Abstract:

Based on the MODIS NDVI vegetation index and meteorological data sets， and by utilizing the methods of Ensemble Empirical Mode Decomposition， trend analysis， and Random Forest Regression， this paper analyzes the spatiotemporal changes in vegetation coverage in the Yellow River Basin from 2001 to 2020 and discusses the driving factors behind the changes. The analysis produced the following findings. （1） The spatial averaged NDVI showed a significant increasing trend across the Yellow River Basin from 2001 to 2020， with a growth rate of 0.055/10a （P<0.05）. The regional growth rates of different land cover types are significantly different. Among them， the growth rate of the conversion of farmland to forest （grass） region is the fastest， followed by the agricultural land region， and the natural vegetation region. （2） Spatially， areas with increased vegetation coverage are mainly distributed in the Loess Plateau of northern Shaanxi， southeastern Gansu Province， the Hetao Plain of Inner Mongolia Autonomous Region， and in other areas where the Sloping Land Conversion Program is implemented. Meanwhile， areas with significant decline in vegetation coverage are mainly concentrated in the Guanzhong Plain urban agglomerations， the Huanghuaihai Plain， and the Qinghai-Tibet Plateau. （3） Regression analysis results show that the overall impact factors such as temperature， carbon dioxide concentration， and precipitation positively promote vegetation growth and the absolute contribution rate will decrease sequentially， while factors such as atmospheric vapor pressure deficit and radiation generally inhibit vegetation growth. The findings of this study provide a reference for assessing the comprehensive impact of climate change on vegetation cover changes across the Yellow River Basin.

Key words: Yellow River Basin, vegetation index, spatiotemporal changes, influencing factors