RESULTS OF CUTTING IN THE SIERRA FORESTS. 23 
heavier cutting than took place on most of these sale areas would 
have favored the pines in the small amount of reproduction which 
actually did come in, because both shade and litter may be so heavy 
as to exclude sugar and yellow pines where incense cedar and white 
fir come in abundantly. 
Another reason for this failure to secure the expected change in 
composition was that early markers did not give sufficient considera- 
tion to the natural succession of tree species. "Where natural con- 
ditions of site favor white fir, which is generally true of Sites I and 
II on north and east slopes, this species is destined to succeed yellow 
pine unless the normal succession is disturbed by fire or other acci- 
dents. Fir seeds more abundantly than pine germinate under 
stands of yellow pine, whose litter and shade exclude their own 
seedlings, and the young trees endure suppression longer. More- 
over, height growth of fir is more rapid, and the total height 
attained is greater than for yellow pine. In the past occasional 
fires have been primarily responsible for sustaining yellow pine on 
fir sites. Fir seedlings and young trees are far more susceptible to 
fire damage than the pine because of their thinner bark with balsam 
cysts, more inflammable foliage, and small resinous terminal buds 
which are far less resistant than those of yellow pine. The fir is 
more often eliminated by fungi entering through fire scars than is 
pine. Exposure of mineral soil and openings created by fire favor 
yellow pine. .Striking examples of the succession of white fir with 
fire exclusion may be seen in many places, notably on the Lassen 
National Forest, where the mature stand is composed of practically 
pure yellow pine, while the reproduction beneath it is over 90 per 
cent white fir. 
Although incense cedar reproduces abundantly under the same 
conditions as white fir and is equally or more tolerant, its slow height 
growth prevents it from becoming anything but a secondary species 
in the final stands. 
Leaving out of consideration, for the present, the possibility of 
using fire to maintain pine in the stands as inefficient and wasteful 
if practicable at all, there remain open only two courses — fir must 
be accepted on fir sites or planting of other species must be resorted 
to. The first course is the only one regarded as feasible at present, 
and from what has been said about growth and the trend of market 
conditions for possible fir products, it is not at all discouraging. 
Under certain conditions, not uncommon, planting may be not only 
the logical but the most economical method, in the long run, for the 
Government. On Sites I and II, where rotations would be less than 
75 years, planting would result in a yield of 50,000 board feet or 
more per acre of desirable species. VvHiere advance reproduction is 
deficient and young trees for reserves are few, clear cutting could 
be practiced, permitting logging to proceed as cheaply as possible. 
destroying inferior trees and brush, and concentrating slash in piles 
and rows, thus obviating expensive brush disposal. Areas treated 
in this way could be planted successfully for Si 5 per acre. 
Present methods of securing natural reproduction on the national 
forests involve leaving at least 5 seed trees, averaging '20 inches in 
diameter, per acre, an investment of about $8. The interest on this 
amount is chargeable to the final crop, provided the trees themselves 
