Research on Spatial and Temporal Changes of Riparian Vegetation Cover in the Three Gorges Dam Area Based on NDVI

The Three Gorges Dam Area was chosen as the study area in this paper.The destruction of the project on vegetation in the ecosystem is obvious,especially near the riparian zone.The vegetation fraction was calculated based on NDVI.Resorting to the comparisons of vegetation coverage in buffer areas along the dam area among three different phase remote sensing images of 1978,1999 and 2006,we detected the dynamic vegetation changes before and after impoundment in September and analyzed the distribution of vegetation cover of each year as well as the areal changes through grade analysis.A nonparametric two-sided t-test,Wilcoxon rank sum test,was used to evaluate significant differences between vegetation changes in different land use types between 1978 and 1999,1999 and 2006,and 1978 and 2006.The results showed the changes are significant.The research concluded that there was a high degree of vegetation damage between 1978 and 1999,the withal drop of vegetation cover area by 3.31km2,but between 1999 and 2006,in the case of 8km2 being inundeted,the area of vegetation cover only dropped by 1.57km2,indicating an evident vegetation restoration.On the whole,during the nearly 30 years,the vegetation cover hes shown an increasing trend.