Regulation of soil phosphorus availability in alpine meadows: Insights from phosphate-mobilising bacteria

The populations, activity, and community of phosphate-mobilising bacteria (PMB) affect phosphorus (P) availability via the solubilisation of PMB metabolites in grassland soils. However, PMB variations and their regulation mechanism on soil P availability across degraded meadows are not fully understood. We conducted the dynamic of bioavailable P, phosphatase activity, and PMB properties using field positioning monitoring, quantitative PCR, and high-throughput sequencing technology across different degraded meadow soils in the Zoige Basin, China. Compared with the non-degraded meadow (NDM), the content of soil Olsen and resin P in degraded meadows decreased by 14.7–58.1 % and 34.8–60.1 % respectively, and the abundance of soil PMB with the phoD and pqqC genes declined by 5.6–75.6 % and 6.5–77.4 %, respectively, at most plant growing seasons. In general, soil phosphatase activity in degraded meadows was lower than that in the NDM, while meadow degradation enhanced the diversity of soil PMB. Decreases in the content water and nutrient altered the PMB community composition in degraded meadow soils, which commonly showed that the relative abundance of copiotrophic PMB (e.g. Burkholderiacea with the pqqC gene) decreased, whereas that of oligotrophic PMB (e.g. Bradyrhizobiaceae with the phoD gene) increased. The lower soil bioavailable P was mainly driven by a decrease in the abundance of organic PMB and phosphatase activity under meadow degradation. These results provide new insights into the regulation of soil P availability through stimulating PMB mineralisation on organic P compounds to restore degraded meadows.