秭归县植被结构演变及土壤侵蚀评价

为详细了解水库建设期秭归县植被结构演变及土壤侵蚀风险情况，使用TM和SPOT等中高分辨率遥感数据获取的秭归县1992、2007年1〖DK〗∶50 000土地利用分类、植被覆盖度、土壤侵蚀风险及1999～2007年SPOT VEGETATION NDVI等。利用景观格局方法研究植被景观格局演变，分析植被结构与土壤侵蚀风险变化特点。结果表明：1992～2007年，植被景观格局更加破碎，斑块离散程度变大，多样性提高，乔、灌等仍是优势类型，受不同人类政策的影响，不同类型植被类型景观特征响应表现出差异性。植被覆盖度得到改善，其中秭归中南部植被水平密度结构得到明显改善，对降低土壤侵蚀风险起到了积极作用。水库周边地区作为人类活动扰动的集中区，水土保持任务依然艰巨。通过遥感和GIS手段分析区域土地景观格局演变及其生态环境效应，分析变化背后的驱动机制和限制因素，甄别人类活动影响力，为研究三峡人地关系和谐发展提供借鉴和参考

CHARACTERISTICS OF VEGETATION STRUCTURE AND SOIL EROSION RISK CHANGES IN ZIGUI

To better know variations of vegetation structure and soil erosion conditions during the Three Gorges Dam construction period in Zigui,this study acquired 1∶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.