Mar. 15,1925 Mortality of Trees Attacked by the Spruce Budworm 549 
Table XIV.— Northern hardwood type, composition of plots 
Bal¬ 
sam 
Bal¬ 
sam, 
over¬ 
topped 
Red 
spruce 
Red 
spruce, 
over¬ 
topped 
White 
spruce 
White 
spruce, 
over¬ 
topped 
Soft¬ 
woods, 
over¬ 
topped 
Yel¬ 
low 
birch 
Maple 
Beech 
Hem¬ 
lock 
Total 
hard¬ 
woods 
Num¬ 
ber 
trees, 
lo 
acre 
Soft¬ 
wood, 
aver¬ 
age 
di¬ 
ame¬ 
ter 
Basal 
area, 
Is 
acre 
P. ct. 
46.7 
P.ct. 
38.8 
P.ct. 
53.3 
P.ct. 
35.7 
P.ct. 
0 
P.ct. 
P.ct. 
59.7 
P.ct. 
20 
P. ct. 
15.3 
P.ct. 
64.7 
P. ct. 
0.4 
P.ct. 
27.4 
32.2 
In. 
6.8 
Sq.ft, 
7.20- 
Table XV.— Radial increment in millimeters at d. h. h. from 1903 to 1912, in¬ 
clusive, and mortality of trees in plots of Table XIV 
Balsam, increment 
Red spruce, increment 
Dead 
Living 
Dead 
All 
Dead 
Living 
Dead 
All 
Per cent 
Mm. 
Mm. 
Mm. 
Per cent 
Mm. 
Mm. 
Mm. 
Free__ 
58.8 
17.7 
14.9 
16.3 
39.6 
18.4 
22.1 
19.8 
Overtopped_ 
9.9 
10.7 
7.5 
10.1 
5.4 
10.0 
5.5 
8. % 
Average_ 
206 trees 
13.2 
234 trees 
14.6- 
whose terminals were above the canopy 
or standing in an opening in the hard¬ 
wood foliage. Since no comparison of 
individual plots was contemplated, the 
tabulated data are a summary for all 
plots. 
The mortality of four softwood se¬ 
ries at Bathurst and Metis (Tables IV 
to XI) and two hardwood series (Tables 
XII to XV) is compared in Table XVI. 
The hardwood mixtures show consider¬ 
ably less mortality for white spruce and 
red spruce, though this is not so marked 
for balsam. If the percentages of mor¬ 
tality among the free and overtopped 
trees are compared, it is seen that the 
reduction in mortality is chiefly due to 
the overtopped trees. 
In these series of plots the rate of 
growth for the overtopped trees is con¬ 
siderably lower than for free trees, so 
this factor would tend to increase 
mortality if it were not overbalanced 
by the protection offered by the hard¬ 
wood canopy. The average rate of 
growth for the species of softwood trees 
in the hardwood series (Tables XII, 
XIII, XIV, and XV) is lower for 
balsam and higher for both red and 
white spruce than in the preceding 
softwood series. 
In the northern hardwood type 
(Tables XIV and XV) the average rate 
of growth for all balsam (13.2) and red 
spruce (14.6) is considerably higher 
than for any other series of plots. 
Likewise the mortality of the over¬ 
topped softwoods is lower and shows a 
greater contrast to the free dead soft¬ 
woods. The total mortality for balsam 
is lower than in the birch-poplar type 
(Tables XII and XIII), while that for 
red spruce is higher. It so happens 
that in these plots the rate of growth 
for the dead red spruce is higher than 
for the living. This discrepancy may 
be due to the method of tabulating free 
and overtopped trees, which does not 
properly group the trees according to 
the relative amount of defoliation. 
Balch recognized this, adding the fol¬ 
lowing note on one plot: 
The free living red spruce are smaller than the- 
free dead red spruce. The free living are in many 
cases partly overtopped, the free dead generally 
almost entirely free. Thus the percentage of 
canopy seems a greater factor than rate of growth. 
These free living dead trees are thus 
subjected to a greater foliage exposure, 
and consequently to heavier defolia¬ 
tion, than those which survived and 
are partly overtopped, though classed 
as free because the terminal was free. 
The lower percentage of mortality of 
the softwoods in hardwood mixtures is 
entirely a matter of protection by the 
hardwood foliage. This protective 
effect is due to concealment of over¬ 
topped softwoods from the ovipositing 
moths and the lessened chance of 
migrating larvae falling on the soft¬ 
woods. 
The mortality among the free soft¬ 
woods of hardwood mixtures is about 
the same or slightly higher for balsam 
than for the pure softwood. This sub¬ 
stantiated many observations in 
the field where high mortality was 
observed, especially in older hardwood 
mixtures when the hardwoods were 
