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生态学报  2004 

Land use/cover changes and its landscape ecological effects in the middle western Hexi Corridor:A case study of Suzhou oases

Keywords: land use/cover changes,landscape ecological effects,middle and western reaches of Heihe River Basin,Suzhou oases

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In recent years, landscape pattern is often combined with land use/land cover changes to study the tendency of structure changes of land use/land cover and their ecological effects. Therefore, it can provide foundation for the planning and designing of sustainable land use. Landscape pattern is the result of different disturbing factors, which in turn, affects the ecological processes of regions. Suzhou was selected as the study area. It is located in the middle western Hexi Corridor. Studies on land use/land cover changes and their landscape ecological effects were carried out by GIS and Fragstats 3.3 according to landscape ecology principles on the basis of two composite Landsat 5 TM (Thematic Mapper)images of band 4,3,2 taken in 1988 and 2000. The results show the following occurred in the past 12 years: Firstly, landscape types are spatially different because of various different natural geographical conditions. For example, Cropland is mainly situated on both sides of the river and on the flood plain, while grassland is mainly located in the Qilian mountains and on the edge of the oasis. In addition, forestland is mainly distributed on both sides of the rivers and on the north slope belt of Qilian mountain. The Gobi and desert are broadly situated among oases, landscape is particularly characteristic patterns of Gobi. The oasis and desert are connected to each other tightly on the background of Gobi matrix. Secondly, great changes have taken place both in land use types and landscape pattern indices. Cropland and water area have increased evidently, and the same as urban land and cultural residences. While grassland, woodland and unused land had decreased, the high-covered grassland had disappeared completely. Thirdly, though the patch fragmentation was decreasing, and so the heterogeneity, and the ecological environment was degrading. For example, most grassland and woodland had been cultivated as cropland, which weaken the capability of maintaining ecological balance of oases. Also, it made the over-loaded oases more urgent in water. Fourthly, the patch dominance index decreased. Different patch types tended to distribute evenly. The decline of heterogeneity and the tendency of evenness certainly will lead to the decline of landscape stability. Fifthly, the edge effect of woodland and grassland decreased. As a result, the function of those kinds of patches in landscape declined. On the other hand, the edge effect of water, saline alkali and barren land increased, which showed the further degradation of landscape.


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