Spatial-temporal variation of NDVI and its responses to precipitation in the upper of Heihe from 2000 to 2019

As the direct result of climate change, Spatio-temporal variation of vegetation cover is an important index in regional ecological change. Based on Google Earth Engine, MODIS-NDVI and precipitation of TRMM from 2000 to 2019 were extracted. Trend analysis method and PCCs were applied to explore the different scales temporal and spatial change of NDVI and the relationship between NDVI and precipitation in the upper of Heihe River Basin. It was found that the annual change of vegetation increased slowly in the study area, and correlation of vegetation NDVI with precipitation are insignificant. On month scale, the vegetation change was cyclical, there was a noticeable increase from June to September, but from November to next February, the vegetation coverage was the lowest, the change of precipitation had the similar variation pattern, and there was a strong positive correlation between precipitation and NDVI. In terms of spatial change, the NDVI rose generally from northwest to southeast, vegetation coverage in northwest was improved.