Spatiotemporal variation of growth-stage specific concurrent climate extremes and their yield impacts for rice in southern China

Abstract. Increasing evidence highlights the disruptive effects of compound climate extremes on global crop yields under climate change. Existing studies predominantly rely on the whole growing-season scale and relative thresholds, and hamper the capture of crop physiological sensitivities and yield responses that vary critically across growth stages. Here, we analyzed the spatiotemporal variations, dominant drivers, and potential impacts on the yields of concurrent heat-drought and chilling-rainy events for single- and late-rice in southern China from 1981 to 2018. Specifically, we carefully distinguished three sensitive growth stages of rice, and used growth-stage-specific physiological thresholds. Temporally, single-rice experienced a significant increase in concurrent heat-drought events, while late-rice experienced a modest rise in chilling-rainy events. Hotspots of concurrent heat-drought events in single-rice systems moved upstream in the Yangtze Basin during the growing season, and the concurrent chilling-rainy events of late-rice were widespread within the planting regions, with a higher incidence in certain areas. These spatial characteristics were primarily driven by spatial differences in phenology rather than the occurrence of extreme events. Path analysis identified heat stress as the primary driver of heat-drought impacts (particularly in jointing-booting and heading-flowering stages), whereas chilling and rainy stress exerted comparable effects for late-rice. Our assessment of compound event impacts and sensitivity to rice yield revealed significant growth-stage-specific differences, with comparable yield losses from both concurrent heat-drought and chilling-rainy events. Single-rice showed the highest sensitivity to heat-drought events during the grain filling stage, whereas the late-rice exhibited greater sensitivity during the heading-flowering stage. The historical yield impact diverged markedly across growth stages, with the largest having occurred in the grain filling stage, particularly for heat-drought events. Our study provided important information on compound agroclimatic extremes, in the context of southern China’s rice production system, and the results provide important information for risk management and adaptation strategies under climate change.