NATIONAL PARK SERVICE Forests of Yosemite, Sequoia, and General Grant National Parks

WESTERN YELLOW PINE (PINUS PONDEROSA).¹

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¹This species is known as yellow pine in Glacier and Yellowstone Parks.

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The yellow pine (figs. 7 and 8) of the Sierras is a magnificent tree exceeded in size and beauty, except for the unique sequoia, among its associates only by the sugar pine. If not so large as the sugar pine, however, the western yellow pine holds one title to preeminence in that it is the most widely distributed of North American pines. It grows from British Columbia to Mexico and from the mountains of the Pacific coast to the farthest outlying spur of the Rocky Mountains—the Black Hills of South Dakota. This wide distribution is due to its great power of enduring all sorts of conditions. It rejoices in the warm, pleasant flats of the lower Sierras and there grows to its best development; but if its seeds alight on a dry, hot ridge, it does not give up and die as many other trees would do, but clings to life and grows the best it can, although it can not grow into as fine a tree as in more favorable locations. In the dry Rocky Mountains it still pushes its way, although stunted, as indeed are all trees by such hard conditions. In the region of the Sierras surrounding the national parks this tree frequently reaches a height of 200 feet and a diameter of 5 feet. Trees are occasionally found with a diameter of 6 or 7 feet and heights up to 230 feet.

FIG. 7.—Western yellow pine (Pinus ponderosa) 70 inches in diameter.

FIG. 8.—Western yellow pine (Pinus ponderosa) 71 inches in diameter.

As might be expected from a tree which can adapt itself to such widely varying conditions, the western yellow pine shows many variations in form. In the Sierras its leaves are from 7 to 10 inches long and are uniformly in bundles of three. In the Black Hills of South Dakota they are 2 or 3 inches shorter and may be found in bundles of two or three upon the same tree. Above an altitude of roughly 5,000 feet in the Sierras it is replaced to a greater or less extent by its closely related form, the Jeffrey pine.

In youth this yellow pine grows very rapidly if conditions are favorable. For the first two or three years of its life, to be sure, while it is establishing its root system upon which its supply of food depends, the height growth of the seedling is slow, but by the time it is passing the height of a man's head it frequently grows at a rate of 2 or 3 feet in height per year. This rapid height growth, however, begins steadily to slacken after youth is passed, and while it never wholly ceases during the life of the tree, the growth of the veterans is extremely slow. In diameter, on the other hand, the tree grows by putting on annually a new layer between the wood and the bark, thus producing the annual rings which can be seen on any smooth stump. In young and vigorous trees these rings may be one-half or even three-fourths of an inch wide, which is equivalent to a growth in diameter of 1 or 1-1/2 inches per year. Such a rate of growth, however, never continues for many years, as the diameter growth is strongly affected by variations from year to year in the moisture supply and other conditions of life. Next to a half-inch ring may readily stand one only one-sixteenth of an inch in thickness. After the tree has reached maturity there is a marked and permanent falling off in the width of the rings and the tree continues to grow slowly until the end of life; for with trees there is no absolute limit of growth or of life, such as is caused among animals by the maturing and decay of organs.

In favorable conditions the yellow pine may grow to 12 inches in diameter in 30 years and to 30 inches in 100 years, while a 5-foot veteran may be 300 years old. Such rapid growth, however, occurs chiefly in the open. In continuous forests the trees grow more slowly in diameter than they do in the open, but faster in height, and make longer and cleaner shafts. Under average conditions a tree 12 inches in diameter is about 80 feet tall and 60 years old, one 30 inches in diameter is 150 feet tall and 200 years old, and one 60 inches in diameter is 180 feet tall and 500 years old. Good site conditions may increase the heights for a given diameter, and poor conditions decrease them, by about 25 feet, while the ages may be increased or decreased by from 25 to 50 per cent.

The western yellow pine in the central Sierras is a very healthy tree. It suffers occasionally from fungous diseases, which cause decay, and also from the attack of mistletoe. Trees are occasionally struck by lightning, but this happens seldom, on the whole. Among the worst enemies of the western yellow pine are the bark-boring beetles. These insects enter through the bark and excavate channels in the thin layer of living tissue between the bark and the wood. If the beetles are in sufficient numbers, they girdle and kill the tree. Nearly all of the dying or gradually yellowing tree tops which are seen in this region of the Sierras are due to the attack of these beetles.

The worst enemy of the forest has been fire. Untold wealth of the Nation has been destroyed thus since the white man came to the forests of America. It has been a long lesson to learn, but the people are every year more careful with their use of fire in the woods, and, with the help of our tourists and travelers, great progress is now being made in protecting our national parks and national forests from such destruction. Every year, however, come some new friends who have never had experience in the forests of the terrible effects of this scourge, and all those who do know should help to spread the gospel of care.

The wide distribution of the western yellow pine makes it a very important tree as a source of lumber supply, to which the quality of its wood makes it excellently adapted. The wood is softer, smoother grained, and less resinous than that of almost any other yellow pine in the United States, and the California-grown timber is so remarkable in this respect as to resemble more the white pine of the East. Indeed it is known in the lumber markets under the name of California white pine. The total lumber cut of this species in the United States for 1912 was 1,220 million feet board measure, or a little over 3 per cent of the total for all species of 39,000 million feet. Of this total for the species California cut 30 per cent. The enormous total stand of the species over its very wide range will doubtless make it a much more important factor in the lumber market of the future than it is at present. An important industrial possibility in connection with this species is the fact, recently determined by experiment, that it can be made to yield turpentine rivaling both in quantity nld quality that of the longleaf yellow pine of the southeastern Atlantic coast.