Dynamic changes of vegetation coverage in Heihe River Basin from 1990 to 2019 and the effect of temperature on it

The change features of vegetation coverage are important for the river ecological detection, and can provide basic information for the comprehensive river management. Heihe River Basin is the second largest inland river basin in the arid-semi-arid regions of Northwest China. In order to investigate the ecological status of the arid-semi-arid regions of Northwest China, the authors have taken Heihe River Basin as the study area and comprehensively applied the pixel binary model and unary linear regression to analyze the dynamic changes of vegetation coverage in Heihe River Basin from 1990 to 2019 and discussed the effect of temperature according to the Landsat NDVI data from 1990 to 2019. The results show that the vegetation coverage of Heihe River Basin decreases from south to north. In the past 30 years, the vegetation coverage area has shown an overall upward trend, and the increasing rate of medium-high vegetation coverage area is the fastest. The vegetation coverage in most parts of the basin remains unchanged and the area with increasing vegetation coverage are larger than those with decreasing vegetation coverage. Due to the effect of global warming, the temperature of the entire basin is increasing. The temperature has the fastest increase in the upstream and the slowest increase in the downstream. The temperature increase in the upstream and downstream promotes vegetation coverage, while the temperature increases in downstream restrains the vegetation growth.