Trait-mediated microbial responses to carbon-phosphorus co-limitation drive necromass accrual and soil carbon sequestration during tropical forest restoration

Cai, Xiaoyi

CATENA

2026

274

Chen, CF; Liu, WJ

Ecological restoration is widely implemented to recover degraded lands, yet the microbial mechanisms underpinning soil organic carbon (SOC) sequestration during this process remain poorly understood, particularly regarding how nutrient availability shapes microbial community traits and necromass accumulation. In this study, we utilized a space-for-time substitution method across a tropical ecological restoration chronosequence (comprising rubber monoculture, near-natural rainforest, and primary rainforest) and integrated analyses of soil properties, microbial biomarkers, and molecular sequencing to investigate the linkages between microbial nutrient limitation, community structural and functional traits, and soil carbon fractions. Our results showed that ecological restoration significantly improved litter and soil nutrient stoichiometry, alleviating microbial carbon (C) and phosphorus (P) limitation. This variation drove a shift in microbial life-history strategies from high growth yield strategies to resource-acquisition/stress-tolerance strategies, increasing microbial carbon use efficiency (19-60%), richness (27-79%), biomass (10-64%), and network complexity (1.9-3.3-fold) while reducing competitive interactions. Concurrently, stochastic processes became more dominant in community assembly. Metagenomic analysis revealed enhanced expression of genes involved in C fixation, recalcitrant C degradation (e.g., lignin degradation), and P cycling. Consequently, microbial necromass C, particularly fungal-derived C, increased significantly (13-61%) and emerged as a stronger direct driver of SOC accumulation than plantderived C, despite a decrease in its proportional contribution to the SOC pool. These results suggest that alleviated nutrient limitation is linked to coordinated shifts in microbial metabolism and community characteristics, which in turn promote necromass accumulation and contribute to SOC sequestration. This study underscores the necessity of integrating microbial metabolic traits into soil carbon management strategies for degraded tropical plantations.