[Evolution of Soil Bacterial Community Assembly Mechanisms in Reclaimed Pinus tabuliformis Forests of Xishan Mining...

Soil microorganisms are pivotal drivers of ecological restoration in reclaimed mining areas, regulating critical processes such as nutrient cycling and ecosystem stability. This study investigated Pinus tabuliformis plantations across a 3-25 year reclamation chronosequence in the Xishan Mining Area. By integrating 16S rRNA sequencing, β-nearest taxon index (β_NTI), Bray-Curtis based stochastic assembly model (RC_bray), and environmental multivariate analysis, the bacterial community assembly mechanisms were elucidated. The bacterial Shannon diversity exhibited a significant unimodal distribution (P<0.001), peaking at intermediate reclamation stages (e.g., YS10). This maximum diversity coincided with elevated total organic carbon (TOC) and higher C/N ratios. Diversity dynamics showed significant positive correlations with both total nitrogen (TN) and C/N ratio (P<0.05). Taxonomic composition shifted substantially during succession: Acidobacteriota abundance surged from 14.8% to 35.9% (P<0.001), ascending to dominance in late-stage reclaimed soils (e.g., YS25). This transition reflected an ecological strategy shift from r-strategists (e.g., Proteobacteria) to K-strategists (e.g., Acidobacteriota), attributable to declining soil C/N ratios and progressive nitrogen enrichment. The β_NTI-RC_bray framework revealed that stochastic processes (dispersal limitation, 57.14% contribution) dominated overall community assembly. However, deterministic processes (e.g., variable selection) increased substantially (30%-60%) between 8-10 years of reclamation. Both TN and urease significantly explained community variation (19.43% and 19.84%, respectively), driving community succession and altering microbial abundance. Although both dominated the deterministic process, dispersal limitation remained the most important stochastic driver, with its contribution reaching 100% in the later stages of reclamation (e.g., YS25), which was caused by physical barriers and the patchiness of microhabitat resources. These findings elucidate the interplay between stochastic and deterministic forces in shaping microbial succession during habitat restoration, providing theoretical and practical guidance for microbiome-directed management in reclaimed mining ecosystems.