Phosphorus Availability Affects the Efficiency of Plant-White Rot Fungus Remediation of Soil Contaminated with Polycyclic Aromatic Hydrocarbons by Altering Microbial Community Structure and Functions

White rot fungi and soil microbial communities at the hyphosphere influence phosphorus availability through their interactions. However, the mechanisms underlying the effects of different phosphorus forms on polycyclic aromatic hydrocarbons (PAHs) during plant-white rot fungus remediation remain unclear. Thus, this study aimed to investigate the effects of different phosphorus addition forms on soil microbial community diversity during plant-white rot fungus remediation and their correlation with PAH biodegradation through amplicon high-throughput sequencing. Pot experiments were conducted in a greenhouse. Salix viminalis was cultivated under two fungal levels (inoculated and non-inoculated with Crucibulum laeve) and three phosphorus levels (no phosphorus addition, potassium dihydrogen phosphate addition, and calcium phytate addition) to remediate phenanthrene (PHE)-contaminated soil. Among the treatments, two potassium dihydrogen phosphate addition treatments exhibited the highest PHE removal rates (74.0% and 79.4%) on day 60. Inoculation with C. laeve significantly increased the relative abundance of Pseudomonas but antagonized other putative indigenous PAH-degrading taxa. Potassium dihydrogen phosphate addition alleviated the antagonistic effect of C. laeve and indigenous microorganisms and synergistically promoted PHE degradation in soil with C. laeve, whereas calcium phytate addition did not significantly improve soil PHE removal rates. Additionally, the simultaneous phosphorus addition and C. laeve inoculation created a unique microbial community structure that facilitated organic phosphorus activation and accelerated phosphorus turnover. However, PHE degradation varied depending on the phosphorus form. Therefore, the addition of soluble phosphorus should be prioritized over insoluble phosphorus to optimize plant-white rot fungus remediation.