基于NDVI数据的双峰县22年植被变化研究

为研究双峰县县域最近20多年来的植被覆盖动态变化，选用Landsat卫星1996年、2007年和2018年3个时相遥感影像，通过影像几何校正、大气校正、影像拼接和裁剪等系列预处理后计算归一化植被指数（NDVI），基于NDVI分级和差值法对植被空间分布及其变化进行分析研究。结果表明，全县植被覆盖空间分布呈现东高西低的规律；高、极高覆盖植被主要分布在北部、东部、南部边缘和东南群山之间，中、低覆盖植被主要分布在中部、西部的丘陵岗地中。1996-2018年22 a间，植被变化表现为随时间先退化后改善的趋势，总体以改善趋势为主，双峰县NDVI均值从1996年的0.532 1提高到2018年的0.705 7。前11 a植被变化以逆向变化为主，主要表现在:低覆盖植被面积增长了18.80%，中覆盖植被和高覆盖植被面积分别减少了21.96%、2.89%。后11 a植被变化以正向变化为主，主要表现在:低覆盖、中覆盖和极低覆盖植被面积分别减少27.27%、15.23%和5.34%，高覆盖和中高覆盖植被面积分别增长了27.34%和20.50%。后11 a间植被指数的增长幅度大于前11 a植被指数的减小幅度，反映出植被发生正向变化的程度要强于植被退化程度，反映了我国生态文明建设近十余年以来取得了较大成果。

Changes in Vegetation Coverage in Shuangfeng County for 22 Years Based on NDVI

In order to understand the dynamic changes of vegetation coverage of Shuangfeng County in recent 20 years,three period temporal remote sensing images from Landsat satellite (1996,2007 and 2018) were selected in this paper.After images were subjected to pre-processing,such as geometric correction,atmospheric correction,mosaic and clipping,the normalized difference vegetation index (NDVI) was calculated.Based on NDVI classification and differential method,the vegetation spatial distribution and its changes were analyzed and studied.The results showed that the spatial distribution of vegetation coverage in the whole county generally presented the rule of high in the east and low in the west.High and extremely high vegetation coverage in the county was mainly distributed in the north,east,south edge and southeast mountains while the medium and low vegetation coverages were mainly distributed in the central and western hilly areas.During the 22 years from 1996 to 2018,vegetation changes in the Shuangfeng County showed a trend of first degradation and then improvement over time.On the whole,the improvement trend was dominant.The average value of NDVI increased from 0.532 1 in 1996 to 0.705 7 in 2018.The increase range of vegetation index in the latter 11 years was greater than the decrease range of vegetation index in the former 11 years,reflecting that the degree of positive change of vegetation was stronger than the degree of vegetation degradation.In the first 11 years,vegetation variation was dominated by reverse change,mainly manifested in the following aspects:the low vegetation coverage increased by 18.80%,medium vegetation coverage decreased by 21.96%,and high vegetation coverage decreased by 2.89%.In the latter 11 years,vegetation variation was mainly positive,which was mainly reflected in the following aspects:the vegetation areas of low,medium and very low coverage decreased by 27.27%,15.23% and 5.34%,respectively,and the vegetation areas of high coverage and medium to high coverage increased by 27.34% and 20.50%,respectively which reflected the great achievements made in China’s ecological civilization construction over the past 10 years.