不同草原防火政策下内蒙古草原火灾发生风险及其驱动因素的研究

Study on Grassland Fire and Its Driving Factors under Different Grassland Fire Prevention Policies in Inner Mongolia

草原火灾是草原生态系统中重要的干扰因子之一,不同时期的草原防火政策可能会导致草原火灾发生概率及驱动因素发生变化。本研究基于内蒙古1981~2020年草原火灾数据,以新旧《草原防火条例》实施时间(旧《草原防火条例》1993年10月5日颁布并实施,新《草原防火条例》2008年11月19日颁布并于2009年1月1日起实施)为界线,通过随机森林模型分4个时期(1981~2020年、1981~1993年、1994~2008年、2009~2020年)对内蒙古草原火灾发生概率与驱动因素进行比较与分析,并绘制草原火灾风险等级区划图。结果表明:(1)4个时期建模的全样本AUC在0.930~0.940之间,精度优异。(2)在不同时期,气象因素(日平均相对湿度、气温日较差等)始终是影响草原火灾的主导因素,海拔、距火点最近公路距离等因素也是内蒙古草原火灾发生的重要驱动因素;(3)1981~1993年和1981~2020年草原火灾风险区基本相似,中、高、极高草原火灾风险区主要集中在呼伦贝尔市大部分地区和兴安盟北部,1994~2008年中、高、极高草原火灾风险区主要集中在呼伦贝尔市,而2009~2020年中、高、极高草原火灾风险区主要集中在呼伦贝尔市西部、锡林郭勒盟北部、阿拉善盟东南部、乌海市和鄂尔多斯市东部。

Grassland fire is one of the important disturbance factors in grassland ecosystems.The policy of grassland fire prevention in different periods may lead to the change of the probability and driving factors of grassland fire.This study was based on grassland fire data from 1981 to 2020 in Inner Mongolia,taking the implementation time of the new and old Grassland Fire Prevention Regulations(The old Grassland Fire Prevention Regulations were promulgated and implemented on October 5,1993,and the new Grassland Fire Prevention Regulations were promulgated on November 19,2008 and implemented on January 1,2009)as the boundary,the probability and driving factors of grassland fire in Inner Mongolia were compared and analyzed by random forest model in four periods(1981-2020,1981-1993,1994-2008,2009-2020),and draw the grassland fire risk grade zoning map.The results showed that:(1)The AUC of the whole sample of the four periods was between 0.930 and 0.940,and the precision was excellent.(2)Meteorological factors(average daily relative humidity,daily difference in temperature,etc.)were always the dominant factors affecting grassland fires in different periods,the altitude and distance from the fire point to the nearest highway were also the important driving factors of the Inner Mongolia grassland fires.(3)The grassland fire risk from 1981 to 1993 and 1981 to 2020 were basically similar.The medium,high and extremely high grassland fire risk area were mainly concentrated in most parts of Hulunbeier City and the north of Xing'an League.The medium,high and extremely high grassland fire risk areas were mainly concentrated in Hulunbeier City from 1994 to 2008.From 2009 to 2020,the medium,high and extremely high grassland fire risk were mainly distributed in the west of Hulunbeier City,the north of Xilingol League,the southeast part of Alxa League,and the east of Wuhai City and Ordos City.