De I. VNER VEW D Forest Trees of the Pacific Slope

FOREST TREES OF THE PACIFIC SLOPE. 81
Grows fairly on dry soils, but usually gives way on porous soils to lodgepole pine, Douglas
fir, and to other trees requiring better drainage. Does well on retentive, fine, loamy soils,
but attains best growth on deep, rich soils of gulches and river valleys. A shallow rootsystem
enables it to grow on thin soils of slopes and on wet margins of rivers, lakes,
and swamps. Forms extensive pure forests and also occurs in mixed stands. Pure stands
are somewhat more frequent in south than in north, where it chiefly meets trees of similar
silvical requirements but of less extended southern range. Most generally with
alpine fir and sparingly with Douglas fir near its lower limits. In Blue Mountains of
Washington and Oregon, with western larch, lodgepole pine, alpine and lowland firs, and
Douglas fir. In Washington, occasionally In pure stands, but usually with amabilis fir,
alpine fir, Lyall larch, black hemlock, yellow cedar, and white-bark pine. In Cascades of
Oregon, with alpine, noble, and amabilis firs, Douglas fir, black hemlock, and lodgepole
pine.
CLIMATIC CONDITIONs.-Subject to varied climatic conditions. Annual precipitation
averages over 25 inches; is largely snow. Seasonal temperature, with a minimum in
north of approximately 40° F., and maximum of about 950 F. in south. Daily range of
temperature great at upper levels, but less at lower altitudes and on north exposures.
Near timber line the growing season is about two months, and freezing occurs almost
nightly, resulting in very slow growth; while at lower elevations the growing season is
about four months and frosts are less frequent, permitting a more rapid growth.
TOLERANCE.-Very tolerant of shade, surpassing most of its associates in this respect;
endures years of shading and makes good growth when released from suppression. Owing
to great tolerance, it forms close stands of many ages and preserves good forest conditions.
Somewhat more tolerant in youth than in old age.
REPRoDUCTIox -A prolific seeder over most of range. Heavy seed years occur locally
at 3-year intervals. Seed with high rate of germination and persistent vitality. Produces
seeds from about txventy-fifth year to an advanced age. Seeds germinate best in moist
mineral soil ; seedlings rarely found in humus. Notwithstanding prolific seed production,
seedlings are not generally abundant. They are most numerous in small protected
openings in the forest. Low branches of isolated trees also favor germination and
protect seedlings, through which groups of trees are built up, and which combine with
other groups to form continuous stands.
Sitka Spruce; Tideland Spruce.
Picea sitchensis (Bong.) Trautvetter and Mayer.
DISTINGUISHING CHARACTERISTICS.
Sitka spruce growing in dense stands is tall, and has short thin open conical
crowns of small branches and long clean trunks of only moderate taper. In
open stands, or as it occurs singly, it develops a shorter, but still tall, rapidly
tapering stem with branches down to or near the ground. The crown is still
open, narrow and sharp in its upper part, but very broad at the bottom, where
the huge branches are often 20 or 30 feet long. The branches have many hanging
slender side branchlets from 1f to 31 feet long. It is a very large and
massive tree when fully grown, attaining a height, exceptionally, of from 160 to
180 feet, with a diameter of from 8 to 12 feet, 5 or 6 feet above ground. Still
larger trees are reported. Ordinarily it is from 80 to 125 feet high and from
40 to 70 inches in diameter. Forest-grown trees are clear of branches for from
40 to 80 feet, or more. The bases of big trunks are swelled by enormous buttresses.
The bark is scaly on very young trees; on large trees it is thin (onehalf
inch thick), is dark purple or deep reddish brown, and has big thin, easily
detached scales. Twigs of the year are always smooth and dark yellow-brown.
The foliage is a bright yellow-green. The bristling habit of the often keenlypointed
leaves, which stand out straight all around the branches (fig. 30), render
it prickly to the touch. The leaves are flat, only very indistinctly 4-angled,
stiff, and rather thick. The cones mature in one season, and hang down conspicuously
from the branches. They vary in length from about 2 to 4 inches
(fig. 30). Soon after maturity, during early fall, their thin papery scales open
and shed their small seeds (fig. 30, a) in a short time. Most of the cones fall