汉江流域上游植被指数变化的影响因素分析

Analysis of the Affecting Factors of Vegetation Index Change in the Upper Reach of Hanjiang River Basin

汉江是南水北调中线工程的水源地,在变化环境下其植被的变化会对流域水文过程产生不可忽视的影响。采用来自MODIS/Terra网站的归一化植被指数遥感影像数据,对汉江流域上游2000—2015年的8月份归一化植被指数遥感影像数据进行像元尺度的影响因素分析。结果表明,7-8月的平均降水量和7月平均气温与归一化植被指数的相关性最强。植被指数与降水呈负相关的区域基本上与气温呈正相关,而植被指数与降水呈正相关的区域基本与气温呈负相关。复直线回归分析显示,气象因素对植被生长、演化起到了促进作用,人类活动使得植被指数等级变得更加均匀。人类活动表现为抑制植被生长演化的区域占汉江流域上游总面积的45. 92%,人类活动表现为促进植被生长的区域占汉江流域上游总面积的54. 08%,说明有一半以上区域的人类活动对植被生长起到了促进作用;与气象因素相比,现阶段人类活动对近年来汉江流域上游植被指数的影响十分微小。

Hanjiang River is the water source region of the middle route of South-to-North Water Diversion in China.The change of vegetation in the changing environment will have an important influence on the hydrological process of the basin.Based on the remote sensing data of Normalized Difference Vegetation Index from the sites of MODIS/Terra,we analyzed the affecting factors of the Normalized Difference Vegetation Index in August from 2000 to 2015 at pixel scale in the upper reach of Hanjiang River basin.The results show that,the July-August mean precipitation and the mean temperature in July are the most correlated with the Normalized Difference Vegetation Index.The area of negative correlation of vegetation index with precipitation is basically positively correlated with air temperature,while the area of positive correlation of vegetation index with precipitation is negatively correlated with air temperature.Complex linear regression analysis shows that,the meteorological factors play a positive role in the growth and evolution of vegetation,and human activities also make the vegetation index become more uniform.The area,where the human activities restrain the growth and evolution of the vegetation,is 45.92%of the upper reach of Hanjiang River basin,while the area where human activities promote the increase of the vegetation index,accounts for 54.96%of the study area,which indicates that on more than half of the region,human activities have played a positive role in the growth of vegetation.Compared with the meteorological factors,human activities have little influence on the vegetation index in the upper reaches of Hanjiang River basin in recent years.