Woody plant phylogenetic diversity mediates bottom–up control of arthropod biomass in species-rich forests
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Global change is predicted to cause non-random species loss in plant communities, with consequences for ecosystem functioning. However, beyond the simple effects of plant species richness, little is known about how plant diversity and its loss influence higher trophic levels, which are crucial to the functioning of many species-rich ecosystems. We analyzed to what extent woody plant phylogenetic diversity and species richness contribute to explaining the biomass and abundance of herbivorous and predatory arthropods in a species-rich forest in subtropical China. The biomass and abundance of leaf-chewing herbivores, and the biomass dispersion of herbivores within plots, increased with woody plant phylogenetic diversity. Woody plant species richness had much weaker effects on arthropods, but interacted with plant phylogenetic diversity to negatively affect the ratio of predator to herbivore biomass. Overall, our results point to a strong bottom–up control of functionally important herbivores mediated particularly by plant phylogenetic diversity, but do not support the general expectation that top–down predator effects increase with plant diversity. The observed effects appear to be driven primarily by increasing resource diversity rather than diversity-dependent primary productivity, as the latter did not affect arthropods. The strong effects of plant phylogenetic diversity and the overall weaker effects of plant species richness show that the diversity-dependence of ecosystem processes and interactions across trophic levels can depend fundamentally on non-random species associations. This has important implications for the regulation of ecosystem functions via trophic interaction pathways and for the way species loss may impact these pathways in species-rich forests.
KeywordsBEF China Biodiversity Ecosystem function Herbivores Predators Species richness Trophic interactions
We thank the administration of the Gutianshan National Nature Reserve and members of the BEF China consortium for support, Stefan Michalski and Walter Durka for providing woody plant phylogenetic data, and Daria Golub, Merle Noack, and Friederike Rorig for help with arthropod sampling. Comments of two anonymous reviewers greatly helped to improve the manuscript. We gratefully acknowledge funding by the German Research Foundation (DFG FOR 891/1 and 891/2),the Sino-German Centre for Research Promotion in Beijing (GZ 524, 592, 698, 699, 785, and 1,020), and the National Science Foundation of China (NSFC 30710103907 and 30930005).
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