Abstract:

To better know variations of vegetation structure and soil erosion conditions during the Three Gorges Dam construction period in Zigui,this study acquired 1〖DK〗∶50 000 land use classifying maps,vegetation cover fractions,soil erosion risk in 1992 and 2007 based on TM and SPOT images respectively,and derived SPOT VEGETATION MVC NDVI during 1999~2007.Changes of vegetation types were first analyzed in detail.Landscape pattern metrics were used to characterize changes of vegetation structure in spatial.Trends about vegetation cover fractions,relationship between vegetation structure and soil erosion risk were also analyzed and discussed. Results indicated that vegetation patches were more fragmentized and equally distributed,and their diversity and dispersion extent were both enlarged in 2007.Forest and shrub were still the dominant landscape types in Zigui.Changing characteristics of various types of vegetation were different due to the different impact intensities by human activities.Vegetation cover fractions were improved as a whole in Zigui in 2007,which produced a positive effect on decrease of soil erosion intensity.Vegetation cover fractions in the middlesouthern part of Zigui were greatly improved.Areas adjacent to reservoir still faced difficulties to prevent and cure soil erosion because of concentrated impacts from human activities and limitations of topographic conditions.With RS and GIS techniques,research on changes of local landscape structures and their influences on ecoenvironment, and the impact intensities by human activities were both significant.The paper provided such a case study in the areas of head part of the Three Gorges Reservoir