Biodiversity–ecosystem functioning relationships (BEFs) have been extensively explored across ecosystems. However, these relationships may change as the forest matures, and the underlying mechanisms remain underexplored. Using large temperate forest datasets from 2,392 permanent plots in northeastern China, we examined the relationships between biodiversity and aboveground biomass (AGB) across different developmental stages from young to over-mature stands. We found the positive BEFs using both species richness and functional diversity, but these positive effects decreased with forest development. However, the effects of community-weighted mean on AGB showed two peaks in young and mature stands. Notably, the effects of community-weighted mean on AGB became larger than the effects of functional diversity after the forests developed to near-mature/mature stands, indicating that BEFs are driven by mass-ratio effects (i.e., dominant species) rather than niche complementarity in old stands. Our findings on how the developmental stage influences the effects of biodiversity on ecosystem functioning in natural forests will help identify effective strategies for maintaining or enhancing ecosystem services at different forest successional stages.

Livestock grazing is a major driver shaping the functioning and stability of grasslands. Although previous studies have documented the effect of grazing on grassland stability, whether this effect is scale-dependent remains unclear. Here, we conducted a sheep-grazing experiment in a temperate grassland to test grazing effects on biomass stability across scales and organizational levels. We found that an increase of grazing intensity increased species stability, but it substantially decreased local ecosystem stability due to reduced asynchronous dynamics among species. Moreover, grazing reduced ecosystem stability at larger spatial scales, but to a lesser extent. By decreasing biodiversity within and across communities, grazing impairs the insurance effects of biodiversity and hence the up-scaling of stability from species to ecosystem and further to larger scales. Our study provides the first evidence for the context-dependence of grazing effects on grassland stability via shaping biodiversity and contributes to bridging fine-scale experiments and broad-scale ecosystem management.