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

FOREST TREES OF THE PACIFIC SLOPE.
pine, lodgepole pines, white and red firs, sugar pine, and incense cedar; in south, associates
with bigeone spruce, white fir, incense cedar, western juniper, and Coulter, sugar,
limber, western white, and lodgepole pines, the last three near its upper limits.
CLIMATIC CONDITIoNs.-Endures wide annual ranges of temperature, but lowest and
highest in regions of best growth are about zero and 1000 F. Mean annual rainfall of
greater part of range varies from 20 to over 60 inches, with an average of about 35 inches
where best growth occurs. Requirements of atmospheric moisture less than for white fir
and sugar pine, but greater than for Coulter pine, western yellow pine, and incense cedar.
ToLEaANcE.-Fairly tolerant in youth, ranking between yellow and sugar pines and
permitting its seedlings and low trees to persist under shade of chaparral on east and
south exposures ; in later life, as tolerant of light as western yellow pine.
REPRoDrcTION.-Prolific seeder. Seed years rather irregular, but seeds locally in range
nearly every year. Seed of high germination (50 or 60 per cent) and persistent vitality.
Produces seed only at rather advanced age, becoming less productive In old age. The
heaviness of its seeds confines reproduction chiefly to neighborhood of seed trees. Range
of reproduction Increased as seed trees stand on slopes, down which seed is washed or
blown. Birds and rodents eat large numbers of seeds and assist some in dissemination.
Ras vigorous reproduction at higher altitudes than has western yellow pine Exposed
mineral soil is the best seed-bed. Germination not prevented by moderate shade.
Lodgepole Pine.
Pinus contorta Loudon.
DISTINGUISHING CHARACTERISTICS.
The pine described under this name is one of the most interesting of Pacific
species on account of its variable characters and on account of its enormously
wide range, which extends from sea level to nearly 11,000 feet elevation. For
many years a fruitless effort has been made to keep the tree which inhabits the
northern Pacific coast region, extending to Alaska and eastward over the
western Cascades, and known as Pinus contorta, distinct from the tree of the
high Sierras and Rocky Mountains plateaus, known as lodgepole pine (Pinus
murrayana and P. contorta murrayana). The distinctions assembled to separate
these trees are one after another broken down when the trees are carefully
studied thoughout their great range. Differences in thickness of bark, size of
cones and leaves, or size and form of the tree, are not too great to be
consistently merged in one polymorphous species, as it is proposed to do here.
The reproductive organs of these supposedly distinct- trees are essentially the
same. With no characters found in these organs to warrant a distinction of
species, the other so-called distinctions depended upon are believed to be unworthy
of serious consideration. Perhaps no other North American trees have
given so much trouble, or left so much uncertainty in the minds of those who
have attempted to hold them separate. Recent students of trees have been slow
to depart from the time-honored judgment of earlier writers. It is confidently
believed, however, that those writers would have taken the broader view had
they been able to study the trees as they grow in all their retreats.
In its Pacific habitat this pine is a low tree with a dense rounded or pyramidal
crown, the large, much-forked branches often extending down to the ground.
This form is the result of an open stand, which permits other pines to produce
a similar form. In very close stands it develops a tall, clean, slender shaft
with a short, rounded, small-branched crown. This is its characteristic form
in its more eastern range, and has there given the name of " lodgepole pine."
The trunk bark of the Pacific coast form is about an inch thick over the lower
half or third of the stem; it is a deep purplish red-brown and has deep, rough
furrows and ridges which are sharply cross-checked; young poles and the crown
branches and stems of old trees have thin, smooth, fine scaly, pale brown bark,
with a grayish tinge. Bark of the latter character is borne mainly by trees
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