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.
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We thank the Minnesota Supercomputer Institute for hosting project data, the University of Minnesota Institute on the Environment for hosting Nutrient Network meetings, and each site investigator for funding their site-level operations. Network coordination and data management were supported by funds from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) to E.T.B. and E.W.S. from the Long Term Ecological Research program (NSF-DEB-1234162) to the Cedar Creek LTER, and from the Institute on the Environment (DG-0001-13). Konza NutNet site was funded by the Konza Prairie LTER; the Saline Experimental Range NutNet site was funded by a Yale Institute for Biospheric Studies Pilot Grant. Nitrogen fertilizer was donated to the Nutrient Network by Crop Production Services, Loveland, Colorado. We thank N. Gotelli for discussions.
Extended data tables
This file contains Supplementary Tables 1-2.
About this article
Functional Ecology (2019)