Unraveling the Divergent Contributions of Plant‐ and Microbial‐Derived Carbon to Soil Organic Carbon During Subtropical Vegetation Restoration

ABSTRACT Soil organic carbon (SOC) pool substantially relies on the sequestration of plant‐derived carbon (C) (indicated by lignin) and microbe‐derived C (indicated by microbial necromass and glomalin‐related soil proteins [GRSPs]). However, how their contributions to SOC accumulation change with vegetation restoration and the underlying regulators remain unclear. We selected five stages of subtropical vegetation restoration (grassland, shrubland, early forest, middle forest, and late forest) to investigate the dynamics of lignin, microbial necromass, and GRSPs, as well as distinguishing their divergent contributions to SOC. We found that microbial necromass, GRSPs, and lignin increased with vegetation restoration, and their accumulation was primarily attributed to changes in soil fertility and microbial activity. Acid phosphatase (AP) activity, SOC, and microbial biomass C (MBC) were identified as the primary factors influencing plant lignin accumulation. The accumulation of microbial necromass primarily depended on MBC, SOC, total nitrogen, and AP activity. For GRSPs accumulation, SOC, AP, and β ‐1,4‐N‐acetylglucosaminidase activity were identified as the dominant factors. The contribution of microbial necromass C to SOC was more than plant‐derived C and GRSP‐C. Fungal necromass C consistently played a more significant role in SOC accumulation than bacterial necromass C. Overall, vegetation restoration enhanced the accumulation of plant‐ and microbial‐derived C. Our results are essential for elucidating the mechanisms controlling soil C accumulation during vegetation restoration and providing valuable insights for effectively managing and enhancing soil C stocks across different vegetation types under climate change.