56 BULLETIN 1496, U. S. DEPARTMENT OF AGRICULTURE 
except that in inaccessible places, where the slash is light and the 
danger from campers, tourists, and travelers starting fires is slight, 
slash may be left scattered and unburned. The sun’s heat near the 
ground will open up enough cones to provide abundant restocking 
. of the land. 
Where jack pine is cut partially, the brush should be burned as 
the logging proceeds. 
PROBABLE YIELDS AND COSTS 
With no more than mere protection against fire young jack pine 
stands will almost certainly yield 20 cords per acre within 40 years 
over wide areas, or half a cord per acre per year. Higher yields can 
be obtained if the land is fully stocked and the young stands are 
thinned in time. The first thinning should take place at the age of 
10 to 15 years and be followed by repeated thinnings at definite inter- 
vals according to the density of the stand and character of the soil. 
Yields of fully stocked stands as they are found to-day are indicative 
of what the yields of jack pine may be over wide areas under forest 
management. Fully stocked stands yield within 40 years on the poor 
souls 16 cords of pulpwood and practically no saw logs, and on the 
good soils 35 cords of pulpwood, or 5,500 board feet Scribner decimal 
C scale and an additional 20 cords of pulpwood. In 50 years the 
yield of fully stocked stands on the poor soils is 22 cords, or 5,000 
board feet and 19 cords of pulpwood; and on the good soils, 43 cords 
of pulpwood, or 11,500 board feet and 14 cords of pulpwood. 
To obtain these higher yields from fully stocked stands, additional 
costs besides that of protection against fire will be involved, namely, 
technical supervision of cutting and slash disposal, and timely thin- 
nings. No data are available as to the cost of thinning. The expense 
of thinning 10 or 15 year old stands of jack pine should not, however 
exceed $2 or $3 per acre, while thinnings in old stands, even to-day, 
can in some parts of Minnesota be made to pay for themselves, 
* ASPEN AND PAPER-BIRCH STANDS 
PERPETUATING ASPEN 
If the object is to perpetuate aspen, clean cutting with fire protec- 
tion is all that is needed. The second-growth aspen does not generally 
depend upon seed but springs up from the roots and, therefore, clean 
cuttings over large areas are safe. At present, aspen should be cut 
to as low a diameter as the market will take. Where there is a market 
only for the larger trees, thinning the larger trees and leaving the 
smaller ones is also a safe method of cutting. 
The returns from aspen stands are comparatively low, and its 
abundance in the region does not promise large future returns from 
such a form of forestry. Aspen and birch are only locally in demand 
at the present time for excelsior, pulpwood, wood turning, box boards, 
and firewood, and, therefore, their value is low. Most of the aspen 
stands have not reached merchantable size and are not so located as 
to be readily marketable. Every timber owner of large areas of 
aspen and paper birch, unless he is primarily interested in an in- 
dustry dependent on these woods, must carefully consider the advis- 
