Response diversity increases functional but decreases compositional stability of grassland communities.

The insurance hypothesis of biodiversity assumes that biodiversity increases ecosystem stability when functionally redundant species exhibit distinct responses to environmental changes, allowing some species to compensate for the loss of others. However, empirical evidence remains scarce. Using a novel approach to quantify the responses of 96 plant species to land use, we tested the hypothesis combining field data with a common garden experiment. By subjecting transplanted grassland plant communities to different land-use intensities, we quantified response diversity (defined as the variability of responses among species to the same environmental factor), species composition, and functionality from spectral data before and after experimental changes. Our results show that land-use intensification reduced response diversity of plant communities in the field and the common garden. Moreover, our results indicate that response diversity increases functional stability but decreases stability in terms of species composition (temporal β-diversity), that is, response-diverse communities tended to lose species with fewer replacements while response-depleted communities mainly experienced species turnover. Our work highlights that response diversity underlies multiple dimensions of ecosystem stability as it stabilizes functionality but destabilizes species composition. We further discuss future research directions to adapt the concept of response diversity under global change scenarios.