Impacts Research Of Climate Change On Forest Fires In Ta He Forestry Bureau In Great Xing'an Mountain Region

The Great Xing'an Mountain region is one of the most important forest areas in north China; meanwhile it is one of severely afflicted areas by forest fires. Ta He Forestry Bureau located in the center of the Great Xing'an Mountain region, it is one of the key forest productions base in northeast China. Fire prevention job is the key work of the Forestry Bureau. So it becomes the most important problems in analyzing and making strategies.As a result of complex reasons major regional difference, the occurrence of forest fires had close coordination with climate, vegetation, topography and human activity. In this article, we used ArcMap software and statistic methods, we gathered forest fires occurrence data from 1974 to 2004 and temperature, relative humidity, rainfall, wind speed data in Ta He forestry bureau from 1972 to 2009. We also analyzed timely and spatial rules during the 31 years, researched average temperature, and average relative humidity, average rainfall, wind speed factors and forest fires occurrence data, searched for their possible relationships and proved their obvious linear relationships.The specific results showed that from 1972 to 2009, the annual average temperature in Ta He Forestry Bureau increased fast, the last five-year average temperature had raised 0.64℃than the first five-year. This number had approached the world average level number (0.74℃) by IPCC 4th report in Februray,2007. The number in each fire seasons and non-fire seasons over the years had also risen.From 1972 to 2009, the annual rainfall in Ta He showed increasing trend. Although the number in last five-year had added 1.26mm than the first five-year, contrast with several former five-year period, this number decreased obviously. That means the climate from 2005 to 2009 would be drier because of less rainfall and higher temperature. Except in the summer non-fire season, the number in other fire seasons and non-fire seasons over the years had also raised.During 1972 and 2009, the annual average wind speed showed decreasing trend. The number from 2005 to 2009 had minus 0.55m/s than the time from 1972 to 1976. The number in each fire seasons and non-fire seasons over the years had also decreased, but it did not means that forest fires danger had decreased. There were still some extrame years such as 1987 and 1995.In the period between 1972 and 2009, the annual average relative humidity in Ta He showed decreaing trend obviously. The relative humidity number in periods from 1972 to 1979, 1983 to 1987 and 2003 to 2006 decreaed most. From 2005 to 2009, the average relative humidity was 63.48%, which was the least five-year period from 1972 to 2009. The number in each fire season and non-fire season over the years and fuel moisture had also decreased obviously. The forest fires prevention situation were still severe.There were 298 forest fires total in Ta He Forestry Bureau from 1974 to 2004. The average number is 9.6 per year. Along with time the number of forest fires show increasing trend and the fire season was about four to five years. The whole areas of forest fires burned were 1.63×106 hectares,5.27×104 hectares per year and 177.71 hectares per year per time. During the 31 years the forest fires occurrence and burned area increased obviously, especially in 1990s, there were more forest fires and burned areas. From 1970s to earlier stage of 1990s, the burned areas declined, but from 1990s till now it increased again. The result was might be fires caused by more thunders.The results of forest fires can be divided into thunder fires, human fires and unknown reason fires. The thunder fires consisted half of the total forest fires, human fires consisted 37.18% and unknown fires 11.74%. Thunder fires were the main reasons of more forest fires and large burned areas.From the seasonal distribution of forest fires, they occurred from February to November and mainly from April to August. In May and July, the fires burned areas were the most with forest severely damaged. In the spatial distribution, Ta Lin forestry station had the most forest fires with the number of 85 times, and Yan Jiang forestry station in opposite with the number of 15. Ta Lin forestry station and Pan Zhong forestry station had the largest burned areas from, major forest fires and extrame forest fires.The Julian date method can be usually used to measure forest fires in one year. In Ta He forestry bureau, the Julian date of forest fires mainly concentrated from April 12th to June 30th and August 28th to October 20th. The Julian date of the first fire delayed a little and Julian date of the last fire delayed obviously in each fire seasons and non-fire seasons over the years. The forest fires prevention situation had been more and more severe. The Julian date of the first major fire and human fire delayed a little and Julian date of the last major fire and human fire delayed obviously in each fire seasons and non-fire seasons over the years. The probability of major forest fires occurrence in autumn became more and more. The Julian date of the lightening fire moved up a little and Julian date of the last lightening fire delayed obviously in each fire seasons and non-fire seasons over the years. The probability of lightening fires occurrence in autumn became more and more.Temperature, relative humidity, rainfall and wind speed are the most important four factors in forest fires researches. Based on the data of forest fires and burned areas and climate in Ta He forestry bureau from 1974 to 2004, there were remarkable linear relationships between forest fires occurrence, burned area and temperature, relative humidity, rainfall and wind speed. Among all the statistic data, the temperature indices had marked relationships with the fire occurrence in each May. The relative humidity indices had marked relationships with the fire occurrence from each April to August, and had marked relationships with fire burned area in each April, May, June and August. The rainfall indices had marked relationships with fire occurrence and burned area in each June. The wind speed indices had marked relationships with fire occurrence in each April.In a word, under the global warming background, the climate in Ta He Forestry Bureau generally evolved to the direction which was beneficial to forest fires. There would be more and more fire weathers which were favorable to forest fires occurrence and fire spread. The fire seasons of major fires, lightening fires and human fires would be more and more than before. Due to the direction of fire weather, the forest fires weather danger rating and forest fires prevention situation would be more and more severe.