Microbial community restoration in abandoned coal mine lands: ecological assembly, functional mechanisms, and restoration strategies.

Coal mining creates coupled physicochemical stresses, including extreme pH, nutrient depletion, metal enrichment, compaction, and loss of plant-derived carbon, that reduce microbial biomass, simplify interaction networks, and suppress biogeochemical functions. This review synthesizes recent evidence on microbial community restoration in abandoned coal mine lands, with emphasis on community assembly, stress adaptation, functional genes, and the interpretive value of high-throughput sequencing and meta-omics. During natural recovery, microbial propagule dispersal interacts with strong habitat filtering and rhizosphere selection. Pioneer plants and biological soil crusts progressively add carbon and nitrogen, stabilize surfaces, and recruit bacterial, fungal, and phototrophic guilds. Active interventions accelerate these processes by correcting substrate constraints and by inoculating soils, planting holes, seeds, or carriers with locally adapted microorganisms. However, field performance is often limited by competition with resident communities, host mismatch, environmental heterogeneity, and declining inoculant persistence. Restoration assessment should therefore combine taxonomic composition with functional-gene abundance, gene expression, enzyme activity, microbial biomass, and ecosystem-level indicators. Across sites, no single strategy is consistently superior: amendments act rapidly but may require repeated inputs, vegetation-based approaches are slower but potentially self-sustaining, and inoculation is most effective after major physicochemical barriers have been removed. Future research should prioritize replicated field trials, standardized and activity-resolved measurements, locally adapted consortia, and early-stage interventions that influence microbiome composition and function without assuming complete control. These priorities provide a practical basis for precision restoration of mine-affected soils.