Editor's summary: It is well established that biodiversity has a positive effect on ecosystem functions such as primary production, but its effects on the diversity of plant litter and of the organisms that break it down are less clear cut. Stephan Hättenschwiler and colleagues examined litter diversity in parallel manipulative experiments at five sites ranging from subarctic to tropical, and including both aquatic and terrestrial ecosystems. Across all of the studied ecosystems, they show that reducing the diversity of litter or of detritivores (the invertebrates and microorganisms that break litter down) slows litter carbon and nitrogen cycling and the rate of decomposition. A reduction in decomposition caused by biodiversity loss would, for example, limit the nitrogen supply to primary producers. Although positive overall, the effects were weaker than commonly reported for primary production, thus challenging current thinking on the generality of relationships between biodiversity and ecosystem processes that are based on assessments of plant productivity.
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