Data and code for "The scale- and environment- dependent limits of biodiversity's influence on ecosystem function"

Biodiversity and ecosystem function often covary, but correlation does not establish causality. Biodiversity’s influence on ecosystem function can be anticipated when it varies independently of environmental drivers. We predict from community assembly theory that this independence is greatest at small spatial scales in low-productivity environments, where stochastic processes generate biodiversity variation not determined by abiotic conditions. Using plant community data from six grassland sites across a precipitation gradient in northern China, we quantified the marginal effect of species richness on aboveground biomass across seven nested spatial scales (0.01–1 m2). Biodiversity’s effect on function was stronger in drier sites at smaller scales, where stochastic assembly permits independent variation. This effect declined with increasing scale across all sites, particularly in wetter environments where environmental filtering couples biodiversity and function. Our results define a scale- and environment- dependent causal domain for biodiversity’s influence on ecosystem function. Recognizing this constraint is essential for applying biodiversity–ecosystem function theory to conservation.