Wetland Extraction And Changes Of A Typical Wetland In Chiangtang Plateau

As an important part of the ground ecosystem, wetland is one of the ecologicallandscapes with the richest biodiversity and one of the most important survivalenvironments of mankind. About80%of wetlands are degrading or disappearing andwetland ecosystem has become one of the most seriously threatened ecosystems inthe world. As a sensitive area to global climate change and an ecological securitybarrier of Asia, Tibetan Plateau is an important wetland distribution area of Chinawith13.19×104km2of wetlands. Basic surveys of wetland types, area, terrain, soil,climate, fauna and flora have been made in Tibetan Plateau by scientificinvestigation before1980s. Then remote sensing technology has been applied inwetland research in this area. And due to its wide observation range, largeinformation capacity, quick access to information, and high comparability, remotesensing has been widely used in wetland type transformation, area change, landscapepattern evolution, and monitoring of ecological environment. Chiangtang plateau isthe main part of Tibetan Plateau, north to Kunlun Mountain, south to GangdiseMountain and Nianqing Tanggula Mountain, east to Nujiang River watershed, andwest to Pamir plateau, covering a quarter of Tibetan Plateau with an area of58.6×104km2. Wetlands in Chiangtang plateau are typical plateau ones, which haveabundant types, especially numerous lakes. Thus Chiangtang plateau becomes thehighest interior drainage area in the world, a lake distribution plateau with the mostlakes and highest lake surface. There are2.14×104km2of lakes here which accountfor more than a quarter of the total in China. Based on Landsat data, this dissertationanalyzed wetland system of Chiangtang plateau in1990and2010and one typicalwetland in this area from1972to2012. The results are as follows:(1) The optimal band combination selection was researched for extractingwetland information in sample region of Chiangtang plateau, covered by one sceneof Landsat from path145, row37, using single-band information, multibandcorrelation coefficient, and OIF index. The results showed5(R)4(G)3(B) was thebest choice. As the false color composited by Landsat bands3,4and5was close toreal color of objects, bright-hued, clear-structured, and easy-to-interpret.(2) This dissertation studied the classification method of Chiangtang plateau wetland suiting remote sensing research. Classification of wetlands in the sampleregion was made using ISODATA classification, maximum likelihood classification,neural network classification, support vector machine classification, decision treeclassification, and object-oriented classification separately. After comparing bothoverall and each type’s classification accuracy of each method, the object-orientedclassification was found most applicable to wetland extraction in the sample region.Overall and single-type extraction (such as water and marsh) with high precisioncould be made with this method, and it could be avoided to confuse ice-snowcovered area and mountain shadow with wetlands, also the geometric shapeextracted was much more smooth and closer to facts.(3) Based on the optimal band combination and applicable classification methodresearched before, analysis on area change during1972-2012of Taohoping Lake wascarried out. It showed that:1) Taohoping Lake experienced a process from shrinkingto extension.2) The lake area kept decreasing from1972to1998.3) The lakeshowed a continuous extension during1999-2012and a dramatic extension during1999-2000. In addition, it was found that Taohoping Lake area change wascorrelated with precipitation and temperature positively and precipitation contributedthe most in typical wetlands change in Chiangtang plateau.(4) Based on the optimal band combination and applicable classification methodresearched before, analysis on area change during1972-2012of typical swampwetland in this paper was carried out. It showed that:1) The typical swamp wetlandexperienced a process from shrinking to extension.2) The swamp area keptdecreasing from1976to1992.3) The swamp showed a continuous extension during1992-2010. In addition, it was found that while using band combination andclassification method of being choosen in this paper, we have higher classificationaccuracy of wetland than other wetland research in Tibetan Plateau.