Читать книгу American Forest Trees - Henry H. Gibson - Страница 27

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This is a magnificent tree of the Northwest, and its range lies principally on the upper tributaries of the Columbia river, in Idaho, Montana, and British Columbia, but it occurs also among the Blue Mountains of Washington and Oregon. It is the largest member of the larch genus, either in the old world or the new. The finest trees are 250 feet high with diameters of six or eight feet, but sizes half of that are nearer the average. The trunk is of splendid form. In early life it is limby, but later it prunes itself, and a long, tapering bole is developed with a very small crown of thin foliage. No other tree of its size, with the possible exception of old sequoias, has so little foliage in proportion to the trunk.

The result is apparent in the rate of growth after the larch has passed its youth. Sometimes such a tree does not increase its trunk diameter as much in seventy-five years as a vigorous loblolly pine or willow oak will in one year. The trunk of a tree, as is well known, grows by means of food manufactured by the leaves and sent down to be transformed into wood. With so few leaves and a trunk so large, the slowness of growth is a natural consequence. Though the annual rings are usually quite narrow, the bands of summerwood are relatively broad. That accounts for the density of larchwood and its great weight. It is six per cent heavier than longleaf pine, and is not much inferior in strength and elasticity. The leaves are from one to one and three-quarter inches long, the cones from one to one and a half inches, and the seeds nearly one-quarter inch in length. They are equipped with wings of sufficient power to carry them a short distance from the parent tree.

The bark on young larches is thin, but on large trunks, and near the ground, it may be five or six inches thick. When a notch is cut in the trunk it collects a resin of sweetish taste which the Indians use as an article of food.

The western larch reaches its best development in northern Idaho and Montana on streams which flow into Flathead lake. The tree prefers moist bottom lands, but grows well in other situations, at altitudes of from 2,000 to 7,000 feet. The figures given above on the wood’s weight, strength, and stiffness show its value for manufacturing purposes. Its remoteness from markets has stood in the way of large use, but it has been tried for many purposes and with highly satisfactory results. In 1910 sawmills in the four western states where it grows cut 255,186,000 feet. Most of this is used as rough lumber, but some is made into furniture, finish, boxes, and boats. The wood has several names, though larch is the most common. It is otherwise known as tamarack and hackmatack, which names are oftener applied to the eastern tree; red American larch, western tamarack, and great western larch.

Some of the annual cut of lumber credited to western larch does not belong to it. Lumbermen have confused names and mixed figures by applying this tree’s name to noble fir, which is a different tree. If the fir lumber listed as larch were given its proper name, it would result in lowering the output of larch as shown in statistical figures. In spite of this, however, larch lumber fills an important place in the trade of the northern Rocky Mountain region.

There is little doubt that it will fill a much more important place in the future, for a beginning has scarcely been made in marketing this timber. The available supply is large, but exact figures are not available. Some stands are dense and extensive, and the trees are of large size and fine form. It is not supposed, however, that there will be much after the present stand has been cut, because a second crop from trees of so slow growth will be far in the future. Sudworth says that larch trees eighteen or twenty inches in diameter are from 250 to 300 years old, and that the ordinary age of these trees in the forests of the Northwest is from 300 to 500 years; while larger trees are 600 or 700. Much remains to be learned concerning the ages of these trees in different situations and in different parts of its range. It is apparent, however, that when a period covering two or three centuries is required to produce a sawlog of only moderate size, timber owners will not look forward with much eagerness to a second growth forest of western larch.

The value of the wood of western larch has been the subject of much controversy. In the tables compiled for the federal census of 1880, under direction of Charles S. Sargent, its strength and elasticity were shown to be remarkably high. The figures indicate that it is about thirty-nine per cent stronger than white oak and fifty-one per cent stiffer. This places it a little above longleaf pine in strength and nearly equal to it in stiffness or elasticity. Engineers have expressed doubts as to the correctness of Sargent’s figures. They believe them too high. The samples tested by Sargent were six in number, four of them collected in Washington and two in Montana.

The wood of western larch is heavier than longleaf pine, and approximately of the same weight as white oak. It is among the heaviest, if not actually the heaviest, of softwoods of the United States. Sargent thus described the physical properties of the wood: “Heavy, exceedingly hard and strong, rather coarse grained, compact, satiny, susceptible of a fine polish, very durable in contact with the soil; bands of small summer cells broad, occupying fully half the width of the annual growth, very resinous, dark-colored, conspicuous resin passages few, obscure; medullary rays few, thin; color, light bright red, the thin sapwood nearly white.” The wood is described by Sudworth: “Clear, reddish brown, heavy, and fine grained; commercially valuable; very durable in an unprotected state, differing greatly in this respect from the wood of the eastern larch.”

The seasoning of western larch has given lumbermen much trouble. It checks badly and splinters rise from the surface of boards. It is generally admitted that this is the most serious obstacle in the way of securing wide utilization for the wood. The structure of the annual ring is reason for believing that there is slight adhesion between the springwood and that of the late season. Checks are very numerous parallel with the growth rings, and splinters part from the board along the same lines. Standing timber is frequently windshaken, and the cracks follow the rings.

All of this is presumptive evidence that the principle defect of larch is a lack of adhesion between the early and the late wood. If that is correct, it is a fundamental defect in the growing tree, and is inherent in the wood. No artificial treatment can wholly remove it. It should not be considered impossible, however, to devise methods of seasoning which would not accentuate the weaknesses natural to the wood.

The form of the larch’s trunk is perfect, from the lumberman’s viewpoint, and its size is all that could be desired. It is amply able to perpetuate its species, though it consumes a great deal of time in the process. Abundant crops of seeds are borne, but only once in several years. It rarely bears seeds as early as its twenty-fifth year, and generally not until it passes forty; but its fruitful period is long, extending over several centuries. The seeds retain their vitality moderately well, which is an important consideration in view of the tree’s habit of opening and closing its cones alternately as the weather happens to be damp or dry. The dispersion of seeds extends over a considerable part of the season, and the changing winds scatter them in all directions. Many seeds fall on the snow in winter to be let down on the damp ground ready to germinate during the early spring. The best germination occurs on mineral soil, and this is often found in areas recently bared by fire. Lodgepole pine contends also for this ground; but the race between the two species is not swift after the process of scattering seeds has been completed; for both are of growth so exceedingly slow that a hundred years will scarcely tell which is gaining. In the long run, however, the larch outstrips the pine and becomes a larger tree. If both start at the same time, and there is not room for both, the pine will kill the larch by shading it. The latter’s thin foliage renders it incapable of casting a shadow dense enough to hurt the pine. The best areas for larch are those so thoroughly burned as to preclude the immediate heavy reproduction of lodgepole pine.

Much of the natural ranges of larch and lodgepole pine lie in the national forests owned by the government, and careful studies have been made in recent years to determine the requirements, and the actual and comparative values of the two species. It has been shown that larch is one of the most intolerant of the western forest trees. It cannot endure shade. Its own thin foliage, where it occurs in pure stands, is sufficient to shade off the lower limbs of boles, and produce tall, clean trunks; but if a larch happens to stand in the open, where light is abundant, it retains its branches almost to the ground. It is more intolerant, even, than western yellow pine, which so often grows in open, parklike stands.

Alpine Larch (Larix lyallii) never grows naturally below an altitude of 4,000 feet, and near the southern border of its range it climbs to 8,000, where it stands on the brink of precipices, faces of cliffs, and on windswept summits. It is too much exposed to storms, and has its roots in soil too sterile to develop symmetrical forms. It is found in Montana, Idaho, Washington, and Oregon. The finest trees are sometimes seventy-five feet high and three or four in diameter, but the average height ranges from forty to fifty, with diameters of twenty inches or less. Its leaves are one and a half inches or less in length; cones one and a half inches long, and bristling with hair; seeds one-eighth of an inch long with wings one-fourth inch; wood heavy, hard, and of a light, reddish brown color. It is seldom used except about mountain camps where it is sometimes burned for fuel or is employed in constructing corrals for sheep and cattle. It is impossible for lumbermen ever to make much use of it, because it is scarce and hard to get at.