@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 {KNZ00924,
	title = {Scale dependence in the relationship between species richness and productivity: the role of spatial and temporal turnover},
	journal = {Ecology},
	volume = {85},
	year = {2004},
	pages = {2701 -2708},
	abstract = {Recent research in aquatic systems suggests that productivity{\textendash}richness relationships change with spatial scale and that species turnover (i.e., spatial and temporal variation in species composition) plays an important role in generating this scale dependence. The generality of such scale dependence and the effects of variation in temporal scale remain unknown. We examined the extent to which the richness{\textendash}productivity relationship in terrestrial plant communities depends on spatial or temporal scale and evaluated how spatial and temporal turnover (i.e., species turnover in space and time) generates scale dependence in these relationships using data from two Long-Term Ecological Research (LTER) sites (Jornada and Konza). We found a weak hump-shaped relationship (Jornada) and no relationship (Konza) between richness and productivity at the smallest focal scale (1 m2 at Jornada and 50 m2 at Konza) at each site, but strong hump-shaped relationships at the largest focal scale (49 m2 at Jornada and 200 m2 at Konza) for each site. Relationships between spatial turnover and productivity at each site mirrored the productivity{\textendash}richness relationships that emerged at the larger spatial scale (i.e., a significant hump-shaped pattern). In contrast, temporal turnover was unrelated to productivity, and hence increasing temporal scale did not appreciably change the form of the productivity{\textendash}richness relationship. Our study suggests that the way in which productivity{\textendash}richness relationships change with spatial or temporal scale depends on the form and strength of the underlying relationship between species turnover and productivity. Moreover, we contend that a dominant effect of increasing productivity is the generation of dissimilarity in species composition among localities that comprise a region, rather than increasing the number of species that occur within local communities. Thus, understanding the mechanisms that cause species turnover to vary with productivity is critical to understanding scale dependence in richness{\textendash}productivity relationships.},
	keywords = {LTER-KNZ},
	doi = {10.1890/03-0561},
	author = {Chalcraft, D.R. and Williams, J.W. and M.D. Smith and M.R. Whiles}
}
