Alpine meadow degradation decreases soil P availability by altering phoD-harbouring bacterial diversity

Context Soil degradation is usually accompanied by significant changes in phosphorus (P) availability, which complicates soil management. However, the effect of ecosystem degradation on soil P availability remains poorly understood, especially in the alpine ecosystem, which is one of the most understudied and vulnerable terrestrial habitats of the planet. Aims Assess the effect of meadow degradation on soil P availability in the alpine ecosystem. Methods Changes in soil P-related properties, phoD-harbouring bacterial communities, and alkaline phosphatase levels were investigated in four alpine meadows along a degradation gradient (non-degraded, lightly degraded, moderately degraded, and severely degraded) on the Tibetan Plateau. Key results We found meadow degradation reduced alkaline phosphatase activity by 6.3–11.22% and soil P availability by 27.1–42.4% compared to the respective values in the non-degraded meadows, but this negative impact was only observed in moderately and severely degraded meadows. Meadow degradation caused a P limitation on the phoD-harbouring community and a decline in the abundance of phoD genes and diversity of phoD-harbouring bacterial communities, with an increase in oligotrophic groups (e.g. Actinobacteria) and a reduction in copiotrophic groups (e.g. Proteobacteria). The degradation-induced reduction in soil C supply and plant biomass decreased soil P availability by lowering the activity of alkaline phosphatases, which are closely associated with phoD-harbouring bacterial structure and diversity. Alloactinosynnema and Actinomadura were identified as the key taxa contributing to alkaline phosphatases activity. Conclusions Alpine meadow degradation decreases soil P availability by altering phoD-harbouring bacterial diversity. Implications Our results revealed the mechanisms of decreased P availability during alpine meadow degradation, which can guide the restoration of degraded meadow ecosystems.