Impacts of drought on the spring phenology of temperate vegetation along a climate gradient: a case study in Inner...

In the context of global warming, drought events are occurring more frequently worldwide, exposing vegetation to diverse drought conditions and resulting in varied responses. Start of greening season (SOS) serves as a vital biological indicator for understanding the response of vegetation growth to climate change. However, the differential impacts of various drought types on SOS and how these effects vary along climate aridity gradients remain unclear. In this study, we constructed four types of drought datasets and analyzed their impacts on the SOS of major vegetation types along a climate aridity gradient in Inner Mongolia, China. We focused on the lag effects, relative importance, sensitivity, and interactions of different drought types. The results indicated that, with increasing drought intensity, atmospheric, shallow-soil, and comprehensive droughts delayed the SOS, while deep-soil drought delayed the SOS in steppe areas but advanced it in forest areas. With increasing climate aridity, the lag effects of atmospheric and shallow-soil droughts on the SOS became pronounced, whereas the effect of deep-soil drought exhibited a weakening trend. The lag effects of comprehensive droughts were stronger in forests than in steppes. Among all the drought types considered, atmospheric drought exhibited the strongest impact on the SOS. Notably, the effect of soil drought in forests was stronger than that in steppes, whereas the opposite pattern was observed for comprehensive drought. In addition, the effects of different drought types on the SOS along the climate aridity gradient demonstrated notable differences in sensitivity. Moreover, we observed distinct interactions between various drought types in their effects on SOS. Our study demonstrates the effects of various drought types on vegetation phenology and can support the development of climate-smart strategies for sustainable vegetation management.