HABITAT USE BY MOOSE OF BURNS, CUTOVERS AND FORESTS IN
NORTH-CENTRAL BRITISH COLUMBIA
by
D.S. EASTMAN, l.
B.C. Fish and Wildlife Branch
Parliament Buildings, Victoria, B.C.
Canada
CONTENTS
Abstract
Introduction
Study Areas
Methods
Results and discussion
Differences between habitat-types
Spatial differences within habitat-types
Temporal differences within and between habitat-types
Conclusion
Literature cited
1.
Presented to Tenth North American Moose Workshop and Conference,
March 26-29, 1974, Duluth, Minnesota.
238
Habitat use by moose of burns, cutovers and forests in north-central
British Columbia.
Abstract
Habitat use by moose was studied in the sub-boreal spruce zone of
British Columbia from 1971-1973 for dry, modal and wet environments.
Comparisons between burns, cutovers and undisturbed forests were
based on post-winter pellet group counts and monthly checks of
tagged twig transects in winter.
Partially logged stands, 11-20
years old, received the greatest use; burns were used at almost
comparable levels.
Recent clearcuts were the least used habitattype, especially in heavy snowbelts.
The use of forests was
intermediate to clearcuts, and burns and partial cutovers.
For
summer habitat, limited data indicated that selectively logged
stands were used more than clearcuts and forests.
In all habitattypes, winter use was greatest at the ecotones.
Browsing rates
varied considerably both within and between habitats, but were
generally highest in partial cutovers.
The apparent contradiction
between pellet group and tagged twig data demonstrated the need to
assess habitat use by more than one method.
Also it revealed the
importance of burns and cutovers as feeding areas in early winter,
and the probable importance of forests for shelter, especially in
late winter.
Introduction
The objective of this article is to describe relative use of burns,
logged and unlogged forests by moose.
My emphasis is on over-winter
use as revealed by post-winter pellet group surveys, and on differences
between winter months as revealed by tagged twig transects.
The
information was gathered as part of a three year study of moose
habitat requirements in north-central British Columbia from 1971-1973.
239
Habitat utilization patterns of moose have been examined for most
of the species' range in North America.
These studies have described
both seasonal variations within habitat-types and type variations
within seasons (Houston 1968, Peek 1971, Stevens 1970, Telfer 1967,
Peterson 1955, and others).
For boreal and sub-boreal regions,
at least, the general pattern appears to be as follows:
forest and
aquatic habitats in summer, open forest and seral shrub types in
fall and early winter, and dense conifer stands in late winter and
spring.
The prime importance of forested habitats has been amply
confirmed.
Despite the rather extensive studies of forested habitats, logged
areas have received surprisingly little attention.
Most have dealt
with natural areas, or where logged areas occurred, they received
almost incidental attention (e.g. Stevens 1970).
Even in studies
carried out primarily on cutovers, e.g. Bergerud and Manuel (1968),
little information on relative use of different types and ages of
cutovers has been provided.
The need for information concerning the effects of logging on moose
grows as man's prevention and substitution of natural factors increases.
This emerging shift from autogenic to anthropogenic forests results
from a combination of increased prevention of natural wildfires
2"40
(3)
(e.g. LeResche, Franzman and Arneson 1973), and increased logging.
More studies such as the one by Peek (1971) are needed if forest
and moose habitat management are to be sensibly integrated.
The report is based on some data collected towards a thesis at the
University of British Columbia.
The help and cooperation of
many people has facilitated work on my thesis in a variety of ways.
I wish to acknowledge the financial and logistical support of the
B.C. Fish and Wildlife Branch; the scholarships awarded by the
Canadian Wildlife Service; the companionship and assistance in
field work from Chris Easthope, John Kelly and Mike Masson; the
help and advice of the regional staffs of the Fish and Wildlife
Branch and the Forest Service; the cooperation of Rustad Brothers and
Co. Ltd., and Northwood Pulp and Timber Ltd., and last but
not least, the support and suggestions offered by my supervisor,
Dr. V.C. Brink.
Study Areas
The ecological zone of interest was the sub-boreal spruce biogeoclimatic
zone of Krajina (1965), that occurs in British Columbia between latitudes
53° and 58° north.
Climatically, the zone is characterized by heavy
snowfall, dry springs and cool, wet summers.
The major conifers are
white spruce (Picea glauca), lodgepole pine (Pinus contorta), subalpine
fir (balsam)
(~
lasiocarpa), with black spruce (Picea marianna)
4
241
on the wettest sites.
Common deciduous trees and shrubs are aspen
(Populus tremuloides), cottonwood(!. trichocarpa), paper and bog
birches
(~
alders(~
species
papyrifera and glandulosa), slide and thinleaf
sinuata and tenuifolia), and a variety of willow
(~ ~·)
Revel (1972) and Wali and Krajina (1973)
provide basic ecological data.
Moose are abundant throughout the zone with average densities
approaching one/sq. mile (K. Sumanik, pers. comm).
Generally,
resident populations occur on the extensive drumlinized till plain
in central B.C. (approximately 3,000 ft.), with migratory herds in
the upland areas to the east, west and north.
Since the mid-1960's, the dominant harvesting method has been clearcutting.
All conifers and usually all deciduous trees are felled,
with the merchantable timber hauled to landings by track or rubber
tired skidders, and the remaining wood left on the ground.
Slash-
burning is an accepted management tool, although the general trend
is to avoid burning if suitable alternatives exist, or if the potential
slash fire hazard is low.
Logging continues in both summer and
winter, but the greatest volume is cut in the latter season when
access for equipment is best.
Partial cutting was practiced, mostly in winter, prior to clearcutting.
Several variations were used including cut and leave strips, tree-marking
242
5
( S)
(single tree selection), and diameter limit where only trees exceeding
specified diameters were taken.
Often limits varied with tree species
so that the amount of timber removed and the amount of canopy opened
varied according to a stand's species composition and distribution of
stem diameters.
This type of logging is apparently out of favour
as it is not amenable to high volume extraction nor does it result
in single-aged stands.
Eight study areas were selected, on the till plain region within a
50 mile radius of Prince George (Table 1).
The areas were selected
to encompass environments ranging from wet to dry, and to contain a
representative variety of cutovers and burns.
Study areas in the sub-boreal spruce zone.
TABLE 1.
Study
Area
Reason for selection
BOWRON
recent large clearcut in pine-spruce forests,
modal environment.
EAGLE
extensive partial logging adjacent to sprucebalsam forests, and an old large wildfire,
wet environment.
GROVE
a recent large wildfire in pine-spruce forests,
modal environment.
HACKENZIE
variety of clearcut and partially logged stands
in pine-spruce forests, modal environment.
SALMON
partial cutovers and undisturbed pine-spruce
forests, modal environment.
HcGREGOR
variety of cutovers in wet environment.
TORPY
recent large clearcut in wet environment.
WELDWOOD
variety of cutovers in dry environment.
Note:
all areas lie approximately between 2000 - 3000 ft.
~!ETHODS
To determine winter habitat use, pellet groups were counted after
snow melt until ground vegetation obscured pellets, usually from
mid-Hay to the end of June, in 1972 and 1973.
tallied in contiguous 10x50 ft. belt plots.
Pellet groups were
Usually, two or more
transects were run for at least 1000 ft. each in each homogeneous
type.
The site and direction of transects were selected prior
to field work to minimize bias in site selection.
Data from both
years were combined and expressed as mean number of accumulated
pellet groups per acre in each habitat-type.
Variations in pellet group densities between habitats on single
areas were considered positively correlated with the time moose
spent in them though not necessarily associated with a specific
type of activity.
Variations between different areas for a part-
icular type were considered partly due to the time spent by moose
in them, and partly due to differences in winter moose densities
on the study areas.
This latter factor was affected by several
things such as winter weather conditions on and adjacent to the
study areas, climate, accessibility to hunters, successional stage
and heterogeneity of the forests, and inherent site features that
modified the quality and quantity of food species.
( 8)
lc>
ietermine the time of use in winter, thirteen tagged twig
transects were set up in the fall of 1972 on the Eagle, Grove and
Salmon areas.
Most transects consisted of five stations, spaced
approximately 200 ft apart.
At each station, five twigs on each
of ten plants were tagged with nJmbered aluminium labels, for a
to~al
of 250 twigs per transect.
record all bro•.vsed twigs.
Mo~thly
checks were made to
For this report, the data are
presented as the mean n'Jlllber of twigs browaed per day, i.e., the
number of twigs browsed since a previo,Js check divided by the
number of elapsed days.
RESULTS AND DISCUSSION
Differences between habitat types
Winter use of the various types of habitats varied greatly both between
areas and within areas (Table 2).
Recent clearcuts were generally
used less than other habitat-types, although this was partly modified
by snow depth, and the size and shape of clearcuts (Table 2).
For
example at the Bowron and Torpy areas, use of the forest was six and
2.5 times greater than adjacent three year old cutovers respectively.
This disparity probably was due in part to the age of the clearcuts,
since the developing vegetation provided little winter forage above
snow depths that average three or more ft.
On a similarly logged
. . • 246
( 9)
area in north-central Alberta, five year old willows and poplars
averaged only 2.4 ft and 2.1 ft, respectively (Stelfox, Telfer and
Lynch 1973).
The size and shape of these clearcuts (approximately
640 acres, and square) also probably deterred moose since the
central portions were more than 0.33 miles from the timber, the
inferred guideline for maxtmum distance to cover in boreal regions.
(Telfer 1972).
Based on this guideline, square cutovers should
not exceed 0.67 miles on edge, nor exceed approximately 285 acres
(Area= 0.67 x 0.67 x 640).
TABLE 2.
Relative winter use of selected natural and cutover
habitats, based on accumulated pellet groups.
Habitattype
Relative use{accumulated eellet sroul!s£acre}
Bowron
MacKenzie
Salmon
To rei
Forest
356{1)*
142(4)
104(3)
232(14)
Burn
10-25 yrs.
old.
26-50 yrs.
old.
Cutovers
clearcut:
1-5 yrs.
6-10 yrs.
Eagle
Grove
542{5)
210(7)
478(12)
303(4)
59{2)
165{5)
218{2)
44(2)
~artial;
1-10 yrs.
11-20 yrs.
old
327(2)
2062(3)
436(1)
385{9)
353(4)
Total
length of
transects
( ft)
7700
3100
16,200
55,500
15,100
29,900
*no. of transects in parentheses.
247
•
10
Compared to these two areas of high snowfall and large clearcuts,
the MacKenzie area had lower snowfall and the recent clearcuts were
slightly smaller.
Relative winter use of these latter clearcuts
exceeded that recorded for the former clearcuts and, more
significantly, was almost equal to use in the MacKenzie forests
(Table 2).
These differences between study areas emphasize the
need for site-specific evaluations regarding logging practices
and their effects on moose.
Partially logged stands were the preferred winter habitat-types
at almost all areas (Table 2).
Except at Eagle, selectively logged
stands were more heavily used than forests, clearcuts and burns.
The greatest difference recorded was at MacKenzie where an older
stand had 14.5 times more pellet groups than the forest,and nine
times more than the clearcuts.
The most likely explanation for
this difference is that partial cutting created mosaics of small
cover - and food-producing units, that most closely resembled
highly productive, naturally heterogeneous ranges (e.g. LeResche,
Franzmann and Arneson 1973).
Whether or not clearcutting, the
major cutting practice now, will eventually produce as good habitat
cannot yet be determined in the Prince George region since this
method has been practiced only for approximately ten years.
The two burns examined showed winter pellet group densities that
generally exceeded those in forested and clearcut habitats, and
( 11)
approximated those in most partial cutovers (Table 2).
The data
indicated that the productive life of a burn for moose can extend
at least over 35 years (the Eagle fire was in 1937) and probably
longer.
This, of course, is dependent upon the make-up of the
seral vegetation and the burn's location.
For example, the
1961 Grove burn regenerated very heavily to willows and paper birch,
both preferred foods of moose, and is considered an important winter
range.
However, the nearby, same-aged 7sus burn regenerated to
lodgepole pine, a scarcely used species, and is not considered a
winter range.
TABLE 3.
A.
Summer use of habitat-types, 1973 data.
Frequency of occurrence of summer use on
Habitat
-t~Ee
coniferous forest
partial cutover
Totals
B.
No. transects
in samEle
transects.'~
No. transects with
summer use
Totals
20
16
4
7
24
23
36
11
47
Relative summer use of habitat-types.
Habitat
-t~e
coniferous forest
partial cutover
clearcut
burn
Relative use ~accumulated
MacKenzie
Salmon
10( 12)"'"'
28(10)
ns
ns
11(4)
87( 1)
15( 11)
ns
feces/acre~
Eagle
0( 1)
87(1)
ns
0~1~
Grove
0( 2)
ns-1•**
ns
32~4~
chi-square = 14.46, p,O.Ol.
no. of transects in parentheses.
*** ns =not sampled.
~~culated
~
. . . 249
(12)
Little information was collected on summer habitat use.
However, the
limited data showed that partial cutovers appeared to be preferred over
forests and clearcuts.
In the 1973 surveys, summer feces were recorded
on more transects through partial cutovers than on those through forest
stands, and the null hypothesis of no difference in frequencies of
occurrence was rejected at P < 0.01 (Table 3A).
Additionally, more
accumulated summer feces were recorded in selectively logged stands
than in forested and clearcut types. (Table 3B).
Spatial differences within habitat-types.
Generally, moose used portions of habitat-types adjacent to the ecotone
more so than portions away from type changes (Table 4).
TABLE 4.
Relative use of selected habitat-types, adjacent
to and away from ecotones.
Relative use ~accumulated Eellet grouEs I acre)
Area
Ecotone
Non-ecotone
Habitat-tyEe
FOREST
Bowron
Eagle
Grove
MacKenzie
Salmon
356( 1)*
815(3)
273(5)
109(2)
254( 8)
n.d.
87(2)
94( 6)
174(2)
302(4)
l'E.!:E.L
12.W.2.
_2.ill:2.
342
142
Grove
Eagle
mean
494(6)
345( 3)
420
1Jill1.2.
Bowron
MacKenzie
McGregor
TorEY
mean
0(1)
203(3)
87(1)
~
94
53(1)
218(2)
43( 1)
_Qill.
79
Eagle
~
mean
598( 2)
65(2)
~
1Q.illl
mean
BURN
12 yrs. old
36 yrs. old
CUTOVER
clearcut:
1-5 yrs. old
partial:
ll-20 yr. old
;"(
no. of transects in parentheses.
497
327(7)
305
185
250
13
(13)
The greatest differences ••ere noted for habitats surrounding the
burns on the Eagle study area.
Use of the ecotonal forest and
partial cutover was more than nine times the use in areas away from
ecotones.
On Grove, the difference was almost three times.
Less marked differences were noted for forests adjoining selectively
logged sites.
Ecotonal areas were used only ewice as much or less
as non-ecotonal areas.
Results for forests adjoining clearcuts
were inconsistent, probably related to site differences, although
the means show a pattern similar to selectively logged stands.
Temporal differences within and beeween habitat-types
Browsing trends differed in each habitat-type as the winter progressed
(Table 5).
At Grove, moose used the burn-forest ecotone and lowland
burn sites increasingly from November to January, and intermittently
thereafter.
The upland burn site was used in January only, probably
by a single moose passing through the area.
14
251
(14)
TABLE 5.
Changes in habitat use (browsing) during the 1972-73 winter
for the Grove, Eagle and Salmon study areas.
Mean no. stems browsed
Eer day*
Feb. Mar.
Nov.
Dec.
Jan.
AEr.
Study area
and habitat
GROVE
Burn-forest ecotone
Open bum-lowland
Open bum-upland
0.04
0.00
0.00
0.30
0.30
0.00
1.32
1.87
0.03
0.38
0.31
0.00
o.oo
0.00
0.48
0.00
0.00
EAGLE
Coniferous forest
Selectively logged forest
Open burn-near forest
Open burn-away from forest
0.00
0.10
1.00
4.20
0.00
3.30
1.30
1.90
0.00
0.17
0.42
0.38
0.00
0.67
0.03
0.00
0.24
0.00
0.00
0.00
0.00
0.57
0.00
0.00
0.00
0.20
0.00
1.80
1.80
5.70
0.10
0.38
0.77
0.26
0.52
0.00
0.00
0.00
0.00
0.14
0.00
0.00
0.00
0.04
0.00
0.00
SALMON
Coniferous forest
Mixed wood forest
Selectively logged forest
River bottom (logged)
o.oo
n.e.**
0.00
*No. of stems browsed/no. of days between field checks.
**Not established.
Browsing on the Eagle winter range varied quite markedly.
The coniferous
forest was used only in late winter, when browsing fell off in most other
habitats.
Use of the selectively logged habitat fluctuated throughout
the season, with a peak reached in December, followed by a decline to no
use in March and then an increase in April.
Use in the burn adjacent to
the forest increased to December and fell off thereafter, while use in the
burn away from the forest declined steadily from November, with no use
after January.
252
15
(15)
At Salmon, four habitats were examined.
The pattern of use at the
coniferous forest site was similar to that at Eagle, with browsing
confined to the late winter.
The differences in browsing levels
may be attributed to a difference in available browse species, since
~
stolonifera occurred at Salmon but not at Eagle.
Also, the
pattern may partly be affected by the closeness of the Salmon River,
a major winter range.
The mixed wood habitat was used almost
throughout the winter, though trailing off in late winter.
The
selectively logged forest and river bottom sites both reached
maximum use in December and tailed off with no use in February,
March or April.
Several interesting aspects of habitat use in average winters were
revealed by comparing data from pellet group counts and tagged twig
transects.
On burns, moose use of the more exposed areas, such as
the upland site at Grove, is minimal in average winters such as
1972-73.
However at favourable elevation,
areas away from the
bum-forest ecotone were browsed more heavily than indicated by
the pellet group counts.
This observation and the timing of heaviest
browsing suggests that the more central areas were used primarily for
feeding in early winter but were less favoured in late winter.
This
trend is probably more pronounced in heavier snowfall areas such as
Eagle.
16
253
For forests, the apparently conflicting data of high pellet group
densities and low rates of browsing indicate that forests were used
primarily for purposes other than feeding, probably for shelter.
From the point of view of methodology, the comparison illustrates
the caution required, and possible pitfalls encountered when judging
habitat use on the basis of a single technique.
CONCLUSION
Patterns of habitat use by moose are complex and variable.
Although
virtually all habitat-types examined showed evidence of use, the most
heavily used types were partially logged stands and burns.
Clearcutting,
the current harvesting method, can probably produce useful moose habitat
though not as good as selective logging.
A mixture of disturbed and
undisturbed habitats is probably important to long term moose production
since no one type provides all the habitat requirements of moose.
Studies of habitat preferences should be based on more than one independent
method.
(17)
LITERATURE CITED
Bergerud, A.T. and F. Manuel.
1968.
Moose damage to balsam fir - white
birch forests in central Newfoundland.
Journal Wildlife Management.
32(4):729-746.
Houston, D. B. 1968.
The Shiras moose in Jackson Hole, Wyoming.
Teton Natural History Association, Tech. Bull. 1.
Krajina, V. J. 1965.
Columbia.
Grand
110 p.
Biogeoclimatic zones and classification of British
Ecol. Western Nor. Amer. 1:1-17.
LeResche, R. E., A.W. Franzmann and P. D. Arneson.
1973.
Moose research
center report, progress report for proj. no. W-17-4, job no. 1.1R.
109 p. + ii.
Peek, J. M.
Alaska Dept. Fish and Game.
1971.
Moose habitat selection and relationships to forest
management in northeastern Minnesota.
Minnesota.
Juneau, Alaska.
Ph. D. thesis, University of
250 p.
Peterson, R. L.
1955.
North American moose.
University of Toronto Press.
280 p.
Revel, R.D. 1972.
Phytogeocoenoses of the sub-boreal spruce biogeoclimatic
zone in north central British Columbia.
British Columbia, Vancouver.
327 p. + appendices.
Stelfox, J., E. Telfer and G. Lynch. 197.
in the Alberta foothills.
Stevens, D. R. 1970.
Montana.
Ph. D. thesis. University of
Effects of logging on wildlife
Alberta Conservationist.
Winter ecology of moose in the Gallatin Mountains,
Journal Wildlife Management.
34(1): 37-46.
255
(18)
Telfer, E.S.
Scotia.
Telfer, E.S.
forest.
1967.
Comparison of moose and deer winter range in
Journal Wildlife Management.
1972.
Nova
31(3):418-425.
The effect of logging on wildlife in the boreal
Paper presented at annual meeting Canadian Society Wildlife,
and Fish. Bio. Saskatoon.
Wali, M.K. and V.J. Krajina.
9 p.
1973.
Vegetation - environment relationships
of some sub-boreal spruce zone ecosystems in British Columbia.
Vegetatio 26 (4-6): 237-381.
Duluth, Minnesota
March 1974
91 DELEGATES TO THE 1974 CONAERENCE
ATTENDED FROM ALL PARTS OF THE MOOSE
RANGE OF NORTH AMERICA