| At present,comprehensive ecological monitoring and assessment have been carried out for major ecological projects such as gain from green project,three-north shelter forest program,and the recovery projects in Sanjiangyuan region,has established a perfect ecological benefit evaluation method system in China.However,the ecological restoration of mining areas,as an important part of ecosystem protection and sustainable development,lacks systematic evaluation of ecological restoration after restoration and cannot quantify its ecological restoration benefits.The following problems exist in the study of ecological restoration in semi-arid underground mining areas: lack of analysis of the impact characteristics of ecological restoration,unknown mechanism and characteristics of ecological benefit formation after restoration,unclear framework of ecological benefit evaluation applicable to semi-arid underground mining areas,etc.Therefore,this study takes the Shendong mining area as the research area,explores the impact characteristics of ecological restoration on the Shendong mining area based on the analysis of ecosystem disturbance and ecological restoration characteristics.Secondly,summarizes the formation mechanism of ecological benefits in semi-arid underground mining area restoration based on scientific theories,clarifies its scale characteristics,and constructs ecological benefit evaluation index system and models.Finally,evaluate the spatial and temporal changes and value of ecological benefits at different restoration scales and make suggestions.The main conclusions of this study are as follows:(1)The characteristics of ecosystem disturbance and ecological restoration impact in mining areas are summarized.The ecosystem disturbance in semi-arid underground mining areas is characterized by four major features: long disturbance time,large disturbance spatial scale,multiple disturbance factors,and strong spatial heterogeneity.The implementation of ecological restoration has significantly improved the vegetation coverage in the Shendong mining area,with 91.78% of the areas with NDVI trend type increasing.Based on the Land Trendr time-series change detection model,the evaluation time for ecological restoration benefits is determined to be 6 time points in2000,2006,2011,2015,2017,and 2020.During 2000-2020,the K-values of urban land and cropland show a continuous increasing trend,while the K-values of shrub grassland and forest change relatively steadily.Thanks to the implementation of ecological restoration,the area of bare land is reduced,but its K-value show a fluctuating trend.The area of water land decreases due to natural factors,and its K-value shows an overall negative trend.(2)The study clarified the mechanism of ecological benefits in the mining area restoration and constructed a multi-scale hierarchical ecological benefits evaluation framework.The formation mechanism of ecological benefits in mining areas restoration is summarized into a four-level mechanism systematics: " improvement of ecosystem elements-stability of ecosystem structure-exertion of ecosystem functionsgeneration of ecological benefits ".Based on the scale-dependent and scale-mosaic characteristics of ecological benefits,thus a multi-scale hierarchical ecological benefit evaluation index system is constructed from the ecological elements,ecosystem structure and ecosystem service functions.The evaluation models of each index are determined according to the indexes,including the construction of the PWV-LST coordination model to evaluate atmospheric benefits,the construction of SNI and ESFI comprehensive benefits index evaluation models,historical growth magnitude and background deviation to guide the quantitative evaluation of the ecological benefits of the ecological restoration project.(3)Analyzes the spatial and temporal changes of ecological restoration benefits under different scales.(1)At the scale of the Shendong mining area,the ESFI value shows a spatial distribution pattern of high in the southeast and low in the north,with a steady increasing trend.In 2020,the ESFI value is 0.46,with an overall growth rate of46.46%,and the total value of ecological benefits quantity is 15.6 billion yuan.(2)Under the scale of the Daliuta mining area,the SNI values ranged from 0.4 to 1.7,the NDVI and ESFI value show a spatial distribution pattern of high in the southeast and low in the west.The ESFI value increases slowly and steadily to a fast and stable growth trend,with a growth rate of 83.46%.In 2020,the SNI value is 1.09,NDVI is 0.54,SHDI value is 0.87,CONTAG value is 48.35,ESFI value is 0.52,and the total value of ecological benefits quantity is 394 million yuan.(3)At the scale of ecological restoration projects,the ecological benefit value of waste dump restoration project is 23 million yuan,among which the ecological restoration of the PGC-3(seabuckthorn+herbaceous)is the best..The ecological benefit value of the subsidence area restoration project in the Daliuta mining area is 50.7 million yuan.Among them,the ecological restoration of DLF-4(super high water material + grass planting),STL-1(pinus sylvestris),SJL-1(sea buckthorn)and FHSB-7(sea buckthorn)are the best.The ecological benefit value of sand-affected restoration project is 22 million yuan,and the restoration of sand fixation by salix cheilophila is slightly better than that of shrub and grass replanting.The ecological restoration projects achieve good ecological and economic values,but different ecological restoration projects have problems of soil nutrient,water content and soil conservation below the background value.Therefore,it is necessary to strengthen soil fertilization and soil and water conservation measures to control and prevent further degradation and promote their recovery.The results of this study can provide a scientific basis for the evaluation of ecological benefits in semi-arid underground mining areas and provide a reference for promoting mining ecological restoration work.The study has 64 figures,27 tables,and 133 references. |
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