. Bulletin (Pennsylvania Department of Forests and Waters), no. 33-35. Forests and forestry. 10 Smooth barked species as beech, and thin sapped species as tulip, are especially liable to fire damage. Species with flaky bark are likely to suffer. Shallow rooted species may be killed by the burn- ing humus injuring the roots, or simply by the exposure of the roots. Hardwoods are likely to have crown fires only in thicket or pole stage, or in dense stand when dead or new leaves are on the twigs. The amount of damage varies greatly according to the age of the woods. In old timber the soil covering
. Bulletin (Pennsylvania Department of Forests and Waters), no. 33-35. Forests and forestry. 10 Smooth barked species as beech, and thin sapped species as tulip, are especially liable to fire damage. Species with flaky bark are likely to suffer. Shallow rooted species may be killed by the burn- ing humus injuring the roots, or simply by the exposure of the roots. Hardwoods are likely to have crown fires only in thicket or pole stage, or in dense stand when dead or new leaves are on the twigs. The amount of damage varies greatly according to the age of the woods. In old timber the soil covering is usually scantier than in young wood, consequently there is less fuel and less damage. Sur- face fires usually burn more slowly in old timber because protected from the wind. As trees grow older the bark of most species grows thicker and more corky. It is a non-conductor of heat, hence it pro- tects the cambium from being scorched. Even to such trees every fire does some damage and a severe fire or frequent fires will kill them. Young seedlings and coppice growth of most species, and even poles of some species are killed by very light fire. Necessarily the kind and severity of the fire will influence the re- sulting damage. A fire in one tree does little damage unless it be- comes*'the means of starting other kinds of fires. Crown fires are destructive because the burning of the foliage usually results in the killing of a tree. Even in hardwoods the leaves, buds and twigs are so badly scorched that death results. In many cases the finer twigs are consumed. Under-ground fires kill everything in their path, by killing or consuming roots, by exposure of roots, or by removal of material from on top and around roots so that it is only a matter of a short time until the trees are blown over by wind, or gradually die. Surface fires vary in their efforts from slight injuries to com- plete destruction, depending upon their severity, fiininf 4inni||,'<rs -liaUiid uliLU hmlitd tii J
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