5 Conclusions
The conversion from natural forest to monoculture plantations decreased C and N contents and related enzymes activities (such as sucrase, acid protease, urease, glutaminase, acid and alkaline phosphatase activities), thereby reducing soil quality. The conversion resulted in markedly differences in the structure of the fungal community between Forest and plantations, and increased microbial α-diversity. According to the life history classification system based on functional traits - Grime’s C-S-R (competitor, stress-tolerator, ruderal) life history framework, forest conversion decreased the abundance of dominant fungal taxa including Basidiomycota (C-strategists), but increased that in Ascomycota (S-strategists) and Zygomycota (R-strategists). The decrease of C-strategists Basidiomycota indicated that forest conversion had a negative impact on the fungal lignin decomposition ability and competitive intensity, especially for oligotrophic taxa. The increase of S-strategists Ascomycota and R-strategists Zygomycota demonstrated that some taxa with stress-tolerating and ruderal survival strategies, such as copiotrophic fungi, maximize occupation and exploitation of available resources after conversion. Correspondingly, Pseudophialophora, Rhytisma and other genera (mostly belonging to Ascomycota) increased, while Russula (mostly belonging to Basidiomycota) decreased. Correlation analysis showed that, in addition to soil pH, the key indicators of SQI, including organic carbon, glutaminase, and phosphorus, were main drivers for fungal community characteristics in subtropical forest conversion. To conclude, forest conversion to monoculture plantations decreased soil quality, but increased the dominance of S and R strategists in a more diverse fungal community, retarding lignin decomposition and increasing the depletion of available resources.