Quantifying Vegetation Stability under Drought in the Middle Reaches of Yellow River Basin, China

Under the background of climate warming, the increase in the frequency and severity of drought leads to vegetation facing severe challenges. A comprehensive and systematic assessment of the stability of vegetation under drought stress in the middle reaches of Yellow River basin (MRYRB) will help to grasp the characteristics of vegetation response to drought. In this study, the normalized difference vegetation index (NDVI) was used to achieve quantitative and qualitative assessments of vegetation stability to drought, and the smoothed monthly standardized precipitation evapotranspiration index (SPEI) was used to describe the characteristics of drought events in 2005/2006 and identified vegetation stability parameters using a standardized anomaly of NDVI across space, which included the resistance duration, resilience duration, drought threshold, and lag time. Vegetation was dominated by less resistance and less resilience. The 2005/2006 drought event affected most of the study area, and vegetation growth was inhibited. The duration of vegetation resistance over 100 days accounted for 65.7%, and vegetation in 89.4% of the regions could return to normal within 100 days. The drought threshold of vegetation gradually decreased from northwest to southeast, and the lag time was mainly concentrated from 1 to 3 months. These findings contribute to a better understanding of the effects of drought on the environment, as well as scientific references for reducing ecological, economic, and social losses in future droughts, and promoting ecological environmental governance and high-quality development in the MRYRB.