138 A MANUAL OF FORESTRY 



tree and, in the case of a conifer, leap into the top. Some farmers 

 claim that annual fires are a good thing, because the ground is 

 thus kept free of material which would make a really hot fire. 

 This, however, is not true, for every fire, in New England at any 

 rate, does more harm than good. Some trees, as the chestnut, 

 arc much more easily damaged by lire than others, like the oak, 

 hickory, and birch; and practically all trees are more tender in 

 youth than later when the bark has thickened. 



Besides the crown fire which leaps from tree top to tree top, 

 and the surface fire which runs over the ground burning the litter, 

 underbrush, etc., a third class of fire occurs in the coniferous 

 forests of the north. In the forests composed of such trees as 

 spruce and fir the ground is often covered with a thick layer of 

 decaying vegetable matter, such as needles and twigs, which in 

 seasons of drought become very dry. If a fire once starts in this 

 "duff" as it is called, it may smolder for weeks on a small area 

 of less than a half acre. At any time such a " ground fire " is apt 

 to flare up, if a strong wind arises, and may become a serious 

 surface or even a crown fire. 



Besides the damage to grown trees one of the worst effects of 

 a forest fire is the killing of the small forest seedlings and sap- 

 lings. This is a damage which is often overlooked and it is 

 more responsible for the present worthless condition of millions 

 of acres in the United States than any other cause. Forest seed- 

 lings, especially those of the evergreens, are practically sure to be 

 destroyed by any fire passing through them. We do not realize 

 the relatively long time required for seedlings to grow the first 

 ten feet in height, as compared to that of subsequent growth. It 

 requires from ten to twenty years for most trees to reach the 

 height of ten feet, while many suppressed spruce and hemlock 

 are fifty years old before they reach it. The destruction of 

 seedlings, therefore, retards the growth of the forest. It often 

 happens, too, that the seed trees have been removed in the mean- 

 time or are killed by the same fire. In this case natural repro- 

 duction of that species will be prevented for many years and the 

 land will either be covered with a worthless tangle of brush or be 



