大兴安岭南部春季火行为特征及可燃物消耗

Fire Behavior and Consumption of Fuel Loadings in Spring Season in Southern Daxing'an Mountains

利用标准地调查分析2007年春季大兴安岭2起森林火灾的火行为及可燃物变化。采用加拿大火险天气指数(FWI)系统分析火险变化,地表可燃物载量调查采用线状相交可燃物调查方法,并利用MODIS遥感数据对火烧程度进行分级。结果表明:FWI系统各指标可以很好地指示森林火险变化,2007年4—5月细小可燃物湿度码(FFMC)基本都在90以上,腐殖质湿度码(DMC)和干旱指数(DC)在4月份持续升高,2场大火也发生在火险高的时段。火烧类型以地表火为主,部分林分有冲冠火。火后阔叶林地表径级可燃物增加不明显,针阔混交林主要是5.0～6.99cm径级可燃物增加,而落叶松纯林火烧后除0.50～0.99cm径级可燃物减少外,其他径级可燃物都明显增加。不同火烧程度对地表可燃物载量的影响有差异。中度和重度火烧后草本盖度明显下降,有些林分下木层死亡率较高。罕诺河火场和松岭区壮志林场过火区重度火烧分别占33.2%和46.4%。

Fire behavior and fuel loading changes were investigated in plots of two burned, occurred in spring of 2007, slashes in Daxing＇an Mountains. We used Canadian fire weather index （FWI） system to analysis fire danger changes in that period. A linear intersect method was used for assessing ground fuel loadings and the MODIS satellite data were used for burn classification. The results indicated that the indexes of FWI system were a good indicator for fire danger rating in Daxing＇ an Mountains. Most fine fuel moisture codes （FFMC） were more than 90 during April and May of 2007, and duff moisture code （DMC） and drought code （DC） were rising continually in April. The two fires occurred in high fire danger period. In Danxing＇ an Mountains most fires were surface fire, and some areas had torching fire. For broadleaf forests ground diameter fuels didn＇t increase significantly after fire, but all diameter fuels increased in coniferous and broadleaf mixed forests except 5.0 - 6.99 cm diameter fuels. Fire intensity had an influence on ground fuel loadings. After the fire with modest and high fire intensity the grass coverage decreased significantly and had a high mortality rate of understory. The areas with high fire intensity of the two fires were accounted for 33.2% and 46.4% of the burned-area respectively.