The Land Use/Cover Changes and the Eco-environmental Responses in the Lower Reaches of Tarim River, Xinjiang

Taking two composite Landsat 5 TM (thematic mapper) images of band 4, 3 and 2 taken in 1988 and 2000 respectively as the data sources, this paper carries out the study on the land use/cover changes in the lower reaches of Tarim River in recent 12 years by using the information about the land use and land cover interpreted from these two images based on the classification system of land use (1:100 000) of the Resources and Environment Database of Chinese Academy of Sciences, and the eco-environmental responses in this area are also researched. The results are as follows: (1) The land use in 2000 was dominated by the unused lands and grasslands. (2) The landscape pattern indexes show that the diversity was increased. The values of fragmentation in the typical regions were less than 0.2. Such a low fragmentation reveals that the landscape connectivity was high and the resistant capability to environment change was strong. The fractal dimension of the sparse woodlands was the highest, which reveals that the shape of every patch was relative simple, the effects of corridors were small, the matrix of landscapes was sandy lands, and the desertification became more serious. (3) During the period from 1988 to 2000, the areas of farmlands, waters, unused lands and urban lands were enlarged but the areas of woodlands and grasslands were reduced. (4) In recent 12 years, the area of unchanged lands occupied 99.645% of the total land area but the area of changed lands occupied 0.355% only, in which the area of the improved lands was larger than that of the degraded lands, and the area of the developed lands was larger than that of the lands discarded from cultivation. (5) Except the land use and land cover in the study area are affected by the warm-temperate continental arid climate, human activities (such as changing the spatial distribution of surface water and destroying the natural vegetation) are the main causes resulting in the degeneration of the eco-environment. The eco-environment responses include the increase of mineralization, drawdown of groundwater level, degeneration of the forests of Populus euphratica, shrubbery and grasslands, enlargement of the area of desertified lands, etc.