Abstract: The decomposition of leaf litter in forest ecosystems is influenced by leaf properties and litter-associated microbial community structure. A 2-year nitrogen (N) and/or phosphorus (P) addition field experiment was established in two forest types (40-50 vs 80-100 years old, representing middle-aged and mature forest, respectively). The decomposition rate of leaf litter and the associated fungal community structures were investigated using litterbag method and high-throughput sequencing technique. The results showed that P addition significantly affected the decomposition rate in the middle-aged forest (P<0.05), with higher decomposition rates being observed in the P addition alone (+20.3%) and NP (+19.5%) addition treatments. N addition alone decreased the decomposition rate by 10.5% in middle-aged forests. However, the addition of N and/or P did not affect the decomposition rate in the mature forest. N addition significantly reduced (-20%) leaf litter-associated fungal richness and Shannon index regardless of forest type. There were significant differences in community composition of leaf litter-associated fungi between the middle-aged and mature forests (PerMANOVA, P=0.001). The fungal community composition was impacted by N or P addition. The contents of soil total carbon, total N, total P and litter total P were important factors affecting fungal community composition. This study emphasizes the importance of exogenous N and P inputs for the decomposition of leaf litter, which improves our understanding of litter decomposition and influencing factors in subtropical forest ecosystems.

Key words: nitrogen addition, phosphorus addition, decomposition rate, leaf litter-associated fungi