Land-use history shapes microbial phosphorus acquisition and use strategies in the Zoige alpine wetland.

Abstract

Alpine wetland conservation and restoration are reshaping wetland use and soil conditions on the Zoige Plateau, but how these changes influence phosphorus (P) cycling remains poorly understood, even though cold, waterlogged soils can constrain P availability and make P cycling critical for ecosystem functioning. Here, we compared soil P fractions and microbial P-use strategies among persistent meadow, natural peatland and meadow-to-peatland transition sites identified from land survey records. Meadow soils contained the smallest P pools across most fractions but supported the greatest abundance of P-acquisition genes, including P-starvation regulators (e.g., phoR, SenX3), phosphate transporters (pstA, pit, ugpC), and P-mobilizing genes (phoD, gcd), indicating an acquisition-oriented P-use strategy. In contrast, natural peatland soils contained higher P concentrations but lower overall P-cycling gene abundance, a more cohesive and modular co-occurrence network, and enrichment of genes for phosphonate/phosphite utilization (phnX, phnC, phnW, ptxC), reflecting a specialized P-use strategy under organic-rich and wetter conditions. Restored peatland displayed intermediate P concentrations and gene composition but the weakest network connectivity, suggesting incomplete reassembly of coordinated P-cycling pathways. Across the land-use histories, soil pH and total N were the strongest environmental correlates of P-cycling gene configuration, while physicochemical conditions structured P pools more strongly than microbial functional potential alone. These findings demonstrate that contrasting land-use histories in alpine wetlands are associated with coordinated shifts in microbial P-use and acquisition strategies, with implications for understanding the long-term biogeochemical cycling in these sensitive ecosystems.