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Abstract Plant productivity varies due to environmental heterogeneity, and theory suggests that plant diversity can reduce this variation. While there is strong evidence of diversity effects on temporal variability of productivity, whether this mechanism extends to variability across space remains elusive. Here we determine the relationship between plant diversity and spatial variability of productivity in 83 grasslands, and quantify the effect of experimentally increased spatial heterogeneity in environmental conditions on this relationship. We found that communities with higher plant species richness (alpha and gamma diversity) have lower spatial variability of productivity as reduced abundance of some species can be compensated for by increased abundance of other species. In contrast, high species dissimilarity among local communities (beta diversity) is positively associated with spatial variability of productivity, suggesting that changes in species composition can scale up to affect productivity. Experimentally increased spatial environmental heterogeneity weakens the effect of plant alpha and gamma diversity, and reveals that beta diversity can simultaneously decrease and increase spatial variability of productivity. Our findings unveil the generality of the diversity-stability theory across space, and suggest that reduced local diversity and biotic homogenization can affect the spatial reliability of key ecosystem functions.
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Species occupancy is inflated by sink populations in productive environments but not unproductive environments
Abstract For decades, community ecologists have examined how diversity varies with ecosystem productivity. Despite this long history, tests of hypothesized mechanisms, namely the interplay between environmental filtering, biotic interactions, and dispersal, are lacking, largely due to the intractability of using traditional approaches. Across a productivity gradient in a serpentine grassland (California, USA), for four annual plant species, we coupled local productivity estimates, occupancy surveys, and measures of persistence tested on transplants under natural conditions and when interactions with neighbors were experimentally reduced. We found a positive effect of productivity on diversity (i.e., the proportion of our focal species occupying a location) despite strong competition limiting species persistence in productive environments. Additionally, across species and for the community, we found a strong mismatch between species occupancy versus persistence, largely due to dispersal excess causing sink populations with negative growth rates. Our results suggest that diversity–productivity relationships can be largely driven by dispersal and its interactive effects with local biotic and abiotic conditions.
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- Award ID(s):
- 2033292
- PAR ID:
- 10584539
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 106
- Issue:
- 4
- ISSN:
- 0012-9658
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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