| The good location conditions of the Xiangjiang River basin bring great development advantages to the social economy.In recent years,regional human activities have intensified,which has a certain impact on the stability of the ecological environment itself,and the reduction of stability has restricted the economic development.Therefore,how to maintain the stability of ecological security in the basin under the background of changes in natural conditions and intensified human activities is one of the current research directions.Taking Xiangjiang River Basin as the object of ecological risk assessment,this paper deconstructs the model from two aspects of external multi-source stress degree and internal system loss degree according to the two-dimensional model of "risk probability loss degree".Taking 70 districts and counties in the study area as the evaluation unit,this paper analyzes the spatial-temporal variation characteristics of ecological risk in Xiangjiang River Basin from 2000 to 2018,explores the spatial correlation,aggregation mode and migration direction on the basis of the evaluation,divides the risk zones according to the combination of external multi-source stress degree and comprehensive ecological risk,and puts forward countermeasures and suggestions for risk reduction,It provides a reference for ecological optimization.The main results are as follows:(1)During the study period,the overall spatial characteristics of external multi-source risk stress were low in the South and high in the north,and the risk value increased.The average values in 2000 and 2018 were 0.2449 and 0.2793 respectively,with an overall increase of 12.32%;The spatial distribution of internal system loss degree is relatively scattered,which is higher in the north and lower in the south.The average value in 2000 is 0.6329,and the average value change in 2018 is 0.6609.The overall increase was 4.24%.(2)The spatial pattern of comprehensive ecological risk was high in the West and North,and low in the East and south from 2000 to 2018.The distribution pattern of comprehensive ecological risk was high in the north and low in the south.The high risk area increased significantly,with an increase rate of 24.86%.The average values in 2000 and 2018 were 0.1654 and 0.2003 respectively,with an overall increase of 17.42%.(3)The spatial distribution of ecological risk shows obvious positive correlation,and the high value and low value cluster distribution characteristics are obvious,and the degree of spatial autocorrelation is increasing.In 2000 and 2018,Moran’Ⅰwas 0.507 and 0.646,respectively.In 2000,the ecological risk center was located in Hengyang County,Hengyang City,and in 2018,it was transferred to the northeast to Hengshan County,Hengyang City.The migration direction of risk center is from southwest to northeast,and the main direction of risk evolution is from southwest to northeast.The hot spots of ecological risk are gradually transferred to Changsha,and the cold spots are gradually concentrated to the south of the study area.The cold spots and hot spots of the risk have been connected and tend to spread to the surrounding areas.(4)High risk area,high risk area,medium risk area and low risk area accounted for 35.71%,7.14%,5.71% and 51.43% of the total number of the study area respectively.For higher risk areas,external risk sources should be identified and potential risk stress should be dealt with.For medium risk areas,it is necessary to recognize the action conditions of regional risk stressors on receptors,and strive to repair the ecosystem through the construction of regional ecological security pattern;For the high-risk areas,we should deal with the high-risk and medium-risk areas.For low-risk areas,natural optimization should be given priority to,without too much human intervention. |
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