Patterns of Soil Microbial Residue Carbon Accumulation in Different Plantation Forest Types: A Case Study from Beijing

Microbial residual carbon (MRC) is a key component of soil organic carbon (SOC) and crucial for SOC stabilization, contributing to the formation of a stable soil carbon pool. However, the accumulation patterns of MRC in different plantation forest types remain unclear. In this study, based on the principle of site condition similarity and supported by field investigations, soils from Populus alba, Salix matsudana Koidz, and Pinus tabuliformis in Beijing were selected as the research objects. The physical and chemical properties of the soils, as well as the microbial residual carbon content, were measured. Correlation analysis and redundancy analysis (RDA) were then conducted to explore the accumulation patterns of microbial residual carbon across different plantation forest types and to identify the factors influencing these patterns. Results showed that fungal residue carbon, bacterial residue carbon, and total MRC were highest in Populus alba, followed by Salix matsudana Koidz and Pinus tabuliformis. The contributions of fungal, bacterial, and total MRC to SOC were greatest in Populus alba, followed by Pinus tabuliformis and Salix matsudana Koidz. In this study, Populus alba were found to be more effective in sequestering microbial residue carbon. Fungal residue carbon content and its contribution to SOC were greater than bacterial residue carbon in all plantation types. Soil organic carbon, nitrate nitrogen, and available potassium were significantly correlated with both MRC content and its contribution to SOC. These findings deepen our understanding of microbial-driven soil carbon accumulation and provide a foundation for enhancing the carbon sequestration potential of plantation forests.