. Bulletin. Forests and forestry -- United States. VOLUME AND YIELD, SECOND-GEOWTH HEMLOCK. 41 was necessary to create an arbitrary standard of merchantable size. It was assumed that in fifty years, the probable shortest time in which land now bare can be logged again with profit, timber will have gained in value sufficiently to warrant the cutting of any tree which will yield a log 20 feet long and 12 inches at the small end. A few of the trees 13 inches in diameter breasthigh will contain such a log, but it was thought safer to take 11 inches as the limit. In the subsequent dis- cussion of s
. Bulletin. Forests and forestry -- United States. VOLUME AND YIELD, SECOND-GEOWTH HEMLOCK. 41 was necessary to create an arbitrary standard of merchantable size. It was assumed that in fifty years, the probable shortest time in which land now bare can be logged again with profit, timber will have gained in value sufficiently to warrant the cutting of any tree which will yield a log 20 feet long and 12 inches at the small end. A few of the trees 13 inches in diameter breasthigh will contain such a log, but it was thought safer to take 11 inches as the limit. In the subsequent dis- cussion of second growth, therefore, all trees 11 inches and over are considered merchantable, and it is assumed that all timber between the stump and a point 12 inches in diameter inside the bark will be 10 20 30 40 30 90 100 I/O 120 60 60 70 AGE - YEARS. FIG. 1.—Diagram showing growth in diameter of second-growth Red Fir and Hemlock in pure stands and of Hemlock in mixture with Red Fir. Such material as piling or trap poles will be produced in less than fifty years. l)ut earlier than this the trees will not clear themselves sufficiently to make merchantable saw-logs, even if a few reach the requisite size. The growth of pure and mixed even-aged forests is very different. In the former, Hemlock grows rapidly, with a normal relation between diameter and height growth. The stand Is exceedingly dense at first, and remains so longer than does a Red Fir forest on account of the greater tolerance of the Ileinloek. The growth in height and diameter is also slower than that of Red Fir. Where, however,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Bureau of Forestry. Washington : G. P. O.
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