Spatial distribution of soil bulk density and its relationship with slope and vegetation allocation model in rehabilitation of dumping site in loess open-pit mine area

Studies of soil bulk density (BD) spatial variations of land reclaimed after mining have become a focus of land reclamation and ecological restoration research. However, there have been few studies on the relationship among the reconstructed BD, terrain conditions, and vegetation growth. We examined the southern dumping site of the Pingshuo Antaibao open-pit coal mine located in a loess area in China. Field sampling data, digital elevation models (DEMs), and high-definition images were obtained, and indoor testing, geostatistics, and inverse distance weighting (IDW) were applied. This paper aims to analyze the spatial distribution law of the reconstructed BD and focus on its relationship with slope and vegetation allocation models. We demonstrated that (1) BD increased with soil depth and varied moderately within each layer. (2) The BD variation amplitude of the top 0-20-cm soil layer in both the east-west and south-north directions was small and more similar in the east-west direction than in the south-north direction, which was affected by herbaceous root systems. In the next four layers from 20 to 60 cm, the variation in BD in the east-west direction was far larger than that in the south-north direction, which was affected by vegetation classification. (3) On the whole, BD decreased with increasing slope, but when the slope was between 0 degrees and 21 degrees, BD exhibited a specific change law. (4) From the perspective of vegetation classification, the orders of magnitude of BD in the 0-20-cm and 20-60-cm layers differed. Overall, BD in areas vegetated with Korshinsk Peashrub was the lowest, and BD was moderate in areas with mixed vegetation, while BD was the highest in areas without vegetation or only vegetated with Black Locust. The mixed grass-bush-tree or bush-tree mode attained the best effect in regulating BD. These results can improve the basic principles of land reclamation in mining areas and provide a basis for further optimizing land reclamation technology in practice.