Spatial And Temporal Change Of Land Ecological Quality In Typical Coal Mining Areas

With the long-term exploitation of coal,the land has been severely damaged in the mining area.The resulting ecological environment damage and pollutant emissions in the mining area pose a serious threat to the sustainable development of the mining area and even to the regional ecological security.The comprehensive treatment of ecological environment and ecological restoration of mining area are imminent.And ecological restoration needs to follow the corresponding laws of land ecological development in order to rebuild the mining area ecosystem.Therefore,it is necessary to systematically study the spatial-temporal variation of land ecological quality in mining areas,and to understand the impact factors of land ecological changes,and to carry out accurate ecological restoration accordingly,which is of great significance for improving the ecological environment of mining areas and realizing the sustainable use of land in mining areas.This paper takes Jiaozuo mining area as the research area.Through the construction of the evaluation index system in the land ecological quality,the acquisition of index data,the identification of the indicator weight and evaluation unit and the selection of evaluation models,this paper used 3S technology and integrated basic geographic data,spot monitoring data and remote sensing data to evaluate the ecological quality of the land in the study area.On this basis,the temporal and spatial variation of land ecological quality was analyzed from multiple perspectives and the driving factors of land ecological quality change were identified in order to provide a theoretical basis for ecological restoration and land reclamation in the study area.The main results of this paper are as follows:(1)This paper established an evaluation index system which includes four criteria layers of ecological foundation,ecological structure,ecological benefits and ecological stress and 13 indexes.The index system integrates multiple aspects of the ecology of the study area and can objectively reflect the process of ecological change caused by natural and human activities in the mining area.(2)The system of acquiring time series data of land ecological quality index had been established integrately.In view of the practical difficulties of evaluating the time series data of indicator data,based on the full utilization of historical data,this paper studied the methods of space-time inversion of soil organic matter,time-series NPP data reconstruction and data acquisition of temporal land use types with multi-source data fusion,which realized accurate and rapid acquisition of multi-period ecological quality index data.(3)After defining the key problems such as evaluation unit and the standardization method,this paper established the weights of the evaluation indicators based on the improved AHP method,the land ecological quality assessment model of the mining area based on the comprehensive index model,and completed the analysis of the evaluation results of the four criteria layer indicators and the comprehensive evaluation results of land ecological quality in the study area.The results show that the ecological basic score shows a rising trend,the ecological structure score shows a decreasing trend,the ecological benefit score experiences a trend of decreasing first and then rising,the ecological stress score is declining,and the land ecological quality composite index shows first rising and then going down from 1990 to 2015 in the mining area.Throughout the study area,the evaluation results of land ecological quality shows a certain geographical differentiation.The proportion of evaluation units with excellent and good ecological quality levels accountes for 41.65%,51.41%,44.31%,and 41.85%,respectively,and experiences the trend of increasing first and then decreasing,which is mainly focused on the eastern plains of the farmland area.The proportion of evaluation units with poor and general grades is 36.36%,21.53%,34.40%,and 35.95%,respectively,which experiences a trend of decreasing first and then increasing.Contrary to the high grade,they are mainly distributed in the western and northern mining areas and the southern built areas.(4)According to the methods of spatial autocorrelation analysis,fan-surface analysis and path analysis,this paper analyzed the spatial and temporal differences of the land ecological quality from the aspects of spatial correlation and spatial orientation,identified the driving factors of the change of land ecological quality,and clarified the interaction and change between various factors and the change of land ecological quality.The results show that during the period 1990-2015,In terms of spatial correlation,the ecological quality of land shows a strong spatial agglomeration,and both the ecological quality hot spot(H-H)and the cold spot(L-L)agglomerating region have undergone varying degrees of changes.Among them,the hot spot area is slightly changed in the eastern farmland area,and the position is relatively fixed,while the cold spot area is repeatedly changed in the north mining area and the southern built area.In the spatial direction,the high value area of land ecological quality is mainly concentrated in the eastern farmland area in the direction from the northeast(NE)clockwise to the southeast-southeast(SSE),and the direction of the low value area is opposite.In terms of influencing factors,each driving factor has direct and indirect effects on the change of land ecological quality in different degrees,among which the change of the index of the degree of interference of industrial and mining land has the greatest impact.