Drought Resistance of Vegetation and Its Change Characteristics before and after the Implementation of the Grain for Green Program on the Loess Plateau, China

Drought affects the growth and productivity of vegetation, and the analysis of drought resistance of vegetation can help ecological and environmental protection and sustainable development in drought-prone areas. The Loess Plateau (LP) is a drought-prone area in China with an extremely fragile ecological environment. This study analyzed the drought resistance of vegetation across different climate regions and vegetation biotypes, explored the characteristics of changes in vegetation drought resistance before and after the implementation of the Grain for Green Program (GGP), and evaluated the relative contribution of climatic factors and human activities to the change in drought resistance of vegetation. The following conclusions are obtained. (1) The drought resistance of vegetation on the LP basically showed a spatial pattern of increasing from northwest to southeast with the degree of aridity. The vegetation in the semi-humid and arid regions showed the strongest and weakest drought resistance, respectively. (2) The drought resistance of vegetation on the LP mainly showed an increasing trend since the GGP was implemented, but there were differences in different climatic zones. In semi-humid regions, the drought resistance of vegetation mainly showed a weakening trend, while in arid and semi-arid regions, it mainly showed an increasing trend. There were differences between vegetation biotypes as well; the drought resistance of forest and grassland showed a different trend in different climatic zones, while that of crops in all climatic zones showed an increasing trend. In the area with cropland returned, the drought resistance tended to increase where crops turned to forests, but the area where crops turned to grassland showed a weakening trend. (3) The positive contribution of climate change and human activities leads to the enhancement of drought resistance of vegetation in most areas of the LP, and the weakening of drought resistance of vegetation in semi-humid regions is dominated by the negative contribution of climate change. The negative contribution of human activities is the main reason for the decrease in drought resistance of vegetation in the area of returning cropland to grassland. This study can provide a reference for ecological protection and high-quality development of the LP.