Replacing soil with waste gangue for the ecological remediation of mining areas facilitated by plant-promoting microorganisms and porous materials

Coal-mining byproducts like coal gangue (CG), green mudstone (GC), and oil shale (OS) pose significant risks to the ecological environment and social safety. In this study, waste gangue was treated in situ without supplementary soil addition. Moreover, the effects of plant growth substrates prepared by incorporating chicken manure (+), plant growth-promoting microorganisms (+M), and porous materials (+MM) on soil nutrients, plant growth, and microbial communities were investigated. Compared with untreated gangue, organic matter, total nitrogen, total phosphorus, available nitrogen, and available phosphorus in the CG + MM, OS + MM, and GC + MM groups increased by 170%, 14%, 93%, 174%, 1951%; 51%, 15%, 262%, 147%, 480%; and 230%, 23%, 85%, 78%, 1,186%, respectively. Regarding plant growth, CG had no significant effect on Lolium growth, whereas GC and OS drastically decreased Lolium biomass. However, the addition of exogenous substances promoted Lolium growth. Microbial community network analysis confirmed the presence of Bdellovibrio, Halomonas, Nocardioides, Sphingobacterium, Streptomyces, and WD2101 soil groups in the CG group; Bdellovibrio, Chloroplast, Lysobacter, Methylophaga, and WD2101 soil groups in the GC group; and Antarcticibacterium, Chloroplast, Methylophaga, Paracoccus, Pontibacter, and Rhodonellum in the OS group. All microbes played key roles in maintaining the microbial community structure. These findings provide novel insights into the ecological restoration of gangue.