Abstract
Open-pit coal mining in grassland ecosystems causes severe soil degradation and disrupts the native soil microbial communities. However, current remediation research predominantly focuses on plant growth or soil physicochemical properties, with a limited systematic analysis of the soil microbial community during remediation in the grassland coal mine dump. To address this gap, this study used high-throughput sequencing integrated with field experiments to systematically evaluate the effects of plant-microbial combined remediation on soil microbial communities in a coal mine dump located in a fragile, severely cold grassland. Our study revealed divergent restoration of soil bacteria and fungi. Bacterial communities demonstrated a strong recovery capacity, with diversity nearly restored to natural levels, while fungal communities remained significantly suppressed. Restoration treatments, especially AMF inoculation, successfully altered overall microbial structure and increased the abundance of key marker taxa. Network analysis further showed that remediation drove bacterial communities toward greater complexity and cooperation, whereas fungal communities responded with increased modularity. Critically, the assembly of the entire soil microbial community was primarily governed by a total phosphorus gradient, which clearly discriminated between bare dump, natural grassland, and restoration plots. Mixed planting fostered the most resilient bacterial community; however, microbial inoculation within this system proved counterproductive. Fungal resilience remained consistently lower than that of bacteria. Crucially, inoculation fundamentally altered ecosystem multifunctionality in monocultures, demonstrating its essential role in functional enhancement. Our results demonstrate that integrating specific plant combinations with microbial inoculation is key to enhancing soil microbial stability and ecosystem multifunctionality during restoration. In summary, our findings reveal the distinct response of soil microbial communities under remediation, and provide critical insights for the ecological restoration of mining areas.