毛乌素沙漠南部植被指数的变化规律研究

为了认识毛乌素沙漠南部植被的变化,基于MODIS的NDVI遥感数据分析了2000-2013年毛乌素沙漠南部植被的变化特征,NDVI年平均值呈上升趋势,年增长率为2.69×10~(-3)/a。各年均值的空间最大值变化幅度不大,基本表现为上升趋势。结合转移矩阵的方法,将NDVI值分为不同级别并建立植被指数转移矩阵,计算分析了NDVI值逐年的级别转移情况。由各年NDVI值较上年的变化及各年植被覆盖级别较上年的变化分析显示,总体NDVI都表现为较上一年变好的趋势,2013年相对2000年的72.37%的像元的植被级别变好。将2013年相对2000年转移矩阵中NDVI值在各等级所占个数进行统计显示,NDVI值由矩阵的下三角向上三角转移,上三角阵中NDVI像元的个数远大于下三角阵,说明NDVI值表现出由低等级向高等级转化的趋势,植被情况逐步转好。整体上,2000-2013年毛乌素沙漠南部整体植被情况在持续转好。

Study on the evolution law of the vegetation index in the southern Maowusu Desert

To know the vegetation changes in the southern Maowusu Desert, the vegetation dynamic in above area from 2000 to 2013 was analyzed from the Normalized Difference Vegetation Index (NDVI), based on the Moderate Resolution Imaging Spectroradiometer (MODIS). The results show that the annual averages of NDVI presented a rising tendency with an annual growth rate of 2.69×10^-3/year. The changes of the spatial maximums of the annual averages of NDVI were insignificant, with an increasing trend. Using the transfer matrix method, the NDVI values were divided into different levels and the transfer matrix of vegetation index was built. The yearly transfers of the NDVI levels were further analyzed. Comparing the NDVI values and NDVI levels of this year to that of last year, the NDVI shows a trend of getting better generally. The vegetation levels of 72.37% of the pixels became better in 2013 compared with that in 2000. The numbers of NDVI values in different levels in the transfer matrix in 2013 compared with that in 2000 were analyzed and the result suggests that, the NDVI values moved from the lower to the upper triangular of the transfer matrix, and the numbers of pixels in the upper triangular were much larger than that in the lower. This result suggests that the NDVI presents a tendency of a transformation from the lower level to the higher, and the vegetation became better gradually. In the whole, the vegetation of the southern Maowusu Desert was getting better continuously from 2000 to 2013.