Decrease of soil total and organic phosphorus with ECM tree dominance in a subtropical mountainous forest

Aims Arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) plants differ in phosphorus uptake strategies and litter quality, but their effects on soil total P (TP) and P fractions along natural dominance gradients remain unclear, especially in P-limited subtropical forests. This study aimed to clarify how tree mycorrhizal associations regulate soil P dynamics. Methods We established 35 plots across an AM and ECM tree dominance gradient. Soil P fractions were determined using the modified Hedley method. Plant traits, litter quality, soil properties, and microbial communities were analyzed to identify driving mechanisms. Results Soil TP, organic P (Po), and primary mineral P (HCl-Pi) decreased significantly with increasing ECM tree dominance. TP content was negatively related to the basal area of trees and the thickness of forest floor, and positively correlated with community-weighted-mean litter P content. Reduced TP was mainly driven by stronger aboveground P translocation and lower litter P input. Declines in Po and HCl-Pi were attributed to accelerated mineralization and dissolution mediated by soil enzymes, phosphorus-solubilizing microorganisms (PSM), and low pH. Conclusions Increasing ECM dominance accelerates soil P depletion and may exacerbate P limitation, but ECM plants can sustain P availability and forest productivity via enhanced organic P mineralization. This study highlights the key role of mycorrhizal fungi in regulating soil P cycling and alleviating P limitation in subtropical forests.