Objective This paper aims to explore the effects of species diversity, structural diversity, species asynchronism, stand density and environmental factors on community biomass stability and their interaction paths at different spatial scales, and to analyze the main driving factors of biomass stability at different spatial scales, so as to provide a theoretical basis for sustainable forest management and scientific management.

Method Based on the survey data of coniferous and broadleaved mixed forest in Jiaohe, Jilin Province of northeastern China from 2010 to 2020, the relationship between biotic factors (species diversity, structural diversity, species asynchronism, stand density) and abiotic factors (topographic factors, soil physical and chemical properties) and community biomass stability at 20 m × 20 m and 40 m × 40 m spatial scales and their mechanism were investigated by structural equation model.

Result At the scale of 20 m × 20 m, biomass stability was significantly positively correlated with species asynchrony, structural diversity, and stand density. Among abiotic factors, topographic factors (slope and convexity) were positively correlated with biomass stability. At the scale of 40 m × 40 m, biomass stability was positively correlated with species asynchrony, while soil physicochemical properties (available potassium, total phosphorus and available nitrogen) were negatively correlated with biomass stability. The structural equation model analysis showed that the effect of species asynchrony on biomass stability was higher than that of stand density and structural diversity at the scale of 20 m × 20 m, and the path coefficient was 0.40. Soil physicochemical properties indirectly affected stand biomass stability by significantly affecting species diversity, and the path coefficient was 0.10. At the scale of 40 m × 40 m, only species asynchrony had a significant positive effect on biomass stability, with a path coefficient of 0.64. Topographic factors (slope and convexity) indirectly affected stand biomass stability by adjusting structural diversity, and the path coefficient was 0.35.

Conclusion At different spatial scales, although biotic factors and abiotic factors have different paths and influences on biomass stability, species asynchrony is the main driving factor for biomass stability. At the scale of 20 m × 20 m, biological factors such as species asynchrony, stand density, and structural diversity affect biomass stability through direct positive effects, while environmental factors affect biomass stability through indirect effects. At the scale of 40 m × 40 m, species asynchrony and soil physicochemical properties (available potassium, total phosphorus and available nitrogen) are the main influencing factors for biomass stability.