Succession law and model of reconstructed soil quality in an open-pit coal mine dump of the loess area, China

Studying the change laws of reconstructed soil quality and constructing succession models are the main components and tools of reconstructed soil quality evaluation for the supervision and management of reconstructed soil. However, the evaluation and management system of reconstructed soil quality suitable for the loess area needs to be improved. This paper aimed to clarify the succession law of reconstructed soil in an open-pit coal dump in the loess area on the temporal scale and to construct a succession model of reconstructed soil quality to evaluate and manage reconstructed soil. The Pingshuo coal mine, a representative open-pit coal mine in the loess area, is the study area. Field investigation and sampling, time-space substitution, and the combination of qualitative and quantitative research methods were used. The reconstructed soil quality succession model was constructed based on the soil quality index method. Results: (1) As the reclamation period increased, the physical and chemical properties of reconstructed soil significantly improved, and reconstructed soil quality generally reached the quality of the original landform after approximately 15 years of reclamation. However, after long-term reclamation, soil physical properties still limited the improvement of reconstructed soil quality to a certain extent. (2) After long-term reclamation, the difference in reconstructed soil quality between layers gradually decreased, and the reconstructed soil condition of the 0-10 cm soil layer was obviously better than that of the other layers. (3) We quantitatively constructed and verified the reconstructed soil quality succession model that is suitable for the loess area, which can be used in conjunction with adaptive management for the evaluation and management of reconstructed soil in the loess area. In conclusion, this study is of great significance to meet the real needs of dynamic evaluation and management of reconstructed soil quality in the loess area and to enrich the soil evaluation and management system at home and abroad.