Soil quality evaluation and limiting factor analysis of a coal mine area with different reclamation years and...

Assessing soil quality is crucial for guiding ecological restoration, mitigating land degradation, and promoting ecological sustainability in coal mining areas. However, the understanding of soil quality recovery across reclamation years and microtopographies and the applicability of different assessment methods remain insufficient. In this study, three minimum data set (MDS) methods were used to evaluate soil quality, which were based on the investigation and analysis of a reclamation chronosequence (0, 1, and 5 years) and two microtopographies (platforms and slopes). The MDS constructed by principal component analysis, hierarchical cluster analysis, and random forest model methods all showed acceptable reliability. Nonlinear scoring exhibited higher evaluation accuracy compared to the linear method. Cation exchange capacity, soil organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and sucrase activity were retained across all three MDS methods. These indicators reflect crucial soil functions related to nutrient retention and microbial activity. Soil quality improved with increasing reclamation age, and recovery trajectories diverged between microtopographies. The 5-year reclaimed slope achieved better soil quality recovery than the platform, while 1-year reclaimed soil remained below undisturbed wasteland levels. Microbial biomass carbon and microbial biomass nitrogen (MBN) were the major limiting factors in initial reclamation. MBN remained the main limiting factor for the platforms after 5 years of restoration, while sand content became the main limiting factor for the slopes. These results could provide insights into microtopography-based reclamation strategies and recovery trajectory prediction in mining areas.