| In the past 100 years,with the global warming and the increasing frequency of human activities,wetlands are facing severe challenges of overall degradation.The Selin endorheic basin,located in the hinterland of the Qinghai‐Tibet Plateau,is an important part of the wetland ecosystem in Qiangtang basin.In this place,the distribution of wetlands are very wide and home to a large number of national protected flora and fauna.However,in recent decades,the degradation of its wetland area has posed a serious negative effect on either the habitats or the migration and reproduction of birds.Firsty,this study conducted extensive field investigations on the study area and collected a large amount of relevant data,thereby grasping the principles of wetland ecosystem composition and functional characteristics,and then carried out a dynamic monitoring of the spatio‐temporal wetland landscape pattern changes and assessed the ecological vulnerability of wetland in the past 42 years,using the "3S" technology methods.The main research contents of the thesis are as follows:(1)This study uses ASTER‐GDEM data to define the basin boundary of the study area,assisted GF‐1 high‐resolution remote sensing images and Tibetan hydrological data.Landsat remote sensing images were collected around 1975,1990,2000,2010 and 2017.The basin wetlands were classified into three major wetlands and nine subclasses.After remote sensing wetland interpretation marks were established,wetland data of 8 different types was extracted by visual interpretation for five periods.(2)In order to learn the dynamic changes of spatiotemporal landscape patterns of wetland,this study used the variation range,rate of change,linear fitting method,transfer matrix of land use and landscape pattern index as the analysis means to analyze characteristics of changes of wetland.Then the drivers of these characteristics are analyzed.The various driving indicators are organized into two categories including 19 indicators.The principal component analysis of the driven indicators was carried out by using the "maximum variance maximum rotation method" to obtain the driving weights of different indicators for wetland changes.(3)In this research,A “sensitivity‐state‐stress‐response” index framewok was established to conduct ecological vulnerability assessment of wetland in Selincuo basin.Data standardization method was used to eliminate the influence of each factor’s dimension.Fuzzy analytic hierarchy process was adopted to determine the weight of each evaluation factor.The comprehensive evaluation results were determined by using ecological vulnerability index(EVI).The results of EVI were reclassified into 5 levels as the evaluation criteria to respect static wetland vulnerability degree.these different levels are conducted deviation analysis method was to dynamically analyze the ecological vulnerability of the wetland in the Selincuo basin and its sub‐basin.Finally,sub‐basin warning for high‐risk areas of wetland ecological vulnerability degree is given.The results showed that the wetland shrinkage ratio in the study area was 8.71% in the past 42 years.The land transfer rate between wetland types is nonsignificance in each period,and the degree of salinization in wetlands is reduced over the last 42 years.The fragmentation degree,the diversity and the heterogeneity of wetland landscape totally has increased.Natural climate change,regional economy and agricultural and livestock development,population change,and anthropogenic land expansion are the main drivers of spatiotemporal changes of the landscape patterns of wetlands.Since 1990,the wetland vulnerability degree has been gradually transformed from the first‐level and the second‐level as domination levels to the second‐level and the third‐level.Especially,it is pointed out that the vulnerability degree of the herbaceous marsh and seasonal or intermittent lakes has increased most significantly between the different types of wetland. |
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