Interspecific collaboration enhances the litter nutrient cycling and fungal network connectivity in mixed forests

Forest succession induced by pine wilt disease can result in changes in vegetation, thereby reducing timber production and impacting the input of belowground litter. Litter decomposition plays a crucial role in nutrient cycling within forest ecosystems. However, studies focusing on the litter decomposition process during forest succession are not common. Therefore, we investigated the decomposition rates of litter, enzyme activities, fungal communities, and functional genes in pine needles and twigs in pure ( Pinus massoniana ) and mixed ( P. massoniana and Liquidambar formosana ) forests over three consecutive years. The results indicated that the decomposition rate of pine needles ranges from 57.79 % to 74.53 %, while the decomposition rate of pine twigs ranges from 24.16 % to 60.57 %. There is no significant difference in the litter decomposition rates between mixed and pure forests. During litter decomposition, the activity of acid phosphatase in pure forests was consistently higher than in mixed forests. Pure forests recruited more unique fungi to participate in decomposition compared to mixed forests. The fungal network connections in mixed forests are more complex than those in pure forests, and they become even more complex in the later stages of decomposition. There are differences in functional gene structure between mixed and pure forests, with an increase in the abundance of nitrogen cycle genes ( nirK 1, nirK 2, nirK 3, nirS 1, nirS 2) and phosphorus cycle genes ( phoX ) in mixed forests, thereby promoting nutrient cycling. In summary, these research results provide new insights into the mechanisms that regulate ecosystem functions and fungal community during forest succession.