| This study chose the Great Xing'an Mountains boreal forests of northeastern China as research object. Monthly projections such as maximum temperature, relative humidity, precipitation and wind speed were used from the Hadley Centre's General Circulation Model HadCM3, using two climate scenarios (A2a and B2a) for both the baseline period of 1961-1990 (referred to as 1980s) and the future scenario periods (the period 2010-2039 referred to as 2020s, the period 2040-2069 referred to as 2050s, the period 2070-2099 referred to as 2080s), then downscaled by the delta change methods and weather generator to represent daily finer local climate variability. Before FWI and SSR were projected, the Canadian Forest Fire Weather Index System was first calibrated and validated using both local weather data and fire data. This study made a quantitative and qualitative assessment of the variation trend of fire dangers and fire regime in Great Xing'an Mountains boreal forests, assuming that the fire regime respond to future warming similar to the manner during the past century.A significant increase in fire weather, fire danger rating and area burned were found for the 21st century in Great Xing'an Mountains under IPCC scenarios (A2a and B2a), and theirs rate of increase varied with the emissions scenarios, statistical downscaling methods and study periods. Whichever emissions scenarios, statistical downscaling methods or study periods were chosen, an increasing trend of fire severity was found, relative to the figure of the baseline period of 1961-1990. Moreover, the trend would be more evident as time goes by.As for the yearly time scale, almost all annual mean FWI demonstrated an increasing pattern under the two climate change scenarios for the three future periods over the 21st century in study region, compared to the figure of the baseline period of 1961-1990. Under DW methods, the annual mean FWI was predicted to rise by about 20% and it would go up by about 30% by the end of this century. Under DA, it was predicted to rise by over 50% and over 70% by the end of this century.In the same period and emission scenarios, the seasonal mean FWI suggested that the study region would experience the highest fire danger in spring fire season. Under DW, the highest increase of the FWI would happen in summer fire season, the seasonal mean FWI was predicted to rise by over 30% and it would double by the end of this century. Under DA, the highest increase of the FWI would happen in autumn fire season, the seasonal mean FWI was predicted to rise by over 40% and it would double by the end of this century.Under DW, the monthly mean FWI would have an increasing trend in the future during the period of 2050s and 2080s which was predicted to rise by over 30%, and the highest increase of the FWI would happen in July and August. For example, under Scenario A2a, the monthly average FWI was anticipated to increase by about 1.5 times and 2 times by the end of the 21st century, respectively. Under DA, the monthly mean FWI would have an increasing trend for the three future periods over the 21st century which was predicted to rise by 30%, and the highest increase of the FWI would happen in July, August, November and December. For example, the monthly average FWI was anticipated to increase by about 1.2,1.2,1,1.2 times by the end of the 21st century, respectively.The fire danger rating under DW was different from that of DA. Under DW, Forest fires that occurred on days with high fire danger tended to be large fires. The study indicated that in the future, the number of days with very high and extremely high danger was anticipated to increase. Under DA, the study indicated that in the future, the number of days with very high and extremely high danger was anticipated to decrease.Our results confirmed that the relationship between historical area burned and average SSR values among the study area was illustrated by a significant linear regression(r,0.16-0.61). The considerable evidence could lead us to conclude that the increased SSR values could translate into increased area burned. As for the annual time scale, almost all annual mean SSR demonstrated an increasing pattern under the two climate change scenarios for the three future periods over the 21st century in study region, compared to the figure of the baseline period of 1961-1990. Under DW methods, the annual mean SSR was predicted to rise by about 30% and it was predicted to rise by over 70% by the end of the 21st century. Under DA, it was predicted to rise by over 50% and would double by the end of the 21st century.In the same period and emission scenarios, the seasonal mean SSR suggested that the study region would experience the highest area burned in spring fire season. Under DW, the highest increase of the SSR would happen in summer fire season, the seasonal mean SSR was predicted to rise by over 40% and it would increase by 1.5 times by the end of the 21st century. Under DA, the highest increase of the SSR would happen in spring and autumn fire season; the seasonal mean SSR were predicted to rise by about 70%,80% and it would double by the end of the 21st century.
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