干旱区生态环境知识资源中心

A long time series ( 20 years) of Advanced Very High Resolution Radiometer (AVHRR) data with 8 km resolution are used to monitor vegetation cover change in the Heihe river basin. Linear regression is used to characterize the trends in vegetation cover change. The yearly Maximum Normalized Difference Vegetation Index (MNDVI) in the Heihe river basin elicits an explicit interannual change in the period 1982-2001. An increase in MNDVI occurs in mid-basin oasis mainly, while a decrease in MNDVI is mainly observed in the mountainous and Alxa’s natural oasis regions of the Heihe river basin. Precipitation is the major climate driving force for vegetation cover changes in the Heihe River Basin. The MNDVI is sensitive to precipitation and its sensitivity decreases with increasing precipitation. Precipitation has a higher effect on the mountainous regions’ vegetation cover than on the oasis regions’ vegetation cover. Precipitation also elicits a lag effect on the MNDVI with a phase of one year at a yearly scale mainly in the mountainous regions of the Heihe River Basin. In the Heihe River Basin, the temperature has a slight and positive effect on the oasis regions’ vegetation cover and a slight and negative effect on the mountainous regions’ vegetation cover.