Drought-flood abrupt alternation in the Huaibei plain and its impacts on crops

Drought-Flood Abrupt Alternation (DFAA) poses a severe threat to agricultural systems. While its ultimate detriment to crop yield is widely recognized, the dynamic response mechanisms of crops across different phenological stages remain poorly understood. Focusing on the Huaibei Plain, a critical grain base in China, this study identified flash drought and flood events using daily soil moisture and precipitation data. Furthermore, by utilizing Normalized Difference Vegetation Index (NDVI) and establishing pre- and post-event feature windows, we quantified the impacts of DFAA on the growth vigor of winter wheat and summer maize. The results indicate that: (1) DFAA events are spatially concentrated in the northern hinterland, showing a recent "rebound" in frequency alongside shortened durations. (2) These events predominantly occur during the summer maize growing season (95.83 %), particularly in the Filling-Maturity stage. (3) Compared to winter wheat, summer maize exhibits significantly higher sensitivity and lower recoverability. We identified a critical "physiological elasticity" threshold (I min2 approx-1); exceeding this limit leads to irreversible damage due to the synergistic "double-strike" of drought and flood. (4) Crucially, anthropogenic interventions (e.g., irrigation) were found to invert the nature of DFAA impacts, converting potential stress into "water-heat synchronization" benefits. These findings provide a scientific basis for developing sub-seasonal early warning systems and proactive resource utilization strategies in transitional climate zones. • Summer maize is more sensitive and less resilient to drought-flood alternation than winter wheat. • Human activities can directly reverse the disaster nature of drought-flood abrupt alternation. • There may be a threshold effect on the effect of drought-flood alternation on crop growth.