Synergistic Effects of Fertilization and Reclamation Age on Inorganic Phosphorus Fractions and the pqqC-Harboring Bacterial Community in Reclaimed Coal Mining Soils.

Fertilization is an effective measure to rapidly improve soil quality in reclaimed mining areas. However, the combined effects of fertilization regimes and reclamation age on phosphorus (P) fraction transformation and the pqqC-harboring microbial community in reclaimed soils remain unclear. In this study, we investigated the dynamics of inorganic P fractions and the pqqC-harboring bacterial community under different fertilization treatments (no fertilizer: CK; chemical fertilizer: CF; organic manure: M) and reclamation ages (1, 5, and 10 years) in a coal mining reclamation area of Shanxi Province, using long-term field experiments combined with high-throughput sequencing. Results showed that compared with the CF and CK treatments, the M treatment significantly increased soil organic matter (SOM), available P (AP), and total nitrogen (TN) content, and promoted the conversion of moderately labile P (NaOH-Pi) to labile P fractions (H2O-Pi, NaHCO3-Pi). Meanwhile, the pqqC gene abundance increased with reclamation age, with the M treatment maintaining the highest levels in all fertilization regimes. Co-occurrence network analysis of core species revealed that the number of connections gradually decreased and the network structure simplified with increasing reclamation age. Correspondingly, the microbial community transitioned from an initial stage characterized by rapid response and intense competition to a stable phase. Specifically, Pseudomonas spp. played a key role in P mobilization. Structural equation modeling (SEM) further demonstrated that reclamation age directly promoted the pqqC gene abundance and AP content, whereas fertilization indirectly influenced P transformation by regulating microbial diversity. Our findings reveal that reclamation age and fertilization synergistically shape the inorganic P profile and the associated bacterial community, providing insights for developing targeted P management strategies in reclaimed lands.