Changes of Wetland in Qaidam Basin in the Past 50 Years and Analysis of Climatic Background

Based on the 1∶100 000 topographic maps of Qaidam Basin on 1956's aerial photographs,remote sensing images of Landsat TM in 1990 and Landsat ETM in 2000,and the temperature and precipitation data of eight weather stations in Qaidam Basin,the distribution patterns of wetland,changes of wetland and background of climate factors were studied by using RS and GIS techniques.During 1956 and 2000,the average annual temperature and average precipitation in Qaidam Basin show an increasing trend,with the former rising significantly,with warm-dry period from 1990 to 2000.The trend of wetland degradation in Qaidam Basin is serious during 1956~2000 especially in 1990s.In the edge area of Qaidam Basin and along large rivers,there was a fluctuation trend of wetland,caused by climatic changes and human activities,i.e.,the degradation of wetland in central and western basin is caused by temperature rise and human activities,while the slight increasing of wetland in edge area of the basin is caused by average annual precipitation change.