Wetland types shape microbial function related to soil phosphorus cycling based on metagenomics analysis

Limitations regarding phosphorus (P) are widespread in ecosystems. Understanding the impacts of the wetland types on microbially mediated soil P availability and cycling is essential for the effective management of wetlands. In this study, the Beidagang wetland, Baodi paddy field, and Dahuangpu wetland in Tianjin, China were chosen as representatives of the coastal wetland (B), constructed wetland (R), and swampy wetland (W), respectively. Sequential P extraction and metagenomics approaches were adopted to explore the soil P fraction and microbially regulated P cycle. Proteobacteria were the predominant microbes-related soil P cycle. IMPA, gph, rsbU_P, ugpQ, and glpK genes were dominant in organic P (Po) mineralization, while gcd, ppa, and ppx genes were dominant in inorganic P (Pi) solubilization. The salinity, NO₃^--N concentration, the ratio of total carbon to total nitrogen (TC/TN), total carbon (TC), and the ratio of soil organic carbon to total P (SOC/TP) were the co-drivers of microbially mediated P cycle processes. Microbial network complexity-relate P cycle was the lowest in the coastal wetland. Salinity and NO₃^--N exhibited a significant negative relation to the abundance of most genes-relate Pi solubilization and a remarkable positive correlation with the abundance of many genes-relate Po mineralization. These findings demonstrated that Po mineralization tended to occur in habitats with high salinity and nutrient imbalances, whereas the dissolution of Pi was prone to occur in low-salinity environments with relatively balanced soil nutrients. This study improves understanding of how salinity and soil nutrients jointly shape microbial-regulated soil P cycle in different types of wetlands.