OCR Text |
Show FIRES CLASSIFIED. It may interest the reader to know, at this time when so many disastrous forest fires are causing widespread alarm, that the Forest Service distinguishes three classes of forest fires, namely, surface fires, which burn the surface layer of leaves, dry grass, brush and small trees ; ground fires, burning the deep accumulation of vegetable mold; and crown fires, which accompany surface fires and burn the crowns of the trees.. Surface fires are the most common and may start under ordinary dry conditions. The severity of the fire, of course, depends largely on the amount of accumulated leaves and brush and the strength of the wind. These fires kill seedlings and young trees, but in many cases do not kill the larger trees. Under some conditions they may kill everything in the area which they ' cover. Ground fires occur only when the vegetable mold has become thoroughly dry.. They burn slowly, but with intense heat, and are exceedingly difficult to extinguish. They have been known to burn all winter, creeping along under a deep layer of snow. Ground fires usually destroy all trees, killing the tissues of the roots, and the trees die and are blown down. Crown fires almost invariably accompany surface fires and occur only when the woods are very dry and there is a high wind. Usually all trees are killed. Sometimes, however, where there are a great many hardwoods in mixture with coniferous trees, single trees or groups of trees may escape injury. |