Abstract:

The upper and middle reaches of Heihe River Basin (HRB), which is the second largest inland river basin in the arid area of the northern China, was chosen as study area. Based on monthly normalized difference vegetation index (NDVI) derived from MODIS sensor, monthly temperature and precipitation data observed by meteorological stations, DEM and basic geographical information, the authors analyzed the spatio-temporal change of NDVI and its relationship with climate from 2000 to 2015 using empirical approach. It was found that NDVI in the upper and middle reaches of Heihe River basin increased generally; the increasing rate of NDVI in summer was higher than that in autumn and spring; the area with rapid increasing rate of NDVI was mainly located in the oasis along the Heihe river; the significant decrease of NDVI occurred in the urban areas of Zhangye, Jiuquan and other cities. It is concluded that the correlation of NDVI with precipitation in summer was higher than that with temperature, whereas NDVI in spring and autumn exhibited higher correlation with temperature. NDVI in the grassland, gobi and desert far away from the main river had significant correlation with precipitation in summer, but NDVI in oasis adjacent to the main river did not show the significant correlation with precipitation. The memory effects was also recognized when NDVI responding to precipitation. The general time lag of NDVI variation in summer responding to precipitation was about a month, but it could extend to 2 months. The results are proposed to provide references for regional vegetation restoration and ecosystem management.

Key words: NDVI dynamics, spatio-temporal change, climate, correlation, upper and middle reaches of Heihe River Basin (HRB)

摘要：

选择西北第二大内陆河黑河流域中上游为研究区, 以2000—2015年逐月NDVI数据、月均温和月降水数据、DEM数据和基础地理信息数据为数据源, 采用RS, GIS 和数理统计分析等方法, 从区域尺度和像元尺度揭示区域NDVI时空变化格局及其与气候的关系。结果显示: 1) 2000—2015年, 黑河流域中上游NDVI总体上呈现增长趋势, 其中夏季的增长速率最大, 明显高于春季和秋季; NDVI快速增长区主要位于中游地区黑河干流两侧的绿洲地带; NDVI显著下降区位于张掖市市辖区、酒泉市市辖区以及其他县城所在地; 2) 夏季NDVI与降水相关性较高, 而春、秋季NDVI与气温相关性较高; 夏季NDVI与夏季降水的显著相关性主要体现在远离黑河干流的大片低覆被草地、戈壁以及荒漠, 而邻近黑河的人工绿洲地带NDVI与降水没有显著相关性; 3) NDVI响应降水的时滞效应较明显, 夏季NDVI对降水的响应普遍存在1个月的时间滞后, 最长能滞后2个月。研究结果可以为区域植被恢复和生态系统管理提供参考。

关键词: NDVI动态, 时空变化, 气候, 相关性, 黑河流域中上游