| China’s large open pit coal mines are mainly distributed in arid and semi-arid regions,of which the coal output in the northwest region accounts for more than 50%of the country.This region has a dry climate,low rainfall,strong evaporation,less vegetation,single biodiversity,fragile ecological environment,and relatively small environmental capacity.The drastic increase of coal mining activities will accelerate the process of land desertification and vegetation degradation,resulting in a series of ecological and environmental problems.Remote sensing technology has the characteristics of rapid and large-scale macroscopical monitoring,which can invert and dynamically monitor the ecological environment factors from mult’iple scales.Based on Landsat TM/OLI,DEM,soil attribute data,meteorological data and other data,this paper constructed remote sensing monitoring indexes of Fractional Vegetation Cover(FVC),soil erosion and desertification degree as the main ecological environment factors in Xinjiang Black Open-Pit Coal Mine area,and then inversion and reveal the spatial and temporal distribution characteristics of each ecological environment factor.Based on the multi-objective evaluation method and objective weighting method,the ecological environment index estimation model was constructed,and the temporal and spatial variation law of the ecological environment in the study area was analyzed,and the following conclusions were drawn:(1)Estimation of FVC and analysis of spatial and temporal characteristicsThe NDVI vegetation index is used to obtain the spatial and temporal distribution of FVC in the study area in 2000,2009,2014 and 2019 using the pixel binary model.The results showed that the study area was dominated by low vegetation coverage types from 2000 to 2019,the area of bare land increased by 28.71%,and the area of low,medium and high coverage types decreased by 13.22%,7.91%and 7.58%,respectively;the average value of the coefficient of variation(CV)of FVC is 0.3841,with large fluctuations;the main conversion methods of vegetation coverage types are:from low coverage to bare land,and medium coverage to low coverage.(2)Estimation of soil erosion modulus and analysis of spatial and temporal characteristicsThe spatial and temporal distribution of soil erosion in 2000,2009,2014 and 2019 in the study area was obtained by using the modified universal soil loss equation(RUSLE)to estimate the soil erosion modulus.The results showed that the study area was dominated by slight erosion from 2000 to 2019,and the change of soil erosion types mainly showed that the slight erosion increased by 37.82%and then decreased by 38.95%,while the other erosion types showed a law of first decrease and then increase.Soil erosion modulus had a high correlation with slope length and slope factor LS,and the correlation coefficient was about 0.6.From 2000 to 2009,the mild and moderate erosion types were improved,and some of them changed to the slight erosion type.From 2009 to 2019,some of the slight erosion types gradually changed to the intense erosion type.Soil erosion showed a law of improvement first and then aggravation.(3)Estimation of DDI and analysis of temporal and spatial characteristicsThe spatial and temporal distribution of desertification in 2000,2009,2014 and 2019 in the study area was obtained by constructing NDVI-Albedo feature space to estimate the desertification difference index(DDI).The results show that the desertification in the western mountainous area of the study area has been improved from 2000 to 2019,and the extremely severe,severe and moderate desertification types are mainly distributed around the mining area.From 2000 to 2009,62.46%of the extremely severe desertification types gradually changed to non-severe desertification types,and from 2009 to 2019,there was an interchange between severe and moderate desertification types.Desertification was improved first and then stabilized.(4)Construction of EI estimation model and analysis of temporal and spatial characteristicsThe weights of vegetation coverage,soil erosion modulus and desertification difference index are determined by CRITIC objective weighting method,and the Eco-environmental Index(EI)estimation model is constructed to obtain the spatial and temporal distribution of the ecological environment in the study area in 2000,2009,2014 and 2019.From 2000 to 2019,the ecological environment types in the western mountainous area of the study area were mainly good and good,and the ecological environment types around the mining area were generally and poor.The change of the ecological environment types in the study area was mainly manifested as the poor types increased by 37.36%first and then decreased by 38.13%.The average value of the CV of ecological environment was 0.1352,and the fluctuation was small.The ecological environment showed a pattern of aggravation,improvement and finally stabilization.To sum up,through the FVC,soil erosion modulus,DDI of ecological environment of the three factors the characteristics of space and time to reflect the strip mining activities on the influence of the main ecological environment,to increase the use of three index method of the ecological environment comprehensive ecological environment factor,can reveal the region ecological environment in time and space distribution characteristics.It provides basis and guidance for ecological restoration and green mine construction in the study area. |
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