Soil carbon fractions drive microbial community assembly processes during forest succession.

Forest succession is one of the foremost ecosystem restoration strategies, while soil microbes play essential roles in the processes by modulating carbon (C) cycling. The fraction of soil organic carbon (SOC) lead to shifts in the selective environment, which in turn contribute to changes in microbial assembly process. Here, by studying the microbial community during forest succession, the main role of SOC composition in determining soil microbial community structure and assembly process during forest succession was revealed in Changbai Mountains, China. We found that forest succession altered the structure and composition of bacterial and fungal communities and might be associated with potential changes in function. The null models indicated that forest succession enhanced the bacterial dispersal limitation process and weakened the fungal dispersal limitation processes. The labile SOC drove the microbial assembly processes by affecting microbial alpha diversity and keystone taxa, providing a new targeted therapy and an indicator of the soil microenvironment. This results highlighted the non-negligible role of labile SOC in determining microbial community assembly during long-term vegetation succession. Overall, this study could provide a perspective on the importance of the composition of SOC in shaping microbial differences and community assembly during forest succession, which cannot be overlooked in forest function studies.