Cross-scale drivers of soil fungal diversity in fragmented forests of southwestern China

While numerous studies have explored the factors influencing soil fungal diversity, few compared the impact of environmental variables across multiple spatial scales. Based on 30 plots spanning a fragmentation gradient in tropical forests of Xishuangbanna, southwestern China, we predicted the diversity and composition of nine soil fungal functional guilds with environmental factors across local-, patch-, and landscape-scales. The results showed that local tree composition was the most dominant factor associating with almost all the detected fungal functional guilds, explaining an average of 45.72% relative contribution. Although patch and landscape factors contributed less, the mean patch area at the landscape scale still showed a significant negative association with the diversity of fungal functional guilds. Some fungal functional guilds showed contrasting patterns to environmental factors. Specifically, the richness and abundance of ectomycorrhizal fungi exhibited opposite trends to forest types relative to other guilds, whereas the community composition of soil/unspecified saprotrophic fungi showed contrasting responses to tree composition compared with other guilds. Our results emphasize that local environments (i.e., soil and tree) remain the main factor affecting soil fungal diversity and composition in tropical forests. Therefore, maintaining diverse forest types and compositional heterogeneity of tree species can help future fungal conservation efforts.