Study On The Temporal-spatial Changes Of Vegetation Cover In Three Gorges Reservoir Area Based On Modis Data

Three Gorges Dam is the largest hydraulic project in the world today, it has been played a positive role in social economy, while the influence of Three Gorges Project on ecology and environment also has long been a hot issue. The completion of Three Gorges Dam had an impact on the vegetation changes.Vegetation cover changes, to a certain extent, have influence on the environment changes which includes the climate change, carbon dioxide change in atmosphere, etc.So it’s very important to study the characteristics of the vegetation changes in Three Gorges reservoir area.Taking Three Gorges reservoir area as the research area, the thesis uses the data of Normalized Difference Vegetation Index (NDVI) and Gross Primary Productivity (GPP) in EOS/MODIS product data, and uses the CASA model to analyze the vegetation cover changes from2001to2008in Three Gorges reservoir. The research is conducted from three aspects: vegetation index, GPP and vegetation productivity,including the spatial distribution characteristics,annual and inter-annual variation law.The results indicate that the vegetation coverage rate of Three Gorges reservoir is on the rise from2001to2008. But due to the construction of Three Gorges Dam, the rising water levels of the reservoir and intensive human activities have had certain influence to the vegetation cover in the reservoir area. Besides, from the analysis of the annual variation, it should be noticed that the vegetation in the reservoir area grow best in July and worst in January. In other words, the growth state of vegetation is good in summer and bad in winter. In the comparative study between the GPP results obtained by MODIS/GPP and CASA model, it is found that the CASA model result is more ideal. The thesis is of certain significance to the further study of variation law and features of vegetation cover in Three Gorges reservoir area.