Soil multifunctionality in arid mining: Driving mechanisms and restoration strategies based on natural succession

Ecological restoration in coal mining areas often relies mainly on artificial intervention. Restoration efficiency and long-term maintenance of soil multifunctionality remain limited due to an insufficient understanding of natural succession mechanisms. To clarify the patterns and driving mechanisms of soil multifunctionality in different succession types, this study used natural succession (NS) as an ecological reference, comparing changes in soil carbon, nitrogen, and phosphorus multifunctionality between artificially restored (AR) and NS. Also explored how microbial communities and environmental factors influence these processes. The results indicated that soil multifunctionality increased significantly during the succession. Bacterial diversity responded more strongly to succession than fungal diversity. Employing multi-threshold and averaging methods, we found bacterial abundance positively influenced multifunctionality in AR (Rmed: 3.834 to 11.035, R2: 0.37 to 0.60) but negatively influenced multifunctionality in NS (Rmed: -5.926 to -3.304, R2: 0.17 to 0.25). Microbial community composition, rather than diversity alone, was identified as the key factor explaining multifunctionality. In AR, multifunctionality was mainly regulated by keystone bacteria and fungi. In NS, it was co-driven by keystone and rare bacterial taxa. While there was no significant correlation between fungal diversity and multifunctionality, certain keystone fungal phyla in AR (Ascomycota, Basidiomycota, and Chytridiomycota) have a significant influence on multifunctionality. Soil physical structure and water-salinity properties explained multifunctionality better than microbial factors. This suggests that improving the abiotic environment was more effective for promoting functional recovery than focusing only on microbial diversity. The study proposes a reclamation strategy of “structure-first and stage-progression” using NS as an ecological template to guide mining restoration. This strategy emphasizes the importance of synergistically optimizing environmental and biological elements.