长江流域NDVI变化及其驱动因素分析

Analysis of NDVI changes and driving factors in the Yangtze River Basin

研究利用1998—2019年归一化差异植被指数(NDVI)和标准化降水蒸散指数(SPEI)等数据,基于Mann-Kendall趋势检验、相关性分析等方法,对长江流域NDVI的时空变化及驱动因素进行研究。结果表明,长江流域NDVI年增长率为0.0042/a,植被改善和退化面积分别占总面积的88.12%和10.09%。流域内有71.68%的区域SPEI减小,整体呈不显著的干旱化趋势。人类活动对植被的破坏主要体现在城市扩张,对植被的恢复主要体现在林地的增加。随着高程和坡度的增加NDVI与SPEI的相关逐渐增强,表明气候对植被的影响程度逐渐增大,但当高程在3400~5300 m之间和坡度大于30°时,由于受高原气候和人类活动的共同影响,气候变化对植被的逐渐减小。

Studying the spatiotemporal evolution of vegetation and its influencing factors is conducive to in-depth understanding of the relationship between vegetation,climate change and human activities,and is of great significance to guiding the scientific management of the regional ecological environment.This study uses data such as normalized difference vegetation index(NDVI)and standardized precipitation evapotranspiration index(SPEI)from 1998 to 2019,based on Mann-Kendall trend test,correlation analysis and other methods to study the spatiotemporal changes and driving factors of NDVI in the Yangtze River Basin.The results showed that the annual growth rate of NDVI in the Yangtze River Basin was 0.0042/a,and the area of vegetation improvement and degradation accounted for 88.12%and 10.09%of the total area,respectively.In the basin,the SPEI decreased in 71.68%of the area,showing an insignificant drought trend.The destruction of vegetation by human activities is mainly reflected in urban expansion,and the restoration of vegetation is mainly reflected in the increase of forest land.With the increase of elevation and slope,the correlation between NDVI and SPEI gradually increases,indicating that the impact of climate on vegetation gradually increases,indicating that the impact of climate on vegetation gradually increases.However,when the elevation is between 3400 m and 5300 m and the slope is greater than 30°,the impact of climate change on vegetation gradually decreases due to the joint influence of plateau climate and human activities.