Soil organic carbon accumulation in response to vegetation restoration across global mining areas: A meta-analysis

Mining activities cause severe land degradation and significant loss of soil organic carbon (SOC). Vegetation restoration has been widely adopted to rehabilitate mining ecosystems; however, its effectiveness in enhancing SOC sequestration at a global scale and the underlying driving mechanisms remain unclear. This study aims to quantify the overall impact of vegetation restoration on SOC in mining areas and identify key environmental drivers. Based on 740 paired observations from 92 published studies, we conducted a meta-analysis using the natural log response ratio (lnRR) as the effect size and assessed the influences of climate, soil properties, mining type, restoration approach, and restoration duration using mixed-effects models. Restoration exhibited better SOC improvement in regions with mean annual temperature ≤10°C and mean annual precipitation <500 mm, because low temperature and drought suppressed microbial decomposition, and low initial SOC magnified carbon input effects; warm and humid conditions accelerated carbon decomposition and shifted dominant drivers toward soil pH, water content and microbial characteristics. Soil pH reshaped SOC regulatory pathways: acidic, neutral and alkaline mining areas required targeted strategies of pH amelioration, moisture-microbial regulation, and soil physical structure improvement, respectively. SOC restoration performance differed distinctly across mine types, ranking as metal mines > coal mines > non-metallic mines, with metal mines dominated by low carbon background and metal-tolerant microorganisms, and coal mines mainly controlled by hydrothermal and soil nutrient conditions,and SOC in non-metallic mines relies more on soil nutrient content. Natural restoration outperformed artificial restoration in SOC sequestration. The early stage (<5 years) was critical for water and nutrient regulation, while long-term single-species restoration caused SOC accumulation rate reaching a plateau. Introducing mixed plant species in the later period could sustain microbial activity and achieve continuous SOC sequestration in mining ecosystems.