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

54
FOREST TREES OF THE PACIFIC SLOPE.
temperature than Douglas fir or yellow pine, but probably less moisture and higher
temperature than Engelmann spruce and alpine fir. Actual climatic requirements not
fully determined.
TOLERANCE.-Very intolerant of shade, especially when young, but able to persist for
a long time (20 or 30 years) in very dense stands or for a shorter period under specially
adverse light conditions. Requires and thrives best in full light. Even aged
stands with full top light, such as commonly follow complete destruction of the former
forest by fire, thrive for many years (50 or 60) in dense stands with little natural thinning
out, while a thinning of overtopped trees at earlier periods in uneven-aged stands
is a proof of its inability to endure long-continued shade.
REPRoDUCTION.-Usui1lly a prolific annual seeder and large numbers of cones are borne.
Seed of high rate of germination, and with persistent vitality. Bears fertile seed at
from 6 to 10 years of age when in the open. In crowded stands cones are borne by trees
from 15 to 20 years old. Small, light seed widely disseminated by wind-to about 200
yards from mother trees. Squirrels and birds destroy great numbers of seeds, but the
effect on reproduction is inappreciable. Extension by natural seeding is ordinarily slow,
scant, and uneven, but with aid of fire is exceedingly thick and even. Full light and
exposed mineral soil are requisites of good reproduction. The latter eondition is produced
by fire, which, when it does not consume the cones, leaves them open or in conditlion
to open and release their seeds. Fire is thus especially Instrumental in the reproduction
of this pine.
Gray Pine; Digger Pine.
Pinus sabiniana Douglas.
DISTINGUISIHING CHARACTERISTICS.
Gray or Digger pine owes its common names to the pale blue-green color of
its foliage and to the fact that the large seeds furnish an important food to the
California Digger Indians. Its gray, thin-foliaged crown of one or two long
upright forks with lower drooping small branches distinguishes it at long dis-
tances from associated trees. The meager foliage permits the big, dark cones
to be seen half a mile away. Young trees form a rounded or pyramidal crown
of upright branches from a short, thick stem. In middle age two or more of
the upper branches grow very large and long, forming conspicuous U-shaped
forks. Old trees are from 50 to 75 feet high, with a bent or rarely straight
trunk from 20 to 30 feet long and from 18 to 30 inches in diameter. Larger
trees are sometimes found. The bark of young trees and of branches is a dull
gray; that of mature trunks is about 2 inches thick and very roughly furrowed
and ridged. The ridges are scaly, wide, irregularly connected, and of a dark
gr-ny-brown, tinged with purple-red in unweathered parts. The thin, drooping
clusters of leaves, a light blue or gray-green, occur two in a bundle (fig. 17, a),
and are from 81- to about 12 inches long. Those of a year's growth remain on
the tree for three or four years. When the tree is planted for ornament in a
rich, irrigated soil, within its natural range, the foliage becomes very much
stouter, giving the tree an entirely different aspect from one grown in its dry
native habitat; the cones of such cultivated trees are usually smaller. With
the exception of the Coulter pine, the gray pine produces the largest and heavx
lest cones of any American pine (fig. 17). They mature by Sept3mnber of the
second season, remaining firmly attached to the branches for a number of years.
The cone scales open very slowly, so that seeds continue to be shed for several
months. Indians hasten the opening of the cones by placing them in a small
fire. Cones are from 6( to 0I inecIes long. The tips of the scales are a red-
dish or chestnut brown, later weathered and grayish brown. The seeds (fig.
17) and short wings are very dark chocolate or blackish brown. Seed leaves
commonly 15, but often 1(. Wood, very coarse-grained (the result of scattered
or open stands), dark yellowish brown, often tinged with red; locally used for
fuel.