Soil organic carbon accumulation pathways and controlling factors for ecological restoration of open-pit mining areas

Open-pit mining removes established soil horizons through severe mechanical disturbance, disrupts aggregates and generates reconstructed mine soils with extremely low and spatially heterogeneous initial soil organic carbon (SOC), heterogeneous parent materials, poor water retention and extreme microclimatic or chemical conditions. These constraints distinguish mine-land carbon reconstruction from SOC development in mature natural and agricultural soils and limit the direct application of conventional stabilization theories. This review provides a mining-specific synthesis of disturbance mechanisms, restoration pathways, coupled controls and monitoring technologies. We interpret SOC formation using the particulate organic carbon (POC), mineral-associated organic carbon (MAOC) and microbial carbon pump frameworks, emphasizing that aggregate protection and mineral binding capacity develop dynamically during substrate reconstruction. We compare vegetation restoration, substrate amendment and integrated ecological engineering, showing that single measures mainly increase carbon inputs or alleviate individual constraints, whereas combined measures better coordinate plant inputs, microbial transformation, erosion control and mineral protection. We then examine how parent material, management, climate and topography interact with restoration age to shift dominant limitations from carbon input to nutrient and decomposition regulation and, eventually, mineral protection. Finally, we evaluate the progression from chronosequences and fixed plots to process-based models, machine learning and multi-source remote sensing, including their application boundaries. Three unresolved disputes concern the persistence of MAOC under environmental change, the dynamic nature of carbon-saturation thresholds and the magnitude of microbial contributions to stable SOC. This synthesis supports restoration strategies that prioritize land stabilization and climate-resilient carbon pools rather than bulk SOC accumulation alone.