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Hazard assessment is the basic work in the field of disaster risk. For the agricultural field which is seriously affected by extreme events, it is necessary to carry out hazard assessment of compound extreme events (CEEs) to increase the accuracy of risk assessment. First, in this study, the SMDI and TCI were used to characterize the spatial and temporal distribution patterns of agricultural drought and heat, respectively, and the drought and heat compound extreme events (DHCEEs) were identified by characterizing the drought and heat events based on runs theory. Then, the compound event magnitude index (CEMI) was constructed by fitting the non-transcendent probabilities. next, the optimal copula function of severity and duration of DHCEEs was screened, and the fitted probabilities were used in the hazard assessment. The hazard assessment model of DHCEEs is constructed by considering the occurrence probability, severity, and duration. We evaluated the hazard of all DHCEEs identified in the Songliao Plain from 1990 to 2020. The results show that the whole study area is affected by agricultural drought, and heat mainly affects the western region. CEMI can effectively determine the severity of DHCEEs. In the study area, 46.51% of the DHCEEs have a hazard less than 0.1, and 2.71% have a hazard greater than 0.5. The event that had the biggest hazard occurred in 2001, and the proportion of high hazard compound events gradually increased after 2000. Similar compound extreme events are gaining attention in important food-producing regions around the world, and the hazard assessment model constructed in this study can be used to assess crop damage from compound extreme events in real-time, increasing the relevance and accuracy of risk assessment.

Sulfur dioxide (SO2) is a major atmospheric pollutant and abiotic stressor. Although physiological studies on abiotic stressors have focused on fully expanded leaves, the resistance of leaf functional traits to SO2 during individual leaf development has not been studied. Thus, this study aimed to conduct SO2 static artificial fumigation experiments to evaluate changes in leaf functional traits and resistance to SO2 for three common landscape tree species (Syringa oblata Lindl. (S. oblata), Prunus cerasifera var. atropurpurea Jack. (P. cerasifera), and Ulmus pumila 'Jinye' (U. pumila)) in Changchun City and ontogeny under SO2 stress. Samples were collected on three days in autumn (1 September, 9 September, and 19 September 2019) for two different leaf stages (10 days and 40 days). In addition, remote sensing data were combined to explore the resistance mechanisms of broadleaf forests to different SO2 concentration classes during different seasons on a large scale. The results showed that the chlorophyll content, leaf temperature, green-peak reflectance, and Fv/Fm (maximal photochemical efficiency) at 10 days were significantly lower than that at 40 days, regardless of sampling date or SO2 concentration. Additionally, in general the SO2 resistance for 10 days leaves was consistently smaller than those for 40 days leaves in 3 tree species. On 9 September, 10 days leaves of the three tree species showed different leaf resistance performances under different SO2 concentrations in the order: P. cerasifera > S. oblata > U. pumila. Lastly, the extent of resistance decreased with increasing ρ(SO2) classes in different seasons, and the SO2 resistance was affected by season. We conclude that mature leaves are more resistant to SO2 stress than young leaves are. These results will provide scientific guidance on artificial plant community construction and prevention of future vegetation degradation. [ABSTRACT FROM AUTHOR]