Effects Of Vegetation Restoration On Soil Environment Of Opencast Coal Mine Dump In The Loess Area

The Loess Plateau region is a typical fragile area of ecology as well as the most important coal production base of our country. The dump is forming in the processing of coal-mining production,which has special poor soil, loosely slope, a extremely low vegetation coverage and will easily bring about a series of ecological and environment problems, especially the soil erosion. Therefore ecological management of dump has important implications for ecological security in this area. Vegetation restoration is the fundamental management to construct ecological environment in the ecological degradation region and many theories and techniques about vegetation restoration in Loess Plateau have come to being, but few research work had been done on vegetation restoration of mining area on the Loess Plateau. In this paper, by the method of soil sampling and laboratory analysis, the effects of vegetation restoration on soil nutrients and soil structure of opencast coal mine dump on the Loess area have been researched. We explored the effects of vegetation restoration on soil environment of reconstructed soil of opencast coal mine dump in loess area and the results are as follows:(1)There was a significant increase in soil fertility of dump through fifteen years of vegetation restoration. Soil organic matter, total N and available N had significant increase but they still at lower level and far below the content of original landform soil. Available P of dump was higher than original landform soil but had a decreasing tendency with vegetation restoration. The soil of dump under vegetation restoration was rich in available K which was still increasing with revegetation. Vegetation types had significant influences on soil nutrient and the nutrient content in grassland was obvious higher than in shurbland and woodland. The influence of vegetation on the surface 0~10 cm soil nutrient was greater than that on the deep 10~20 cmoil, also the soil nutrient was to surface enrichment under the action of vegetation. The content of organic matter had a linear positive correlation with the total N, available N and available K in 0~10 cm soil layer. Therefore soil organic matter could be selected as a primary index for evaluating soil fertility. In terms of improving soil fertility, it was better to select grassland as the main vegetation type in early restoration in dump and then combined grass with tree to maintain soil fertility and the stability of plant community. Soil organic matter, nitrogen and phosphorus deficiency was the limiting factor in vegetation restoration on coal mine dump in the Loess area.(2)The R0.25, MWD and GMD of 0~20 cm soil layer were significantly increased in revegetation land than that in abandoned land on both platform and slope. The R0.25, MWD, GMD and D in 0~20 cm soil layer of revegetation land were 31.1%, 0.70 mm, 0.26 mm and 2.91 respectively on platform, and 13.3%, 0.37 mm, 0.17 mm and 2.96 respectively on slope. The soil aggregates quality was better on the platform than on the slope. Artifical grassland had a more significantly improvement for soil aggregates quality than the shrubbery on the platform of dump. While on the slope, the shrubbery was better than the artifical grassland. The soil aggregates quality was lower in surface layer than sub-surface layer on the platform. Soil organic carbon content and soil clay content were significantly related to soil aggregate quality. Our results suggested that soil aggregates quality was improved significantly after 15 years of vegetation restoration, and vegetation types and landforms had significant influences on soil aggregates properties in this studied mining area on the Loess Plateau.(3) Artificial grassland reconstruction improved SOC, nutrient and soil aggregates quality significantly. The soil quality in surface soil layer had been near the level of original landform soil but in deep soil layer was still in a poorer conditions. Improvement on soil environment of Medicago sativa was the best in different grassland but it had a low effect on deep soil layer and tend to degradation at the later stage of revegetation due to its strong consumption of soil water. It was better to select grassland as the main vegetation type to fertilize soil in early restoration in dump and then combined with other grass community with low water consumption, which could improve the stability of plant community and improve soil quality continuously.