Research On Landscape Ecological Risk Assessment Of Xi'an City Based On Land Use Change

With the acceleration of my country's urbanization,the increase in population and the expansion of urban scale have caused strong human disturbance to the regional ecological environment.Among them,the unreasonable use of land resources seriously affects the stability of regional ecology.Landscape ecological risk assessment is based on the land-use landscape as a risk assessment complex.By constructing a model and calculating a risk index,the characteristics of landscape ecological risk changes in the assessment area are evaluated to reflect the impact of human activities on the ecological environment.Therefore,the study of landscape ecological risk assessment based on land use change has important practical significance for the rational allocation of land resources,ecological environment protection and promotion of sustainable use of resources.Taking Xi'an as the research area,this paper analyzes the spatial and temporal changes of land use and the spatial heterogeneity of landscape patterns in the study area based on land use data.On this basis,appropriate landscape indexes are selected to construct a landscape ecological risk assessment model.The characteristics of the temporal and spatial changes of landscape ecological risks in Xi'an from 1990 to 2018 were analyzed,and the main driving forces of dynamic changes of landscape ecological risks in Xi'an were explored.The main research contents and conclusions of the thesis are as follows:(1)Based on land use data,analyze the spatiotemporal characteristics of land use change in the study area using methods such as land use dynamics and land use transfer matrix,and analyze the spatial heterogeneity of landscape pattern in the study area using landscape index and moving window method.The results show that the area of cultivated land,grassland,and waters showed a decreasing trend from 1990 to 2018,decreasing by 565.842km2;138.797km2,and 6.079km2 respectively.The area of construction land,woodland and unused land showed an increasing trend,increasing by 621.786km2,87.971km2,and 0.18km2 respectively,but cultivated land and woodland are always the dominant land use types in Xi'an.Among the single dynamics,the construction land changes the fastest,up to 3.37%,and the change speed of the comprehensive dynamics continues to increase over time,up to 10.23%.The transfer of cultivated land area and the transfer of construction land area are the main forms of land use change in Xi'an.In the analysis of the spatial heterogeneity of landscape pattern,each index showed significant change characteristics,indicating that there is a clear correlation between changes in land use types and ecological effects.(2)Based on the method of landscape pattern,the index of landscape disturbance,landscape vulnerability,landscape loss,etc.was selected to construct a landscape ecological risk assessment model,and the characteristics of the spatial and temporal changes of landscape ecological risk in Xi'an from 1990 to 2018 were analyzed,and the spatial autocorrelation model was used to explore it Spatial autocorrelation and heterogeneity.The results show that the spatial distribution characteristics of landscape ecological risk levels in Xi'an from 1990 to 2018 are higher in the east than in the west and higher in the north than in the south.The overall ecological risk is at a medium risk level,and the overall risk index is reduced from 0.6935 to 0.6753,a decrease It was 2.6%,and showed a continuous decreasing trend over time.In terms of area changes,high and high ecological risk areas showed a decreasing trend,medium ecological risk areas increased first and then decreased,and low and low ecological risk areas showed an increasing trend.Among them,the area of high ecological risk areas decreased by 440.48km2 and low ecological risk areas.Area increase by 271.32km2;Among the transfer rates of each ecological risk level,the high and high transfer rates are larger,the low and low transfer rates increase year by year,and the changes in the medium risk area are susceptible to human disturbance and the transfer rate is unstable.Based on the above analysis,the ecological risk status of Xi'an is in a benign development trend.In the spatial autocorrelation analysis,the global autocorrelation index is around 0.55 for the four periods,indicating that the landscape ecological risk value of the study area has a significant positive correlation in space;The local autocorrelation shows that the spatial distribution of ecological risk is dominated by "high-high" and "low-low" aggregation,with obvious characteristics of "homogeneous aggregation and heterogeneous separation".(3)Exploring the influencing factors and driving forces of the dynamic changes of landscape ecological risk in Xi'an from multiple angles,and firstly analyze the ecological risk response from the perspectives of natural factors and human factors;then,based on the geographic detector model,select factor and interactive detectors quantitatively analyze the main driving forces of dynamic changes.The results show that in the analysis of ecological risk response,natural factors have a controlling effect on the dynamic changes of ecological risks,and human factors are the main influencing factors to promote its dynamic changes;the results of the factor detector show that the degree of human disturbance and elevation have the greatest explanatory power for the dynamic changes of ecological risks,which are 51.14%and 25.24%,respectively;The results of the interaction detector show that the interaction of any two influencing factors has a synergistic effect on the explanatory power of the dynamic changes of ecological risks.Among them,all kinds of factors have the same explanatory power on the dynamic changes of ecological risks after interacting with the human disturbance factor.There is a big improvement.Comprehensive analysis shows that the degree of human disturbance has the greatest explanatory power for the dynamic changes of ecological risk among the single factors;the interaction between the degree of human disturbance and topographic factors in the interaction is the main driving force for the dynamic changes of landscape ecological risk in Xi'an.