南方人工林地阴燃火温度变化特征研究

Research on variation of temperature of underground fire in south China plantation

阴燃火具有隐蔽性强、持续时间长、目测难度大等特点,它不但能烧毁树根和地下微生物从而导致树木死亡,而且在一定条件下会复燃,进而引发更大森林火灾,对森林生态系统的破坏性极大,当前对其温度变化特征尚缺乏深入了解,其科学问题亟待解决。笔者以南京市栖霞区丁山的地表可燃物为研究对象,针对不同燃烧条件(可燃物类型、风速、可燃物含水量),开展野外调查实验、燃烧床火烧实验、模型模拟等,通过室内外实验和数据统计,分析地表可燃物的阴燃温度变化特征和转换为明火的临界温度及其温度变化过程。结果表明:枯立木燃烧的温度最高,阴燃最高值可以达到690℃,腐殖质阴燃产生的温度和持续性远高于其他可燃物类型,因此复燃的概率高于枯立木、枯枝落叶、鲜活植物等可燃物阴燃后复燃概率;森林可燃物阴燃温度上升速度随风速的增大而逐变快;地表可燃物阴燃下温度上升速度与可燃物含水量成反比,即含水量越大,森林可燃物阴燃温度上升速度越慢,当含水量超过42.3%,可燃物能够复燃的概率极低。

Smoldering fire in forestry has the characteristics of strong concealment,long duration and difficult visual inspection,etc.It can not only burn tree roots and underground microorganisms causing tree death,but also will re-ignite under certain conditions,leading to greater forest fires,which is extremely destructive to forest ecosystems.However,there is still a lack of in-depth understanding of its temperature change characteristics,and its scientific complications need to be solved urgently.In this study,the surface combustibles of Dingshan of Nanjing Forest Police College were taken as the research object,and field investigation experiments,simulated bed fire experiments and model establishment were carried out through different combustion conditions,including different combustible types,different wind speeds,and different water content of combustibles,to analyze the characteristics of the smoldering temperature change of the surface combustibles,temperature change process and the critical temperature of smoldering fire occurring open flame.The results showed that the temperature of burning dead wood was the highest,and the highest temperature of smoldering can reach 690℃.The temperature and persistence of humus smoldering were much higher and longer than other combustibles types,so the probability of re-ignition was higher than that of dead wood,litter and fresh plants.The rising rate of smoldering temperature increased with the increase in wind speed.The rise rate of temperature under the surface fuel smoldering was inversely proportional to the moisture content of fuel,that was,the greater the moisture content was,the slower the rise rate of forest fuel smoldering temperature would be.When the moisture content exceeded 42.3%,the re-igniting probability of fuel was extremely low.This study explored the influence of moisture content,wind speed and fuel type of combustible on the smoldering conversion to open fire,which enriched the forest combustion theory and provided data support for the smoldering fire substance cleaning in forest fire prevention.