Functional Reorganization of Microbial Decomposers Drives Differentiation in Dead Biomass Degradation During Plantation Development

Afforestation enhances soil carbon storage through plant and microbial necromass accumulation, yet the roles of carbohydrate-active enzymes (CAZymes) and the microorganisms that encode them (biomass-decomposers) during plantation development remain poorly understood. Here, we integrated shotgun metagenomics with network analysis to decipher the successional dynamics of CAZyme-encoding genes, biomass-decomposers, and their functional linkages across a chronosequence of plantation development in northeastern China. Plantation development increased the abundance of CAZymes involved in lignin, chitin, and glucan degradation. Network analysis of biomass-decomposers revealed that the dominant function of key module M1 gradually shifted from peptidoglycan to lignin degradation through network reorganization during development. Across all developmental stages, the key modules whose dominant functions were peptidoglycan and hemicellulose degradation consistently harbored keystone species. In the overlap-network, these two functions served as dominant functions in more than one key module, confirming their essential role in maintaining fundamental community functions. Stochastic processes predominantly governed the assembly of biomass-decomposers, with increasing influence during development (R2 > 0.6). Variation in both biomass-degrading CAZymes and decomposers showed the strongest association with soil organic carbon, with CAZymes further structured by pH and nitrate nitrogen, whereas biomass-decomposers responded to moisture and total nitrogen. Overall, these findings provide new insights into belowground C cycling during plantation development, potentially guiding improved ecosystem management practices for forest restoration.