Species Asynchrony and Large Trees Jointly Drive Community Stability in a Montane Subtropical Forest

The relationships between biodiversity and community stability have been well-documented in grassland ecosystems, yet the diversity–stability relationship and the mechanisms driving community stability in forests remain poorly understood. In this study, we examined the community stability of a tropical montane forest in China over 10 years to explore the effect of multiple facets of biodiversity (that is, taxonomic, functional, and structural diversity). We further tested the relative importance of biodiversity, functional traits, species asynchrony, species stability, and abiotic factors (that is, soil nutrients) on community stability. We found that multiple facets of biodiversity had inconsistent effects on stability, including a neutral effect of species richness, and weak positive effects of functional diversity and structural diversity. Species asynchrony, rather than biodiversity, was the greatest predictor of community stability, followed by the stability of large trees. Consistent with the mass-ratio hypothesis, the stability of dominant species also had an important direct effect on community stability. Although functional trait composition had no direct effect on stability, it regulated stability via species asynchrony, large tree stability, and dominant species stability. Similarly, soil nutrients conferred minor effects on community stability. Our results indicated that the insurance effect is the main mechanism driving community stability in this subtropical forest. Meanwhile, the mass-ratio hypothesis also played an important role, which suggested that the management and protection of forest ecosystem should not only focus on biodiversity but also the community structural attributes.