Response of soil microorganisms to soil fertility in the process of vegetation rehabilitation of degraded Pinus massoniana forest

The rehabilitation of diverse and three-dimensional forest vegetation patterns is crucial for preventing forest degradation and improving soil fertility. However, the relationship between soil microbial community and soil fertility was not clear. To accurately assess the capability of vegetation restoration measures on the real impact on degraded soil ecosystems. We selected three vegetation rehabilitation models of degraded Pinus massoniana forests in typical soil erosion areas in China as the research objects, with untreated bare land as the control. All three vegetation construction patterns increased the abundance and diversity of soil bacteria and fungi, thereby enhancing the stability of the soil ecosystem. Additionally, the vegetation rehabilitation models also altered the community structure of soil bacteria and fungi in the degraded P. massoniana forests. The pH and soil fertility index (IFI) were the main factors leading to variations in the community structure of the soil bacteria and fungi. Among them, the grass-planting model showed a significantly greater improvement in the soil fertility of degraded P. massoniana forests than the shrub-planting and arbor-planting models. Furthermore, Ascomycota, Basidiomycota, and Glomeromycota exhibited the most significant response to IFI, indicating their potential as indicator microorganisms for soil fertility changes. The improvement in soil fertility in degraded P. massoniana forests was influenced primarily by the increase in urease activity (S-UE) according to the vegetation rehabilitation models (84.20%, p = 0.000). In conclusion, the grass-planting system effectively improved the soil ecosystem quality of degraded P. massoniana forests in southern erosion-prone areas of China and was suitable for further application.