Analysis On Land Ecological Security Change And Affect Factors Based On RS And GIS In Danjiangkou Reservoir Area, China

China has a large population,but land resources are scare.With the rapid development of urbanization process,the ecological environment are more easily affected by human activities.Soil erosion and land desertification increase gradually.Land ecological risk increases as the population size gets larger,and the regional eco-environment deteriorates gradually.As the water source of the Middle Line South-to-North Water Diversion Project,the situation of eco-environment has a significant impact on the quality of water source and the smooth implementation of the project.However,less research was focused on the ecological security in the Danjiangkou Reservoir Area(DRA).Thus,it is imperative to conduct the study on the spatio-temporal variation characteristics of eco-security.In this study we chose some regions which has the direct impact on the eco-environment of the reservoir,including Zhangwan District,Maojian District,Yunyang District,Dangjiangkou City and Xichuan County,to conduct the study.The ecological security index of the DRA from 1996 to 2016 were identified using the spatial principal component analysis(sPCA)method based on the nature-society-economy index system,referring to the eco-environmental characteristics and socio-economic information.Then,we used the Exploratory Spatial Data Analysis(ESDA)method to analyze the space-time distribution and evolution pattern from the trend and spatial autocorrelation.Finally,a comprehensive study on the spatio-temporal response mechanism of eco-security using the Ordinary Least Square(OLS)and Geographically Weighted Regression(GWR)models was conducted.The main conclusions are as follows:1.Land eco-security assessment by remote sensing using the sPCAUsing GIS and RS technologies,we built the land eco-security evaluation system of nature-society-economy based on 30m×30m grids.The last assessment result showed the spatial heterogeneity.Verification accuracy of assessment result using sPCA method was high,which proved the feasibility of sPCA method in eco-security assessment.In view of the overall situation,the level of eco-security for the most of the land in the DRA was relatively high.However,the last evolution characteristics of eco-security showed that the land eco-security declined during the study period.In the spatial distribution,areas where eco-security rating was relatively lower was mainly located on the regions which were easily affected by human activities and soil erosion around the reservoir.2.Variation in Spatial Pattern of eco-security based on the ESDABased on the last results using ESDA method,the spatio-temporal heterogeneity of land eco-security distribution in different years was presented from the perspective of quantitative statistics and spatial visualization.In spatial trend the eco-security was low on the edge and high in the middle in the north south direction,and the eco-security gradually decreased in the west east direction.From the view of spatial clustering,in general the overall degree of clustering for land eco-security in the DRA reduced first and raised then.In the spatial pattern of hotspot,the ecologically secure regions,including HH and LH types,were mainly located on the higher ground and where were less affected by human activities.And the ecologically insecure regions,including LL and HL types,were mainly located around the reservoir,which should be paid more attention.3.Study on the spatio-temporal eco-security response mechanism to key influence factors using OLS and GWR modelsThe eco-security in the DRA were affected by the combined effects of the multiple factors.In this study we used the OLS and GWR models to study the response features in eco-security variation.The last result showed that final model fitting degree of GWR model was higher than OLS model.The selected indicators which were the major determinants of the eco-security were soil erosion and the distance from the resident areas using the OLS model,and the last fitting coefficient(R~2)from GWR model also underscore it.Moreover,the eco-security response to soil erosion and distance from the resident areas also showed the significant spatio-temporal heterogeneity.Over time,the effect of soil erosion on eco-security has weakened and the effect of human activities on eco-security has strengthened.The different response characteristics in different areas from 1996 to 2016 could offer some reference to the eco-environmental protection and control.