Theory and method of soil reconstruction of reclaimed mined land

Soil is the basis of life, and soil reconstruction is the key and foundation of mine land reclamation and ecological restoration. The purpose of this paper is to innovate the concept of soil reconstruction, simplify and improve the theory and method of soil reconstruction, and provide support for the unique basic theory of land reclamation and ecological restoration in the mining areas. This paper reviews the research history of soil reconstruction in mine reclamation and proposes the concept of fourdimensional reconstruction from the perspective of the space reconstruction of the element soil, namely soil profile reconstruction in the vertical direction (Z), landform remodeling in the horizontal direction (X,Y) and soil improvement in the time dimension direction (t). Among them, the vertical profile reconstruction is the core of soil reconstruction and is also a narrow concept of soil reconstruction. Summarizing the successful experience and failure lessons of mine ecological restoration worldwide, based on the principle of soil genesis and the concept of learning from nature, the concepts of “the niche of soil layer” and “the critical layer of soil” are put forward. It is believed that different soil layers have their unique ecological functions and spatial positions. The position of each soil layer in space and its functional relationship and role with related soil layers are called as “the niche of soil layer”. In addition, the key soil layers that affect the overall function and productivity of soils are called as “the critical layer of soil”. The principle of soil profile reconstruction in mine reclamation is the process of designing and optimizing soil profile configuration and putting it into practice with the niche of soil layer as the theoretical basis and the critical layer of soil as the core of soil reconstruction. The key is to optimize the design of the niche of each soil layer, to identify and optimize soil critical layers. Therefore, the method of soil profile reconstruction is to determine the goal of reconstructing the soil profile based on the local needs and characteristics of damaged land. Then it is to analyze the niche suitability of each soil layer. The next step is to analyze the properties of the niches of soil layer such as niche space, niche breadth, niche overlap, niche difference, and niche competition of soil layer to determine possible soil profile configurations and critical layers. Finally, through indoor and outdoor planting experiments or simulation experiments, it is to verify and determine the optimum soil profile, so as to obtain the best productivity function of soil profile configuration. Based on this principle and method, the author proposes the general technical principle of soil reconstruction called “layered stripping and staggered backfilling”. “Layering” is to meet the requirements of constructing “the niche of soil layer” and “the critical layer of soil”. “Staggering” is a construction technology that realizes continuous and efficient soil reconstruction. In addition, the soil reconstruction method is introduced by taking the concurrent mining and reclamation for openpit coal mines and the nonfill subsidence land reclamation as examples. Finally, the application and practice of soil reconstruction principle are introduced by taking the filling reclamation of coal mining subsidence with Yellow River sediments in Shandong Province as an example.