Plant Diversity and Aboveground Biomass Interact with Abiotic Factors to Drive Soil Organic Carbon in Beijing Mountainous Areas

Abstract

We analyzed and compared the effects of biotic factors (species diversity, structural diversity, and aboveground biomass) and abiotic factors (topography and soil properties) on soil organic carbon in selected mountainous areas of Beijing China. An overall goal is to provide a preliminary scientific basis for biodiversity protection and coordinated development of forest ecosystems and the subsequent carbon balance in this region. Our study ecosystems were coniferous forests, mixed coniferous and broadleaved forests, and broadleaved forests in the western mountainous area of Beijing. We determined both direct and indirect effects of abiotic and biotic factors on soil organic carbon using multiple linear regression and a structural equation model. Results showed that the biotic factors aboveground biomass and structural diversity were the main driving forces of organic carbon accumulation in the soil surface layer (0–10 cm), but species diversity had no significant effect (p > 0.05). Abiotic factors (altitude, total nitrogen, and total potassium) had some influence on soil surface organic carbon but were subordinate to the biotic factors. The biotic factors had no significant effect on soil organic carbon in the subsurface layers (10–20 cm) and (20–30 cm) (p > 0.05), whereas the abiotic factors altitude and total nitrogen played a dominant role in subsurface soil organic carbon accumulation of both layers (p < 0.01). The influences were both direct and indirect influences, but the direct influences played a major role. Our results form an initial reference for afforestation management (Beijing-Tianjin Sandstorm-source Control Project) from the perspective of biodiversity protection and carbon storage enhancement.