Phenology-modulated Crop Responses to the 2024 Spring-Early Summer Compound Dry-Hot Event in the North China Plain

Abstract. Compound dry-hot events are intensifying under climate change and pose growing risks to agricultural production. From April to June 2024, the North China Plain (NCP) experienced an extreme compound dry-hot event. Using satellite-based normalized difference vegetation index (NDVI), gross primary productivity (GPP), and crop yield statistics, this study quantified crop growth responses and identified the dominant climatic drivers during this event. The climate anomaly was characterized by pronounced warming in April and June, a continuous decline in precipitation and soil water from April onward, and a record-high vapor pressure deficit (VPD) in June, forming a persistent dry-hot stress. NDVI and GPP increased markedly in April and remained slightly positive in May, but both collapsed to their lowest levels since 2000 in June. Consistent with these vegetation signals, provincial yield statistics and experimental plot observations showed increased winter wheat yields but reduced summer maize yields. Sensitivity and contribution analyses revealed distinct phenology-modulated mechanisms: in April, elevated temperatures and vegetation carryover effects comparably enhanced vegetation activity in winter-wheat-dominated croplands; in May, vegetation dynamics were controlled almost entirely by the previous-month carryover effect, reflecting the growing influence of accumulated vegetation state; and in June, as winter wheat reached maturity and newly sown maize entered early establishment, VPD emerged as the primary limiting factor, strongly suppressing photosynthetic activity and seedling establishment. These findings demonstrate how phenological transitions modulate crop vulnerability to compound dry-hot events and provide useful insights for agricultural early warning, crop management, and climate adaptation strategies in the NCP.