Mechanistic links between biodiversity effects on ecosystem functioning and stability in a multi-site grassland experiment

Although the positive effects of biodiversity on ecosystem functioning and stability have been extensively documented in the literature, previous studies have mostly explored the mechanisms of functioning and stability independently. It is unclear how biodiversity effects on functioning may covary with those on stability. Here we developed an integrated framework to explore links between mechanisms underlying biodiversity effects on functioning and those on stability. Specifically, biodiversity effects on ecosystem functioning were partitioned into complementarity effects (CE) and selection effects (SE), and those on stability were partitioned into species asynchrony and species stability. We investigated how CE and SE were linked to species asynchrony and stability and how their links might be mediated by species evenness, using a multi-site grassland experiment. Our mixed-effects models showed that a higher community productivity was mainly due to CE and a higher community stability was mainly due to species asynchrony. Moreover, CE was positively related to species asynchrony, thus leading to a positive association between ecosystem productivity and stability. We used a structural equation model to illustrate how species evenness might mediate links between the various mechanisms. Communities with a higher evenness exhibited a higher CE and species asynchrony, but a lower SE and species stability. These evenness-mediated associations enhanced the positive relationship between CE and species asynchrony, but blurred that between SE and species asynchrony. Synthesis. Our findings demonstrate mechanistic links between biodiversity effects on ecosystem functioning and stability. By doing so, our study contributes a novel framework for understanding ecological mechanisms of the functioning–stability relationship, which has important implications for developing management plans focused on strengthening synergies between ecosystem functioning and stability over the long term.