Study On The Impacts Of Climate Change On Forest Fires In Inner Mongolia Daxing'anling Forest Region

After extensively collecting meteorological data and forest fire data, the changes ofweather index which are closely correlated with forest fires during 1961～2005, the changes offorest fire weather indexes during 1972～2005 and the changes of fire regime during1980～2006 have been studied. Then, the impacts of climate change on forest fires were studiedfrom two points of forest fire weather and fire regime.The results show that the climate of Inner Mongolia Daxing'anling forest region hasevolved to warmer and dryer during 1961～2005. Annual temperature average has increasedsignificantly. The average of annual temperature average of last 5 year was 1.57℃higher thanthat in initial 5 years during studied time period. The increasing extent of annual temperatureaverage on west aspect of Daxing'anling mountain was more than that on east aspect. As awhole, annual precipitation showed a tendency to rise. But the annual precipitation of last 5years decreased, the main reason was that the precipitation of summer non-working fire seasonin last 5 years decreased obviously. Annual wind speed average decreased markedly. Theaverage of annual wind speed average of last 5 years was 0.5m/s less than that in initial 5 years,approximately 17.2%. Though the annual precipitation increased and the annual wind speedaverage decreased, the annual air relative humidity average decreased. It was inferred that theclimate of the region changed for warming and drying. The annual air relative humidityaverage decreased slowly in the period when precipitation increased, and decreased obviouslyin the period when precipitation decreased.When the daily temperature maximum in the region is more than 12℃, the probability offorest fire occurrence increased significantly. The average of Julian date when daily airtemperature maximum was more than 12℃in spring working fire season of last 5 years was6.4 days earlier than that in initial 5years. It was inferred that the favorable forest fire weatherwould occur earlier in spring. The Julian date when daily air temperature maximum was lessthan 12℃in autumn working fire season in last 5years was 3.7days later than that in initial5years. It was inferred that the unfavorable forest fire weather would occur later in autumn.Because the climate of the region has changed for warming and drying, the fire weatherseverity rose during 1972～2005. The fire weather index FFMC (Fine Fuel Moisture Code) rose,which was the represetive of fire ignition. It was indicated that the probability of forest fireoccurrence would increased. The fire weather indexes including DMC (Duff Moisture Code),DC (Drought Code) and BUI (Initial Spread Index) all increased, which were the represetivesof the fuel moisture. It was indicated that, the fuel in the region had a tendency to become dryerthan before, which would induce fire intensity to increase. The indexes mentioned aboveincreased markedly in summer non-working fire season. Among indexes mentioned above, theincreasing extent of DMC was largest. The DMC average of working fire season of last 5 yearswere 14.1%, 47.0% and 30.6% more than that of initial 5 years respectively in spring workingfire season, summer non-working fire season and autumn working fire season. The high fireweather rating days decreased slowly in spring and autumn working fire season whileincreased obviously in summer non-working fire season. The average of high fire weather daysin summer non-working fire season of last 5 years increased 8 days than that in initial 5 years. Under the situation that the climate of the region was warmer and dryer, the fire regime of1995～2006 has changed obviously, but the changes differed in different working fire seasonand different period. As a whole, forest fires increased in all working fire season. Theincreasing extent of fires in summer working fire season was largest. There were few fires insummer of 1980～1998, but the fires and large fires in the summer all increased markedly after1999. In last few years, lightning fires increased obviously in spring working fire season. Thelightning fires and lightning large fires increased markedly in summer working fire season. Inlast few years, the latest fire occurring Julian date in spring became later and extended tosummer non-working fire season markedly. The earliest fire occurring Julian date becameearlier in spring. The latest fire occurring Julian date became later in autumn. Northern area ofthe region was the area that fire regime changed mostly.In a word, under the global warming, the climate of Inner Mongolia Daxing'anling forestregion during 1961～2005 has evolved to warmer and dryer, which was more favorable to forestfire occurrence than before. The forest fire weather severity rose. Forest fires and forest largefires increased. Fire season extended obiously. It was predicted that the continued warming willlast for centuries, so the forest fire weather severity in the region will become severer in thefuture.