Carbon quality mediates the nutrient accelerating effects of fungi on wood decomposition

Fungi are key agents in decomposing high-lignin, low-nutrient content deadwood, yet how variations in carbon quality and nutrient availability shape fungal communities and their decay activities remains poorly understood. Here, we investigated how carbon quality (lignin vs. cellulose) and nutrient inputs (nitrogen and phosphorus) interact to influence fungal community composition and decomposition of angiosperm versus gymnosperm deadwood in a subtropical forest. Our results reveal contrasting fungal responses to nutrient additions in angiosperm and gymnosperm deadwood, leading to distinct impacts on decomposition rates. In nutrient-rich, low-lignin angiosperm wood, nitrogen and phosphorus additions shifted the community from Basidiomycota dominance toward Ascomycota and markedly increased fungal diversity. Fungal community shifts enhanced hydrolytic enzyme activity targeting decomposition of cellulose, accelerating overall carbon mineralization rates. Conversely, in nutrient-poor, high-lignin gymnosperm wood, nutrient additions strengthened the dominance of Basidiomycota, reduced fungal diversity, and disproportionately enhanced lignin decomposition. These findings emphasize that wood carbon quality mediates how nutrient inputs accelerate deadwood decomposition through the reassembly of fungal taxa with specific metabolic traits. The nutrient–carbon trade-off in fungal communities highlights a previously underappreciated mechanism controlling wood decay and carbon cycling in tropical forest ecosystems. Understanding these processes is pivotal for improving predictions of carbon storage and turnover under changing nutrient regimes.