Soil pH and total phosphorus regulate bacterial community assembly in slope restoration areas of the Tibetan Plateau's metal mining areas

Microbial community development is a crucial aspect of soil restoration. The employment of frame beams in conjunction with external soil has demonstrated efficacy in the rehabilitation of degraded roadside ecosystems within mining regions. Nonetheless, the effects of frame beams on the composition and stability of soil bacterial communities remain inadequately comprehended. We conducted a one-time soil sampling on a three-year restored slope in a large-scale metal mining area on the Tibetan Plateau, providing a snapshot of the current conditions and evaluating the restoration progress. Frame beams with external soil covers were applied at three different altitudes: A1 (4800-5000 m), A2 (4500-4700 m), and A3 (4200-4400 m). Restoration significantly altered bacterial community composition compared with controls. Proteobacteria had a higher relative abundance in the restoration area (average: 31.16 %), whereas Acidobacteriota were more abundant in the control area (average: 24.68 %). In the restoration area, soil bacterial α-diversity increased as elevation decreased, with the Shannon index rising from 5.34 (A1) to 5.82 (A3), suggesting that bacterial communities at higher altitudes are more sensitive to environmental conditions. Species turnover was the primary driving factor of β-diversity, accounting for 96.26 % under A1, 94.71 % under A2, and 91.94 % under A3, respectively. The nearest taxon index of bacterial communities shifted from negative to positive along the elevation gradient (-0.25 to 1.14), indicating an increasing trend toward community clustering. Within the bacterial co-occurrence network, soil pH and total phosphorus contribute significantly to network strength, closeness, and betweenness. Concluding, soil pH and total phosphorus were identified as key factors shaping bacterial diversity and assembly mechanisms. Our research contributes to the development of effective soil restoration strategies for alpine mining regions, providing insights into microbial community assembly and stability mechanisms.