Grazing-to-fencing increases alpine soil phosphorus availability by promoting phosphatase activity and regulating the phoD-harboring bacterial communities

Soil available phosphate (AP) is largely dependent on phoD-harboring bacteria, which can release alkaline phosphatase (ALP) to transform insoluble P for plant absorption. However, the way of phoD-harboring bacterial communities responding to restoration measures in alpine ecosystems, which are among the least studied and most vulnerable ecosystems, remains largely unknown. This knowledge is fundamental for formulating effective ecosystem management and soil conservation policies. By combining quantitative PCR and amplicon sequencing, we examined the alterations in phoD-harboring bacterial communities across four distinct meadow types, and explored the potential environmental drivers of alpine soil P availability. The results indicated that the fenced and fenced + reseeded meadows exhibited higher ALP activity and soil AP content compared to the grazed meadow, but lower than that of the undegraded meadow. The fenced meadow had the highest phoD-harboring bacterial community diversity. Rare genera such as Rhizobium, Breoghania, and Actinomadura, played a critical role in regulating ALP activity. A structural equation model demonstrated that soil pH, nutrient supply (e.g., soil organic carbon, NO3−-N), and vegetation together drove the improvement of soil P availability by enhancing ALP activity, which was closely related to phoD-harboring bacterial communities. These findings suggest that fencing could promote alpine soil P availability by adjusting phoD-harboring bacteria and ALP activity. Our results demonstrate the beneficial impacts of grazing-to-fencing conversion on meadows in alpine ecosystems and can contribute to the development of sustainable management strategies for degraded alpine ecosystems.