The influence of balanced and imbalanced resource supply on biodiversity–functioning relationship across ecosystems

Numerous studies show that increasing species richness leads to higher ecosystemproductivity. This effect is often attributed to more efficient portioning of multiple resources in communities with higher numbers of competing species, indicating the role of resource supply and stoichiometryfor biodiversity– ecosystemfunctioning relationships. Here, we merged theory on ecological stoichiometrywith a framework of biodiversity– ecosystemfunctioning to understand how resource use transfers into primary production. We applied a structural equation model to define patterns of diversity–productivity relationships with respect to available resources. Meta-analysis was used to summarize the findings across ecosystemtypes ranging from aquatic ecosystemsto grasslands and forests. As hypothesized, resource supply increased realized productivity and richness, but we found significant differences between ecosystemsand study types. Increased richness was associated with increased productivity, although this effect was not seen in experiments. More even communities had lower productivity, indicating that biomass production is often maintained by a few dominant species, and reduced dominance generally reduced ecosystemproductivity. This synthesis, which integrates observational and experimental studies in a variety of ecosystemsand geographical regions, exposes common patterns and differences in biodiversity–functioning relationships, and increases the mechanistic understanding of changes in ecosystemsproductivity.