CANCELLED - The contribution of composition: Is species richness or community composition more important for the functioning of ecosystems?

Background/Question/Methods

Global change is driving global biodiversity loss at unprecedented rates. This global biodiversity loss alters how ecosystems function and provide services to humans. Current evidence suggests declines in the number of species (richness) will lead to declines in ecosystem functioning. Yet, at the local scales represented by biodiversity experiments, the composition rather than the richness of the community is more likely to change initially as species go locally extinct but are replaced by other species. Here, we leverage the initial design of the Biodiversity and Climate Variability Experiment at Utrecht University to answer the question: How important are changes in community composition for biomass production?

Results/Conclusions

We find that species composition in terms of the community identity, the proportion of the community that is composed of a specific species, and the identity of individual species are all more important for biomass production than species richness by an order of magnitude. However, community composition variation depends on the species richness of the community, especially through time. Higher diversity communities vary more during establishment and lower diversity communities vary more under stress. These findings indicate that changes in community composition are likely to alter ecosystem functioning even without concurrent changes in species richness.