Analysis of Spatial and Temporal Variation of the NDVI in the Upper Reaches of the Heihe River from 2001-2017

Vegetation is an important part of terrestrial ecosystem, and the change of vegetation cover can reflect the change of regional environment, and the normalized difference vegetation index (NDVI) can effectively reflect the growth status of vegetation. In this study, based on Moderate-resolution Imaging Spectroradiometer (MODIS) NDVI data from 2001 - 2017 in the upper reaches of the Heihe River, we analyzed the spatial and temporal variation characteristics of the NDVI in the upper reaches of the Heihe River for 17 years using spatial autocorrelation analysis method, trend analysis, accumulative anomaly method and Pettitt mutation test method. The results showed that the spatial distribution of the NDVI in the upper reaches of the Heihe River was high in the southeast and low in the northwest, and the spatial trend was increasing in the northwest and decreasing in the southeast; the mean values of the NDVI from 2001 to 2017 showed an overall increasing trend with an increase rate of 0.0017/a and the NDVI changed abruptly around 2009-2010. This study contributes to a better understanding of vegetation cover changes in the upper reaches of the Heihe River, which is important for ecological conservation in the upper reaches of the Heihe River.