Landscape Ecological Risk Assessment And Ecological Security Pattern Optimization In Middle And Upper Reaches Of Xinjiang River

The deterioration of ecological environment caused by the continuous development of social economy will directly affect the survival and life of human beings and other organisms.The Xinjiang River is one of the important tributaries of the Poyang Lake system,the largest freshwater lake in China.Although the ecological environment base of the middle and upper reaches of the Xinjiang River is good,the intensification of human activities has caused many adverse effects on the ecological environment of the basin.Therefore,this study takes the upper and middle reaches of the Xinjiang River Basin in Jiangxi as a study area,according to remote sensing image information and DEM,NDVI and other data from 1990 to2020,on the basis of analyzing the dynamic evolution of landscape pattern in the upper and middle reaches of the Xinjiang River Basin,quantitative evaluation of landscape ecological risk level is realized by constructing evaluation model.Taking the obtained landscape ecological risk index as one of the resistance factors,the comprehensive resistance surface is constructed.Based on the MCR model,the ecological security pattern of the middle and upper reaches of the Xinjiang River Basin is obtained,and the optimization countermeasures of the ecological security pattern are put forward.The main research results are as follows :(1)In the dynamic evolution analysis of landscape pattern,the landscape in the middle and upper reaches of Xinjiang River is dominated by forest land and cultivated land;from1990 to 2020,the landscape types of the upper and middle reaches of the Xinjiang River Basin showed a change of “two increases and four decreases”.It shows that water area and area of construction land increased,while the area of the four landscape types decreased.Among them,the construction land has increased rapidly,showing cluster distribution in space,especially after 2000.At the same time,the overall landscape fragmentation in the middle and upper reaches of the Xinjiang River Basin increased,and the complexity and diversity of landscape shapes increased.(2)In the landscape ecological risk assessment,the landscape ecological risk in the middle and upper reaches of the Xinjiang River Basin showed an overall upward trend from1990 to 2020.The proportion of high and high landscape ecological risk areas in the total area increased from 24.06 % in 1990 to 34.32 % in 2020.From the perspective of spatial distribution,the landscape ecological risk index of the middle reaches of the Xinjiang River is higher than that of the upper reaches,and the landscape ecological risk index has a strong spatial positive correlation.At the same time,from 1990 to 2020,there were 16 kinds of complex conversion between landscape ecological risk grades.The proportion of conversion from low risk to high risk was 25.59 %,and the proportion of conversion from high risk to low risk was 2.02 %,which reflected the impact of landscape urbanization on landscape ecological risk in 30 years.(3)In the construction and optimization of ecological security pattern,based on morphological spatial pattern analysis method and landscape connectivity evaluation,the initial ecological source area was determined in the range of forest land and water area in the low ecological risk area in 2020.And then all kinds of forest parks and nature reserves in the upper and middle reaches of the Xinjiang River Basin were superimposed to determine 31 ecological sources.Taking the obtained landscape ecological risk index as one of the resistance factors,the comprehensive resistance surface is constructed,and then 68 ecological corridors,22 ecological pinch points and 17 obstacle points are identified by using the Linkage Mapper toolbox in Arc GIS software,which jointly constitute the ecological security pattern.On this basis,the optimization countermeasures of ecological security pattern are put forward,such as building a good buffer zone,accelerating the restoration of ecological breakpoints,giving priority to the key areas of ecological restoration and strengthening the ecological construction of the urban belt of the Xinjiang River valley.