DEPARTMENT OF LANDS AND FORESTS
British Columbia Forest Service
C. D. ORCHARD, D eputy M inister

HON. E. T. KENNEY, M inister

Regeneration and Growth
of White Spruce
After Logging
By

H. M. POGUE
Economics Division
F. S. McKINNON, Forester

THE GOVEPN MENT O F
THE PROVINCE O F BRITISH C O LU M BIA

C iiA iiL E S F. B a n f t e l d ,

VICTOKIA, B.C. :
P rin te r to the K ing’s Most Excellent Majesty.
1946 .

DEPARTMENT OF LANDS AND FORESTS
British Columbia Forest Service
HON. E. T. KENNEY, M inister

C. D. ORCHARD, D eputy M inister

Regeneration and Growth
of White Spruce
After Logging
By

H. M. POGUE
Economics Division
F. S. McKINNON, Forester

THE GOVERNMENT O F
THE PROVINCE O F BRITISH C O LU M BIA

C h a rle s

VICTORIA, B .C .:
F. B a n b ^ i e l d , P rin te r to the K ing’s Most Excellent Majesty.
1946 .

Technical Publication T. 29
First Edition, 1946

CONTENTS

Page
Introduction ------------------------------------- —

1

Method of Survey-----------------------------------

2

Results
Spruce ----------------------------------- — --Balsam ____
H e l d ---------------------------------- — ---

3
7
8

Effect of Excessive Utilization --------------------

13

Other Factors
Type of Terrain------------------------------Soil________________________ ^----------------Humus----------------------------------------Former Stand__________________________________
Windfall-------------------------------------Slash----------------------------------------Undergrowth ---------------------------------Burning
^ _________________________________

14
14
16
16
16
18
18
22

Summary and Conclusions ---------------------

23

Application of Results -----------------------------

26

REGENERATION AND GROWTH OF WHITE SPRUCE AFTER LOGGING

INTRODUCTION
East of Prince George in Central British Columbia is a
large, accessible area representative of the vast North Central In­
terior spruoe-balsam forest. In this area the portion of the Rocky
Mountain trench occupied by the headwaters of the Fraser River breaks
into the Interior Plateau. The valleys of the Upper Fraser, Willow,
Bear, and McGreggor rivers provide ideal conditions for the develop­
ment of the characteristic uneven-aged spruce forest. The climate
is severe, with long, cold winters and a short, but warm summer
growing-season which produces good sized timber suitable for sawlogs. The area has been accessible since the completion of the Grand
Trunk (now Canadian National) Railway and permanent forest industries
based on this spruce forest have been developed at Shelley, Giscome,
Aleza Lake, Hansard, Sinclair Mills, and Penny.
White spruce (Picea glauca Voss.) is the principal species
and is associated with balsam fir (Abies lasiooarpa Nutt.), some birch,
cottonwood, Douglas fir, cedar, and lodgepole pine. In actual log­
ging practice, spruce has been cut to a diameter limit of 12 inches
d.b.h. ^hlch is, to alx intents and purposes, clear cutting. On the
average, the volume removed is 10 to 15 M.B.M. per acre. Very little
balsam has been utilized. Slash has not been disposed of, although
some piling has been done in the past. As a result, the cut-over
lands vary from devastated to well-stocked, residual stands, depend­
ing on the effect of a uniform cut upon a variable virgin stand.
Considerable work has been done in the past in investiga­
ting the problem of spruce reproduction in this region. In 1929,
Garman (l) reported that natural reproduction following fires was
unsatisfactory, 75 per cent, of the area of all burned sites being
understocked. In 1930, Barr (2) studied the relation of soil moi­
sture to the establishment of spruce reproduction and concluded that
the seedbed of moss and litter limited the available moisture and
restricted germination. In 1931, Griffith (3) showed that natural
regeneration of spruce can be secured under mature forests by arti­
ficially breaking up the layer of raw humus and exposing mineral soil.

References:
(1)

Garman, E.H., 1929. Natural Reproduction following Fires in Central
British Columbia. For. Chron. 5: 3: 28-44.

(2)

Barr, P.M., 1930.The Effect of Soil Moisture on the Establishment
of Spruce Reproduction in British Columbia. Yale Univ. School
of Forestry, Bull. 26.

(3)

Griffith, B.G., 1931. The Natural Regeneration of Spruce in Cen­
tral British Columbia. For. Chron. 7: 4: 204-219-

In 1937, Barnes' (4) studies indicated that, in 120 years after log­
ging, a satisfactory second crop could be matured from the residual
stand. In 1940, McKinnon (5) published a review of the work done and
concluded that the key to the problem of regeneration lay in the con­
servation of the understory. He suggested raising the cutting limit
to 18 inches to improve the residual stand by reducing windfall and
slash.
The present survey was made in 1945 to obtain an over-all
picture of conditions on the cut-over lands in order to estimate the
requirements for adequate restocking. On the completion of the study
the results were incorporated into an experimental cutting area of
160 acres in the Aleza Lake Experimental Forest.

METHOD OF SURVEY
Before going into the field a history map was made to show
the date of logging or burning for all areas studied. In the field,
basic data were obtained by strip plots 10 chains long and 1 chain
wide. Strip width was estimated with particular care and checked
frequently. This method was adopted after trying out line plots and
transect plots which did not prove satisfactory owing to the scattered
nature of the residual stand. In the course of the survey 504 circular
plots of 4 mil acres each were distributed along 138 of the 218 strip
plots and were used to note the occurrence of trees 7 inches d.b.h.
and under, by species, on each quarter of the plot. The following
information was obtained:
(a)

Tally of all spruce by 2 inch d.b.h. classes. It was found
that no significant suppression of spruce occurred after
cutting and the tally was divided into "free," "cull," and
"dead." In recently logged areas, the trees under the 2
inch d.b.h. class were separated into 0-2, 3-5, and 6-9
foot height-classes.

(b)

Tally of other species 7.1 inch d.b.h. and up by 2 inch
d.b.h. classes. Occurrence and distribution of trees 7
inches d.b.h. and under.

(c)

Stiunp count of trees logged.

(d)

Sample trees and borings to show d.b.h. growth.

References:
(4)

Barnes, G.H. 1937. The Development of
Unevenaged
Standsof Engelmann Spruce, and Probable Development of Residual Stands after
Logging. For. Chron, 13: 3: 417-457.

(5)

McKinnon, F.S., 1940. Spruce Regeneration.
Special Number: 38-45-

For. Chron.

16:

(e)

Notes on conditions affecting the establishment and develop­
ment of spruce regeneration as follows:
1.
2.
3.
4.
5.
6.
7.

Type of terrain; e.g., river flat, bench, slope, and aspect.
Soil type; whether loam or clay.
Litter; depth of raw humus layer.
Former stand; whether first generation or climax forest.
Windfall; whether heavy, moderate, or light.
Slash; whether heavy, moderate, or light.
Undergrowth; whether sparse, sparse to moderate, mod­
erate, moderate to dense, or dense.

RESULTS
Spruce. Most of the recently logged areas look to be in
bad shape, with heavy slash, broken and blown-down trees, very little
new reproduction, and a patchy residual stand. In places, especially
flat areas along the river banks, the original stand was light and

THIS AREA WAS A WELL DEVELOPED SELECTION SPRUCE FOREST
AND WAS NOT OPENED UP EXCESSIVELY BY LOGGING. THE RESIDDAL STAND HAS RESPONDED TO THE RELEASE.

cutting has created excessive openings which choke up with dense brush
and grasses. In other places, the original stand was composed of
smaller-sized, nearly even-aged, first generation stands which, when
cut, show the lack of an understory and produce extensive areas of
brushy, unsatisfactorily-stocked forest. However, on the average,
the older logging shows that, in time, the spruce forest will be re­
produced naturally. The crop trees are developing from the residual
stand. In the typical cut-over areas new seedlings take too long a
time to establish themselves in sufficient numbers to form a signifi­
cant part of the second crop. Once established in the openings, how­
ever, they develop rapidly, often catching up with the surrounding
advanced growth. Where more than the average number of openings
occur, the form of the trees is poor but after 20 years the crowncover closure is appreciable and height growth begins to be noticeable,
also the undergrowth starts to thin out and, in places, new seedlings
dominate the undergrowth in the openings.
It was observed that the main difference between parts which
are under-stocked and adjacent parts which are better stocked is that
the fail spots were created by over-cutting. When natural openings
are enlarged or new openings created, the underbrush spreads and grows
luxuriantly. It is mainly these brushed-filled openings which persist
for years and reduce average stocking below a satisfactory level.

Table 1
Stand Table for Spruce-balsam Forests at Intervals of Five, Fifteen,
and Twenty-five Years After Logging
Spruce
D.B.H.

Balsam

Spruce

Balsam

Spruce

Balsam

11-20 yrs. after
0-10 yrs. after
21-30 yrs.. after
logging (av. 5yrs.)logging (av.l5yrs.) logging (av. 25 yrs.)

0
2
4
6
8
10
12
14
16
18
20

48.7
12.2
13.0
7.1
5.1
3.8
4.5
2.0
.33
.07

Total

96.8

7.2
4.2
4.3
3.1
1.6
.4

53.6
23.1
15.6
10.9
6.7
5.5
5.8
3.5
.7
.16

125.6

14.2
8.1
5.5
2.3
.5
.2

48.9
25.5
21.1
14.9
8.9
8.1
7.1
4.1
1.1
.3
.1
140.1

14.3
9.3
5.7
2.0
.4

Continued
Spruce
D.B.H.

Culls
Dead
Stumps
Over 8"
2- 6"

0"
Basis

Balsam

Spruce

Balsam

Spruce

Balsam

21-50 yrs. after
11-20 yrs. after
0-10 yrs. after
logging(av. 5yrs.) logging (av. 15 yrs. logging (av. 25 yrs.)

2

1

5
57.5

1

1
1

57.5

39.5

15.8
32.3
48.7

20.8

84.8 acres

22.4
49.6
53.6

30.8

81.15 acres

29.7
61.5
48.9

31.7

39.0 acres

The stand tables in Table 1 were obtained from the field
data and, in addition to showing the diameter distribution of live
trees, presents a tally of those removed in logging. The number of
cull and dead trees is also given, thereby presenting a complete in­
ventory of stand conditions at intervals of five, fifteen, and twentyfive years following logging operations.
It is of interest to note that approximately equal numbers
of "zeros" (trees up to 1 l/2 inches d.b.h.) were found in the three
age-classes of cut-over. IWenty-five years after logging there are
over forty new spruce present, thus showing that there has been a
small but persistent seeding-in. The increase in the number of trees
in the upper d.b.h. classes is the result of growth from the small
trees left after logging. The number of trees in the 4-inches-d.b.h.olass and over has increased by thirteen at fifteen years after log­
ging and by thirty at twenty-five years after logging. • It is evident
that most of, if not all the spruce trees which survive the logging
remain in the stand and, although temporarily set back by the opening
of the stand, respond to the release. Apparently spruce is well
adapted to the environment and is capable of maintaining its dominance
even under the adverse conditions created by existing logging practice.
The average number of trees logged in recent logging is the same as
fifteen years ago. At least as many or more were taken twenty-five
years ago. It may be assumed, therefore, that development of the
recent logging should be identical with the development of the past.
In the 0-10 year age-class a representative sampling showed
that approximately 20 per cent, of the zero-d.b.h.-class spruce trees
are less than 2 feet in height, 40 per cent, are 3-5 feet and 40 per
cent., 6-9 feet. Table 2 shows the diameter-height relationships of
residual stand trees up to 6 Inches d.b.h. for spruce and 2 inches
d.b.h. for balsam. The table is based on sample trees from all ageclasses of out-over as critical examination showed no differences
between the various age-classes.

Table 2
Diameter-Height Data for Resldueil Stand
Height
D.B.H.

Spruce

Balsam

(Inches)

(Feet)

(Feet)

1
2
3
4
5
6

8 1/2
13
17 1/2
22
27 1/2
34 1/2

8 1/2
15

Table 3 shows the height-age relationships of the small
trees in the residual stands, based on the same sample trees. Prom
Tables 2 and 3 it is evident that spruce trees require about 20 years
to grow out of the zero d.b.h. class, and this confirms the conclusion
that most of the trees in Table 1, in the 0-10 year age-class, haye
grown into the upper d.b.h. classes of the 21-30 year age-class.
Table 3
Height-Age Data for Residual Stand
Age
Height
(Feet)
1
2
3
4
4 1/2
5
6
7
8
9
10
11
12

Spruce

Balsam

(Years)
6
10
13
15
16
16 1/2
17 1/2
18 1/2
19 1/2
20
20 1/2
21
21 1/2

(Years)
6
11
16
19
20 1/2
21 1/2
23 1/2
25 1/2
27 1/2
29 1/2
31 1/2
33 1/2
35

Balsam. In most places, balsam reproduction and advanced
growth is dense compared to spruce. In the early stages following
cutting, this is particularly noticeable and has led to the assump­
tion that the proportion of balsam in the new forest would be in­
creased. This impression can persist for about fifteen years follow­
ing logging but after that the dominance of the spruce forest is more
evident. Table 1 shows that, after fifteen years, there is little or
no increase in the number of balsam in the 8 inches d.b.h. class and
over, while the increase of spruce is marked. Table 3 shows that the
height growth of the small balsam is much less than that of spruce
of the same age. Evidently spruce responds to the release better
than balsam. No evidence of spruce being suppressed by balsam was
found. On the other hand, there is much evidence that the presence

RECENTLY LOGGED AREA. NOTE LARGE BALSAM
TREES LEFT STANDING AND EXCESSIVE OPENING
UP OF FOREST.

of a fair residual stand of balsam is of great value in the proper
development of the spruce forest. The balsam stand helps to shade
the ground and this slows down the development of dense undergrowth
and encourages the establishment of spruce seedlings in sufficient
numbers. Furthermore, balsam acts as a nurse crop for the advanced
spruce and new seedlings causing them to develop rapidly and with good
form. By contrast, open-grown spruce have to pass through a long
period of crown development before satisfactory height growth begins.
Records of 2040 individual mil acre plots were compiled to show the
occurrence and distribution of the trees in the understory. In all
age-classes of logging, the percentage of plots on which balsam 7
inches d.b.h. and under occurred was more than double the percentage
of plots on which spruce 7 inches d.b.h. and under occurred.
Yield. In the course of sampling the cut-over areas, a
growth study was made to find the rate-of-d.b.h. increment of indiv­
idual spruce trees under actual residual stand conditions. The trees
checked were average trees chosen at random to obtain a sample of all
diameter classes. The total growth since logging was measured and
broken down into 5-year periods. In Figure 1, all the sample trees
are plotted to show the relation between diameter and number of years
after cutting. In the 15-year period between the tenth and twentyfifth years after cutting, the growth in d.b.h. averages about 4
inches.
In order to predict a future stand table and estimate the
yield the growth for the past 15-year period (1930-1944 inclusive) was
applied to the 25-year stand table of Table 1. When the diameters of
fifteen years ago were grouped by diameter classes it was found that the
actual present diameters formed a frequency distribution approximating
a normal curve about a mean. The mean diameter after fifteen years
growth, when plotted against initial diameter class, appears to form
a straight line with the formula: ^^15 yrs. = 3.82 + 1.047 (^Initial).
This shows that, in fifteen years, the trees will grow 3.82
inches plus a small amount which increases with the initial diameter.
This has been shown graphically in Figure 2. The trend compares
favourably with 15-year studies of growth on 5.2 acres of permanent
sample plots in the region.
When the standard error of the mean for each successive
diameter class was plotted in the same way the curve again indicated
a straight line with the formula: S.E. = 1.563 - .0076 (^^Initial).
This indicates that the standard error of the mean diameter
attained in fifteen years will be 1.563 minus a small amount which
increases with the initial diameter. This has been shown graphically
in Figure 3.

2S

20

7

>0
t;
/5
I

o

>21

A)

+0
28

•5i !0

53

I

F ig . Z
Re/at/on beti^een /n /t/a / D /am eter &
Mean D iam eter a fte r /5_years Grotvth.
R eleased S ta n d s __ W D/te S p r u c e .

6

6
/ m tia /

/O

12

D / a m e te r ^ Inches.

1 ... . . . 1

/■s'

/6

1

/a

20

I1:5 ,
( Y^o

Q

^sa

J> 53

2a
c

2!

C
(

63/

r

k

FIG. 3 .

R e la t io n b e tw e e n I n i t i a l D / a m e t e r a n d
S ta n d a r d E r r o r o f th e M e a n D ia m e t e r
a f t e r 15y e a r s ^ r o i w t h — R e l e a s e d
s t a n d s — W h it e S p r u c e .
1
\
' \
\

c
aV)
\
I n it ia l

D ia m e . t e . r _ I n c h e s .

Assuming the growth rate in the next fifteen years to be
the same as the past fifteen years, a stand table for forty years
after logging can be prepared by applying the frequency distribution
determined above to the actual stand at twenty-five years. The result
is as follows.
Table 4
Estimated Stand Table for Spruce Forty Years after Logging

D.B.H.
(Inches)
8
10
12

Trees Per Acre

Volume Per Acre*

(Number)

(f.b.m.;

20.2

545
910

14
16
18

14.7
10.1
7.8
6.7
4.5

20
22

2.1
.8

24

.3

1110

1405
1675
1575
840
385
175

*B.C. Log Scale.
The total volume, 11.1 inches d.b.h. and over, forty years
after logging is 7,150 f.b.m., which corresponds to a mean annual
increment of 179 feet per acre per year. Omitting the one cull and
one dead tree per acre from the stand table shown in Table 1 should
account for mortality during the period. Assuming mortality propor­
tional to number of trees this would correspond fo a reduction of 6
per cent, of gross volume.
The most important fact brought out is that this determina­
tion, being substantially in agreement with Barnes' (4 ) results, does
not alter the 120 year cycle between successive cuts as indicated by
him.
It was noted, however, that loggers will re-log the old cut­
over areas adjacent to new logging. One such area originally logged
in 1922 was cut over again in 1945. The old stumps and the new stumps
were well intermixed. Many trees, which were 8 inch d.b.h. at the
time of the 1922 logging, were now 16 inch d.b.h. or over and were
cut this year. One tree was 10 inches d.b.h. at the first cut and
was 24 inches d.b.h. after twenty-three years' growth. Although it
is a mistake to allow a second cut in twenty-three years, the fact

that it happened indicates that something better than 120 years
between cutting cycles is possible. The yield from the area which
was recut in twenty-three years is obviously much higher than the
average yield from the cut-over land as indicated by Table 4". This
is because over large areas the yield is reduced by the fail spots
created by over-cutting.

EFFECT OF EXCESSIVE UTILIZATION
It was observed that over-cutting has an adverse effect on
the residual stand and on regeneration. It seems safe to estimate that
an average of thirty-five spruce trees per acre have been logged. How-

THIS AREA WAS OPENED UP TOO MUCH AND THE
RELEASED TREES SHOW POOR FORM, HEAVY LOWER
LIMBS, AND INSUFFICIENT HEIGHT GROWTH.

ever, the fact is that the forest is not uniform but is patchy with
small openings and groups of large spruce trees. It is apparent that
the degree of cutting has been very heavy, inasmuch as the scattered
trees within and surrounding the openings are removed, undoing the
effort of the forest to close the gap. Furthermore, the groups of
large spruce are entirely cut out thereby creating openings. In
these places the degree of cutting approaches 100 per cent, and this
is largely responsible for lowering the average stocking below satis­
factory levels. The remainder of the forest is typically uneven-aged
and the removal of merchantable material is not particularly detri­
mental to the re-establishment of the stand although the damage caused
by logging is severe in places— sometimes turning an otherwise satis­
factory residual stand into a shambles of battered and broken young
trees. One of the bad features has been the use of residual growingstock in the construction of plank roads. Small spruce trees, which
would have provided the best part of the residual stand, have been
taken for cribbing and other uses and this is a serious consideration
in view of the marginal nature of the results following logging. The
use of spruce for roads and miscellaneous purposes is absolutely un­
necessary when balsam is available in large quantities and its utiliza­
tion constitutes a major problem.

OTHER FACTORS
The conclusion that adverse cutting practice is mainly re­
sponsible for the marginal condition of the cut-over lands is supported
by a study of the other factors which were expected to influence the
degree of stocking. The results are discussed below.
1. Type of terrain. Various degrees of stocking are found
to be independent of the type of terrain. Plots were segregated
into groups representative of river flat, bench, and slope. The
slope areas are further classified as "aspect north" and "aspect
south." Table 5 lists the percentage number of plots, in each
age-class of logging, classified as above and distributed ac­
cording to the number of spruce trees per acre. It should be
pointed out that the river-flat plots used in this table do
not include those representative of places subject to periodic
flooding, which are in a class by themselves as a result of
logging the scattered trees. In such places the lack of under­
story and previously established dense undergrowth can only
produce thick underbrush after logging.
2. Soil. Only 31 of the 218 plots occurred on clay soil and
more than half of these were stocked better than the average.
It has been considered that clay soil was inferior to loam but,
if this is true, it is not apparent so soon after logging. Table
6 lists the percentage number of plots in each age-class of log­
ging classified as clay or loam soil and distributed according
to the number of spruce trees per acre.

- Class of Logging
0-10 years after logging
TYPE OF
TERRAIN

21-30 years after logging

11-20 years after logging

(No. of spruce trees per acre) (No. of spruce trees per acre) (No. of spruce trees per acre)
a\
cr»
cn
cn
cn
cn IT cn ■H- cn
cn
cr»
cn
'ft
cn
cn CM
t>- cn C O ■Hcn CM
CM
CTl
rH
rH
<N
rH
1
1
1
1
1 V 7 7 CM
-V 7
I
I
I
1
1
1
1
I
I
V
V
I
I
+
m
o
in O
lA O
o o LA o LA O
o
LTi
LA
O
LA
m
n
O
o
o
m
C-CM
O,'
LA
C o CM L A ( 7 - O
in
- o
CVJ
CM
<N
o
C- O
f(H (— 1 t
CM
rH
CM
CM
CM
(H
rH
rH
rH
X l. JzL - d . _S!_ _£iL

River Flat
15 32 15 14 8
Bench
Slope, Aspect N. 7 20 27 20 13
Slope, Aspect S. 33 67 - - -

-

4

2

-

6

3
-

7
7

2
-

16

12 25 _
15 12 38 24 25 24 10 7 5 5 17 22 17 5 17
5 37 16 — 10 5 —

3
17

17 - 33 - 7 7 14 22 7
6 12 1325 38
20

-

-

20

-

17 17
14 7
- -

- 16
- 22
6 -

20 20

-

20

Table 6
Percentage nunfcer of Plots classified by Soil Type and distributed by Spruce Trees per Acre.
Age - Class of Logging
SOIL
TYPE

0-10 years after logging

21-30 years after logging

(No. of spruce trees per acre) (No. of spruce trees per acre) (No. of spruce trees per acrel
c
«

n
^
^ c 1

O

c
c

1
O
l

Loam
Clay

11-20 years after logging

l
A

n
n
1
A

t

-

c

^
M
rH
1

O
L
O
C
•H

o
>

^
^
^ t rH
rH
I
I
A
O
M
l A
rH
H

13 33 14 17 7
20 25 25 5 15

4
-

rH
I
LA
|>rH

^
CM
CM
i
O l
O C
CM

2
5

3 7
- 5

<n

+
A
M
CM

c n ^ c n ^ c n v f - c T i
■ s t c ^ c n c M
- ^ o - c
H
r H
r H
1
1
1
1
1
i
O
O
I
A
O
I
A
O
L
L A O - O C M L A C ^
H
r H
H

. . : n c M
r H
CM
1
1
A
O
.
O
rH
CM

4 14
12 13

9
-

24 20 10 11
25 - 12 -

H
+
LA
CM
<V

5 5
13 25

-

t

^

1
O

O

c

n

1
l

L

8
-

-

1
A

A
t

c M
rH
1
O
l
- O C
r-i

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H
i H
rH
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A
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M
L A t r -i
f-i

11 16 21 18 8
- - - - 33

cm

CM

i

+

O
O
CM

LA
CM
CM

5 3
34 -

10
33

3. Humus. Table 7 lists the percentage number of plots in
each age-class of logging classified according to the depth
of the raw humus layer and distributed according to the number
of spruce trees per acre. No particular significance can be
attributed to this factor from this evidence.
4. Former Stand. Plots were segregated into two types. Type
1 is a first generation forest with a poorly developed under­
story and, as a result, these areas run to average or less than
average stocking after cutting. Type 2 is the climax forest and
is typically uneven-aged. Table 8 lists the percentage number
of plots in each age-class of logging, classified as to type,
and distributed, according to the number of spruce trees per acre.
The type 1 plots used in the table do not include those repre­
sentative of one large area of this type which was badly blown
down after logging and as a result has developed into thick
underbrush.
5. Windfall. Considerable blowdown occurs throughout the cut­
over areas. Most of this comes from the balsam which fall down
or break off during the winter. Normally this process takes
several years to complete and does not affect the stocking of
spruce significantly.
In the mature forest the old-growth balsam are
characteristically diseased and cutting of these trees has been
optional under timber sale contracts. When the spruce are re­
moved, most of the large, old, balsam trees are left without pro­
tection or support. As a result, there is a gradual process of
disintegration due to snow and windbreak which eventually elimin­
ates this class of material from the residual stand.
No factual data was gathered on the proportion
of balsam in the total windfall but from observation it is esti­
mated at around 90 per cent.
In some places, particularly those which were more
or less even-aged stands before logging, winter wind-storms will
cause devastated blow-down areas but these are special cases not
representative of the great bulk of the spruce-balsam forest.
Table 9 lists the percentage number of plots, in each age-class
of logging, classified as to the degree of windfall and distributed
according to the number of spruce trees per acre. The table shows
that light blowdown is rare, except in the early stages following
cutting, and this may be accounted for by the fact that the mater­
ial keeps on coming down for a number of years after the stand is
first opened up. By the same standards most of the logging in
the 11-to 20-year-old class runs to moderate or heavy blowdown.

Age - Class of Logging
DEPTH OF
HUMUS

0-10 years after logging

21-30 years after logging

(No. of spruce trees per acre (No- of spruce trees per acre) (No. of spruce trees per acre)
.
O

1"
2"
3"
4"
5"

11-20 years after logging

t~-cr»oj
1 1 V
o m o
m t— o

T*-t-cryc\j
V V V 7
m o m o m
o j m t — cvjcvj
rH rH iH OJ OJ

4 30 15 18 4
19 34 13 13 6
14 33 34 5 14
33 11 34 22 -100 - - -

4 7
6 - - - -

7 11
9
- - - -

H-DII
o o
m

(T \

CMH-C-CnCM
(
—I iH iH rH CM
1
1 1 1 1 1
m
o m o m o
t - o c M m t - o
iH cH rH iH CM

9 6
3 11
32
- 17

21 20 17 15 6 3 3
25 11 11 11 14 3 11
26 26 5 - 11
33 16 - - 17 17 -

+
m
CM
CM

H-t"I .
o o
m

CTiCM
1 7
m o
[^-o
H

^C~-(nCM
7 7 7 7-"
m o m o m
C N j m c — ocsi
H rH iH <M CV)

- 17
11 4
- 20
33

17 16
15 22
20 20

16 17 18 4 11
- 20
34 33 -

-

-

17

-

15
- 20

-

-

-

I

Table 8
Percentage number of Plots classified by former Stand and distributed by Spruce Trees per Acre
Age - Class of Logging
0-10 years after logging
FORMER
STAND

cn
O

C "-CT\O J
iH
I
I
I

O
LT» O
m t - o

rH

2
1

21-30 years after logging

(No. of spruce trees per acre (No. of spruce trees per acre) (No. of spruce trees per acre)

1

Type
Type

11-20 years after logging

12
43

29 18 16
57 -

cn
^
rH
1

..j-crv'j-

D—
r-l
I

CTVCM
H
CM +
I I

H-C"I I

CMH-f-O^CM

I

rH
1

iH
1

rH
1

rH
1

CM
1

+

m o m
om
CM
mc^ocvj

m

iH

iH

rH

O O
m

rH

r-i

CM

CM

10

4

227

5 14

22 19 10 11
67 - 33 -

8

4

7

--

CM CM

--------------------

-

-

tr—

o m o m o
o c M m r - o
H

rH

-

-

m
cm

-

I

CTiCM
rH
I I

m o
t-o

m o m o m
C M m c ^ o c M

6 9
14 14

18 14
- 43

14 12
29 -

I

O O
m

rH

- s f t ^ - C T i C M
iH
rH
rH
CM
t
i
l
l

+

rH

CM

rH

rH

CM

9
-

3 15
- -

No classification was attempted for the 21-to 30-year age-olass
of logging because of the difficulty of distinguishing blowdown
from logging slash, etc., and also because, after that length of
time, it is difficult to estimate the degree of the blowdown.
6. Slash. Table 10 lists the percentage number of plots in each
age-class of logging classified as to the relative density of log­
ging slash and distributed according to the number of spruce trees
per acre. No classification was attempted for the 21-to 30-year
age-olass of logging because of the difficulty of determining the
degree after that length of time. The table shows that heavy
slash predominates on recently logged areas, becoming moderate
after about ten years. For three or four years after logging,
debris, due to blowdown and snowbreak, is added to logging slash
and the general effect is the same as new logging. By the fourth
year, tops are beginning to settle, needles are mostly off the
twigs, branchlets are beginning to break, some branches are broken,
and the bark starts to come off the bases of the branches. At the
fifth year, most slash has settled appreciably and branchlets are
hare, branches noticeably broken, and bark is beginning to come off.
Between the sixth and tenth years, slash rots appreciably, tops are
flattened and become buried in the underbrush, the bark comes off
the tops, and most branches break off. By this stage all flash
hazard has abated. After fifteen years it is unusual to find un­
rotted slash or sound stumps.
7. Undergrowth. In the virgin forest it is not unusual to find
a forest floor covered by green mosses and a light scattering of
ferns, herbaceous plants such as bunchberry, Tiarella, Clintonia,
Smilacina, Streptopus, Linnea borealis, etc., with oooasional plants
of the larger kinds such as Aralia, Rosa, Rubus, Ribes, devils club,
etc. In these places the forest cover is typically well developed,
the crown cover is uniformly closed, and all ages of trees are pre­
sent.
Whenever the original forest is disturbed, conditions become
more favourable to the development and growth of the ground-cover
and underbrush. Low, flat places, periodically flooded, have not
developed complete crown closure and the forest floor is grown up
with grasses, nettles, cowbane, mints, ferns, devils clubs, and
patches of willow, alder, elderberry, Lonicera, dwarf maple, rasp­
berry, thimbleberry, etc. The more open the stand, the thicker is
the undergrowth. On moist benches and slopes with moderate crown
closure, devils club often grows very densely. From place to place
there is considerable variation between the ideal forest floor and
the extreme development of underbrush. It is usual to find moderate
clumps and patches of undergrowth, with small herbaceous plants, ferns
and grasses. The natural openings contain the thickest undergrowth.

_____________ ^
----- --------- ---------------- --------------- *-------- Age - Class of Logging
0-10 years after logging
WIND-FALL

(No. of spruce trees per acre)
I I I
o o m
me--

Light
Moderate
Heavy

18
9
21

36
28
33

18
16
16

11-20 years after logging

21-30 years after logging

(No. of spruce trees per acre)

CM ^
t--Cr\CM
rH
rH rH rH CM +
rH rH rH rH ^
+
I I I
1
1
I I I
1 1 1 1 1
o
o
m
o
m
o
m o m
O L A O L A O m
m to
CM m c - O C M
ocvimt-ocM
rH rH rH rH CM CM
rH H iH rH CM CM
- 1 0 0 - - - 11 3 3 - 4
7
18 12 5 2 3 7 5 12 19 22 12 12 10 3 5
4 7
4 4 11
10 10 - 5 5 4 18 37 11

No Classification
Made.

Table 10
Percentage number of Plots classified by degree of Slash and distributed by Spruce Trees per Acre
Age - Class of Logging
0-10 years after logging

11-20 years after logging

21-30 years after logging

SLASH

Light
Moderate
Heavy

(No. of spruce trees per acre) (No. of spruce trees per acre)
H-cn
C
i-- o
cT\
H --ccrnvoHjCM
c^cncM
T7Tj --"s
t
^ CHM-Hc-n ^
rH rH H
rH CM +
rH 1—1 1—1 1—1 CM
+
1 1
1
1 1
1
1 1
1
1
1
1 1 I 1 1
m o m
o
m o m
o o m o m o m o
m o om
r-oc\j
mt-ocvi
m c - - o c M m t - o
cm
iH i-l rH rH CVI CM
H
r-\
r-\ r -i
CSi
CM
- 3 4
25
- 25 25 - 25 - 4 26 33 15 11 4
6 35 6 29 - - 6 18 5 8 20 20 10 13 12 3 9
16 32 19 10 12 4 1 2
4

No Classification
Made.

M
D
I

When the forest is opened up by logging, the underbrush and
ground-cover generally flourish. The areas which were fairly open to
start with are left with a bare scattering of trees and a poorly
developed understory. The average forests become more densely stocked
with devils club, thimbleberry, raspberry, Lonicera, elderberry.
Viburnum, Corylus, ferns, false hellbore, willow and alder clumps.
Devils club seems to grow and spread under intermediate light condi­
tions. In places where the stands were fairly open, devils club may
have been dense before logging, but after logging the extra light and
drying out which results tends to eliminate it and other shrubs come
in. In places where devils club flourished after logging the subse­
quent closing of the crown cover also tends to eliminate it. The
openings run more to thimbleberry and clumpy shrubs. After logging
these spread to the extensions of the openings and to newly created
openings. The density of the undergrowth and brush which follows
logging seems to depend on the degree of shading obtained from the
residual stand. As regards interference to seedling development and
growth, the presence of many of the smaller herbaceous plants such
as Tiarella, twinflower, Fyrolas, mayflower, evening primrose, bedstraws, vetch, mints, etc., is not significant. Bunchberry is pro­
bably the most widely distributed of all, yet it plays only a very
minor role in interfering with seed. Others in the same class are
Rubus pedatus, Clintonia, Streptopus, Smilacina, Thalictrim, horse­
tails, false hellbore, etc., and other plants not forming thickets.
Of the commonly observed plants, thimbleberry, ferns, devils
club, Ribes, Lonicera, raspberry, blueberry, elderberry, Corylus,
Aralia, Viburnum, Rosa, Spirea, osier, willow, alder, dwarf maple,
snowberry, etc., are typical of the growth which occurs generally
throughout the average cut-over area filling up the openings with
dense underbrush, excluding seed from the mineral soil, and hinder­
ing seedling development. Thimbleberry seems to be one of the worst
offenders and is almost always present mixed, in varying degrees,
with other species. When the area has been opened up excessively,
it takes about twenty years for the residual stand to develop suf­
ficiently to affect the underbrush, after which there is a tendency
towards thinning out, thus permitting seeding in of coniferous
species. It is estimated that parts of the forest, amounting to
about half the area, are well-developed, uneven-aged stands and
logging does not open these up excessively. The normal cycle is
for devils club and a few other shrubs to flourish briefly and,
after a few years, the crown-cover closes in sufficiently to re­
duce the ground-cover.
The other parts of the forest do not fare so well, due to
the present method of logging which removes all merchantable trees
regardless of their location or of the character of the virgin
stand. Trees are removed from openings and from the margins of
openings thus increasing the density and area of patches of esta­
blished underbrush. Trees are removed in groups from patches of

Table 11
Percentage number of Plots classified by Degree of Undergrowth and distributed by Spruce Trees per Acre

Age - Class of Logging
0-10 years after logging
No. of spruce trees per acre)
UNDER­
GROWTH
}
o

rH
t

»—I
t

<T\

21-30 years after logging

(No. of spruce trees per acre)

(No. of spruce trees per acre)

+
m
CM
CM

-^4-i^-cr»CM
r-l
1
1
1
1
o
o
m
o
m t - o
i-»

-

-

4

-

-

6

6 12 41 17 6 - 12
3 6 21 23 12 12 12

Oi

rH
CM
1
1
1
I I
o
m
o
m
o
m o
m t > * o c M m t > - o
iH
H
iH
H
CM

30 60 - 10 - Sparse
Sparse to
Moderate
14 34 21 17 7 - 3
17 42 25 - 8 - Moderate
Moderate to
7 20 13 20 13 20 Dense
Dense
12 17 17 17 12 - 4

11-20 years after logging

-

7
4 17

33

-

67

T ^ ^ - c ^ v
H
f-H
1
1
1
m o
m
c M m c ^
rH rH
i -l

CM
CM
1
o
o
CM

-

-

-

50 37 - 8 12 16 12 16 20

-

4

-

6
-

4

+
m

c r \ T i - c r t T j - c n - ^
^ t ^ C n C M

cr>

T V T
o t n o

T
m

7
o

12 13

o

.

cm

CM
-

1
o

m

i

t

n

1
-

o

c
rH

\ i
cH

CM

^
^
m t - o c y
rH
rH
CM Oi

-

12 25 13 12 13

-

-

14 - 43 14 29
7 21 7 29 -

-

6
6

-

-

7

7

-

22

13
8

25 25 - 25 25 - 12 - 13 25 - 12 25

-

-

-

13

relatively uniform-sized spruce which have very little reproduction
or advanced growth, thus creating openings which fill up with dense
underbrush.
Table 11 lists the percentage number of plots in each ageclass of logging classified according to the relative density of
the undergrowth. The results in this case are particularly dis­
appointing inasmuch as a correlation between degree of stocking
and density of undergrowth, which might be expected, is not evident.
The explanation is that the method of cruising ten-ohaln strip
plots, which was considered necessary for proper sampling of the
scattered residual stands, was not well adapted to relating the
tally obtained with the density of the undergrowth. It would have
been better to note the incidence of brush filled openings, brushy
scattered stands, etc. It is felt that this would have provided
the proper evidence, as it was noted that the degree of stocking
was dependent on the size and frequency of occurrence of brushy
openings, rather than on the density of the undergrowth in the
openings.
8, Burning. In view of the doubtful results in restocking ob­
tained after cutting it might be argued that burning would be help­
ful inasmuch as the debris caused by slash and windfall would be
disposed of and the raw humus layer removed. To check on this, a
number of burned areas were examined with the following results:
(a) Burned. An extensive area burned in 1927 was found to
be satisfactorily restocked with an average of over 1,000
spruce stems per acre, averaging 10 feet in height and rang­
ing from zero to 4 inches in d.b.h., average about 2 inches
in d.b.h. This area had not been logged and was burned by
a fairly hot fire which destroyed most of the original stand
and cleaned up the ground thoroughly. Seed source was the
only requirement for regeneration and in most places this
was available from unburned patches and scattered trees which
survived long enough to reseed the area.
(b) Logged and Burned. An extensive area logged in 1925 and
burned in 1927 was found to be unsatisfactorily restocked
with an average of only thirty-five spruce stems per acre.
The light stand left after cutting was destroyed and seed was
not available. Brush invaded the area and a normal humus
layer was soon restored. The fact that a seed source is the
main requirement was demonstrated by examining an ideal
sample, a small burn located centrally within an extensive
area of logging. This area was logged in 1927 and in 1930
a hot fire burned out about forty acres. The distance to
marginal unburned logging averaged about ten chains. An
average of 310 spruce and 380 balsam stems were established
and these were considered sufficient for satisfactory re-

stocking. In comparing this burn with adjacent unburned log­
ging, however, it appeared that the fire, by destroying the
advanced growth and established reproduction, had set the
development of the second crop back forty years and had created
a fire hazard which had persisted long after the abatement of
the flash hazard in the unburned logging.
(c) Logged and Burned, Reburned. A number of examples of old
logging which had been burned twice or more were seen and in
every case the result was definitely unsatisfactory.
(d) Slash Disposal. It does not seem likely that slash dis­
posal at the time of cutting would have any significant effect
in clearing the area as the bulk of the debris comes from
broken and fallen balsam which keep on coming down for two to
four years after cutting. Under existing logging practice a
spring flash hazard exists for at least five, and in some oases
for ten, years after cutting, abating thereafter. There is
little more hazard in the older logging than in the virgin
forest. Cleaning up the cut-over areas by lopping and scatter­
ing would reduce the hazard period but, if this is done sooner
than two years after logging, it is doubtful if it would help.
For adequate results snags should be felled at the same time.
Any burning which kills or damages small established spruce
should be avoided.
Introducing a method of cutting which would provide a
uniform degree of shade on the ground after logging would
serve the piirpose, by diminishing the slash and blowdown, and
minimize the spring flash hazard by preventing the sudden dry­
ing out of the debris before the appearance of the new leaves.
At the same time some treatment which would ensure the esta­
blishment of suitable seed-bed conditions and enable new seed­
lings to enter the stand without the usual time lag, would be
helpful. Spruce comes in quickly on roads and it is likely
that oat logging, which is now general, will improve seed-bed
conditions oy exposing much more mineral soil than horse log­
ging- Cat hauling of tree lengths probably causes more damage
to the residual stand but this may be more than offset by the
beneficial effect on the seed-bed.

SUMMARY AND CONCLUSIONS
The logged over areas in the region east of Prince George from
Shelley to Dome Oreek were examined in 1945■ It was found that, as a
result of clear cutting, the cut-over areas are poorly stocked but not
devastated due to the recuperative powers of the residual stand. On the
average, they can be considered as satisfying the barest minimum require­
ments for restocking if 120 years is allowed between cuts.

Adequate restocking of cut-over areas was found to be the re­
sult of a well distributed residual stand, rather than any other factor
or combination of factors. On the average the virgin stands are patchy
with small openings alternating with clumps of large spruce trees and
areas of well developed uneven-aged selection type forest. The openings
and the clumps of large spruce trees create a special problem in applied
silviculture which has not been taken care of by standard cutting practice
with the result that fail spots have been left and the degree of restock­
ing lowered below that required for satisfactory regrowth.
It is thought that these problems could be overcome largely
by marking the trees to be cut, in combination with a flexible diameter
limit. Marking seems necessary to handle the special problems presented
by the openings and groups, while an increase in the cutting limit will
serve many useful purposes., such as raising the standard of restocking
to a satisfactory level and improving the residual stand by diminishing
the slash and blowdown, protecting advanced growth, and preventing the
development of dense underbrush. In addition to attaining the required
growing-stock for a second out in less time, it is expected that the
method recommended will reduce the spring flash hazard by providing a
uniform degree of shade and prevent the sudden drying out of slash and
dead vegetation before the appearance of the new leaves.
The openings usually have marginal spruce trees and contain
scattered spruce trees. These trees should not be out if the size of
the opening will be increased. The clumps of large spruce may cover
half an acre or more and consist of relatively even-sized even-aged
trees which have a oomparitively poorly developed understory. When all
or most of these trees are logged, the result is a new opening which be­
comes choked with dense underbrush. Raising the cutting limit will not
produce the desired result because most of the trees which need to be left
will be large enough to cut-in any case. Furthermore, the areas of welldeveloped, selection-type forest do not require a big raise in the cut­
ting limit. It is recommended that trees in the 12-inch diameter class
(13 inches d.b.h. and under) be left in all cases and that the trees
associated with openings be left regardless of d.b.h. if their removal
would increase the size of the openings or unduly increase the amount
of light falling on the forest floor in the vicinity of openings. In
the case of groups with a poorly developed underwood, marking should be
done to leave a fair amount of shade on the ground, distributed as uni­
formly as possible. Consideration should be given to improving the
quality of the residual stand. The trees to be left should be selected
with care, regardless of d.b.h., and, if possible, should be trees with
large crowns which are capable of healthy growth, or thrifty trees from
any of the crown classes. Further study is necessary to determine
whether spruce can be classified into vigour classes as a guide for
marking.

TYPICAL SPRUCE IN CUT-OVER. NOTE OLD STUMPS
IN LEFT F0REC210UND. THIS TREE HAS RESPONDED
TO RELEASE AND IS GROWING FAST.

In order to approximate the yield capacity of the forest
something needs to be done to protect the established spruce which do
not form part of the first cut. Every time small spruce are swamped
out or knocked over the length of time between cuts is increased. The
objective should be to leave behind the maximum number of undamaged
spruce trees, from small timber right down to reproduction. Spruce
poles and small timber should not be taken to make roads and the first
step in this direction would be to enforce the substitution of balsam
for spruce in road-making.

One of the problems associated with partial cutting is assess­
ing the damage arising out of the scarring of the trees in the residual
stand. It is recommended that the Dominion Laboratory of Forest Pathol­
ogy be asked to study the incidence of decay in the older cut-over areas.
Extensive areas of virgin timber such as are found in this
region should be guarded against the possibility of insect damage. It
has been reported that budworm infestations are extending into the
Upper Fraser valley, one from the south by way of the headwaters of the
Goat River and another from the McGreggor Mountains. If this is true,
inestimable damage might be done. It is recommended that the Dominion
Forest Insect Investigations Laboratory be asked to study the require­
ments of the region with regard to protection from insects.

APPLICATION OF RESULTS
It is recommended that the Aleza Lake Experimental Forest be
utilized for controlled cutting by the various methods which offer the
best chances of producing satisfactory results and that the areas be
studied and the data secured analyzed until definite conclusions can be
reached. Marking for various degrees of cutting, various diameter
limits, strip logging, etc., should be carried out on extensive areas.
This could be done in connection with the logging being done by Eagle
Lake Sawmills Ltd., on the west of the Forest, and by S. B. Trick Lumber
Co., Ltd., on the east. It is recommended that these companies be ap­
proached and requested to co-operate in experimental sales.
One such sale, X 37528, was made this year. This area of
160 acres in the extension to the Forest was marked to demonstrate the
requirements for satisfactory restocking as determined by the results
of this survey. It is expected that this sale will be logged in the
winter of 1945-46 and, after logging, the area should be examined to
determine the success of the method. Approximately 65 per cent, of the
merchantable volume was removed and preliminary calculations indicate
that the residual stand will produce a second cut in 60 to 70 years.

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