The Impacts Of El Ni?o/La Ni?a Events On Forest Burning Probability In Daxing'anling

Fire is an important interfering factor in the global forest ecosystem.The occurrence and spread of forest fires are affected by climate.Some extreme climate events such as El Ni?o and La Ni?a events impact the fire occurrence in some regions.Daxing'anling is a key region with fire management in China,and the forests in there are sensitive to climate change.The thesis analyzes the fire weather indices and burn probabilities in fire seasons under the scenarios of the El Ni?o and La Ni?a events with the Fire Weather Index System(FWI)and the Burn Probability Model(BURN-P3).The results may provide a scientific basis for fire management in the Daxing'anling,which also helpful to understand the effects of climate events on the fire weather and forest burn probability.1.El Ni?o events and La Ni?a events have significant effects on the daily average maximum temperature and annual precipitation of the fire season in the Daxing'anling.During spring fire season,the daily average maximum temperature decreases by 0.21? and the annual precipitation increases by 6.78% in super-strong and strong El Ni?o years than that of normal years.In La Ni?a years,the daily average maximum temperature increases by 0.44? and the annual precipitation increases by 2.77 mm.During autumn fire season,the daily average maximum temperature in super-strong and strong El Ni?o years,medium and weak El Ni?o years and La Ni?a years is lower than that of normal years,and the annual precipitation increase compared with that of normal years.2.El Ni?o and the La Ni?a events impact on the fire weather indices.During spring and autumn fire seasons,the average of FFMC(fine fuel moisture code),DMC(duff moisture code),DC(drought code),BUI(build up)and FWI(fire weather index)in the super-strong and strong El Ni?o years were lower than those of normal years.The all fire weather indices in the medium and weak El Ni?o years were lower than those of normal years.DMC,DC,and BUI in the La Ni?a years were higher than those of normal years.During autumn fire season,the fire weather indices in the super strong and strong El Ni?o years were lower significantly than those of normal years.There was no significant difference between the fire weather indices of the medium and weak El Ni?o years and those of normal years.The fire weather indices of the medium and weak El Ni?o years were higher than those of normal years except for FFMC.In La Ni?a years,only DC was higher than that of normal years.3.The El Ni?o/La Ni?a events have effects on the spatial distribution of FWI.During spring fire season,the FWI of the super strong and strong El Ni?o years decreases gradually from southwest to northeast.In the eastern and southern of the region,the FWI in the medium and weak El Ni?o years was higher than that of normal years.In La Ni?a years,the FWI was low in the east and high in the central and western region.In autumn fire season,the FWI in the western region was higher than that in the eastern region during super-strong and strong El Ni?o years.In the medium and weak El Ni?o years,the FWI was low in the southeast,and higher in northwest and central than that of normal years.The FWI in the La Ni?a years was lower than that of normal years.4.The El Ni?o/La Ni?a events affect the burn probability of forests.The average burn probability of the El Ni?o and La Ni?a years in whole fire season is higher significantly than that of normal years.In the spring and autumn fire seasons of El Ni?o or La Ni?a years,the northwest,northeast and southwest parts of the region have the burn probability values..In summer fire season,the burn probability in El Ni?o and La Ni?a year is lower than that of normal years,and the northwest and northeast region show relatively high burn probability.5.The El Ni?o/La Ni?a events showed influences on the burn probability of each fuel type.In whole fire season during El Ni?o and La Ni?a years,the simulated burned area of each fuel type is higher than the normal year significantly.In the spring and summer fire seasons,the burn probabilities of each fuel type in El Ni?o and La Ni?a year are higher than those of the normal years.In autumn fire season,the burn probabilities of each fuel type in La Ni?a years are higher than those of the normal years and El Ni?o years.Deciduous coniferous forest has the highest average burn probability among the fuel types under all simulated scenarios.