16 BULLETIN 14 9 9, U. S. DEPARTMENT OF AGRICULTURE 
In the Douglas fir type in the southern and eastern portions of 
the region satisfactory reproduction is usually obtained without diffi- 
culty on cut-over areas if fire has not occurred and if the cover and 
slope give the necessary protection from the direct rays of the sun. 
(PI. 5. A.) In this respect the young fir seedlings are very different 
from those of lodgepole pine. In fact, advance growth is generally 
present on these areas at the time of cutting, and on many sites the 
stand of immature trees is so dense that it seriously interferes with 
subsequent development. Thus a future crop is insured, the trees of 
unmerchantable size — those less than 10 inches in diameter — being 
generally sufficiently numerous to aid greatly in reducing the period 
which must elapse between cuttings. This characteristic is very im- 
portant wherever continuous production is attempted. 
On the drier sites, particularly toward the southern limits of the 
region, conditions on burned-over lands are usually less favorable 
for reproduction of Douglas fir than for lodgepole pine and aspen. 
This has resulted in many areas that originally supported stands of 
Douglas fir going over to these other types. There are. however, some 
good examples of abundant reproduction of Douglas fir coming in 
on burned-over lands, such as the tracts on the Pike Xational Forest 
in Colorado, where Christmas-tree thinnings have been made. (PI. 
5. B.) It is probable in this instance that a good seed crop occurred 
the year of the fire or directly following it, and that moisture con- 
ditions were favorable for natural reproduction. 
MEASURES NECESSARY TO KEEP FOREST LANDS 
PRODUCTIVE 
Forest lands are regarded as productive when they are so managed 
as to produce continuous crops of timber that, at intervals consistent 
with the growing time required by the principal species, are worth 
harvesting. Facts regarding growing conditions in the lodgepole 
pine region have already indicated that the forests of the three main 
types tend to remain productive if they are protected from fire. 
However, even with the assistance of this great natural advantage, 
the mere mechanical compliance with certain prescribed measures 
for the protection of the timber stands is not likely to produce re- 
sults that are fully successful. It is essential that operators and 
owners of forest property be genuinely interested in the future of 
the forest if stability of production is to be assured. 
The measures necessary to keep forest land productive in the lodge- 
pole pine region generally fall into three main categories — fire pro- 
tection, slash disposal, and method of cutting. In the lodgepole type, 
no limitation on the degree of cutting is necessary to keep the land 
productive. In the Engelmann spruce and Douglas fir stands, ad- 
vance growth, consisting of trees under 10 inches in diameter, is 
usually present at the time of cutting. As trees less than 10 inches 
in diameter are ordinarily unmarketable, other limitation than the 
normal market demand is rarely necessary. Very occasionally a 
local demand for mine props or other small material will take trees 
below 10 inches, or in some instances; trees below this diameter will 
be so few as to make the operation practically a clear cutting. In 
these exceptional circumstances from three to five trees per acre 10 
inches in diameter or larger should be left as seed trees. 
