Analysis on Land Use Change in the Mainstream Area of the Tarim River in Recent 20 Years

This paper analyzed the land use change under natural and artificial flooding before and after implementing the water redistribution project in the mainstream area of the Tarim River based on four sets of land use data in 1990,2000,2005 and 2008.The results showed that the land use change was obvious after implementing the project.The area of farmland was enlarged by 1.03×105 hm2 in recent 20 years,and the dynamic degree of land use was highly increased after implementing the project,the area of alkaline land was enlarged by 7.13×104 hm2,area of steppe was reduced by about 4.91×105 hm2,the areas of forests and waters were enlarged at first and then reduced in recent 20 years,but the dynamic degree of land use was decreased,these indicated that the land use types were changed frequently from 1990 to 2008.Enlargement tread of alkaline land and sand land was restricted to some extent after implementing the water redistribution project.The mutual transition of land use types occurred mainly in steppe,woodland,farmland and sand land.At landscape level,the Contagion Index(CONTAG),Landscape Division Index(DIVISION),Shannon's Diversity Index(SHDI) and Simpson's Diversity Index(SIDI) were calculated.The results showed that the landscape fragmentation and connectivity were decreased,but the diversity index and evenness index were increased,which revealed that the heterogeneity and stability of landscapes were increased.These changes may result in a salt accumulation in topsoil and the reduction of wetland.The study results could be applicable in assessing the effect of implementing the water redistribution project.