森林可燃物是发生森林火灾的重要物质基础,研究其特征对预研森林火灾发展规律具有重要作用。以粤北地区的5种典型森林(桉树林、马尾松林、杉木林、毛竹林和木荷林)为研究对象,测定了森林的灌木(Ⅰ)、草本(Ⅱ)、腐殖质(Ⅲ)和枯落物Ⅳ(d<0.6cm)、Ⅴ(0.6cm≤d<2.5cm)和Ⅵ(2.5cm≤d<7.62cm)的可燃性指标(干鲜比、平衡含水率、燃点和热值),分析可燃性指标间的差异及其关系,初步评价森林的可燃性。研究结果表明,可燃物的干鲜比位于41.88%~85.99%,枯落物Ⅴ最大,且不同可燃物类型间具有极显著的差异(P<0.01)。5种林分类型的腐殖质层(Ⅲ)、枯落物Ⅳ、Ⅴ和Ⅵ平衡含水率变幅分别为4.77%~5.01%,6.86%~7.27%,8.26%~9.64%和9.94%~10.58%;枯落物的平衡含水率随直径增大而升高,枯落物Ⅵ的平衡含水率显著高于Ⅲ(P<0.01)。腐殖质和枯落物的燃点分别为264.67~271.00℃和248.00~255.17℃,热值则分别达8.47~11.50kJ/g和16.11~17.92kJ/g;腐殖质的燃点显著高于枯落物(P<0.01),热值则与之相反。Person相关分析表明,所有可燃物的干鲜比之间具有正向共性,即两两之间干鲜比正相关;平衡含水率对燃点的影响大于干鲜比。5种森林的抗火性强度分成3类,第1类为木荷林,抗火性强林分,第2类是毛竹林,为抗火性中等林分,第3类包括马尾松、杉木和桉树林,为相对易燃林分。

Forest fuels,as the essential material for forest burning,constitute the main body of forest fire behavior.The physicochemical characteristics of forest fuels play an important role in forest fire prevention and fighting.The flammability indexes,including dry-to-fresh quality ratio,equilibrium moisture content,ignition point,calorific value,of shrubs (I),herbs (II),humus (III)and litter IV (d<0.6cm),V (0.6cm≤d<2.5cm)and VI (2.5cm≤d<7.62cm)were determined in five types of plantations (Eucalyptus robusta,Pinus massoniana,Cunninghamia lanceolata,Phyllostachys pubescens,Schima superba)in northern Guangdong Province.The flammability indexes of difference and relationship between different typical forests were analyzed to evaluate the flammability of five types of forest.The results showed that the dry-to-fresh quality ratio of forest fuels were from 41.88% to 85.99%,and the litter V had the highest dry-to-fresh quality ratio among all typical fuels.Moreover,there were significant differences between different typical forest fuels (P<0.01).The content of equilibrium moisture of humus (III)and litter IV,V and VI in five typical forests were 4.77%~5.01%,6.86%~7.27%,8.26%~9.64%,9.94%~10.58%,respectively.The content of equilibrium moisture of litter increased with the increase of diameter,and the content of equilibrium moisture of litter VI was significantly higher than III (P<0.01).The range of ignition points of humus and litter were 264.67~271.00℃ and 248.00~255.17℃,respectively.Moreover,the range of calorific values were 8.47~11.50kJ/g and 16.11~17.92kJ/g,respectively.And the ignition point of humus was significantly higher than litter (P<0.01).Conversely,the calorific value of litter was higher than humus.Person correlation analysis showed that there had a positive commonality between the dry-to-fresh quality ratios of all fuels.Namely,the dry-to-fresh quality ratios were positively correlated between different typical forests.The impact of the equilibrium moisture on the ignition point was greater than dry-to-fresh quality ratio.The fire resistance strength of five plantations was divided into 3 categories,the first group was Schima superba forest with strong fire resistance.The Phyllostachys pubescens forest with medium fire resistance was followed.The third group,including Eucalyptus robusta forest,Pinus massoniana forest and Cunninghamia lanceolate forest,were relatively flammable forests.