Land Use And Landscape Pattern Changes Of Sugan Lake Wetland From 1988 To 2018

Plateau wetland is the water supplier and regulator of the whole river basin.It is called the "water tower" in the world.It has typical closed and semi-closed geographical environment characteristics.It plays a key role in preventing the global water crisis.It also involves the environmental problems of the whole river basin.It has a very high value and an irreplaceable important position in the protection and utilization.In recent years,due to the impact of global climate change and human activities,plateau wetlands have been seriously degraded,which has affected the habitat,migration and reproduction of wetland birds.Land,as an important component of ecosystem,is closely related to the environmental change of ecosystem.Through the study of land use/cover change,it is found that land use has an important impact on regional climate,hydrology,soil and vegetation.Land use,as one of the driving forces of environmental change,changes the quality of ecosystem.Therefore,the study of land use and landscape pattern change of wetland in the plateau can not only play an active and effective theoretical basis and guidance role in ecological reconstruction of wetland areas seriously damaged by the environment of Sugan Lake,but also provide a regional example for the sustainable development of wetland in the Tibet Plateau.In this study,the wetland of Sugan Lake was taken as the research area.Landsat TM and OLI remote sensing images were taken as data sources.This study combined with the remote sensing classification,spatial analysis method and mathematical statistics analysis method.The decision tree classification method was used to classify the images in order to extract the land use area information.Land use structure change,quantity change,degree change and dynamic transfer change analysis are combined to study the process of land use change.Landscape pattern change process is analyzed by landscape pattern analysis method from the temporal and spatial distribution changes of landscape fragmentation and diversity.Based on the above analysis,the driving mechanism of land use and landscape pattern change in Sugan Lake wetland was discussed by combining natural and human factors.The following conclusions were gotten in this study:(1)Four remote sensing images are classified,and the overall classification accuracy is above 85.00%.This shows that the decision tree classification method is suitable for the classification of Plateau wetlands.From the point of view of space-time change,grassland distribution is the most,mainly concentrated in the central part of the study area,and the area fluctuates greatly in the four periods;swamp and grassland are interlaced in the central part of the study area,and the area fluctuates in 1988,1998,2008 and 2018;lakes mainly include the western dasugan Lake area and the northeastern xiaosugan Lake area.The distribution of saline-alkali land was the smallest,mainly in the eastern edge of the study area and some areas between grasslands,and the area changed greatly in the four periods.(2)From 1988 to 2018,the land use of wetland in Sugan Lake changed obviously.The orderly decrease of land use shows the trend of rationalization,and the land use structure has not changed obviously;the grassland has the strongest evolution,followed by swamp,the smallest change of saline-alkali land,and the land use is in an unstable state;the land use is in a period of adjustment or decline,and the degree of land use is declining in general,and at present it is in the middle and upper level;the land use types are in the middle and upper level.Spatially,it shows that wetland area expands to non-wetland area.From the spatial and temporal distribution of landscape fragmentation,the degree of landscape fragmentation has increased significantly in the past 30 years,and the low-value areas are mainly located in the western part of the study area and its marginal areas,and most of them are in 1998.The area of dominant type decreases,while the area of low value tends to expand and the area of high value tends to shrink.Patch shape is becoming more complex.The high value mainly distributes in the middle of the study area,showing a decreasing trend,while the low value area increases.(3)From the point of view of the spatial and temporal distribution of landscape fragmentation,the degree of landscape fragmentation in the study area has increased significantly in the past 30 years,the area of dominant types is decreasing,and the patch shape is becoming more complex;from the spatial and temporal distribution of landscape diversity,the landscape connectivity is declining as a whole,showing a uniform trend,with the exception of the Sugan Lake and the Sugan Lake.From the patch type level,the dominance of lakes and swamps to the overall landscape increased,while the fragmentation degree and shape complexity of grasslands and saline-alkali land increased,and the aggregation degree decreased.(4)In terms of natural factors,during 1988-2018,the annual average precipitation and temperature in Sugan Lake wetland were consistent with the changes of land use and landscape pattern in time and space.In terms of human factors,the government's policy changed the economic structure of the study area.Grazing activities promoted the consolidation of grassland and desertification of swamp from two aspects: unbalance of grassland and livestock and drainage of ditches,which led to the change of land use and landscape pattern of wetland in Sugan Lake.