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

FOREST TREES OF THE PACIFIC SLOPE.
to Bear Lake. In timbered portions of San Jacinto Mountains, generally at elevations
of 5,800 to 9,000 feet, sometimes descending to 5,000 and ascending to 9,800 feet; common
on westside trail at 6,000 feet, and also on southwest side of Tahquitz-Strawberry
Divide. In Cuyamaca Mountains, at from 5,500 feet, on east side Cuyamaca Peak, to
6,500 feet on summit.
LOWER CALIFORNIA.-Frequent in forests of San Pedro Martir Plateau at elevations
from 8,000 to 10,000 feet.
OCCURRENCE.
Chiefly on north slopes and benches and in ravines and canyons; occasionally on low
mountain summits; found also on south and west slopes at higher altitudes. Grows on
variety of soils from glacial drift and volcanic ash to deep, loose sands and clays; fresh,
rich, well-drained, sandy loam or gravelly soils are most characteristic.
Never in pure stands. At lower elevations, mainly with western yellow pine. incense
cedar, Kellogg oak, and, in northern California, also with Douglas fir; occasionally with
tanbark oak. At high elevations yellow pine and incense cedar decrease, and white fir,
and occasionally red fir, together with the big tree, become chief associates, especially on
east and north slopes.
CLIMATIC CONDITIONs.-Atmospheric moisture is essential ; hence it prefers cool, moist
sites on north and east slopes and in heads of gulches and canyons. Doubtless on account
of this requirement its altitudinal range of 1,000 to 3,000 feet at the north increases,
going southward, roughly at the rate of about 500 feet to every 200 miles, until, at its
southern limit, 9,000 feet is reached.
TOLERANCE.-In early youth requires partial shade, especially on dry, south slopes;
when older it becomes very intolerant, even more intolerant than western yellow pine.
REPRODUCTION.--Not a regular or prolific seeder. A little seed is produced locally each
year, but good crops occur locally at intervals of abort from four to six years; regularity
in seed years doubtful. Trees below 20 inches in diameter seldom bear seed to any extent.
Ordinarily trees shed seed over ground for a distance from base of tree about equal to
their height; distribution occasionally farther through increased wind, slope, or water.
Limber Pine.
Pinus flexilis James.
DISTINGUISHING CHARACTERISTICS.
Comparatively little known, doubtless on account of its high, inaccessible
range. It is a low, thick-trunked, much-branched tree, from 25 to 30 or sometimes
50 feet in height, with short trunk from 12 to 30 inches in diameter;
occasionally very old trees are 34 to 4 feet in diameter. Young trees are
peculiar for their regular, distant whorls of short, very tough branches which
stand at right angles to the trunk and extend down to the ground. Middle-aged
and old trees (75 to 200 years) are characterized by extremely long and
slender branches, especially near the ground and at the top; the latter are
often 16 or 1S feet in length, falling gracefully at a sharp angle with the trunk.
These branches appear to develop entirely at the expense of the trunk, which
remains stunted. Old trunks have bark from 14 to nearly 2 inches thick,
blackish or very dark brown, with deep furrows between wide rectangular
blocks. On trunks from 8 to 12 inches thick the bark is broken into small, thin,
gray-brown plates; when separated, the scales expose a dull reddish inner bark.
The thin, smooth bark of young pole trees and of branches is a bright whitish
gray, often silvery. The foliage, densely set at the ends of the branches, is
dark yellow-green, and the needles are 5 in a cluster (fig. 5). They are from
about 14 to nearly 3 inches long. Each year's growth of leaves persists for
approximately five years. Cones (fig. 6), mature in late summer or early
autulmn of the second year, shed their seed in September and early in October.
They are from 34 to 10 inches long and peculiar in having their light yellowishbrown
scale tips greatly thickened; inner portions of scales, pale red,
27