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

'14
INTRODUCTION.
This is brieflv recorded for the benefit of those who desire just this
information. But for the benefit of very many more it has seemed
proper to include also a brief detailed description of the local range,
vertical and horizontal, by States, Territory, and other geographical
subdivisions in the region occupied by the species or subspecies. The
fullest information possible has been given for commercial trees.
A very much more definite knowledge is greatly and generally
needed of the local distribution of our trees. Extreme extensions or
outlying stations for each tree require to be recorded. No observers
have done more along this line than authors of State and county
floras, by whom actual limits of range have been carefully worked
out for the trees and other plants of their special localities. There
are too few of these painstaking workers, and their work can not be
too highly praised. The writer wishes to emphasize the fact also that
the numerous unpublished silvical, National Forest boundary, and
other field reports by members of the Forest Service, as well as
special field reports by members of the IU. S. Geological Survey and
the Biological Survey, have proved rich sources of new information
on the local and general range of Pacific trees. Through these sources
the distribution of some trees has been extended hundreds of miles
beyond previously recorded limits. Finally, it is hoped that by giving,
in detail, what is now known the many observers and lovers of
trees who are scattered throughout this region will be stimulated to
make further contributions. Much is yet to be learned of where the
trees of this region grow.
OCCURRENCE OF TREES.
Closely connected with a study of the areal and altitudinal range
of trees is the equally important determination of where, in their
respective ranges, this or that species lives-by necessity or by virtue
of special fitness. Like animals. trees have what may be termed a
more or less definite habitat, defined by such physical conditions as
soil, moisture, topography, and, to a greater or less extent, temperature.
The likes and dislikes, as it were, of one species are. of course,
shared by a number of others, so that several species may have their
habitat in wet, in moist, or in dry situations; while different individuals
of the same species may accommodate themselves to all of
these situations.
It would lead too far, for present purposes, to discuss, even briefly,
the factors upon which the adaptation of trees to environment appear
to depend. The effects of mutual likes and dislikes upon species
are to be seen in the occurrence of certain trees in pure stands only
and the occurrence of others with different kinds of trees or with
different species of the same kind.