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    陶长森, 牛树奎, 陈锋, 李连强, 陈羚, 张鹏. 北京山区主要针叶林潜在火行为及冠层危险指数研究[J]. 北京林业大学学报, 2018, 40(9): 55-62. DOI: 10.13332/j.1000-1522.20180109
    引用本文: 陶长森, 牛树奎, 陈锋, 李连强, 陈羚, 张鹏. 北京山区主要针叶林潜在火行为及冠层危险指数研究[J]. 北京林业大学学报, 2018, 40(9): 55-62. DOI: 10.13332/j.1000-1522.20180109
    Tao Changsen, Niu Shukui, Chen Feng, Li Lianqiang, Chen Ling, Zhang Peng. Potential fire behavior and canopy hazard index of main coniferous forests in Beijing mountain area[J]. Journal of Beijing Forestry University, 2018, 40(9): 55-62. DOI: 10.13332/j.1000-1522.20180109
    Citation: Tao Changsen, Niu Shukui, Chen Feng, Li Lianqiang, Chen Ling, Zhang Peng. Potential fire behavior and canopy hazard index of main coniferous forests in Beijing mountain area[J]. Journal of Beijing Forestry University, 2018, 40(9): 55-62. DOI: 10.13332/j.1000-1522.20180109

    北京山区主要针叶林潜在火行为及冠层危险指数研究

    Potential fire behavior and canopy hazard index of main coniferous forests in Beijing mountain area

    • 摘要:
      目的树冠火作为一类对森林生态系统特别是针叶林造成严重损害的森林火灾, 一旦发生树冠火, 其在林火蔓延过程中起主导作用。通过对针叶林潜在火行为大小和冠层危险指数的探究, 以及其在一天中的变化情况, 了解树冠火危害大小及发生的条件, 为预防及扑救林火提供科学依据。
      方法本文以北京山区主要的针叶树种油松和侧柏作为研究对象, 通过对2种林分可燃物的载量、理化性质、分布规律的调查, 计算林分潜在火行为随风速变化的趋势, 并利用树冠火发生和发展的气象因子临界指标来建立冠层危险指数。最终, 结合该地区的气象资料, 选取外业调查期间的2 d为例, 计算冠层危险指数, 判断2种林分可能发生树冠火的类型、时间、持续时长以及林分潜在火行为大小。
      结果2种林分的理化性质差距较小, 但冠基高度上相差较大; 在高风速(40 km/h)天气下, 油松林发生连续型树冠火, 蔓延速度和火线强度分别为17.0 m/min、16079 kW/m, 侧柏林发生间歇型树冠火, 蔓延速度和火线强度分别为11.4 m/min、5290 kW/m, 油松林和侧柏林分别在风速为30、37 km/h时达到高强度火; 油松林的冠层危险指数TI(torching index)和CI(crowning index)值随时间分别在17.1~29.6 km/h和33.9~38.8 km/h范围内波动, 侧柏林的波动范围分别为11.9~21.1 km/h和47.5~54.9 km/h, 油松林在48 h内发生地表火、间歇型树冠火、连续型树冠火的时间占比分别为87%、9%、4%, 其最高速度和火焰最大强度分别为17.5 m/min、8598 kW/m, 而侧柏林只能发生地表火和间歇型树冠火, 其比例为56%、44%, 最大潜在火行为指标分别为14.5 m/min、4506 kW/m。
      结论2种林分中, 冠基高度是树冠火发生最主要的影响因素之一; 林分整体潜在火行为随风速变化明显, 且能在5级风速下形成高强度森林火灾; 侧柏林更易形成树冠火, 油松林发生极高强度火灾的可能性大。

       

      Abstract:
      ObjectiveCrown fire is a serious type of forest fire, which plays a leading role in the spread of forest fires, especially to coniferous forests. This study aims to provide scientific basis for preventing and saving crown fire through the investigation of daily variation trend of the potential fire behavior and the canopy hazard index of stand.
      MethodThe principle coniferous forests (Pinus tabuliformis and Platycladus orientalis) of Bejing mountain area were selected as main research object of the study. The establishment of the canopy risk index was based on critical meteorological factors for occurrence and development of crown fire, which was calculated by the survey data of combustibles load, physicochemical properties and distribution which can count the trend of variation of the potential fire behavior with wind speed. The type, time, duration of crown fire could be judged by meteorological data in the region.
      ResultThe difference in physicochemical properties between the two stands was small, but there was a certain gap between the fuel load and distribution rules, especially the crown base height; at a high wind speed (40 km/h) condition, the active crown fire occurred with spread rate of 17.0 m/min and flame intensity of 16 079 kw/m in Pinus tabuliformis forest, and the passive crown fire occurred in Platycladus orientalis forest with 11.4 m/min, 5 290 kW/m. From the trend of potential fire behavior with wind speed, Pinus tabuliformis and Platycladus orientalis forest reached high-intensity fire at wind speeds of 30 km/h and 37 km/h, respectively; the canopy hazard index TI and CI of Pinus tabuliformis forest fluctuated over time 17.1-29.6 km/h and 33.9-38.8 km/h, respectively, while the range of Platycladus orientalis forest was 11.9-21.1 km/h and 47.5-54.9 km/h, the percentage of time of occurrence of surface fire, passive crown fire, and active crown fire in Pinus tabuliformis forest within 48 hours accounted for 87%, 9%, and 4%, respectively. The maximum speed and maximum flame intensity were 17.5 m/min and 8 598 kW/m, the Platycladus orientalis forest could only occur with surface fires and passive crown fire, the proportions of which were 56% and 44%. The maximum potential fire behavior indicators were 14.5 m/min and 4 506 kW/m.
      ConclusionIn two kinds of stands, CBH is one of the most important influencing factors of crown fire; the overall potential fire behavior of the stands changes significantly with wind speed, and it can form high-intensity forest fires at moderate wind speed (level 5); it is easier to form a crown fire in Platycladus orientalis forest, and there is a high possibility of extremely high-intensity fires in Pinus tabuliformis.

       

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