1242 
Journal of Agricultural Research 
Vol. XXVIII, No. 12 
and clear-cutting systems. Humus depth, which does not represent the average 
depth to be encountered upon the various plots, and, therefore, can not be com¬ 
pared with previous measurements, was least for the “clear-cut” seedlings, which 
averaged next to the “shelterwood” seedlings in height, and was greatest for the 
old stand. Except for the latter plot where the humus depth was 1.93 inches, 
the depths at the points where the seedlings are growing (1.30 inches upon the 
cleared areas and 1.65 inches under brush) are fairly uniform, and suggest, 
perhaps, the most favorable depth for fir survival. The average, also uniform 
difference between the depths of humus under the two methods of slash disposal, 
was 0.35 inches, with scattering naturally resulting in the deeper humus. 
The variation in ages was also fairly small, the average age of the surviving 
seedlings, or those over 3 years, ranging from 5.52 years for the shelterwood to 
5.74 years for the virgin stand. 
Spruce shows a reaction similar to fir in the shelterwood cutting, but the 
“selection” seedlings are somewhat larger than those upon the clear-cut plot. 
Average heights upon the shelterwood area were 3.26 inches with slash burning 
and 3.21 inches under scattered slash; upon the clear-cut area these heights 
were 2.13 and 2.18 inches, and upon the selection 2.78 and 1.79 inches respec¬ 
tively. If the results are correctly interpreted, slash burning has a beneficial 
effect. Spruce here again shows its preference for open conditions and shallower 
humus. The average height of this species for five-year seedlings in the original 
stand is only 0.97 inches, whereas the fir seedlings are 1.49 inches tall but a year 
older. The low average age of spruce on this plot is typical of all plots, and 
indicates, in view of the relatively large number of seedlings which start, that 
this species is being surpassed by the fir, contradictory though this may appear 
to the common idea of what is actually taking place. The difference in average 
ages upon the other plots was slightly lower than under the original stand, vary¬ 
ing from 0.4 to 0.7 years. 
Limber pine seedlings are much larger upon the shelterwood (6.60 inches under 
brush and 6.40 inches in the open) and clear-cut areas (7.63 and 6.95 inches) 
than upon the others (3.15 and 5.22 inches for the selection and 2.56 inches 
under the original forest), but show no decided preference for either method of 
slash disposal. The average age of these trees, 6| years, shows that little new 
reproduction of this species is coming in. Practically all of the reproduction 
can be traced to seed originally stored in the duff or cached by squirrels. 
This study of reproduction under the various cutting methods in Douglas fir 
stands has brought out the desirability of the shelterwood system, as particularly 
adapted to Douglas fir stands. It has not proved that slash scattering, employed 
mainly to furnish shade for the seedlings and help conserve soil moisture, has 
any decided silvicultural advantages over piling and burning of slash, save that 
it is the less expensive and therefore more desirable method. This is more or less 
a question to be decided upon the ground. The natural debris resulting from 
logging operations should ordinarily furnish all the protection the seedlings will 
need. 
The success secured in regenerating under shelterwood and to a great extent 
under selection cutting is so obvious that it is now planned to make the second 
cut on the shelterwood stand within the next two years. Periodic reproduction 
counts will no doubt be continued, to show the effect of this final cutting and 
the course of development in the other plots. 
