Studies on the Landscape Dynamics of the ShiyangRiver Watershed and Its Typical Oases

Using GIS and landscape structure analysis program FRAGSTATES, based on the TM image of Shiyang River watershed in 1986 and 2000, in this paper the landscape metrics of the watershed in 1986 and 2000 are calculated and analyzed at class metrics level and landscape metrics level respectively. The transformation matrix of the landscape mosaics is also got, which is the base for spatial change analysis of the landscape patterns. The results show that: although the landscape patterns have changed at the whole watershed level, the landscape is at a relatively stable status; but at the typical oases level, landscape patterns have changed remarkably. In Minqin oasis, desertification develops evidently, as a result the area of farmland and sandy land increases observably, and the area of woodland and grassland decreases markedly. The sequent of these changes is fragmentation of landscape, simplification of landscape mosaics and decrease in landscape diversity. The reason is over use of the limited water resources in the middle reaches, shortage of surface water, and over pumping groundwater. But in Wuwei oasis, the development trend is different; the result is decrease in sandy land and increase in farmland.