Characteristics and driving factors of vegetation changes in the Gannan Plateau from 2001 to 2020

Using the maximum composition method (MVC), Theil-Sen slope estimation, Mann-Kendall mutation test, correlation analysis, partial correlation analysis, and multiple regression residual analysis, the vegetation on the Gannan Plateau during 2001－2020 was investigated, for an understanding of the temporal and spatial evolution, and the influence of the climate and human activities. In this study, we used the normalized vegetation index (NDVI) to represent the status of the vegetation growth. The study shows that 1) the normalized vegetation index (NDVI) on the Gannan Plateau has an increasing trend with time, and the growth rate is 0.019 per ten years over the past 20 years. 2) the spatial distribution of the NDVI is also in homogeneous and the growth rate of the NDVI in the forest areas is faster than that in the pastoral areas. The vegetation coverage along the Bailong River, Zhouqu is higher than in other areas. 3) Over the past 30 years, the temperature of the Gannan Plateau increased significantly, with a rising rate of 0.35 ℃ per ten years, while the precipitation is not significant. 4) There is a positive correlation between NDVI and air temperature and precipitation. 5) Climate and human activities majorly impact the NDVI of the Gannan Plateau, particularly the human activities. The average contribution rates of the climate and human activities to NDVI are 0.009 and 0.01 per ten years, respectively.