Study On Landform Characteristics And Vegetation Succession Of Glacier Retreated Area Based On Hyperion

The Hailuogou Glacier is located on the east slope of the main peak of the Gongga Mountain which is the most representative monsoonal temperate glacier in the Hengduan Mountains.Since the Quaternary,persistent and intense glacial movement has shaped the unique "U" ice-eroded valley in the Hailuogou Basin,the upstream gully which is a modern glacier covered with surface moraine,and the rich glacial sedimentary landforms that developed downstream.Form the end of the Little Ice Age on,Hailuogou glacier,a retreated area of about 2km in the downstream of glacier,has formed a typical primary succession.The sedimentary landform at the end of the glacier contains rich information on ancient glacier changes and climatic environment,and the vegetation developed on the sedimentary landform after the glacier recedes records the time series of the glacier retreat.Therefore,as a complete system,it is of great significance to analyze and study the glacial terminus landform and the vegetation community developed.as a complete system.According to the hyperspectral technique and aerial photogrammetry,this paper discusses the characteristics of sedimentary landforms and vegetation succession communities in the glacier retreated area.Based on the above,remote sensing identification and classification experiments were carried out to explore the development characteristics of glacial sedimentary geomorphology and the succession law of vegetation community on the time series from the spatial scale.The specific tasks and conclusions are as follows:(1)According to the position of the glacier terminus in different periods,the formation age and range of the receding area were obtained.Combined with aerial survey images of unmanned aerial vehicles(uav),historical remote sensing images and previous research materials,the time sequence chart of the retreat of Hailuogou glacier terminus from 1930 to 2019 was drawn.(2)Based on the digital surface model obtained by unmanned aerial vehicle,the overall topographical characteristics of glacier valleys and the development characteristics of sedimentary landforms such as lateral moraine and terminal moraine were discussed in terms of elevation,slope,aspect and valley profile.Based on this,the spectral characteristics of various landforms in the glacier retreated area are compared and analyzed from the hyperspectral perspective.The results show that the spectral reflectance of the sedimentary landform is related to the type of moraine covered by the surface,and the higher the gravel composition,the higher the spectral reflectance.The continuum-removaled of the geomorphological spectrum information found that the de-envelope features of the geomorphic morphology are consistent with the gravel lithology in the sediment,which indicates that it is feasible to judge the main lithology of geomorphic morphology by using hyperspectral data.(3)Based on the division of vegetation succession stages in the glacier retreated area,the hyperspectral data of dominant vegetations in the vegetation succession community were collected using a field spectroradiometer,and the spectral characteristics and differences of vegetation in each succession stage were analyzed.The results showed that sea buckthorn,populus purdomii,salix rehderiana and Fir are dominant vegetations at different stage of vegetation community succession and could be used as a division of succession community.The first-order differential transformation and the calculation of three-sided parameters were found that from the perspective of overall reflectivity,sea buckthorn > populus purdomii > fir> herb community,the differences in their spectral reflectance are mainly reflected in the red valley,red edge,and near-infrared bands.The method of mahalanobis distance can be used to extract these different bands.(4)Using Sentinel-2 satellite image data and a decision tree classification method based on prior knowledge to achieve fine recognition of landform information and vegetation information.From the results of classification,the terminal moraine of the ancient glacier in the retreated area is basically covered by vegetation,while the vegetation coverage of the lateral moraine is related to the distance to the glacier's end and the slope.On the condition of the location of the glacier's end in different periods,and the spatial distribution of the vegetation community,the succession rule in the time series was discussed.The order of vegetation community in the retreated area is herbs,sea buckthorn,populus purdomii,and fir.Herbs and sea buckthorn became dominant vegetation after 11 years of glacier retreated.After 53 years,the populus purdomii replaced the sea buckthorn as the main vegetation,while fir became the dominant vegetation after 1989.