Reconstruction Of Tree-Ring Fire History In The North Daxing'an Mountains

Daxing'anling region is not only one of the major forest zones but also one of the fire-prone forest areas in China. Forest fire, a major disturbance factor in this ecosystem, can influence the progress of an entire forest ecosystem. Boreal forest in water conservation, water and soil conservation, and maintaining ecological balance and protecting biodiversity has irreplaceable status and role. Frequent forest fires have recently caused a sharp decrease of boreal forest area. Therefore, we are now using tree-ring scars to reconstruct forest fire history and place current wildfires in a historical perspective.One hundred and two fire-scar discs were collected and used to create a fire chronology for the past 250 years, most for larch. In the samples taken, the lowest number of fire scars was one and the maximum was ten. Sample preparation and crossdating took place at Mangui, Walagan, Pangu and Mengkeshan, located north of the Daxing'an Mountains. Using tree-ring scars to reconstruct four larch fire scar chronologies (visualization map) and one Mongolian fire scar chronologies. Through comparing with two species in pine and larch in the study of fire history, I fond two species have the same function on recording forest fire history. Seasonal of forest fire is too synchronous at the four areas, located north of the Daxing'an Mountains. There were a total of three hundred and twenty-seven scars recorded from the samples. Most of the scars came from the earlywood (about 2/3), and the rest came from the latewood or could not be accurately determined. Using the FHX2 software, mean fire interval (MFI) and fire return interval in the four areas were 24.8 and 33 years,22.4 and 24.8 years,29.3 and 28.2 years,24.8 and 33 years, respectively. The three areas forest fire history, including Walagan, Pangu and Mengkeshan, can be roughly divided into three historical periods depending on fire frequency distribution. There were few fire occurrences because of the "Closure Policy" and few human activities during the mid-Qing Dynasty (past-1850). During the period of late-Qing Dynasty and the Republic of China (1851-1949), forest fire numbers increased rapidly due to the "Open Policy", huge crowds flocking into this area, and frequent wars. After the foundation of the P. R. China (1950-present), forest fire numbers decreased sharply because the new Chinese government implemented a strict forest prevention policy in Daxing'an Mountains region. There is not without fire intervals at Walagan, located north of the Daxing'an Mountains. Mangui can be divided into two historical periods. Before the foundation of the P. R. China (past-1949), forest fire numbers increased rapidly due to the "Open Policy", huge crowds flocking into this area, and frequent wars. After the foundation of the P. R. China (1950-present), Boreal forest fire history is severely affected by the local human activities, human migration, the nearby nation or country war and the policy of government. Composite fire chronologies were tabulated on four levels. Forest fires may took placed in two successive years in each region, Maximum fire interval of each areas were 61 years,62 years,43 years and 80-102 years, In the case of human interference severe. Maximum fire interval of large-scale, high intensity fire is 60 years. In human interference weaker region, Maximum fire interval of large-scale, high intensity fire is 80-100 years. This research provides basic data for studying forest fire spatio-temporal regime and its causal mechanisms in Daxing'an Mountains.