Atmospheric hydrothermal dynamics influence vegetation drought resistance in the Mu Us Sandy Land

The Mu Us Sandy Land (MUSL) is a typical ecologically fragile region in northern China. Large-scale ecological restoration projects have improved regional vegetation coverage while potentially modifying hydrological processes, making it necessary to further evaluate the drought characteristics and vegetation responses to drought. In this study, three drought indices were applied to characterize drought variations from 2000 to 2022, and the Standardized Evapotranspiration Deficit Index (SEDI) was identified as the most suitable indicator in MUSL. Moreover, vegetation dynamics were represented using the Normalized Difference Vegetation Index (NDVI) and gross primary productivity (GPP), which were further used to quantify vegetation drought resistance. The results showed that SEDI significantly increased at a rate of 0.08 per year ( P < 0.05), reflecting a notable wetting trend in the region, which was generally favorable for vegetation growth. However, eight drought years with varying severity were identified during the study period, and vegetation responses to drought exhibited spatiotemporal heterogeneity. Overall, vegetation drought resistance significantly decreased with increasing drought severity ( P < 0.05); however, considerable differences in vegetation responses and drought resistance remained among different years within the same drought severity. Further analyses indicated that atmospheric hydrothermal conditions during the growing season were key factors explaining variations in vegetation drought resistance. The growing-season maximum temperature anomalies (TMXano) emerged as the most significant explanatory factor, accounting for 63.4% of the variance ( P < 0.05). Increased TMXano and potential evapotranspiration anomalies (PETano) diminished vegetation drought resistance, while the positive effects of precipitation anomalies (PREano) and SEDI increases were relatively limited. This study highlights the important role of growing-season hydrothermal conditions in influencing vegetation drought resistance in arid and semiarid sandy regions, providing scientific insights for drought risk assessment and sustainable ecosystem management in future ecological restoration scenarios.