Abstract: Litter turnover is a key ecological process that sustains nutrient cycling and resource reutilization in forest ecosystems. Based on the Nutrient Addition and Biodiversity Ecosystem Function（NaBEF） experimental platform in Shanghang County, Fujian Province, we examined 17 common subtropical plantation tree species to quantify litter leaf traits, soil physicochemical properties, and soil microbial community composition, aiming to elucidate microbial mechanisms influencing annual litter-layer turnover rates. Turnover rates varied markedly among species, ranging from 0.80 in Lithocarpus glaber to 2.38 in Euscaphis japonica. Stepwise regression analyses showed that litter maximum water-holding capacity had a significant positive effect on turnover, whereas litter lignin content and nitrogen-to-phosphorus ratio had significant negative effects. Stepwise regression of soil properties and microbial indicators further revealed that the fungal-to-bacterial ratio（F∶B）, Gram-positive to Gram-negative bacteria ratio（G⁺∶G⁻）, and total phospholipid fatty acids（PLFA）were all positively associated with litter turnover. Structural equation modeling demonstrated that species with higher litter water-holding capacity could indirectly promote litter turnover by increasing soil microbial biomass, whereas species with higher litter nitrogen-to-phosphorus ratio inhibited turnover by reducing the proportion of soil true bacteria. Although lignin content did not directly affect microbial community structure, it indirectly influenced microbial composition by lowering soil pH. These findings indicate that interspecific variation in litter leaf traits regulates annual litter-layer turnover through direct effects and indirect pathways mediated by soil microbes and environmental factors, providing theoretical support for tree species selection and soil nutrient management in subtropical plantations.