The Research Of Eco-environment Remote Sensing Monitoring And Ecological Vulnerability Spatiotemporal Process Driving Mechanism In The Forest-grass Ecotone Of Northwest Sichuan

The United Nations Conference on Environment and Development in 1992 adopted the theory of sustainable development as a global common development strategy.For more than 20 years,the concept of sustainable development has been deeply rooted in the hearts of the people and made significant progress in achieving the UN Millennium Development Goals.Under the current dual drives of global climate change and human activities,environmental degradation,ecological damage as well as the environmental disasters and ecological catastrophe caused by them have not been alleviated,posing major challenges to sustainable development.The forest-grass ecotone of Northwestern Sichuan is located at the eastern margin of the Qinghai-Tibet Plateau,the Hengduan Mountains strongly eroded and cut the alpine valley to the plateau landform transition zone.It belongs to the upstream source zone of the Yangtze and Yellow River water systems,as the national ecological function zone and the ecological barrier of upper Yangtze River.However,the landform undulates terribly,geological structures are complex,the hydrothermal condition is vertically changed,the soil layer is hypolastic and the soil is thin,what's more,the ecological environment is inherently fragile.At the same time,it is strongly influenced by natural and human activities,and the regional ecological degradation is obvious.It is an ecological fragility area of forest-grass ecotone,a poverty area fixedly,an ethnic minorities area.It has a great significance for the forest-grass ecotone in northwestern Sichuan to understand the dynamic process of ecological environment and the ecological vulnerability spatiotemporal process mechanism.Although theories and methods for the protection and construction of ecological barriers in the zone have been studied and explored,the research on time-space process mechanism is still lackingThe thesis relies on the National Natural Science Foundation of China,“Spatial and Environmental Impacts of Grassland and Pastoral Areas,Space-Time Process Analysis and Early Warning-Taking the Source Region of the River in the Northwest of Sichuan Province as an Example(41401659)”,and the national key research and development plan project(2017YFC0505000),the special topic “Alpine subalpine cutting vegetation restoration technology”.The methods are RS,GIS and field survey,which can quantitatively monitor and analyze the spatial and temporal changes and characteristics of the ecological environment in the forest-grass ecotone of Northwestern Sichuan,It provides technical and methodological support for the protection and construction of the area by constructing model,mastering the characteristics of the spatiotemporal process,exploring the causes and mechanism of eco-environmental vulnerability.The main research results and innovations obtained in this thesis are as follows:(1)Aiming at the complex geological and geographical conditions of the zone,the multi-type and multi-temporal remote sensing image was applied to extract the NDVI,land use,geological hazard and soil erosion sensitivity of the alpine plateau forestry-pastoral ecotone.The MODIS sensor only get the data after 2000 and the spatial resolution of other satellite NDVI data are not matched.It is difficult to monitor the dynamic change of NDVI around 2000.This study realized the forest-embedding complex mountainous area GIMMS based on ESTARFM algorithm.The product,the MODIS and NDVI data are effectively extracted,and the NDVI spatio-temporal fusion data of the GIMMS product matching the spatial resolution of the MODIS sensor NDVI data is obtained.Aiming at the complex terrain of the forest-grass ecotone in the alpine plateau and the diversity of landform types,the difficulty of extracting remote sensing information of land use types is rather big and the accuracy is not high.This study constructs object-oriented technology-visual interpretation-mixed pixel decomposition.Based on the Landsat imagery,the high-precision extraction of land use types in the complex mountainous areas of forest and animal husbandry based on Landsat imagery is realized.At the same time,based on the high-resolution remote sensing data,the remote sensing interpretation marks of mountain-morning disasters in the forest-pastoral zone are established,and the remote sensing information of dynamic changes of geological disasters in long time series is obtained.Based on the USLE equation,the soil erosion sensitivity of the alpine plateau forest-pastoral ecotone is obtained.Dynamic change information.On this basis,the spatial and temporal processes of climate,soil type,vegetation type,NDVI,land use,landscape pattern,geological hazard and soil erosion sensitivity are analyzed systematically from 1990 to 2015 in the forest-grass ecotone.(2)In view of the evaluation index weight is difficult to determine effectively,this study integrates the projection pursuit model-genetic algorithm to construct a regional ecological vulnerability assessment model,which guarantees the high-dimensional nonlinear characteristics of the ecological vulnerability assessment index system and improve the objectivity.The integrated genetic algorithm better solves the problem that the projection direction vector of the projection pursuit model is difficult to optimize.The model can better realize the objective and effective evaluation of the spatial and temporal processes of ecological vulnerability of forest-grass ecotone in alpine plateau.(3)This study systematically analyzed the overall characteristics of the spatial and temporal processes of the ecological vulnerability of the forest-grass ecotone in northwestern Sichuan from 1990 to 2015.The spatial and temporal distribution characteristics of ecological vulnerability is discussed according to elevation,slope and aspect change.The relationship between spatiotemporal distribution process of ecological vulnerability and land use type is analyzed.The character and the change are discussed in Hong Yuan,Ruo Ergai,Song Pan and Jiu Zhaigou.(4)Aiming at the scientific problems of the current spatial and temporal process mechanisms of ecological fragility in the study area,the geological elements(lithology,structure,hydrogeology),topographical elements(elevation,slope),soil elements(type,erodibility),vegetation elements(type and coverage),climatic factors(temperature and precipitation),land use,population and GDP are systematically analyzed based on the geo-detection algorithm and projection pursuit-genetic algorithm.In addition to this,the genesis mechanism of ecological vulnerability caused by related elements.The grey theory are used to analyze the overall driving mechanism and spatial differentiation driving mechanism of NDVI,temperature,precipitation,geological disasters,land use,population,GDP and other dynamic change factors on the spatial and temporal processes of ecological vulnerability in research area.On this basis,the ecological vulnerability of the study area is divided,and suggestions for ecological protection and construction of different zones are proposed.(5)This study is aimed at the ecologically fragile area of forest and grass in the alpine plateau,and has formed a set of eco-environment remote sensing monitoring-analysis of the spatiotemporal process of ecological environment-the construction of ecological vulnerability assessment model-analysis of spatial and temporal process mechanism of ecological vulnerability,which provides technical support for remote sensing monitoring and ecological vulnerability assessment of ecological environment in the region and similar ecologically interlaced fragile zones.