Community leaf nutrient characteristics drive soil carbon stabilization by regulating soil nutrient and microbial community in a subtropical forest plantation

Abstract Tree species diversity has been found to promote soil organic carbon (SOC) in forests, but its effects on SOC stability have been poorly studied. Using a 6-year-old forest biodiversity experiment with monocultures and mixtures of two, four, and eight tree species, we evaluated how functional diversity (FDis) and community-weighted mean (CWM) of leaf nutrients influence the formation of mineral-associated organic carbon (MAOC) via altering the soil microbial community. Our results revealed that FDis of leaf nitrogen (LNmass) and phosphorus (LPmass) contents, as well as CWM of LPmass were negatively associated with MAOC, patterns that were mediated by microbial biomass. In addition, CWM of LNmass was negatively associated with the MAOC:SOC ratio, a relationship mediated by a decrease in the ratio of fungal to bacterial biomass (F:B ratio), while CWM of LPmass exhibited a direct positive effect on the MAOC:SOC ratio. Our results also showed that soil nutrient availability mediated the relationship between the diversity of leaf nutrients on the soil microbial community. These results suggest that the diversity of leaf nutrient contents may shape SOC stabilization through moderating microbial biomass and F:B ratio, offering insights into the ecological importance of plant chemical traits in driving SOC stabilization in forest ecosystems.