Warming-Induced Phenological Change Regulates Extreme Climate Risk During Winter Wheat (Triticum aestivum L.) Growing Season in the North China Plain

Abstract

Clarifying the variation patterns of extreme climate events during crop growing period has important implications for mitigating agricultural disaster risks. However, previous studies have usually relied on fixed crop growing dates, without considering warming-induced phenological responses. Moreover, the large-scale climate driving mechanisms of climate extremes during crop growing period remain inconclusive. In this study, changes in winter wheat phenological phases under long-term climate trends and the associated variations in climate extremes were evaluated. The aim was to investigate whether phenological responses to climate warming could, in turn, regulate extreme climate risks during crop growing period, and to clarify how large-scale climate factors influence extreme climate events in the growing period. The results showed that the anthesis and maturity dates of winter wheat in the North China Plain advanced significantly with climate warmi ng from 1960 to 2020. Once warming-induced phenological changes were considered, the patterns of extreme climate events during the crop growing period differed from those observed across the entire year. From 1960 to 2020, warming reduced the intensity and frequency of pre-anthesis low temperatures but did not intensify post-anthesis high temperature stress. This was ascribed to the significant advancement of the anthesis date, which allowed the reproductive phase to avoid seasonal high temperature events. Nevertheless, this heat avoidance strategy may be unsustainable, as the rate of temperature increase tends to exceed the rate of anthesis advancement. The diurnal temperature range during the winter wheat growing period declined in most regions due to the asymmetric rise between daily minimum and maximum temperatures. Spatially, both pre-anthesis cold and post-anthesis heat stresses were more severe in the northern region than in the south. The pre-anthesis low temperature differences were mainly attributed to climate heterogeneity, whereas post-anthesis high temperature differences were more ascribed to the disparities in anthesis timing. The lower pre-anthesis temperatures in the north resulted in later anthesis than in the south, thereby postponing the maturity phase to a relatively hotter period. Across the North China Plain, winter wheat universally experienced prolonged drought before anthesis, with drought duration in the northern region being twice as long as in the south. The Global Mean Land–Ocean Temperature Index and Arctic Oscillation significantly influenced the frequency and extremes of pre-anthesis low temperatures. Their increasing trends in the continuous time-frequency domain could reduce cold-related risks. Increase in the Western Pacific Index could reduce the post-anthesis high temperature frequency. These findings offer new insights into the role of phenological shifts in modulating extreme climate risks, which are valuable for optimising extreme climate mitigation options.