Research On Ecosystem Service Value Change In The Middle And Lower Reaches Of Tarim River

Due to limited water resources in arid areas,the existence of artificial oasis is often at the expense of sacrificing the area of natural oasis,and artificial oasis often developments in the upper and middle reaches which have a better water environment.As a result,the ecosystem services of this region overall degradation because of the phenomenons such as reduction of water flow and devascularization of downstream.Tarim Basin is a typical valley.Form the point of Landscape Ecology,based on the Remote Sensing Image combined with the technology of GIS,this paper discusses the landscape pattern change in Yuli oasis in the lower reaches of Tarim River from 1990 to 2000, and calculates ecosystem service value of the upper and lower Reaches of Tarim River,It draws a conclusion as follows.(1)Since 1990,Yuli county has appeared desert as matrix,Tarim River as covered way and cropland and grassland as main patch.This pattern almost has not changed.The area of water,cropland,saline,residential site,desert increased.(2)The heterogeneity degree reduced.The pattern with desert existing predominantly will last.Analysis on the fragementation shows that residential fragmentates increased;water increase to concerntrate and link;farmland detract little;wetland was disturbed more and more;desert is the matrix and connectivity is the best.(3)According to Xiegaodi's research,the total value is 104.102×108 yuan in 1990,and 93.439×108 yuan in 2000.The total value reduces 10.663×108 yuan.The economic value per hectare from 1760.318 yuan reduce to 1579.975 yuan.(4)Calculated with the same standard,the ecosystem service value in Akesu oasis in the upper Reaches of Tarim River is 163.386×108 yuan in 1990,and 138.373×108 yuan in 2000.The reductive value is 25.012×108 yuan, The economic value per hectare from 5134.34 yuan reduce to 4348.32 yuan.(5)The ecosystem service value reduced in the upper and lower Reaches of Tarim River during the past 10 years.The degressive extent in the upper Reaches is more faster than in the lower reaches.The woodland,grassland,wetland and desert are the main patch to constitute the ecosystem service value in the lower reaches in 1990 and in 2000. In the upper Reaches of Tarim River,the value of woodland,grassland,waterarea and wetland is the main part of the total value in 1990, in 2000 the value of cropland,woodland,grassland,waterarea becames the main part of total value.(6)Analysis on meteorologic factors in Yuli shows that yearly total precipitation has a little decrease,yearly average temperature and yearly average relative humidity increase.Compared with meteorologic factors in Akesu oasis in the upper Reaches of Tarim River,the precipitation increases in the upper reaches,but decreases in the lower reaches.The area of oasis is enlarged,the result shows that the enlarged oasis area may takes advantage to the increased precipitation.The ecosystem service value reduces in the Tarim River.Because of ample water resource,in the upper reaches,the cropland area is 37% larger than in 1990,the desert area enlarges 43%,the woodland and grassland decrease.In the lower reaches,because of limited water resource,the cropland enlarged 24%,but the wetland reduced 23%,which has important function.So the economic value reduced.Human's movement is frequent in Tarim River,it becomes the main factor to change the landscape in the whole reaches.Ecological environment is fragile in arid areas,there should be overall planning on the basin development.In order to guarantee the sustainable development of this area, we should guarantee the basic using of water for the ecosystem.