Much the same conditions exist on extensive areas of the plateau and Rocky Mountain regions, wherever warm, bright, growing seasons and a light rainfall create conditions favourable to decomposition, though not for rapid growth. It is believed that such conditions prevail on one-half of this type, or on an area of 13,000,000 acres. Here, as in the yellow pine region, disposal of logging debris should be treated solely as a fire protective measure, and, if the fire hazard is not great, the only action necessary is such disposition of the slash as will result in rapid decomposition.
On about 10,000,000 acres of the northern coast region the soil consists almost entirely of partially decomposed vegetable material, the accumulation of centuries of growth, lying on a rock surface. The destruction of this layer, besides being practically impossible on account of its saturation with water, would prevent further forest growth. As the forest growth on this area is not commercially valuable, it need not be considered. Altogether, then, the area of forest land from which the removal of the logging slash is either not necessary or not possible as a sylvicultural measure, amounts to approximately 28,000,000 acres. On the remaining 77,000,000 acres—which includes practically all the valuable timber-producing lands, and by far the most productive forest lands—the accumulation of dead vegetable material during a single rotation is so great as to materially reduce the fertility and productivity of the soil, prevent or hinder the regeneration of desirable species and greatly increase the fire hazard. When to this layer is added the immense amount of slash resulting from logging the heavy stands of timber which characterize these lands, a condition is produced which effectually prevents the regeneration of the forest and the utilization of the full productivity of the soil, and creates a fire hazard which it is hopeless to attempt to overcome. Further profitable use of the land for the production of timber is therefore necessarily contingent on the removal of the layer of undecomposed vegetable material and the slash resulting from logging.
The removal of debris can, of course, only be accomplished by the use of fire, and, owing to the danger of its escaping to surrounding timber, destroying seed trees and injuring the soil, burning must be undertaken only under conditions which make its control certain. To do this is often expensive, the cost ranging from a fraction of a cent, in the case of broadcast burning under the most favourable conditions, up to as high as fifty cents and one dollar per thousand feet of timber removed. This constitutes a serious tax on an industry subject to such severely competitive conditions as is the logging and lumber industry, and its universal application can only be obtained gradually.