Objective Open-pit coal mine dumps in cold and arid regions are ecologically fragile areas formed under extreme disturbance. However, systematic studies on vegetation-soil spatial variation patterns and their synergistic mechanisms resulting from vertical differences in dumps are lacking, leading to a lack of theoretical basis for formulating differentiated ecological restoration strategies in engineering practice.

Methods We conducted a comprehensive study on a 2498-2632 m elevation gradient at the Heishan coal mine dump in the Tianshan Mountains, Xinjiang. Field surveys were combined with laboratory analyses to characterize vegetation community structure and soil properties across the elevation gradient. Redundancy analysis (RDA) was used to examine the relationships between vegetation and soil variables, while Pearson correlation analysis quantified the contribution of soil factors to plant diversity patterns.

Results and Conclusions  The naturally restored communities in the dump are dominated by Agropyron cristatum + Halogeton glomeratus + Lepidium alashanicum, showing obvious local characteristics. The plant community structure exhibited significant vertical differentiation characteristics, with the number of species reaching a peak of 11 at an elevation of 2553-2576 m.Species richness and diversity increased significantly with increasing elevation, while species evenness showed a decreasing trend. Soil nutrients (available phosphorus, available potassium), activities of key soil enzymes (urease, invertase, alkaline phosphatase), and total microbial count first increase and then decrease with elevation, reaching the maximum at 2553-2576 m, which is consistent with the variation of vegetation communities along elevation. The contents of soil total nitrogen and dissolved organic carbon are the highest at 2632 m. Redundancy analysis of the correlation between plant-soil factors shows that soil oxidation-reduction potential, microbial biomass carbon, soluble carbon, total nitrogen, polyphenol oxidase activity, and bacterial count are significantly positively correlated with vegetation richness and community diversity (P<0.05), which are the key factors driving vegetation community structure and affecting the settlement and growth of restored plants. The research results can provide a scientific basis for precise ecological restoration of open-pit coal mines in cold and arid regions.