The areas burned once, as indicated on the map (facing page 166), aggregate 18,898 acres. Deducting one-quarter of these as areas occupied by marshes and swamps, there are left 14,174 acres occupied by poplar and pine. The patches that escaped the fire, in the areas burned more than once, total 3,175 acres. Therefore, the total number of acres burned but once is 17,349. It will be seen, by referring to the accompanying table (page 175), that white pine on this area aver-ages 65 trees and red pine 45 trees per acre, or a total of 110 pine trees. Seventy-nine per cent of these trees are from one inch to three inches in diameter. Judging from the results of the growth studies, it takes about 25 years, on the average, to make a three-inch pine tree. These areas were burned about 25 years ago; therefore, practically four-fifths of the present quantity of pine has established itself since the last severe fire.
Regarding the trees eight inches in diameter and above as capable of producing viable seeds, there are on the average three seed trees per acre on the area as a whole, an ample quantity, if properly distributed, to fill up the open places and to replace the trees that die from natural causes. If the 110 trees per acre were allowed to come to maturity, the area would probably be more fully stocked with pine than it was at the time the first lumbering operations began, for the original forest was a very old one, with large trees, a condition under which the trees must necessarily have been scattered to have received light and food enough to reach large dimensions. But, with the present high price of pine lumber, and the consequent utilization of comparatively low grade stock, pine forests like the original will never be duplicated. Instead of cutting trees 200 to 300 years old, as was originally done, the trees will be harvested at 100 years, 80 years, and even, in some cases, 60 years of age. The pine trees standing at present will be cut at these ages, if not burned in the meantime, and the present number of trees per acre on the areas severely burned once is about right for proper development for harvest in that condition. It would seem, therefore, that one burning after lumbering does not seriously interfere with the reproduction of pine in commercial quantities. This statement, of course, is based on the assumption that the fire came very soon after lumbering, since otherwise it would destroy the first crop of seedlings established.
The pine trees above ten inches in diameter on the average acre would yield only 185 board feet, a very small amount, but when multi-plied by the number of acres, it becomes 3,000,000 feet of commercial material.
It will be seen from the table (page 175) that the poplars con-tribute the largest number of trees per acre, the trembling aspen having