June 14,1924 
Growth, on YeUow Pine Lands in Idaho 
1141 
Like the bulk of virgin western yellow pine forests, the uncut stands are made 
up mostly of mature or overmature even-aged groups. Some immature groups 
have, however, become established in the openings in the forest cover caused 
by the death of old trees. Each of the plots is 5 acres in extent, with the excep¬ 
tion of plot No. 16, which covers 20 acres. Plots Nos. 4 to 15 are located on 
Big Pine Creek, at an altitude of 4,000 to 4,500 feet. Plots Nos. 1 to 3 are on 
Carpentier Creek, at an elevation of approximately 3,700 feet, while plot No. 
16 is located on Poorman Creek, at about the same altitude as plots Nos. 1 to 3. 
All of these plots are in pure stands of western yellow pine. Of tho uncut plots, 
Nos. 4, 5, 6, and 7 are on ridge tops and south aspects where western yellow pine 
occurs in practically pure stands. Plots Nos. 8, 9, 10, and 11 are in basins and 
coves where both species are found in mixture, but with western yellow pine 
still in the ascendency, while plots Nos. 12, 13, 14, and 15 are located on north 
aspects, with Douglas fir (Pseudotsuga taxifolia) predominating, but with an 
admixture of yellow pine. 
The conditions in the cut and uncut plots as to vigor, mortality, and growth 
during the five-year period will be brought out in summarizing the results of 
remeasurement. 
INCREASE IN NUMBER OF TREES 
The stocking on the cut-over plots is conspicuously incomplete, while the 
characteristic occurrence of western yellow pine in groups gives an appearance of 
still greater inadequacy. There are indeed many small saplings on the ground, 
established before the cutting took place, but these have not yet had time to 
grow into the 4-inch class, and so did not appear in the records used in this 
study. The cut-over plots show a somewhat greater increase in number of trees 
than the virgin plots; an average increase of 4.2 trees an acre during the five- 
year period as compared with an average increase of 2.5 trees on the uncut 
plots (see Table I). This difference will in all probability become more pro¬ 
nounced in the course of the next decade or two. It can reasonably be expected 
that there will be comparatively little loss due to disease and overmaturity in 
cut-over areas if all defective trees and those of poor vigor be removed at the 
time of cutting. 
INCREASE IN VOLUME 
Table II is a summarized statement of the increment on the sample plots 
during the five-year period. In order to show the actual amount of new wood 
added each year by growth, the gross increment is also given. Since loss of 
volume through death of trees can not be avoided under present economic con¬ 
ditions, which render impracticable a return in less than 40 years and possibly 
longer, it is plain that the figures on net growth, indicating the actual gain or 
loss in volume, are at present the more significant. It is important to note that 
without cutting, many of the causes of loss in these overmature stands can not 
be eliminated. 
The table following reveals a wide range in the net increments on the various 
plots. Other things being equal, the growth on basin plots Nos. 8 to 11 should 
have been the highest of all, but because of a large number of young thrifty 
trees (especially Douglas fir) on the northern aspects the growth is actually 
greater on plots Nos. 13 to 15. The low increment on plot No. 12 is due largely 
to the high percentage of insect-infested trees. The next lowest rate of net 
growth per cent is on plot No. 11, where Dendroctonus bark-beetle infestation 
also is serious. Mistletoe, which is prevalent on plot No. 9, does not appear 
to retard the growth of Douglas fir so much as do bark beetles. Net losses are 
shown for only three of the uncut plots (plots Nos. 10, 11, 12), though the west¬ 
ern yellow pine shows a net loss on five plots in all and Douglas fir on two. 
