Tree mycorrhizal types drive divergent soil fungal communities and biomass but not soil carbon metrics in a subtropical young forest

The selection of appropriate tree species is of paramount importance in plantation forest management for improving timber production and soil carbon (C) sequestration. However, we know little about how different mycorrhizal-type trees influence soil microbiomes and microbial biomass related C stocks. Here we investigated the relationships between arbuscular and ectomycorrhizal (AM vs. EM) types and soil C metrics in a short-term field-controlled experiment. Our results showed that EM forests had significantly higher fungal biomass (as revealed by ergosterol) but lower fungal richness and AM fungal biomass than AM and mixed (AM + EM) forests. Tree mycorrhizal type exerted no significant influence on soil C metrics, while soil properties and microbes showed significant correlations with soil C metrics. Soil moisture was positively correlated with soil total carbon (TC), soil organic carbon (SOC), and mineral-associated organic carbon (MAOC). Total nitrogen was positively associated with soil TC and MAOC. Soil fungal functional guild parasites and the dominant bacterial phylum Actinomycetota were positively linked to SOC and particulate organic carbon, respectively. Moreover, soil ergosterol content was positively associated with acid phosphatase activity, while negatively correlated with phosphorus cycling gene abundance in AM forests. Altogether, these findings demonstrate that tree mycorrhizal types exert direct impacts on fungal diversity and biomass, and indirect impacts on soil C metrics, highlighting the importance of mycorrhizal associations in elucidating the intricate relationship between soil microbial community and soil C stocks in subtropical forests.