ning operations can be realized economically only 
in extraordinary cases. They are dependent upon 
standards of utilization much more intensive than 
the prevailing average, and at present possible 
only on a few of the most accessible operations near 
adequate pulpwood, piling, or fuel-wood markets. 
The extent to which yield can be increased when 
opportunity is afforded for thinnings varies with 
utilization standard or type of product, as well as 
with site quality and with age and density of stands. 
Analysis of the normal mortality rates of Douglas- 
fir stands reveals that ultimately increase in yield 
resulting from thinnings may approximate one- 
third of the cubic-foot yields shown in the pub- 
lished tables. 
Tf Selective Cutting Is Widely Employed 
A revolution in logging methods is now taking 
place the The steam- 
donkey, high-lead method, which is associated 
in Douglas-fir region. 
with clear cutting, is giving way to the crawler- 
tractor method, which facilitates selection in cut- 
ting. If selective cutting came into practice on a 
wide scale as a result of this change in logging pro- 
cedure, the total increment in succeeding stands 
would probably be somewhat different from that 
assumed in this discussion, which applies specifi- 
cally to the even-aged second-growth stands that 
develop after clear cutting. Whether the incre- 
ment of a given forest would be greater or less, or of 
improved quality, and whether the species compo- 
sition would be altered, would depend largely on 
what kind of selective cutting was practiced. 
Changes in prospective growth that might be 
brought about by substitution of different kinds of 
selective cutting for clear cutting are as follows: 
AREA-SELECTION CUTTING 
If the selective cutting were predominantly in 
the nature of area selection, no material change in 
potential growth would be effected. In the long 
run, the growth on a series of patches clear cut in 
an operation of this sort would be about the same 
as that on a continuous clear-cut area of the same 
acreage. 
ply, almost always assured under this system, 
The proximity of an adequate seed sup- 
would favor prompt, denser, and more uniform 
regeneration. 
64 
ZERO-MARGIN CUTTING OR “CREAMING” 
If the selective cutting were predominantly zero- 
margin cutting, which takes all the trees of positive 
value and leaves the trees of minus value, the re- 
sults of the change would probably vary widely. 
In some stands, such as the decadent even-aged 
Douglas-fir occurring on much of the privately 
owned forest land, such cuttings would frequently 
leave only defective and malformed trees, or sup- 
pressed trees of inferior species, which might pro- 
duce little or no net growth and would be likely to 
cast too much shade to permit establishment of 
reproduction of desirable species; in this case less 
usable increment would become available than 
In 
other kinds of stands—for example, certain two- 
following clear cutting and full restocking. 
story stands—zero-margin selection would remove 
only scattered veterans and leave well-stocked, 
thrifty stands; in such cases, growing stock that 
would otherwise have been wasted would be pre- 
served and many years’ growth would be saved. 
In the many kinds of stands intermediate between 
these two, substitution of zero-margin selection 
would probably have widely varying effects on 
growth, 
LIGHT, FREQUENT CUTTING 
If the selective cutting prevailingly took the form 
of light cuts made at relatively short intervals and 
leaving well-distributed stands of thrifty trees— 
such cutting as is consistent with continuous forest 
management and is now being practiced experi- 
mentally in certain forest types—the reserve stand 
could be expected to produce a mean annual 
volume increment comparable in amount and 
greatly superior in quality to that of a normal 
forest composed of even-aged stands. To the ex- 
tent, therefore, that this was done, selective cutting 
could be expected to result in greater realizable 
growth, particularly board-foot growth, over the 
whole forest area in the succeeding few decades 
than the method assumed in this report. 
SECONDARY CONSIDERATIONS 
Under selective cutting the fire hazard might be 
considerably different from what it is under clear 
cutting. If the selective cutting were light it might 
make possible better fire control: if heavy, it might 
