Identifying Key Indicators for Soil Quality Assessment in Reclaimed Loess Coal Mining Areas of China: A Case Study of the Suancigou Coal Mine, Inner Mongolia

Abstract

Mining activities cause severe degradation of soil structure and nutrient loss, making land reclamation a crucial measure for restoring ecosystem functions in mining areas. Investigating the key indicators of reconstructed soil quality and their succession patterns enables a robust assessment of reclamation measures, providing a scientific basis for optimising land reclamation strategies and ecological management in mining regions. Existing studies on soil quality assessment have primarily focused on general evaluations, with limited attention given to the specific challenges associated with reconstructed soils in reclaimed underground coal mine areas. This study examines the reclaimed land of the Suancigou coal mine in Inner Mongolia, China. Ten soil physicochemical properties were selected as potential evaluation indicators. Through correlation analysis and principal component analysis, a minimum data set (MDS) was identified for assessing soil quality in reclaimed lands, and a soil quality index (SQI) was subsequently constructed. The findings revealed that: (1) reconstructed soils of different reclamation ages exhibit significant discrepancies in physicochemical properties at the 0-10 cm and 10-20 cm depths compared to the original landscape. Despite variations in correlations among soil properties across depths, total nitrogen content (TNC), soil organic matter (SOM), hydrolysable nitrogen and available phosphorus consistently display strong synergistic relationships. (2) The overall quality of the 0-20 cm reconstructed soil is primarily influenced by pH, soil sand content (SSD), soil silt content (SST) and TNC. Specifically, the MDS for the 0-10 cm soil layer includes bulk density, SSD, SST and TNC, whereas for the 10-20 cm layer, the MDS comprises pH, SSD, SST and SOM. (3) The comprehensive soil quality assessment followed the order: OL > R-7a > R-11a > R-3a. By quantifying the interrelationships among soil attributes in reclaimed lands, this study streamlines the soil quality evaluation system, offering theoretical foundations and technical support for evaluating reconstructed soils and optimising land reclamation in mining areas.