ATLAS OF AMERICAN AGRICULTURE. 
Figure 12.—Pacific Douglas fir forest. (Cedar-hemlock.) Western hemlock is shown in the photo¬ 
graph, entering as an understory. As a result of fires, the Douglas fir starts in pure stands. The hemlock 
begins to come in only after the ground is shaded and duff is accumulated on the ground. If left to itself 
the forest would gradually revert to hemlock. The present uniform Douglas fir stands are due to the large 
forest conflagrations of the past. Oregon. Photographed by F. G. Plummer. 
common traits and gravitate toward the same ultimate 
forest—the western red cedar and hemlock (Thuja pH- 
cata and Tsuga heterophylla). 
Western white pine-western larch (fig. 11).—This 
region is confined chiefly to northern Idaho and adja¬ 
cent portions of Montana and Washington. In the 
Coeur d’Alene Mountains, the Cabinet Mountains, the 
western spurs of the Bitterroots, and the south end of 
the Selkirks in Idaho, extreme western Montana, and 
extreme northeastern Washington, the western white- 
pine forests predominate. Pure stands are not com¬ 
mon. Occasionally, as the result of the accident of 
seeding or because it is an especially favorable site, 
western white pine ( Pinus monticola ) will form 80 to 
95 per cent of the stand. Altitudinally, 4,500 feet may 
be assumed as the upper limit for western white-pine 
forests. 
The western red cedar, the western hemlock, and the 
lowland white fir form usually an undergrowth in a 
white-pine forest. The cedar and hemlock commonly 
predominate on the more moist sites and lowland white 
and alpine firs on the drier. In some forests toward the 
upper limit of western white pine, especially in north¬ 
western Montana, hemlock, lowland white fir, and cedar 
are scarce or absent, and Engelmann spruce forms the 
ultimate type. A study of the life history of these 
stands has shown that often after a severe burn the first 
tree to occupy the ground suitable to western white pine 
is the western larch (Larix occidentalism , which comes 
in as the pioneer tree, shades the ground, and thus af¬ 
fords the protection necessary for the western white 
pine to establish itself. The western white pine, soon 
after it becomes established under the shade of the 
larch, begins to crowd the latter, overtops it, and grad¬ 
ually exterminates all but the most vigorous specimens. 
Under the shade of the western white pine, larch, and 
red cedar, hemlock and lowland white fir (Abies 
grandis ) begin to come up, and these eventually crowd 
out the white pine and become practically the sole occu¬ 
pants of the ground. Stages in this development can 
be found throughout the western white-pine region. 
An average annual precipitation of about 30 inches 
is characteristic of the western white pine region as a 
whole. The bulk of the precipitation throughout the 
western white-pine region comes during the autumn, 
winter, and spring. The summer is relatively dry. 
Within the western white-pine region the days when the 
humidity is less than 20 per cent are very few, the av¬ 
erage humidity for the dry summer season usually 
Figure 13.—Engelmann spruce forest (Spruce-fir). The principal forest of high altitudes in the Rockies 
above lodgepole pine or Douglas fir forests. In the Cascades and Sierras true firs take its place, similar 
to the spruce-fir of the Northeast (see fig. 15.). Uinta Mountains, Utah. Photographed by Edw. J. 
Ludkin. 
ranging from 30 per cent in the drier regions to 60 
per cent or more in the more moist. The mean annual 
temperature varies from 41° to 51° F., and the mean 
July and August temperatures from 50° to 68° F. 
The Pacific Coast Douglas fir (fig. 12).—This region 
is marked by a number of distinct forest types which 
also gravitate toward a western red cedar-hemlock 
forest. Thus on low, moderately humid slopes, from 
Figure 14.—Redwood forest. (Cedar-hemlock.) Limited to the 
coast region of California and Oregon; fast disappearing; occupies 
some potentially agricultural land. Bullcreek Flat, Dyerville, Calif. 
Photographed by R. T. Fisher. 
sea level to 3,000 feet, there are found large stretches 
of pure Douglas fir. On exactly similar areas there 
occur mixed stands of Douglas fir-hemlock-cedar which 
are a further stage in the development of the pure 
Douglas fir. If it were not for the periodical occur¬ 
rence of fires, the pure Douglas fir stands would give 
way to a forest in which western red cedar and hem¬ 
lock would be the principal species. Both the western 
white-pine region and the Douglas fir region, although 
they have different starting points, in their ultimate de¬ 
velopment tend to become one type of forest and there¬ 
fore biologically form virtually one large unit. 
The Pacific Douglas fir region includes the forests of 
western Oregon and Washington, and occupies about 
54,000 square miles. Up to date there have been utilized 
from this region nearly 135 billion feet of lumber, 
cut from something like 4 million acres. Of the total 
land area, most of which is in forest, 60 per cent of 
that in the State of Washington is capable of agricul¬ 
ture or grazing, while in Oregon one-third may be 
classed as tillable land. The climate is generally mild 
and uniform, with frequent fogs and gradual and mod¬ 
erate changes in temperature. The summers are cool 
and the winters mild, with an interval of six or seven 
months between killing frosts. 
The so-called Sitka or Alaska spruce belt belongs also 
to the cedar-hemlock forest region. It occurs in coastal 
valleys and benches and is associated with western hem¬ 
lock, western red cedar, and Douglas fir. 
Within the cedar-hemlock area agricultural develop¬ 
ment is limited largely to the lower and more level lands 
in western Washington and Oregon, where a portion of 
the cedar and hemlock forests have been cut away or 
destroyed and the land cleared for agriculture. Oats, 
wheat, hay, and other forage crops are grown with suc¬ 
cess within this area. It is also productive of grain 
crops cut for hay, of clover, and miscellaneous tame 
grasses, of potatoes, cabbages, onions, and other vege¬ 
tables, and of fruit. A large proportion of the hops 
grown in the United States are from this section. 
Spruce-Fir Forest. (Fig. 13 .) 
The high altitude forests, whether of the Rocky 
Mountains, Cascades, Arizona, or the Sierras, have a 
similar biological physiognomy peculiar to spruce and 
alpine fir and may be grouped into one big unit. In 
the central Rockies, at elevations of from 7,500 feet 
to timber line (11,000 to 11,500 feet), the predominant 
stands of this forest are Engelmann spruce-alpine fir. 
In the mountains of Arizona, at elevations of from 
10,000 to 11,500 feet, they are largely Engelmann 
spruce mixed with bristle-cone pine (Pinus aristata) 
and cork-bark fir (Abies arizonica ). On the west slope 
of the Cascades, at moderate elevations, on all aspects, 
and at altitudes of from 3,000 to 4,500 feet, this type of 
forest consists largely of the true firs, noble fir (Abies 
nobilis) and red fir (Abies magnifioa). In some places, 
