Land subsidence, which has caused large-scale settlement loss and farmland degradation, was regarded as the main constraint for land reclamation in the High Groundwater Coal Basins (HGCBs) in the eastern China plain. Both coal mining and agricultural production are important for regional development in this area. In general, the land reclamation direction in this area is greatly affected by the adequacy of filling materials and the land use demand of regional economic development. Taking seven coal mining subsided areas in Pei county, located in the eastern China plain, for example, this study proposed an integrated model (including the Limit Condition model, Logistic Regression model, Grey Linear Programming model and the conversion of land use and its effects at small regional extent (CLUE-S) model) to simulate and optimize the post-mining land use structure to meet the economic development needs of Pei county. Then, the post-mining land use structure under different scenarios, which were set based on the subsidence depth, were compared to explore the optimal collapse depth for separating the damaged land into the filling area and non-filling area. The landscape structure, ecological benefits, engineering quantity and reclaimed farmland area were used to compare the reclaimed land use structure of different scenarios. The results showed that the integrated model could efficiently simulate the reclaimed land use structure to meet the land demand for regional development. The optimal collapse depth for separating the damaged area into the filling area and non-filling area was 2.6 m. Currently, the reclaimed land use structure not only needs a low quantity of filling material, but also obtains a good landscape structure and elevated ecosystem services value. Furthermore, the reclaimed urban land was mainly distributed around Pei town, and the reclaimed farmland was mostly distributed in the area between Pei town and Weishan lake, which were consistent with the pattern of urbanization. The study provides valuable information for future land use plans for Pei county and will contribute to the methods of post-mining land reclamation in other HGCBs.
Information on the spatial variability of soil-available micronutrients is important for farming and soil management practices. As current knowledge of factors influencing soil available micro-nutrients in the long-term scales is limited, we analyzed 821 and 812 representative surface (0–20 cm) soil samples from five sub-catchments in the Ping Gu intermontane basin in Beijing, China in 2007 and 2017. The objectives of this study were to assess the temporal and spatial distribution characteristics of soil-available micronutrients (Cu, Zn, Fe and Mn) and their relationships with soil’s chemical properties. The concentration of available Cu ranged from 1–2 mg∙kg−1 distributing over a large area in 2007, but it was more than 2 mg∙kg−1 in the hilly regions in 2017. The concentration of available Zn (>5 mg∙kg−1) increased significantly from 2007 to 2017, and showed an uneven distribution. The distribution of available Fe and Mn decreased from the northeast to the southwest region of the study area between 2007 and 2017, this being consistent with the topography in this area. Soil’s available P (AP) had a higher contribution to available Cu and Zn in different sub-catchments. In addition, soil pH had a significant negative influence on available Fe in sub-catchments 1, 2 and 3, and on available Mn in all sub-catchments, except for sub-catchment 4. Moreover, the effects of soil chemical properties on soil-available micronutrients increased in each sub-catchment from 2007 to 2017. We conclude that differences in soil properties and land-use types were the main reasons for the spatial variability of soil-available micronutrients in the Ping Gu intermontane basin.