4 BULLETIN 1200, U. S. DEPARTMENT OF AGRICULTURE 
always checked and sometimes inhibited by exposure to severe winds. 
For this reason it is not found near the open sea in exposed localities, 
although it occurs near by in sheltered inlets where protection is | 
afforded. | 
In eastern Oregon and Washington the Douglas fir either forms 
a mixed stand with species which usually occur on drier sites, sueh 
as western yellow pine (Pinus ponderosa Laws.) and lodgepole pine | 
(P. contorta Loud.), or it is found on moist slopes in mixture with 
species that require more moisture, such as western larch (Larix 
occidentalis Nutt.), white fir (Abies concolor Lindl. & Gord.) and | 
western hemlock. In either situation it produces inferior trees as 
compared with those produced in the western sections. This condi- | 
tion is readily explained by the limited precipitation during the 
P orine season, the shorter growing season, and cther climatic 
actors. 3 
In southwestern Oregon‘ the Douglas-fir forest meets the western 
yellow pine, knobcone pine (Pinus attenuata Lemm.), and other 
species, and forms what may be called the border type, which is 
typical of the region. Deuglas fir covers the north slepes, and 
western yellow pine the south slopes, and many variations of these 
types also occur. 
CLIMATE AND SITE. 
Before proceeding to the main discussion of natural regeneration, 
it is desirable to consider briefly some of the climatic and site re- 
quirements of Douglas fir and its habits of seeding, because it is in 
these peculiarities that the solution of the problem les. These cub- 
jects are discussed in the next two chapters. 
LIGHT. 
The western white pine (P2nus monticola Doug].) is the only tree 
of the Pacific Northwest that requires more light than Douglas fir. 
The Douglas fir will grow in about one-fourth of the full ight in 
adjoining open areas, although under these conditions its develop- 
ment is retarded, and the more shade-enduring species, such as west- 
ern red cedar, western hemlock, and Sitka spruce (Picea sitchensis 
(Bong.) Traut & Mayer) have the advantage. 
The inability of Douglas fir to thrive in diffused light makes it in- 
capable of forming an understory. This characteristic is a disad- 
vantage to the tree in retaining its position in the forest, for the 
more shade-enduring species crowd out the Douglas fir and often 
completely replace it in the stand; but it is an advantage from a com- 
mercial standpoint, for this inability to withstand shade results in 
early pruning of the branches, so that a comparatively clear, straight 
bole is produced early in the development of the tree. On favorable 
sites, where the stands are dense, clear boles begin to form at 30 to 
40 years of age, and at 40 to 50 years of age clear boles as high as 
40 feet are often found. These characteristics illustrate the im- 
portance of a complete stand of young growth and the advantages’ 
of an even-aged stand. The relatively greater height growth of 
This region, bounded on-the west by the towns of Riddle, West Fork, Galice, and 
Mountain Ranch, on the north by the Umpqua River, and on the east by the Cascade ; 
Mountains, is referred to hereafter as southwestern Oregon. 
