昆明地区华山松纯林枯枝的燃烧性研究

Combustibility of Dead Branches in Pure Forest of Pinus armandii in Kunming

【目的】枯枝是在垂直方向上的连续性可燃物,是地表火转化为树冠火的关键,研究华山松纯林枯枝的燃烧性,以评估其可能形成树冠火的危险性。【方法】森林防火期内在云南森林自然中心华山松纯林连续分布区,进行外业调查,采集样品并进行室内燃烧试验,结合野外状态和实验室分析测定,利用含水率、载量、热值、引燃时间、火焰维持时间、无焰燃烧维持时间等指标,研究了华山松纯林枯枝的燃烧性。【结果】在防火期,华山松纯林枯枝的含水率为5.97%~15.66%,载量为0.09~0.57 kg/m²,热值为17291~18812 kJ/kg,引燃时间为3.5~4.1 s,火焰维持时间达到9.2~16.9 min,无焰燃烧维持时间26~36 min。【结论】华山松纯林枯枝的含水率极低,载量不大,灰分含量较高;在防火紧要期,枯枝很易燃,只要有火源就能轻易被引燃,而一旦发生火灾,火焰能顺着枯枝快速蔓延至树冠形成树冠火。

[Objective]Dry branches are continuous combustibles in the vertical direction and are the key to the conversion of surface fire to canopy fire.The combustibility of dead branches in the pure forest of Pinus armandii was investigated so as to evaluate its danger of causing canopy fire.[Method]After setting plots of Pinus armandii pure forests,which continuously distribute in Yunnan natural centre of forestry,northeastern Kunming,during the forest fire period between 2018 and 2019,field investigation was carried out,samples were collected and laboratory combustion test was carried out.Combined with field conditions and laboratory analysis,moisture content,fuel load,heat values,ignition time,flame holding time,flameless combustion maintenance time and other indicators were used to study the combustibility of the dead branches of Pinus armandii in order to evaluate the risk of crowning fire.[Result]In the forest fire period,the moisture content of the dead branches of Pinus armandii forest was 5.97%~15.66%,the fuel load was 0.09~0.57 kg/m2,the heat values were 17291~18812 kJ/kg,and the ignition time was 3.5~4.1 s.The flame holding time reached 9.2~16.39min,and the flameless combustion was maintained for 26~36 min.[Conclusion]The moisture content is very low,fuel load is small,but ash content of pure forest of Pinus armandii reached a high level.In the critical period of fire prevention,the dead branches of pure forest of Pinus armandii are easily flammable.As long as there is a fire source,it is easy to be ignited.In the event of a fire,the fire is likely to burn along the surface of the dead branches,spreading among the dead branches to the canopy and convert to canopy fire.