Biodiversity stabilizes productivity via trait–mediated drought resistance

As climate change increases the frequency and intensity of extreme events, understanding the mechanisms that stabilize ecosystem functioning has become increasingly important1–5 . Biodiversity is widely thought to enhance ecosystem stability6–10 , yet whether this arises primarily from increased resistance to climatic extremes or faster recovery afterward remains unclear11–17 , partly because most biodiversity experiments rely on precipitation manipulations conducted under ambient climatic variability. Here we present causal evidence from the Utrecht University Biodiversity and Climate Variability Experiment18 , the first outdoor mesocosm experiment combining replicated plant diversity gradients with controlled drought manipulations independent of ambient precipitation. Across grassland communities spanning 1-12 species, higher diversity increased the temporal stability of productivity primarily by enhancing resistance to drought, with no detectable effect on recovery. Structural equation models showed that diversity effect on resistance was mediated by community trait composition and functional diversity. Communities composed of species with more conservative strategies and communities with both conservative species and acquisitive species were more resistant to drought. These results demonstrate that biodiversity stabilizes ecosystem functioning by buffering productivity against climatic extremes through trait-mediated resistance rather than recovery, highlighting the importance of conserving functional composition and trait diversity for reliable ecosystem service provision.