基于NDVI的三峡大坝岸边植被时空特征分析

三峡工程建设对生态系统中植被的破坏很明显,尤其是岸边带附近。本文基于多时相遥感图像,采用NDVI序列计算植被覆盖度,通过比较三峡大坝蓄水前后1978、1999、2006年3个时期坝区9月份岸边3km缓冲区的植被覆盖度特征、动态变化,描述了研究区各年份植被覆盖分布以及近30年的植被覆盖变化特征;同时,从面积角度定量,采用分级分析了变化大小,并应用统计学的非参数Wilcoxon秩和检验方法对不同时期、不同土地利用类型的覆盖度样本进行了检验,得到如下结论:近30年间,三峡大坝岸边带植被覆盖变化显著,1978～1999年时间段,由于大坝工程建设植被破坏程度较高,有植被覆盖的区域面积下降了3.31km²;1999年至2006年时间段,在有8km²的淹没区情况下,有植被覆盖的区域仅下降1.57km²,说明植被恢复较明显。近30年间,三峡大坝植被覆盖度整体上有增加的趋势。

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.