Periphyton-associated combined restoration promotes microbial restructuring and phosphorus cycling in gleyed paddy soil

Persistent reductive stress and soil acidification impose strong environmental filtering in gleyed paddy soils, suppressing microbial activity and limiting phosphorus (P) bioavailability. Inspired by natural soil-water interface dynamics, we developed a restoration strategy combining slow-release CaO2, periphyton development, and phosphate-solubilizing bacteria (PSB) to alleviate habitat constraints and reactivate endogenous P cycling under field conditions. Slow-release CaO2 provided initial oxidative and alkalizing conditioning, effectively elevating soil pH and reducing total reducing substances (TRS). This initial habitat amelioration was accompanied by periphyton proliferation and a marked reduction in within-treatment community heterogeneity (microbiome convergence). Co-occurrence network analysis revealed topological realignments, with PSB taxa (Bacillus and Pseudomonas) occupying module hubs and periphytic microalgae acting as connectors between photoautotrophic and heterotrophic guilds. Metatranscriptomic profiling demonstrated coordinated upregulation of complementary P-cycling pathways, including pyrroloquinoline quinone (PQQ)-dependent inorganic P solubilization and organic P mineralization (phoD, pqq, phn, and bpp). These functional transcripts were positively correlated with soil pH, phosphatase activities, and available P, but negatively correlated with TRS. Overall, this integrated conditioning strategy alleviated environmental filtering and was associated with coupled multi-guild functional responses, ultimately boosting endogenous P-cycling potential in degraded paddy soils. These findings suggest that a functional complementary framework may help inform microbiome-assisted restoration of constrained agricultural soils.