The Timber Management Task 
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ONTANA’S commercial forest is adding 
M wood at an annual rate of 38 board feet per 
acre.’ As already pointed out, this net- 
erowth rate is not at present a limiting factor in the 
timber cut because there is an excess of mature 
timber. It is significant, however, because it is an 
unsatisfactory yield in terms of the capacity of the 
forest to produce. In the long run, as the older 
stands are cut over, the growth rate can be greatly 
increased. A realistic goal is an annual growth of 85 
board feet per acre, but to reach it involves con- 
siderably more than liquidating old stands. It will 
require both reduction of present heavy timber 
losses and conversion of the forest to a condition 
where it can produce maximum growth. 
Reduction of Losses 
In 35 years, 1910-44, mortality in Montana’s 
forests amounted to 25.6 billion board feet. Half 
of that loss was caused by insects, one-fourth by 
fires, and the rest by diseases, windthrow, suppres- 
sion, etc. The loss in those 35 years exceeded the 
cut by 26 percent. Even more startling is the fact 
that for every 100 board feet of saw timber added 
to the commercial forest by growth, 88 board fect 
died. 
Insects 
While some losses have been caused by defoli- 
ators that apparently work upon trees of all ages 
and vigor, the principal infestations of the past 
half century have been by mountain pine beetles 
that attack ripe timber. An outbreak of this beetle 
was reported on Flathead National Forest in 1909. 
During the following years the epidemic swept 
~4'-The growth and drain comparisons in this section are 
mainly confined to saw timber to avoid confusion. However, 
the story is in general the same for all timber. Growth and 
drain data for both saw timber and all timber are in the 
appendix tables, p. 63. 
a 
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southward, causing havoc in timber stands until 
1933 when it subsided. As the result, insect losses 
from 1910 to 1944, inclusive, mounted to 12.8 bil- 
lion board feet. Most of the timber killed was 
lodgepole pine, but much ponderosa pine was also 
lost. 
In those areas heaviest hit by insect epidemics, 
For example, the 
beetles killed 85 percent of the mature lodgepole 
pine in Ravalli County, causing destruction which 
in places was almost as complete as if those areas 
had been swept by fire. It is estimated that 25 per- 
cent of the ponderosa pine saw timber in that 
county was also killed. Although the lodgepole 
pine thus lost had no high commercial value, the 
resulting jungles of fallen trees have been a fire 
hazard and have rendered some areas unsuitable 
for grazing. Even more serious, from the stand- 
point of commercial value is the loss of the large 
the effect was catastrophic. 
volume ol ponderosa pine. 
In addition to the losses caused by the mountain 
pine beetle, many other insects have been respon- 
sible for a constant, heavy drain on all timber 
specics. While these losses are not as spectacular 
as the epidemic ones, they are widespread and have 
already killed many million feet of timber. 
Figure 34 shows the trend of insect losses in 
During the period 
1921-30, bug-infested timber was dying at the rate 
Montana for four decades. 
of 500 million board feet a year. During the period 
194144, the annual mortality declined to 200 mil- 
lion board feet, but the rate of loss 1s believed to 
have risen since then. Unlike fire losses, the down- 
ward trend of damages by insects after 1931 was in 
no way the result of man’s efforts. It was due to the 
natural cycle of insect attacks. Up to July 1, 1950, 
a total of only $570,000 had been spent to combat 
insects in Montana. Twice that amount is spent 
for fire control in a single year. 
Timber stands are not static. If man does not 
12 Forest Resource Report No. 5 U. §. Department of Agriculture 
