Fungi stimulate organic phosphorus fraction transformation in subtropical masson pine plantation soils after nine years of thinning and understory removal

Background Phosphorus (P) availability in soils regulates forest productivity. However, the drivers of soil P dynamics following forest management remain poorly understood, particularly in P-deficient forests in tropical and subtropical regions. Method Soil samples of 0–10 cm were collected from the plots after 9 years of thinning and understory removal (UR) in Pinus massoniana plantations in subtropical China. Soil physicochemical properties, microbial biomass and community composition, and Hedley P fractions were measured to assess the underlying mechanisms for the dynamics of soil P fractions. Results Compared to undisturbed plots, total soil inorganic P (Pi; + 24%) within the dominant species thinning (DST) plots showed a significant increase, which was associated with the accrual in resin-Pi (+ 30%), NaHCO 3 -Pi (+ 21%), and C.CHl-Pi (+ 45%). These Pi fractions were primarily correlated with increased relative abundance of Ascomycota , Rozellomycota , and Proteobacteria . Conversely, post-management (thinning and UR) assessments revealed no significant changes in total P, total organic P (Po), and residual P. The observed decrease in total Po (– 9%) in DST plots was linked to reductions in NaHO-Po (– 7%) and C.CHl-Po (– 24%). Notably, these Po fractions were negatively affected by the relative abundance of Glomeromycota . Furthermore, variations in soil fungal and bacterial community structures accounted for 44.3% and 26.3% of the variances in soil Pi fractions, respectively, similarly explaining 20.4% and 33.3% for soil Po fractions, respectively. Conclusions These results indicate that P availability following forest management interventions within subtropical pine plantations is intricately connected to microbial community composition that enhances the transformation from Po into Pi forms.