On the area burned three times there are, on the average, seven pine trees to the acre, three white pine and four red pine,—a reduction of one-half from the number on the areas burned twice, and approximately only one-sixteenth of the number on the areas burned but once. The reduction, in terms of the reproduction, is even greater than this indicates, for 30 per cent of the trees are of such size as to show that they antedate the first fire; that is, they are the larger trees which have withstood all the fires.
The trembling aspen is represented by 95 and the large-toothed aspen by 70, a total of 165 per acre, compared with 258 trees on the areas burned once and twice. Although the percentage ratio of the poplar of the one-inch and two-inch diameter class to the other diameters is practically the same as on the areas burned twice, as a matter of fact, the condition is really not as favourable as would appear, since a large proportion of the smaller material has been materially weakened as the result of the successive fires; it is crooked, deformed, and already attacked by disease. The lower illustration opposite shows two shoots springing from a root collar that has been injured by fires. The swollen portion on a similar stock was about 25 years old. It had sent forth shoots twice before, only to be burned to the ground. Shoots arising in this manner are weak and probably never make trees of commercial size. The amount of commercial pulp-wood is reduced from one-fifth of a cord on the areas burned twice to one-eighth of a cord per acre on the areas burned three times.
The number of other species of potentially commercial trees, such as oak, basswood, balsam, cedar and spruce, reaches approximately 100 on the average acre on the areas burned once and twice, but the same or similar species total only 18 per acre on the areas burned three times.
AREAS SEVERELY BURNED MANY TIMES
Thirteen thousand acres of the region examined have been burned over many times. Making the usual deduction of one-quarter of the area for swamps, and a deduction of five per cent for patches which escaped most of the fires, there are still 9,260 acres actually included in this class. The greater portion of the area so designated has been severely burned seven times, five of which have occurred since lumbering operations began in the vicinity. Practically all of the few old pine trees still standing show from five to seven fire scars. One of these, which little by little had been severed at the base by fires, disclosed the fact that it had been fire-scarred when 25, 43, 55, 64, 82, 88 and 96 years old. It finally succumbed to the last fire at the age of too years. This means that the tree was burned, on the average. at