3) BULLETIN 1493, U. S. DEPARTMENT CF AGRICULTURE 
aes entirely to mature stands, unless otherwise specifically 
statea. 
Of the entire lumber cut of western Oregon and Washington 
(excluding cedar shingles), 82 per cent is Douglas fir. Of the 
371,000,000,000 feet of privately owned timber, at least 70 per cent 
is Douglas fir. But the timber of the entire region, though so pre- 
lominantly and characteristicaily Douglas fir, is by no means homo- 
geneous. Although Douglas fir occurs more or less on nearly every 
site, the physical differences between high and low altitudes, between 
coastal, valley, and mountain sites, are reflected in pronounced 
differences in the forest cover. 
For clarity in this discussion, it is convenient to recognize the 
several forest types which occur in the Douglas fir region. They 
are the Douglas fir type proper, the fog-belt type, and the upper- 
slope types. Most of the timber cutting is in the Douglas fir type 
proper and the fog-belt type, which together include practically all 
the privately owned timberlands. 
THE DOUGLAS FIR TYPE PROPER 
A forest in which Douglas fir (Pseudotsuga taxifolia) comprises 60 
per cent or more of the timber volume is classed as the Douglas fir 
type proper. ‘This type covers at least three-quarters of the forested 
area of western Washineton and Oregon and an even larger propor- 
tion of the area of commercial forest. Though it is spoken of as the 
Douglas fir type, western hemlock (J'suga heterophylla), western red 
cedar (Thuja plicata), Sitka spruce (Picea sitchensis), silver fir 
(Abies amabdilis), nobie fir (A. noéilis), lowland white fir (A. grandis), 
western white pine (Pinus monticola), and several other species of 
eer consequence are mingled with the Douglas fir in greater or less 
egree. 
Roughiy speaking, the wetter the site the larger the proportion of 
other species in the virgin timber. The proportion of hemiock 
imereases with altitude and with approach to the coastal fog belt. 
Aliso northward the proportion of other species than Douglas fir 
Increases with increasing humidity and coolness. 
On the other hand, in southern Oregon on the foothills of the warm 
dry valleys and on the hotter slopes in the mountains, Douglas fir ~ 
gives place to western yellow pine (Pinus ponderosa). 
Again, the proportion of Douglas fir diminishes as the age of the 
stand increases. In very old stands there is apt to be more hemlock 
and cedar than in young timber. The so-called second-growth 
stands on old burns and logged-off lands are composed to a striking 
degree of Douglas fir, and are therefore justly spoken of as pure 
Douglas fir forests. 
The younger Douglas fir forests are often referred to by lumbermen 
- as ‘“‘red fir stands,’ while the overmature forests are ealled ‘‘ yellow 
fir stands.” The siash disposal and fire problem in these two sub- 
types is quite different in intensity. 
THE FOG-BELT TYPE 
The humid western slopes of the Olympic Mountains and Coast 
Ranges, within the so-called fog belt, carry a somewhat different 
type of forest from the Douglas fir type proper. Here the principal 
