关键词: 大兴安岭, 重大历史事件, 1987年森林大火, 预测精度, 驱动因素

Abstract:

Objective: It is clear whether China’s “forest fire in 1987”, a major historical event, has caused changes in the probability and driving factors of forest fires in Inner Mongolia’s Daxing’an Mountains. Method: Based on historical fire data (1980—2018), taking the“forest fire in 1987”in China as the dividing line, two models, Logistic regression (LR) and boosted regression tree (BRT), were used to analyze and compare the occurrence probability and driving factors of forest fires in Daxing’an Mountains in Inner Mongolia before, after, and throughout the“forest fire in 1987”. Meanwhile, the areas of low, medium, and high fire risk grades in each banner and county were calculated, and the differences in forest fire driving factors and fire risk changes in different periods were interpreted. Result: 1) Whether using all years or data before and after 1987 for modeling, both BRT and LR models demonstrated higher forecasting accuracy compared to each other. Although the accuracy of LR model is slightly lower, it can still meet the prediction requirements. 2) The accuracy of both models in predicting at three different periods was observed to be: all years > post-1987 > before-1987, indicating that with sufficient sample data, the prediction models based on major historical events such as the forest fire in 1987 did not improve the forecasting accuracy. This finding suggests that the model built using all years of data has a higher degree of reliability in terms of accuracy. 3) Climate factors have been the dominant factors influencing forest fires throughout all periods, contrary to previous studies. This study found that it is particularly important to pay attention to relevant meteorological indicators such as average/maximum temperature, average/maximum surface temperature, and sunshine duration during the pre-fire season one year prior to the occurrence of a fire. 4) Obvious changes have occurred in the medium- and high-risk areas of forest fires in three different periods. The eastern part of Daxing’an Mountains in Inner Mongolia (the southeast of Elunchun Autonomous Banner, most of Morin Dawa Daur Autonomous Banner and the central of Arug Banner) have relatively high risks of forest fires in all three periods. In the northern virgin forest areas (the northern part of Argun City), there were few medium- and high-risk areas before 1987, but the number of such areas increased significantly after 1987. Conclusion: The occurrence of the major historical event“forest fire in 1987”led to a significant change in China’s forest fire prevention policies, resulting in the transformation of the dominant factor affecting the probability and driving factors of forest fires in Daxing’an Mountains, Inner Mongolia from human factors to natural factors (lightning fire).

Key words: Daxing’an Mountains, major historical events, forest fire in 1987, prediction accuracy, drivers