Occurrence, evolution and causes of different drought levels affecting winter wheat in the Huang-Huai-Hai Plain, China

Drought, affects agricultural production and winter wheat, a crucial staple crop, is continuously exposed to drought stress in the Huang-Huai-Hai Plain, which has notable implications for global food security. Here, we used the 1981–2020 meteorological datasets to calculate the monthly standardized precipitation evapotranspiration index and combined this with the standard deviation ellipses and the geodetector model to investigate the spatio-temporal patterns of drought occurrence, its evolution, and the potential drivers of different drought levels across the growth stages of winter wheat. The results showed that (1) drought primarily occurred during the greening-jointing to booting-heading stages of winter wheat, particularly in regions, such as Hebei, where mild and moderate droughts were more frequent, whereas severe and extreme droughts were concentrated during the booting-heading stage; (2) the spatial evolution of drought revealed a gradual expansion from the southern to the central and northern regions (from Anhui to Henan, Shandong, and Hebei) as the growth stages progressed. Drought was more widespread in the later growth stages, with the affected area of moderate drought being four times larger than in the early stages. (3) Geodetector analysis revealed that precipitation and minimum temperature notably influenced drought occurrence. Interaction analysis highlighted that the combination of precipitation with soil type and minimum temperature significantly enhanced the explanatory power of drought occurrence. The explanatory power for moderate, severe, and extreme droughts increased by 0.08, 0.16, and 0.13, respectively, emphasizing the importance of these interactions. The interaction between precipitation and minimum temperature strongly influenced severe and extreme drought occurrences. These findings provide a scientific foundation and practical insight for drought risk assessment and agricultural management.