Optimized fertilizer–microbe ratios enhance synergistic restoration of alpine mining ecosystems

The optimized fertilizer-microbe treatment (W3J1: 375.00 kg·hm^-2 forage-specific fertilizer + 350.00 kg·hm^-2 compound microbial inoculant) significantly promoted vegetation growth, increased soil carbon and nitrogen contents, and effectively alleviated soil salinization. This treatment reshaped soil bacterial community structure, enriched functional taxa (e.g., <i>Pseudomonadota</i> and <i>Bacteroidota</i>), and enhanced the complexity and functional potential of microbial interaction networks. Mechanistic analysis revealed that the synergistic effect of fertilizer and microbes primarily drove ecosystem recovery through a dual-pathway mechanism: direct microbial regulation and vegetation-soil feedback. The direct effect on bacterial <i>α</i>-diversity was extremely significant (<i>β</i> = 0.76, <i>p</i> < 0.001). Soil pH was identified as the key driver of microbial community assembly, while excessive fertilization induced salinity rebound, indicating a clear application threshold. This study provides a theoretical basis and technical support for the precise ecological restoration of fragile ecosystems in alpine mining areas.