Yosemite > Library > Handbook > Trees >
Next: The Giant Sequoia • Contents • Previous: Insects of Yosemite
By Ansel F. Hall
U. S. National Park Service, Formerly Instructor in
Forestry, A. E. F. University, Beaune, France
The forests of the West, although the grandest in the world, are not at all complex, for where one might find two hundred and fifty varieties of trees in some of the eastern hardwood forests, he would find but thirty-five species within the 1125 square miles of Yosemite National Park. Of these few species the conifers (cone-bearing trees) are by far the most important. They may easily be identified by the aid of the Key to the Trees in the appendix of this volume.
In the Sierra Nevada Mountains the abrupt rise from almost sea level to twelve or thirteen thousand feet causes within a few miles as great a diversity of climates as one would encounter in traveling from Mexico to Alaska. Each tree species has its own climatic requirements. We therefore find the trees Occurring in definite belts, one above the other. Those hardy pioneers which can withstand the long and intense cold of arctic winters have been driven to timberline, while the most drought-resistant species have claimed the dry foothill regions. So definite is this balance in Nature that, by observing the trees, one can estimate quite definitely the altitude at which he stands.
Entering the park from the west, one first passes through the treeless or oak-dotted San Joaquin Valley and lower foothills. In the upper foothills and lower mountains (1000 to 3000 feet altitude) is the Foothill Forest (Upper Sonoran Zone). Only a few species can withstand the severe drought of the long arid summers and these grow in open park-like stands. The one characteristic conifer of the region is the silvery gray, many-branched digger pine (Pinus sabiniana). The small knobcone pine (Pinus attenuata) occurs but infrequently. Of the hardwoods, the oaks are predominant. Among these are the valley oak (Quercus lobata), the California black oak (Q. californica), the interior live oak (Q. wislizeni), and the canyon live oak (Q. chrysolepis). Along the streams. may be found several species of willow (Salix sp.), black cottonwood (Populus trichocarpa), California buckeye (Aesculus californica), mountain laurel (Umbellularia californica), and California nutmeg (Tumion californicum). The brush or chaparral which covers many of the hillsides is often interspersed with scattered specimens of mountain mahogany (Cercocarpis parvifolius).
At about three thousand feet elevation one enters the Main Timber Belt (Transition Zone) of the Sierra Nevada. This forest, which extends from three thousand to seven thousand feet altitude, is one of the finest in the world both as regards size and value of timber and perfection of its charming landscapes. At the lower elevations the first trees to greet one are the brilliantly green western yellow pine (Pinus ponderosa), the fragrant incense cedar (Libocedrus decurrens), and
A Yosemite forest of Pine, Fir, Incense Cedar, and Sequoia
Photo by A. C. Pillsbury
Above the Main Timber Belt between the altitudes of seven thousand and nine thousand feet is the Sub-alpine Forest (Canadian Zone), a region characterized by dense forests of small or medium-size trees. The typical trees of the region are the red fir (Abies magnifica), white fir (Abies concolor), lodgepole pine or "tamarack" (Pinus contorta), and Jeffrey pine Pinus jeffreyi). On open rocky sites the western juniper (Juniperus occidentalis) is conspicuous, and near the upper limit of the belt the western white pine (Pinus monticola) occurs scattered throughout the forest. The only hardwood of the region is the quaking aspen (Populus tremuloides) which forms beautiful groves in some of the high mountain garden-spots.
In the Alpine or Timberline Forest (Hudsonian Zone), which extends from approximately nine thousand feet elevation to timberline, only the hardiest species can exist. The two principal trees are the graceful mountain hemlock (Tsuga mertensiana) and the storm-resistant white bark pine (Pinus albicaulis). At the lower edge of the belt these merge with red fir (Abies magnifica), western white pine (Pinus monticola) and lodgepole pine (Pinus contorta).
Yosemite Valley might be called the meeting place of the trees. Although at an altitude of but four thousand feet, several species which are normally found at twice that elevation thrive in the shade of the great south wall. The opposite side of the Valley is so warm that we find many patches of vegetation typical of the foothill region. For the tree-lover and botanist the Valley is therefore an ideal vacation land, both because of the great variety of plant life within its walls and the accessibility to the high country beyond.
So much for the trees as they live together in communities—but let us now seek to know then, as individuals. Botanists have grouped all plants according to their relationship into divisions, classes, orders, families, genera, and finally species. Since some trees have as many as twenty different names, each of which is used exclusively in a different locality, it is important to state also the botanical (or universal) name. This is a combination of the names of the genus and species to which the plant belongs.
Everyone is familiar with the two broad classes of trees—the broadleaf trees or hardwoods, and the evergreen trees or conifers. The former group, although abundantly represented in Yosemite Valley,
Red Fir—White Fir forest on the Pohono Trail which passes
through miles of most exquisite wild flower gardens
Photo by Ansel F. Hall
Cone-bearing trees are classified by dendrologists into three families: the Pine Family (Pinaceae), the Redwood Family (Taxodiaceae,), and the Cypress Family (Cupressaceae). Their leaves are retained from two to ten years, which causes them to be called evergreens.
The Pine Family is by far the most important in the park—for that matter, in all the world. It contains all the pines, firs, hemlocks, and the Douglas fir and also the spruces, larches, and true cedars. The latter do not occur in the Sierra. All these trees have needle-like leaves and bear but two seeds beneath each scale of their cones.
The pines (Genus Pinus) are represented in the park by eight species, some of which may be found at any altitude. The characteristic distinguishing this from all other genera is the occurrence of the needles in bundles of five, four, three, or two (and in one species singly), the base of each bundle being surrounded by a paper-like sheath. The five-needle Pines are called the white pines and those with three needles the yellow pines.
Of the three five-needle pines of the Park, the sugar pine (Pinus lambertiana) is by far the most important. It is not only the largest pine in the world but also One of the most majestically beautiful. It may easily be recognized (a) by its carmine-brown flaky bark which is generally divided into long plates by longitudinal fissures, (b) by its five-needle bundles about three inches in length, and (c) by the immense cones (twelve to twenty-four inches long) which hang pendent from the tips of the long straight horizontal branches, or which may be found on the forest floor beneath. A white sugar which exudes from the heartwood when the tree is wounded gives it its common name. On the floor of the Valley are but few specimens, but a short distance up the slopes the species enters into the forest composition and grows abundantly up to about seven thousand feet elevation.
The western white pine (Pinus monticola) which forms an important part of the forests of Idaho and Montana, occurs in California—the southern part of its range—only on the higher mountain slopes, ranging in the park from 6500 to 10,000 feet elevation. The young trees with their bluish-green foliage and silvery gray bark are exceedingly symmetrical. Trees over two feet in diameter take on a more rugged appearance and their bark, which then continuously flakes off, checks into very distinctive five-sided grayish-purple plates. The tree is one of the largest in the sub-alpine forests and may be distinguished (a) by its five-needle bundles which range from two to four inches in length, (b) by its long feathery cones (length five to eight inches) which are borne in clusters at the ends of the long straight branches, and (c) by the very characteristic five-sided small plates in the bark of the older trees.
Hardiest of all Yosemite trees is the five-needled white bark pine (Pinus albicaulis). A few large specimens 2 1/2 feet in diameter and up to 30 feet in height are sometimes encountered between 9000 and 10,000 feet elevation, but the species is most evident at timberline where it forms a scattered forest of dwarf or prostrate trees. These trees, always in keeping with their bleak surroundings, are the delight of the mountaineer. In early spring the raspberry-red of the fragrant flowers, the chocolate brown or purple of the immature cones, the yellowish-green of the short leaf-tufts, and the silvery white bark of the branches and trunk contrast most harmoniously. Specimens may be identified (a) by having five short leaves per bundle (length 1 1/2 to 2 1/2 inches) which are tufted at the ends of the flexible branchlets, (b) by the small hard cones (about the size of a hen’s egg), and (c) by the smooth white bark.
Least important of the park’s three yellow pines is the digger pine (Pinus sabiniana) of the low dry foot-hill country. Its wide-branching habit and sparse silvery gray foliage set it apart from all other species. Most important of its distinguishing characteristics are (a) the gray-green clusters of long flexible leaves (length 8 1/2 to 12 inches) which occur three in a bundle, (b) the low-branching habit, and (c) the large heavily armed cones which generally remain on the trees.
The western yellow pine (Pinus ponderosa) and the Jeffrey pine (Pinus jeffreyi) are so closely related that even botanists differ as to their separation. Both trees reach a large size (maximum diameter 8 to 10 feet) and are tall and symmetrical. They are exceedingly abundant within the park and form the greater part of the forests of Yosemite Valley. The rich green foliage is made up of three-needle bundles which range from 5 to 11 inches in length. The flaky bark of all older trees is distinctively divided into large Yellow plates by deep fissures. The two species grow abundantly from 3000 to 7500 feet elevation, the Western yellow pine preferring the lower altitudes and the Jeffrey pine the heights. The chief contrasts between the two species are (a) in the cones, which are 2 1/2 to 5 1/2 inches in length in the western yellow Pine and 5 1/2 to 11 1/2 inches in the Jeffrey pine, (b) in the bark which is yellowish-brown in the former and reddish-brown in the latter, and (c) in the foliage which is a deep yellow-green in the former and a dark blue-green in the latter.
The only two-needle pine of the park, the lodgepole pine or "tamarack" (Pinus contorta), forms extensive forests at elevations of 7000 to 9500 feet—indeed, it is so abundant as to be the one plebian tree of the High Sierra. In general the tree is not more than 2 feet in diameter and 50 feet in height, but much larger specimens may be found. The species may be distinguished (a) by its two-needle bundles which range in length from 1 to 2 1/2 inches and are generally curved, (b) by its small cones (length 3/4 to 2 1/2 inches), and (c) by its thin, flaky, purplish bark.
The only known specimen of the one leaf pinyon of nut pine (Pinus monophylla) in the park grows in Pate Valley in the gorge of the Grand Canyon of the Tuolumne. It probably sprang from a seed carried over the mountains by the Indians from the Mono Lake region where the nuts of this small tree form an important part of the food of the natives.
Of the four American hemlocks but one species occurs in the Sierra Nevada. The mountain hemlock (Tsuga mertensiana) ventures southward from Alaska along the mountain sides, ascending higher and higher until, in Yosemite National Park, it is found only in alpine forests above 9000 feet elevation. It is universally proclaimed the most graceful tree of the mountains. The beautiful drooping tip and branches set it aside from all other conifers, and its customary
Western Juniper Trees at Benson Lake
Photo by A. C. Pillsbury
The Douglas fir (Pseudotsuga taxifolia) is the most important timber tree in the world. In Oregon and Washington it forms great forests, but here near the southern limit of its range we find it sparsely mixed with other species of the middle altitudes. There are some splendid old specimens in the cool shade of Yosemite’s great south wall and on the talus slopes up to 6500 feet elevation. The tree is most easily recognized (a) by its medium sized pendulous cones which are two to four inches in length and have trident-shaped bracts sticking from between the scales, (b) by its drooping lower branchlets which are clothed all around with petioled leaves from 3/4 to 1 1/4 inches in length, and (c) by the thick, deeply furrowed ashy brown bark.
The true firs (genus Abies) differ from all their American relatives of the Pine Family by bearing erect cones. These generally occur at the very tips of the trees, and since the scales and seeds are shed one by one and blown away by the winds, they are almost never found beneath the trees. Of our nine American firs two species inhabit the Sierra Nevada. The white fir (Abies concolor) is common at middle altitudes, ranging from 3500 to 8000 feet, while the red fir (Abies magnifica) claims the higher slopes. Both Species are beautifully symmetrical with erect, narrow, dense, spire-like crowns and delicate regularly whorled branches. All firs are lovers of shade and therefore grow in dense stands crowding out the less tolerant species. The white fir may be identified (a) by the leaves, which are 1 to 2 inches long, without leaf stalks, and flattened or two-ranked on the lower branchlets, (b) by the bark which in the younger trees is white and bears balsam blisters and in the older trees is deeply furrowed, corky, and ashy gray in color, (c) by the cones which are 3 to 5 inches in length and borne erect near the tops of the trees, and (d) by the habitat, the tree generally occurring at middle altitudes as an associate of yellow and sugar pines. The red fir (Abies magnifica) may be identified (a) by its short needles 3/4 to 1 inch in length which generally curl upward on the branchlets, (b) by the bark which in the young trees is silvery gray but in middle aged and older trees is a deep carmine-red and divided into small plates, (c) by the large cones 6 to 8 inches in length, which are borne near the tips of the trees and generally have bracts sticking from between the scales, and (d) by the altitude, the tree generally occurring between 7500 and 9500 feet elevation.
The Redwood Family (Taxodiaceae) is represented in the United States by only three species and in Yosemite National Park by a single species, the giant sequoia (Sequoia gigantea). This tree, widely famed as the oldest and largest living thing, occurs in but twenty-six groves which are all found in the middle elevations of the Sierra Nevada from the vicinity of Lake Tahoe on the north to the region about Kings River Canyon on the south. There are three groves in the park, the nearest to Yosemite being 17.2 wiles distant. The following chapter is entirely devoted to the habits and history of this most wonderful tree. In its natural habitat the tree is seldom confused with any of its associates. Among its distinguishing characteristics are (a) the massive clear trunks with their cinnamon- or chocolate-brown fibrous bark, (b) the closely overlapped leaves which are awl-like on the lower part of the tree and scale-like near the top, and (e) the brilliant brown cones which vary in length from 1 1/2 to 3 inches.
The members of the Cypress Family (Cupressaceae), in which are the many so-called American cedars, all have scale-like leaves and stringy fibrous bark. Two Yosemite trees belong to this family. The incense cedar (Libocedrus decurrens) is one of the most abundant trees in the Valley and on the talus slopes above. The vivid green of its perfectly formed crown contrasted with its fluted brown trunk make it a constant object of admiration. Chief among the distinguishing characteristics are (a) the flat sprays which are made up of scalelike leaves, the bases of which are closely adherent to the branchlets, (b) the small cones which range from 3/4 to 1 1/4 inches in length and are made up of five (apparently three) scales, and (c) the golden- or cinnamon-brown fibrous bark.
The western juniper (Juniperus occidentalis) is an inhabitant of the upper slopes and is generally found above the Valley rim on exposed rocky sites where its gnarled form picturesquely decorates the bare granite pavements. Scattered specimens may be found struggling upward in most unhospitable places almost to timberline. The characteristics which easily identify the species are (a) its gnarled form, (b) its thin, stringy, light cinnamon-brown bark, (c) its tiny scale-like leaves which are arranged in whorls of three around the branchlets and are closely pressed to the twigs, and (d) its fruit which is a small blue berry with a sweetish, pungent, aromatic taste. The berries are really modified cones.
A most interesting little evergreen is the California nutmeg (Tumion californicum), a close relative to the conifers. A few specimens may be found in the canyon of the Merced below Cascade Falls. The sharp-pointed needle-like leaves which range in length from 1 to 2 inches are flattened in two ranks along the branchlets and omit a very characteristic pungent odor when bruised. The fleshy fruits average about 1 1/2 inches in length and have a hard-shelled kernel which, when dried, looks much like the nutmeg of commerce.
The broad-leaved trees of the park are of comparatively little importance—far less so than would appear from a casual inspection of the oak-dotted floor of Yosemite Valley. These deciduous trees grow at the lower elevations and prefer the rich bottomlands and moist stream margins. The oaks are predominant. In the hot foothills is the valley white oak (Quercus lobata) which, in the region about El Portal is replaced by the Caldomia black oak (Quercus californica), gigantic specimens of which may be seen throughout the canyon of the Merced and in Yosemite Valley. The latter may be distinguished by its large leaves, the deep lobes of which are sharply pointed, and by the dark bark which is deeply checked into small plates. The talus slopes above the Valley floor are the favorite habitat of the canyon live oak (Quercus chrysolepis) which may be distinguished by its whitish bark and by its small entire and toothed leaves on the same twigs, the old leaves being lead color beneath,
Mountain Hemlocks on the rim of Matterhorn Canyon
Photo by Walter L. Huber
Another common tree of the talus slopes is the California laurel or "bay" (Umbellularia californica). The evergreen, smooth, shiny leaves have a most agreeable camphoric-pungent odor when crushed, and are dried and used for spice. The yellow flowers of early spring develop into olive-like fruits which mature in autumn.
Along the streams, especially within the Valley, are a number of moisture-loving species. Of these the tree which excites the most admiration is the flowering dogwood (Cornus nuttallii). In early spring the showy white flowers (really modified flower-bud scales) appear even before the leaves and often completely cover the crown. In autumn the clusters of bright red fruit and brilliant red, orange, and yellow foliage make it the most beautifully colored of all Yosemite trees. The broadleaf maple (Acer macrophyllum) is abundant in moist shady spots, especially in the shadow of the great south wall of the Valley and in the deep canyon of the Merced at its head. The dwarf maple (Acer glabrum) has been reported from Yosemite but is very rare. The alder (Alnus rhombifolia) is never found far from water. It may easily be identified by its rather coarsely veined, toothed leaves and by the peculiar little cones which are retained on the trees after the seeds are shed. Twelve species of willow occur within the park but all except the yellow and black willows (Salix lasiandra and S. nigra) are shrubs. The black cottonwood (Populus trichocarpa) is the largest of our poplars. It is a common tree of the moist bottomlands of middle elevations and may be distinguished by its yellowish white bark and by its thick leathery leaves which are deep shiny green above and silvery white beneath.
The little quaking aspen (Populus tremuloides) is one of the most lovable of all mountain trees. When unexpectedly found in meadows and garden spots of the High Sierra it is always an object of delight. The small delta-shaped leaves which are yellow-green above and silvery beneath are so fastened to their twigs that they tremble with the least breeze. This characteristic, together with the smooth, white bark make it impossible to confuse the tree with any other species.
The mountain mahogany (Cercocarpis parvifolius) is a small tree of the foothill region. Being generally found in the chaparral areas it enters the park only in the lower reaches of the great canyons. Specimens may be taken in the region about El Portal.
By using the Key to the Conifers presented in the Appendix of this volume one may easily identify any evergreen in the park.
Hill, C. L., 1916. Forests of Yosemite, Sequoia, and General Grand National Parks. U. S. Dept. of the Interior, 39 pp., 22 illus.
Jepson, W. L., 1909. Trees of California.
(Cunningham, Curtis & Welch, San Francisco)
228 pp., 117 figs., illus., pls.
1910. Silva of California. (University Press, Berkeley) 480 pp., 85 pls., illus.
Muir, John, 1907.
Mountains of California.
New York), 381 pp., illus.,
The Forests on pp. 139-225.
1912. The Yosemite. (Century Co., New York), 284 pp. illus., maps, The Trees on pp. 87-147.
Sargent, C. S., 1905. Manual of the Trees of North America (Houghton, Mifflin Co., New York) pp. xxiii + 826, 642 illus.
Sudworth, G. B., 1908. Forest Trees of the Pacific Slope. Dept. Agric., Div. Forestry, 441 pp., 207 figs., maps.
Next: The Giant Sequoia • Contents • Previous: Insects of Yosemite