Biodiversity mitigates drought effects in the decomposer system across biomes

Multiple facets of global change affect the Earth System interactively with complex consequences for ecosystem functioning and stability. Simultaneous climate and biodiversity change are of particular concern, because biodiversity may contribute to ecosystem resistance and resilience and may mitigate climate change impacts. Yet, the extent and generality of how climate and biodiversity change interact, remain insufficiently understood, especially for the decomposition of organic matter, a major determinant of the biosphere – atmosphere carbon feedbacks. Decomposition depends on the characteristics and diversity of plant-produced organic matter as the primary energy source, and is further regulated by an astounding diversity of soil organisms ranging from prokaryotes to macro-invertebrates that are organized in highly complex food webs. With an inter-biome experiment, we tested here how biodiversity in the multi-trophic decomposer system drives decomposition in forest ecosystems under drier conditions. Our results show at a relevant spatial scale covering distinct climate zones that forest floor biodiversity across trophic levels has a strong potential to mitigate drought effects on C and N dynamics during decomposition.  Preserving biodiversity at multiple trophic levels contributes to ecosystem resistance and appears critical to maintain ecosystem processes under ongoing climate change.