[Age- and organ-related variances in fire resistance traits of typical tree species in subtropical China].

We investigated the fire resistance conferred by different forest age groups (young, middle-age and mature forest) and organs (leaf, branch, and bark) of six typical tree species (Myrica rubra, Schima superba, Symplocos sumuntia, Machilus pingii, Castanopsis eyrei, and Quercus glauca) in Qingshigang national forest farm, Yanling County, Hunan Province, subtropical China. We measured morphological, physical, and chemical properties that could be used as proxies for fire resistance and examined the variances of fire resistance among different organs and age groups in the same tree species. Further, we comprehensively ranked all the tree species by their capacity in fire resistance. We found considerable variation in fire resistance among organs and age groups. Compared with branches and barks, leaves had relatively higher water content (53.7%), higher crude ash content (4.5%), and lower crude fiber content (23.9%). Fire resistance of trees decreased first and then increased with increasing stand age. Trees in middle-aged stage showed the lowest contents of water, crude ash, and crude fiber. The comprehensive scores of fire resistance for diffe-rent organs were significantly different among species. Fire resistance of leaves generally decreased in the order of M. pingii > C. eyrei > S. sumuntia > M. rubra > S. superba > Q. glauca. For branches, M. pingii and C. eyrei showed the strongest fire resistance, followed by M. rubra and S. superba. For barks, S. superba and C. eyrei were relatively stronger in fire resistance than other species, while M. pingii and Q. glauca were the weakest. The comprehensive scores of fire resistance performance of species were different. S. superba (1.033) and M. rubra (0.526) were the most fire-resistant species, while M. pingii (-0.405) and Q. glauca (-1.151) were the least fire-resistant. Therefore, S. superba and M. rubra were the preferred tree species for fire prevention forest belt in forests of subtropical southern China.