Response of community diversity and productivity to canopy gap disturbance in subtropical forests

Forest ecosystem productivity is crucial for regulating global climate change and carbon budget. Previous studies have shown that community diversity (such as species, functional and structural diversity) promotes forest productivity. However, species, functional, and structural diversity are often affected by canopy gap disturbance. In the context of global change, increases in canopy gap disturbance can augment the uncertainty in these relationships. Here, we used forest inventory, functional traits, and environmental data from a 20-ha subtropical forest plot located in the Zhejiang Province of China. We applied spatial synchronous autoregressive error modeling and structural equation models (SEMs) to analyze the effects of environmental factors (topography and soil properties), canopy gap disturbance (with and without the inclusion of the effect), community diversity variables on productivity. Results showed that stand structural diversity explained the largest amount of variation in productivity, followed by initial above-ground biomass and stand density. For canopy disturbed quadrats, stand structural explained the largest amount of variation in productivity, followed by stand density and species richness. For canopy non-disturbed quadrats, initial above-ground biomass explained the largest amount of variation in productivity, followed by stand density and stand structural diversity. Canopy gap disturbance enhanced the effect of stand structural diversity on productivity and reduced the effect of initial above-ground biomass. Our results provide strong evidence for the effect of canopy gap disturbance on the relationship between biodiversity and productivity in a subtropical forest. We argue that canopy gap disturbance reduces competition and promotes complementary utilization of resources, thus enhancing the impact of niche complementarity on productivity through species richness, stand density, and tree DBH diversity in forests.