz, M. and Simonsen, A. and M.D. Smith and Stevens, C. and Sullivan, L. and Wardle, G.M. and Wolkovich, E.M. and Wragg, P.D. and Wright, J. and Yang, L.} } @article {KNZ001540, title = {Sensitivity of grassland plant community composition to spatial vs. temporal variation in precipitation}, journal = {Ecology}, volume = {94}, year = {2013}, pages = {1687 -1696}, abstract = {

Climate gradients shape spatial variation in the richness and composition of plant communities. Given future predicted changes in climate means and variability, and likely regional variation in the magnitudes of these changes, it is important to determine how temporal variation in climate influences temporal variation in plant community structure. Here, we evaluated how species richness, turnover, and composition of grassland plant communities responded to interannual variation in precipitation by synthesizing long-term data from grasslands across the United States. We found that mean annual precipitation (MAP) was a positive predictor of species richness across sites, but a positive temporal relationship between annual precipitation and richness was only evident within two sites with low MAP. We also found higher average rates of species turnover in dry sites that in turn had a high proportion of annual species, although interannual rates of species turnover were surprisingly high across all locations. Annual species were less abundant than perennial species at nearly all sites, and our analysis showed that the probability of a species being lost or gained from one year to the next increased with decreasing species abundance. Bray-Curtis dissimilarity from one year to the next, a measure of species composition change that is influenced mainly by abundant species, was insensitive to precipitation at all sites. These results suggest that the richness and turnover patterns we observed were driven primarily by rare species, which comprise the majority of the local species pools at these grassland sites. These findings are consistent with the idea that short-lived and less abundant species are more sensitive to interannual climate variability than longer-lived and more abundant species. We conclude that, among grassland ecosystems, xeric grasslands are likely to exhibit the greatest responsiveness of community composition (richness and turnover) to predicted future increases in interannual precipitation variability. Over the long term, species composition may shift to reflect spatial patterns of mean precipitation; however, perennial-dominated systems will be buffered against rising interannual variation, while systems that have a large number of rare, annual species will show the greatest temporal variability in species composition in response to rising interannual variability in precipitation.

}, keywords = {LTER-KNZ}, doi = {10.1890/12-1006.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/12-1006.1}, author = {Cleland, E.E. and Scott. L. Collins and Dickson, T.L. and Farrer, E.C. and Gross, K.L. and Gherardi, L.A. and Hallett, L.M. and Hobbs, R.J. and Hsu, J.S. and K.N. Suding and Turnbull, L.} } @article {KNZ001616, title = {Temperature dependant shifts in phenology contribute to the success of exotic species with climate change}, journal = {American Journal of Botany}, volume = {100}, year = {2013}, pages = {1407 -1421}, abstract = {

\• Premise of the study: The study of how phenology may contribute to the assembly of plant communities has a long history in ecology. Climate change has brought renewed interest in this area, with many studies examining how phenology may contribute to the success of exotic species. In particular, there is increasing evidence that exotic species occupy unique phenological niches and track climate change more closely than native species. \• Methods: Here, we use long-term records of species\’ first flowering dates from five northern hemisphere temperate sites (Chinnor, UK and in the United States, Concord, Massachusetts; Fargo, North Dakota; Konza Prairie, Kansas; and Washington, D.C.) to examine whether invaders have distinct phenologies. Using a broad phylogenetic framework, we tested for differences between exotic and native species in mean annual flowering time, phenological changes in response to temperature and precipitation, and longer-term shifts in first flowering dates during recent pronounced climate change (\“flowering time shifts\”). \• Key results: Across North American sites, exotic species have shifted flowering with climate change while native species, on average, have not. In the three mesic systems, exotic species exhibited higher tracking of interannual variation in temperature, such that flowering advances more with warming, than native species. Across the two grassland systems, however, exotic species differed from native species primarily in responses to precipitation and soil moisture, not temperature. \• Conclusions: Our findings provide cross-site support for the role of phenology and climate change in explaining species\’ invasions. Further, they support recent evidence that exotic species may be important drivers of extended growing seasons observed with climate change in North America.

}, keywords = {LTER-KNZ, flowering time, introduced species, invasion biology, non-native species, North American prairies, plant phenology, temperate grasslands}, doi = {10.3732/ajb.1200478}, url = {https://bsapubs.onlinelibrary.wiley.com/doi/full/10.3732/ajb.1200478}, author = {Wolkovich, E.M. and Davies, T.J. and Schaefer, H. and Cleland, E.E. and Cook, B.I. and Travers, S.E. and Willis, C.G. and Davis, C.C.} } @article {KNZ001497, title = {Incorporating clonal growth form clarifies the role of plant height in response to nitrogen addition}, journal = {Oecologia}, volume = {169}, year = {2012}, pages = {1053 -1062}, abstract = {

Nutrient addition to grasslands consistently causes species richness declines and productivity increases. Competition, particularly for light, is often assumed to produce this result. Using a long-term dataset from North American herbaceous plant communities, we tested whether height and clonal growth form together predict responses to fertilization because neither trait alone predicted species loss in a previous analysis. Species with a tall-runner growth form commonly increased in relative abundance in response to added nitrogen, while short species and those with a tall-clumped clonal growth form often decreased. The ability to increase in size via vegetative spread across space, while simultaneously occupying the canopy, conferred competitive advantage, although typically only the abundance of a single species within each height-clonal growth form significantly responded to fertilization in each experiment. Classifying species on the basis of two traits (height and clonal growth form) increases our ability to predict species responses to fertilization compared to either trait alone in predominantly herbaceous plant communities.

}, keywords = {LTER-KNZ, Clonal growth, Competition, grassland, Nitrogen addition, productivity}, doi = {10.1007/s00442-012-2264-5}, url = {https://link.springer.com/article/10.1007\%2Fs00442-012-2264-5}, author = {Gough, L. and Gross, K.L. and Cleland, E.E. and Clark, C.M. and Scott. L. Collins and Fargione, J.E. and Pennings, S.C. and K.N. Suding} } @article {KNZ001455, title = {Abundance of introduced species at home predicts abundance away in herbaceous communities}, journal = {Ecology Letters}, volume = {14}, year = {2011}, pages = {274 -281}, keywords = {LTER-KNZ}, doi = {10.1111/j.1461-0248.2010.01584.x}, url = {https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1461-0248.2010.01584.x}, author = {Firn, J. and Joslin L. Moore and MacDougall, A.S. and E.T. Borer and Seabloom, E.W. and HilleRisLambers, J. and Harpole, W.S. and Cleland, E.E. and C.S. Brown and Knops, J.M.H. and Prober, S.M. and Pyke, D.A. and Farrell, K.A. and J.D. Bakker and O{\textquoteright}Halloran, L.R. and P. Adler and Scott. L. Collins and D{\textquoteright}Antonio, C.M. and Crawley, M.J. and Wolkovich, E.M. and Kimberly J. La Pierre and Melbourne, B.A. and Hautier, Y. and J.W. Morgan and Leakey, A.D.B. and Kay, A.D. and McCulley, R. and Davies, K.F. and Stevens, C.J. and Chu, C. and Holl, K.D. and Klein, J.A. and Fay, P.A. and Hagenah, N. and Kirkman, K.P. and Buckley, Y.M.} } @article {KNZ001452, title = {Patterns of trait convergence and divergence among native and exotic species in herbaceous plant communities are not modified by nitrogen enrichment}, journal = {Journal of Ecology}, volume = {99}, year = {2011}, pages = {1327 -1338}, keywords = {LTER-KNZ}, doi = {10.1111/j.1365-2745.2011.01860.x}, url = {https://www.jstor.org/stable/41333056?seq=1$\#$page_scan_tab_contents}, author = {Cleland, E.E. and Clark, C.M. and Scott. L. Collins and Fargione, J.E. and Gough, L. and Gross, K.L. and Pennings, S.C. and K.N. Suding} } @article {KNZ001448, title = {Productivity is a poor predictor of plant species richness}, journal = {Science}, volume = {333}, year = {2011}, pages = {1750 -1753}, abstract = {

For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters\−2) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.

}, keywords = {LTER-KNZ}, doi = {10.1126/science.1204498}, url = {http://science.sciencemag.org/content/333/6050/1750}, author = {P. Adler and Seabloom, E.W. and E.T. Borer and Hillebrand, H. and Hautier, Y. and Hector, A. and Harpole, W.S. and O{\textquoteright}Halloran, L.R. and Grace, J.B. and Anderson, T.M. and J.D. Bakker and L.A. Biederman and C.S. Brown and Buckley, Y.M. and Calabrese, L.B. and Chu, C.J. and Cleland, E.E. and Scott. L. Collins and Cottingham, K.L. and Crawley, M.J. and Damschen, E.I. and Davies, K.F. and DeCrappeo, N.M. and Fay, P.A. and Firn, J. and Frater, P. and Gasarch, E.I. and Gruner, D.S. and Hagenah, N. and HilleRisLambers, J. and Humphries, H.C. and Jin, V.L. and Kay, A. and Kirkman, K.P. and Klein, J.A. and Knops, J.M.H. and Kimberly J. La Pierre and Lambrinos, J.G. and Li, W. and MacDougall, A.S. and McCulley, R.L. and Melbourne, B.A. and Mitchell, C.E. and Joslin L. Moore} } @article {KNZ001424, title = {Contrasting trait responses in plant communities to experimental and geographic variation in precipitation}, journal = {New Phytologist}, volume = {188}, year = {2010}, pages = {565 -575}, abstract = {

\•Patterns of precipitation are likely to change significantly in the coming century, with important but poorly understood consequences for plant communities. Experimental and correlative studies may provide insight into expected changes, but little research has addressed the degree of concordance between these approaches. \•We synthesized results from four experimental water addition studies with a correlative analysis of community changes across a large natural precipitation gradient in the United States. We investigated whether community composition, summarized with plant functional traits, responded similarly to increasing precipitation among studies and sites. \•In field experiments, increased precipitation favored species with small seed size, short leaf life span and high leaf nitrogen (N) concentration. However, with increasing precipitation along the natural gradient, community composition shifted towards species with higher mean seed mass, longer leaf life span and lower leaf N concentrations. \•The differences in temporal and spatial scale of experimental manipulations and natural gradients may explain these contrasting results. Our results highlight the complexity of responses to climate change, and suggest that transient dynamics may not reflect long-term shifts in functional diversity and community composition. We propose a model of community change that incorporates these differences between short- and long-term responses to climate change.

}, keywords = {LTER-KNZ}, doi = {10.1111/j.1469-8137.2010.03382.x}, url = {https://nph.onlinelibrary.wiley.com/doi/full/10.1111/j.1469-8137.2010.03382.x}, author = {Sandel, B. and Goldstein, L.J. and Kraft, N.J. and Okie, J.G. and Shuldman, M.I. and Ackerly, D.D. and Cleland, E.E. and K.N. Suding} } @article {KNZ001181, title = {Rank clocks and plant community dynamics}, journal = {Ecology}, volume = {89}, year = {2008}, pages = {3534 -3541}, abstract = {Summarizing complex temporal dynamics in communities is difficult to achieve in a way that yields an intuitive picture of change. Rank clocks and rank abundance statistics provide a graphical and analytical framework for displaying and quantifying community dynamics. We used rank clocks, in which the rank order abundance for each species is plotted over time in temporal clockwise direction, to display temporal changes in species abundances and richness. We used mean rank shift and proportional species persistence to quantify changes in community structure in long-term data sets from fertilized and control plots in a late successional old field, frequently and infrequently burned tallgrass prairie, and Chihuahuan desert grassland and shrubland communities. Rank clocks showed that relatively constant species richness masks considerable temporal dynamics in relative species abundances. In the old field, fertilized plots initially experienced high mean rank shifts that stabilized rapidly below that of unfertilized plots. Rank shifts were higher in infrequently burned vs. annually burned tallgrass prairie and in desert grassland compared to shrubland vegetation. Proportional persistence showed that arid grasslands were more dynamic than mesic grasslands. We conclude that rank clocks and rank abundance statistics provide important insights into community dynamics that are often hidden by traditional univariate approaches.}, keywords = {LTER-KNZ}, doi = {10.1890/07-1646.1}, author = {Scott. L. Collins and K.N. Suding and Cleland, E.E. and Batty, M. and Pennings, S.C. and Gross, K.L. and Grace, J.S. and Gough, L. and Fargione, J.E. and Clark, C.M.} } @article {KNZ001226, title = {Scale-dependent responses of plant biodiversity to nitrogen enrichment}, journal = {Ecology}, volume = {89}, year = {2008}, pages = {2165 -2171}, abstract = {Experimental studies demonstrating that nitrogen (N) enrichment reduces plant diversity within individual plots have led to the conclusion that anthropogenic N enrichment is a threat to global biodiversity. These conclusions overlook the influence of spatial scale, however, as N enrichment may alter β diversity (i.e., how similar plots are in their species composition), which would likely alter the degree to which N-induced changes in diversity within localities translate to changes in diversity at larger scales that are relevant to policy and management. Currently, it is unclear how N enrichment affects biodiversity at scales larger than a small plot. We synthesized data from 18 N-enrichment experiments across North America to examine the effects of N enrichment on plant species diversity at three spatial scales: small (within plots), intermediate (among plots), and large (within and among plots). We found that N enrichment reduced plant diversity within plots by an average of 25\% (ranging from a reduction of 61\% to an increase of 5\%) and frequently enhanced β diversity. The extent to which N enrichment altered β diversity, however, varied substantially among sites (from a 22\% increase to an 18\% reduction) and was contingent on site productivity. Specifically, N enrichment enhanced β diversity at low-productivity sites but reduced β diversity at high-productivity sites. N-induced changes in β diversity generally reduced the extent of species loss at larger scales to an average of 22\% (ranging from a reduction of 54\% to an increase of 18\%). Our results demonstrate that N enrichment often reduces biodiversity at both local and regional scales, but that a focus on the effects of N enrichment on biodiversity at small spatial scales may often overestimate (and sometimes underestimate) declines in regional biodiversity by failing to recognize the effects of N on β diversity.}, keywords = {LTER-KNZ}, doi = {10.1890/07-0971.1}, author = {Chalcraft, D.R. and Cox, S.B. and Clark, C.M. and E.E Cleland and K.N. Suding and Weiher, E. and Pennington, D.} } @article {KNZ001180, title = {Species responses to nitrogen fertilization in herbaceous plant communities, and associated species traits}, journal = {Ecology}, volume = {89}, year = {2008}, pages = {1175 -}, abstract = {

This synthetic data set contains plant species relative abundance measures from 35 nitrogen (N) fertilization experiments conducted at 10 sites across North America. The data set encompasses the fertilization responses of 575 taxa from 1159 experimental plots. The methodology varied among experiments, in particular with regard to the type and amount of N added, plot size, species composition measure (biomass harvest, pin count, or percent cover), additional experimental manipulations, and experimental duration. At each site, each species has been classified according to a number of easily identified categorical functional traits, including life history, life form, the number of cotyledons, height relative to the canopy, potential for clonal growth, and nativity to the United States. Additional data are available for many sites, indicated by references to publications and web sites. Analyses of these data have shown that N enrichment significantly alters community composition in ways that are predictable on the basis of plant functional traits as well as environmental context. This data set could be used to answer a variety of questions about how plant community composition and structure respond to environmental changes.

}, keywords = {LTER-KNZ}, doi = {10.1890/07-1104.1}, url = {https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/07-1104.1}, author = {Cleland, E.E. and Clark, C.M. and Scott. L. Collins and Fargione, J.E. and Gough, L. and Gross, K.L. and Pennings, S.C. and W.D. Bowman and Robertson, G.P. and Simpson, J. and Tilman, D. and K.N. Suding} } @article {KNZ001094, title = {Environmental and plant community determinants ofspecies loss following nitrogen enrichment}, journal = {Ecology Letters}, volume = {10}, year = {2007}, pages = {596 -607}, abstract = {Global energy use and food production have increased nitrogen inputs to ecosystems worldwide, impacting plant community diversity, composition, and function. Previous studies show considerable variation across terrestrial herbaceous ecosystems in the magnitude of species loss following nitrogen (N) enrichment. What controls this variation remains unknown. We present results from 23 N-addition experiments across North America, representing a range of climatic, soil and plant community properties, to determine conditions that lead to greater diversity decline. Species loss in these communities ranged from 0 to 65\% of control richness. Using hierarchical structural equation modelling, we found greater species loss in communities with a lower soil cation exchange capacity, colder regional temperature, and larger production increase following N addition, independent of initial species richness, plant productivity, and the relative abundance of most plant functional groups. Our results indicate sensitivity to N addition is co-determined by environmental conditions and production responsiveness, which overwhelm the effects of initial community structure and composition.}, keywords = {LTER-KNZ}, doi = {10.1111/j.1461-0248.2007.01053.x}, author = {Clark, C.M. and Cleland, E.E. and Scott. L. Collins and Fargione, J.E. and Gough, L. and Pennings, S.C. and K.N. Suding and Grace, J.B.} } @article {KNZ00977, title = {Do individual plant speciesshow predictable responses to nitrogen addition across multipleexperiments?}, journal = {Oikos}, volume = {110}, year = {2005}, pages = {547 -555}, abstract = {A number of experiments have addressed how increases in nitrogen availability increase the productivity and decrease the diversity of plant communities. We lack, however, a rigorous mechanistic understanding of how changes in abundance of particular species combine to produce changes in community productivity and diversity. Single experiments cannot provide insight into this issue because each species occurs only once per experiment, and each experiment is conducted in only one location; thus, it is impossible from single experiments to determine whether responses of particular species are consistent across environments or dependent on the particular environmental context in which the experiment was conducted. To address this issue, we assembled a dataset of 20 herbaceous species that were each represented in at least 6 different fertilization experiments and tested whether responses were general across experiments. Of the 20 species, one consistently increased in relative abundance and five consistently decreased across replicate experiments. A partially-overlapping group of 8 species displayed responses to nitrogen that varied predictably among experiments as a function of geographic location, neighboring species, or a handful of other community characteristics (ANPP, precipitation, species richness, relative abundance of focal species in control plots, and community composition). Thus, despite modest replication and a limited number of predictor variables, we were able to identify consistent patterns in response of 10 out of 20 species across multiple experiments. We conclude that the responses of individual species to nitrogen addition are often predictable, but that in most cases these responses are functions of the abiotic or biotic environment. Thus, a rigorous understanding of how plant species respond to nitrogen addition will have to consider not only the traits of individual plant species, but also aspects of the communities in which those plants live.}, keywords = {LTER-KNZ}, doi = {10.1111/j.0030-1299.2005.13792.x}, author = {Pennings, S.C. and Clark, C.M. and Cleland, E.E. and Scott. L. Collins and Gough, L. and Gross, K.L. and Milchunas, D.G. and K.N. Suding} } @article {KNZ00967, title = {Functional and abundance based mechanisms explain diversity loss due to nitrogen fertilization}, journal = {Proceedings of the National Academy of Sciences}, volume = {102}, year = {2005}, pages = {4387 -4392}, abstract = {Human activities have increased N availability dramatically in terrestrial and aquatic ecosystems. Extensive research demonstrates that local plant species diversity generally declines in response to nutrient enrichment, yet the mechanisms for this decline remain unclear. Based on an analysis of >900 species responses from 34 N-fertilization experiments across nine terrestrial ecosystems in North America, we show that both trait-neutral and trait-based mechanisms operate simultaneously to influence diversity loss as production increases. Rare species were often lost because of soil fertilization, randomly with respect to traits. The risk of species loss due to fertilization ranged from >60\% for the rarest species to 10\% for the most abundant species. Perennials, species with N-fixing symbionts, and those of native origin also experienced increased risk of local extinction after fertilization, regardless of their initial abundance. Whereas abundance was consistently important across all systems, functional mechanisms were often system-dependent. As N availability continues to increase globally, management that focuses on locally susceptible functional groups and generally susceptible rare species will be essential to maintain biodiversity.}, keywords = {LTER-KNZ}, doi = {10.1073/pnas.0408648102}, author = {K.N. Suding and Scott. L. Collins and Gough, L. and Clark, C.M. and Cleland, E.E. and Gross, K.L. and Milchunas, D.G. and Pennings, S.} } @article {KNZ00957, title = {Invasion in space and time: non-native species richness and relative abundance respond to interannual variation in productivity and diversity}, journal = {Ecology Letters}, volume = {7}, year = {2004}, pages = {947 -957}, abstract = {Ecologists have long sought to understand the relationships among species diversity, community productivity and invasion by non-native species. Here, four long-term observational datasets were analyzed using repeated measures statistics to determine how plant species richness and community resource capture (i.e. productivity) influenced invasion. Multiple factors influenced the results, including the metric used to quantify invasion, interannual variation and spatial scale. Native richness was positively correlated with non-native richness, but was usually negatively correlated with non-native abundance, and these patterns were stronger at the larger spatial scale. Logistic regressions indicated that the probability of invasion was reduced both within and following years with high productivity, except at the desert grassland site where high productivity was associated with increased invasion. Our analysis suggests that while non-natives were most likely to establish in species rich communities, their success was diminished by high resource capture by the resident community.}, keywords = {LTER-KNZ}, doi = {10.1111/j.1461-0248.2004.00655.x}, author = {Cleland, E.E. and M.D. Smith and Andelman, S.J. and Bowles, C. and Carney, K.M. and Horner-Devine, M.C. and Drake, J.M. and Emery, S.M. and Gramling, J.M. and Vandermast, D.B.} }