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• Rice cultivation areas continue to expand from tropical and subtropical areas to high altitudes and high latitudes, and the chances of rice suffering from chilling injury gradually increase. • Regional-scale chlorophyll fluorescence data show a close correlation with the monitoring chilling injury losses in rice. • Real-time hazard assessment of the occurrence of chilling injury in rice and its intensity, and estimation of the possible loss of rice yield caused by different disaster-causing intensities. Rice is a warm-temperature crop, and sterile-type chilling injuries may be induced by acute periods of low-temperature weather during the reproductive growth period. This study considered the daily mean and minimum temperatures in Northeast China from 1979 to 2018 as influencing factors to construct a process-based rice accumulated intensity index (PARII) and hazard assessment model based on known crop disaster periods, analyzed the spatiotemporal distribution characteristics of chilling injury during the rice growth period (booting and flowering stages), used solar-induced chlorophyll fluorescence (SIF) and yield fluctuation data to calculate the adaptability of the hazard assessment model, and selected two typical events of disaster processes to verify the proposed real-time hazard assessment model. The change in the cumulative intensity index of rice sterile-type chilling injury indicated an increasing trend in chilling injury in the rice booting stage. Based on the probability density static hazard and cumulative probability dynamics, the results of real-time hazard analysis showed that the chilling injury hazard area was significantly expanded compared with the sterile-type chilling injury during the booting and flowering periods. The hazard value was greater than 0.2 in central and southeastern Heilongjiang, and the static hazard index was significantly negatively correlated with SIF and fluctuating yield, which indicated the chilling injury impacted rice yield and physiology. Regional-scale hazard levels were assessed by daily real-time hazard evaluation to highlight spatial heterogeneity in crop stress and damage. The results of this study provide a scientific basis for real-time risk assessment and management of chilling injury in rice crops and may support future adaptation strategies for addressing risks associated with severe low-temperature events. [Display omitted] [ABSTRACT FROM AUTHOR]

• A quantitative assessment framework for ecosystem drought risk was established. • Nearly 45.4% of ecosystem vegetation in NEC has a moderate or high risk of drought. • Quantitative assessment of vulnerability is the key point to drought risk assessment. • The drought risk patterns driven by climate variability and human activities are different in farmland and natural vegetation. Given the significant increasing trend of droughts in Northeast China (NEC) under climate change, it is of particularly urgency to quantify the drought risk to vegetation in different ecosystems. Based on the theory of risk formation, we developed a quantitative framework for the assessment of ecosystem drought risk that integrates both drought hazard and vulnerability (sensitivity and adaptability). To quantitatively assess the drought risk to different vegetation types in NEC, we used long-term (1982–2015) normalized difference vegetation index (NDVI) data and standardized precipitation evapotranspiration index (SPEI) data. The effects of climate change and non-climatic factors (mainly human activities) on the NDVI dynamics and drought risk were analyzed using the partial least squares regression method to explore key drivers of risk formation. Our findings indicate that almost 45.4% of ecosystem vegetation in NEC is at a moderate or high risk of drought. Our findings indicate that vulnerability is key to NEC drought risk assessment, and adaptability plays an important role in regulating sensitivity. Land cover is the main driving factor for the spatial pattern of drought vulnerability in NEC, and forests have the lowest vulnerability. The impact of climate change on vegetation dynamics in dry years (R2 dry = 0.35) is significantly higher than over the entire study period (R2 all = 0.20). Cropland drought risk is dominated by human activities, whilst woodland and grassland drought risk is controlled by temperature and precipitation variability, respectively. The driving force analysis of vegetation dynamics and drought risk improves our understanding of the mechanisms behind the formation of risk patterns in NEC. Our study provides a basis for land use management and the formulation of drought adaptation options for vegetation types at different growth stages. [ABSTRACT FROM AUTHOR]