广西苍梧马尾松林和大叶栎林的火行为比较

马尾松(Pinus massoniana)是中国南方大面积造林的树种,也是抗火能力最弱的树种。研究了广西苍梧11龄马尾松用材林和4龄大叶栎萌芽林在正常冬季和干旱夏季情景下的火行为,用behaveplus计算了火线强度、蔓延速度、树冠火可能性等参数。结果表明,两种林分在干旱夏季的火行为高于在正常冬季的火行为。无论是在正常冬季还是在干旱夏季,都没有出现马尾松可燃物模型的火行为一致高于大叶栎可燃物模型的情况;天气、地形、可燃物床结构对可燃物含水率有很大影响,而含水率是火行为的决定因素。虽然大叶栎被划分为难燃树种,大叶栎萌芽林的火行为高于成年大叶栎乔木林,苍梧大叶栎萌芽林在极端干旱的夏季情景有被火把点燃的可能性。如果将大叶栎萌芽林作为防火林带使用,需要经常清除林下枯枝落叶,割除黑莎草,减少细小可燃物。

Assessing fire potential of Pinus massoniana and Castanopsis fissa forests in Cangwu by fuel modelling

Pinus massoniana is a tree species widely used for afforestation in southern China, and one most flammable and weakly resistant to fire. Eleven-yr-old P. massoniana plantations and 4-yr-old Castanopsis fissa coppices on different topographies were investigated and fuel models were developed by BehavePlus 5.0 to evaluate their fire potential in normal winter and summer drought moisture scenarios, comparing their fireline intensity, rate of spread and crown fire possibilities. The result showed that fire potential was higher in summer drought than in normal winter. However, neither in normal winter nor in summer drought, fire behavior of pine fuel models was consistently higher than that of C. fissa fuel models; and weather, topography, fuelbed composition contributed heavily on fuel moistures which always were dominating factors for fire behaviors. Although C. fissa was classified as nonflammable tree species, its coppices were more flammable than its mature arbor forests; and the coppices in Cangwu were possible to be ignited by brands in extreme summer drought. If the C. fissa coppices are used as firebreak belt forest, understory dead fuels, herbs and other fine fuels should be treated regularly.