RESULTS OF CUTTING IN THE SIERRA FORESTS. 21 
The method of brush disposal practiced has a very important in- 
fluence on advance growth. Where piling and burning is done the 
area covered by the piles, even with careful burning under ideal 
conditions, is considerable. On the 24-acre Plumas plot in the mixed 
coniferous type, yellow pine predominating, from which a cut of 
13,480 board feet per acre was removed, the number of piles per 
acre was 24 and the percentage of the area covered by closely con- 
fined brush-burning fires was 6.7. On a more recent sale area of 
the Lassen National Forest, pure yellow pine type, from which an 
average of 17,500 board feet per acre was cut, the number of piles 
indicated by a strip cruise was 20 per acre, which covered 6.2 per 
cent of the area before burning and 9.2 per cent after burning. A 
more extensive airplane photographic survey of the same sale area 
gave an average of approximately 15 piles per acre, or 6.7 per 
cent covered by fire. This was with careful burning under 
favorable conditions. The period during which satisfactory brush 
burning can be done is usually short, and frequently fires spread 
much more than indicated above. On the eight Feather River plots, 
where the average cut was 34,770 board feet per acre, brush-burning 
fires covered 8 to 17 per cent of the area. With careful supervision 
piles can be placed away from reproduction, so that the area burned 
does not necessarily mean proportionate destruction of advance 
growth. The areas covered by the fires are rendered unfavorable to 
establishment of seedlings for several years. Formerly practically 
all piles were burned, regardless of proximity to advance growth, 
but it is customary now to leave 10 to 20 per cent of the piles where 
their location close to clumps of seedlings is unavoidable. Careless 
piling and burning may result in great damage, particularly with 
donkey logging, where the seedlings which escape yarding are left 
in narrow sectors between the skidding trails radiating out from the 
lead block. Slash and other debris is likewise pushed aside into 
these same sectors by incoming logs. If the brush pilers merely heap 
the trash up where it is found, burning may easily destroy what 
reproduction escapes logging. 
The piling and burning method of brush disposal was adopted 
because of the extreme difficulty of controlling slash fires, the un- 
certainty as to the effect of slash on increasing insect depredations, 
and the belief that in most cases new reproduction could be secured 
easily. We have long realized that the most abundant and thriftiest 
young growth in this region is found in areas where abundant ad- 
vance growth was fully released by a heavy cutting, no slash disposal 
was practiced, and the area accidentally escaped fire, rather than on 
areas where new reproduction was established after cutting. Ex- 
perience has shown that there is slight danger of the spread of bark 
beetles due to slash. (This is true" at least, of Dendroctonus, al- 
though the less destructive Ips may spread under certain condi- 
tions.) The expense is a serious factor. There remains, then, only 
the reduced fire hazard to justify the method. The Forest Service 
has hesitated to change its method until it is certain of the results 
or can find a more effective substitute. Modified methods whereby 
slash is cleared from control lines separating the areas into natural 
protection units are now being tried out on a large scale, with the 
hope that, combined with more intensive fire protection, they will 
give better results at less cost. 
