Prince George
Forest Region
——————
Forest
Resources &
Practices Team
May 1999
Note #PG-19
Selection silvicultural systems in mountain caribou
habitat: Logging and learning at Pinkerton Mountain
by Susan K. Stevenson, Mike Jull, and Darwyn S. Coxson
Background
Effects of
selection
harvesting on
stand
dynamics,
structural
biodiversity,
and caribou
habitat.
Experimentation with the selection silvicultural system in the
Engelmann Spruce-Subalpine Fir (ESSF) Zone of east-central
British Columbia began nearly ten years ago. The initial impetus for partial cutting came from concerns about specific nontimber resources, such as scenic values, water quality for domestic use, and habitat for mountain caribou ( Rangifer
tarandus). A set of first-generation management trials was
established through the Mountain Caribou in Managed Forests program to assess whether it was feasible to use partial
cutting to maintain both timber harvest and caribou habitat
(Stevenson et al. 1994, Armleder and Stevenson 1996, Jull
et al. 1996). One of these was a single-tree selection harvest
block at Pinkerton Mountain (CP 376), established in 1991.
The results at CP 376 and the other management trials have
been monitored and used to design new silvicultural systems
blocks.
Maintaining caribou habitat remains one of the core
reasons for using the selection silvicultural system in the ESSF.
Some land use plans, including the Prince George Land and
Resource Management Plan (LRMP) call for the use of partial
cutting rather than clearcutting in specified caribou habitat
zones. But there are other reasons for using selection silvicultural systems in wet forest types. Forest management that
mimics natural disturbance regimes is expected to maintain
biodiversity better than past forestry practices. In the Interior
Wet-belt, where forest fires and other stand-destroying events
occur infrequently, selection silvicultural systems are likely to
produce stands that are more natural in structure than those
that result from clearcutting. Selection silvicultural systems
have the potential of combining timber harvesting with management for a wide variety of resource objectives.
There has been little testing or monitoring of singletree selection or group selection in the ESSF, and there is
controversy over their potential advantages and disadvantages. Harvesting concerns focus on the cost and complexity
of these systems. Silvicultural concerns focus on regeneration
composition and growth, regeneration risks, logging damage
to the residual stand, and windthrow potential in partial-cut
stands. Wildlife habitat concerns include the short- and longterm abundance of arboreal lichens for mountain caribou forage, and the continuing presence of wildlife trees and coarse
woody debris. The Pinkerton Mountain trial is structured to
provide a side-by-side comparison of the short- and long-term
effects of two stand management options across an equivalent
range of elevations and site types.
Project overview and objectives
FIGURE 1. Aerial view of the Pinkerton Mountain area.
Building on the results of earlier trials, a second
silvicultural systems block at Pinkerton Mountain, CP 377,
was harvested in late winter 1998. It is the first of a set of
replicated silvicultural systems trials to be established under
the Northern Rockies Wet-belt ICH/ESSF Silvicultural Systems Research Project. These trials have several purposes.
They help to build a pool of local practitioners who have
experience with design, layout, harvesting, and silviculture in
partially cut blocks. They allow us to examine the short-term
and long-term responses of key indicators of stand dynamics
and biodiversity to variations in opening size and level of
volume retention. And they serve as study sites for other
research projects that examine other ecosystem responses to
partial cutting.
The Silvicultural Systems project is linked to other
projects that share study sites through the Northern Wet-belt
Forest Research Co-operative, an informal collaboration of
• Extension • Research • Consulting •
researchers from universities, government, and the private
sector; public groups; and forest licensees. One such project is
Forest Canopy Processes and Partial-Cutting Silvicultural
Systems in Northern Wet-belt Forests. The Canopy project
focuses on the effects of partial cutting on the arboreal lichens
that mountain caribou eat during winter. Some of the research
questions that these two projects are addressing at CP 377 are:
•
•
•
How do partial-cut silvicultural systems affect the development of growing stock, including stand productivity,
stand structural development, species composition, logging
damage, wind damage, and mortality?
How do partial-cut silvicultural systems affect the loss
and creation of structural biodiversity attributes, specifically wildlife trees and coarse woody debris?
How do the changes in canopy architecture brought about
by partial cutting affect the distribution and abundance,
physiological activity, growth and fragmentation, and
litterfall rates of arboreal forage lichens?
Prescribed harvest treatments
The silvicultural systems applied at the Pinkerton
Mountain site include two contrasting types of uneven-aged
selection systems: group selection (GS) on a 59-hectare treatment unit, and single-tree selection (STS) on a 40-hectare treatment unit (Figure 3). In the selection areas, wildlife-tree reserves totalling approximately 6 hectares were retained. There
is a 25-hectare unharvested control area just outside the northwest boundary of the block.
Prescription objectives
The operational motivation for partial-cutting at
Pinkerton Mountain results from its status as “Caribou Medium” habitat, as designated by the Ministry of Environment,
Lands and Parks and approved under the Prince George Land
and Resource Management Plan. Forestry activities in Caribou Medium areas must maintain mountain caribou habitat
values, as described by Stevenson et al. (1994). The general
management intent is to maintain late seral stand conditions and
high proportions of large trees which bear abundant arboreal lichens for forage. Partial cutting systems should remove no more
than 30% of the timber volume from the stand every 80 years.
Target stand conditions
Thirty percent basal area removal (or 70% retention)
was prescribed for both GS and STS treatment units. Up to
one-third of this basal area removal (or 10% of the pre-harvest
total) in both units was anticipated in the cutting of designated
FIGURE 2. The group selection unit (left) and the single tree selection unit (right).
Site description
The study area is located in the Cariboo Mountains
about 90 km ESE of Prince George, British Columbia, in the
Wet Cool Quesnel variant of the Engelmann Spruce-Subalpine
Fir Zone (ESSFwk1) and the Quesnel Highlands Ecosection
of the Columbia Mountains and Highlands Ecoregion (Figure
3). The mesic to subhygric site is on a southwest-facing slope at
an elevation of 1350 to 1470 m. Slopes are moderate, ranging
from 0 to 40% . Pre-harvest basal area was approximately 35
m2/ha, composed of 78% subalpine fir (Abies lasiocarpa) and
22% Engelmann spruce (Picea engelmannii). The stand is
uneven-aged and many of the trees occur in clumps, separated
from one another by gaps in the canopy. The original
understorey vegetation was dominated by white-flowered
rhododendron (Rhododendron albiflorum) in the shrub layer
and Sitka valerian (Valeriana sitchensis), Indian hellebore
(Veratum viride), five-leaved bramble (Rubus pedatus), and
oak fern (Gymnocarpium dryopteris) in the herb layer.
FIGURE 3. Pinkerton
Mountain study area.
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skid trails, assuming a maximum width of four metres and
spacing of approximately 40 metres. Twenty percent of the
basal area and volume in the areas in between designated trails
was marked for harvest removal (Figure 4).
The 30% removal was expected to yield approximately 80 to 100 m3/ha, providing a marginal but adequate
economic return for costs.
Group selection
In the group selection system, the level of removal
and timing of future stand entries is controlled by area regulation (Smith 1986), and removal is measured as the total percent of the area harvested in a given period. To maintain the
pre-existing clumpy nature of the stand, we also defined the
desired shape of harvest groups. Rather than geometric shapes,
harvest groups were irregularly-shaped aggregations of one or
several pre-existing clumps of trees ranging from 0.1 to 0.4
hectares, with a target mean opening size of 0.25 hectares
(Figure 5). This approach works with, rather than against, the
existing spatial structure of the stand, and avoids arbitrary
division of natural clumps by regular geometric harvest boundaries. It also provides a less regular, more “natural” appearance
to the final partial-cut stand. Area-based regulation of cut is
maintained by Global Positioning System (GPS) traverses of
cut areas within this treatment unit.
Single-tree selection
In the single-tree selection system, level of removal
and timing of future stand entries is controlled by BDq regulation (Alexander and Edminster 1977, Guildin 1990), in
which the residual stand is defined by setting stand targets for
residual basal area (B), maximum residual diameter (D), and
the shape of the post-harvest diameter distribution (q) (Figure 6).
We used operational cruise data to assess pre-harvest
stand structure and basal area, and determine targets for the
residual stand. The cumulative target basal area was determined by the 30% constraint on level of removal in caribou
habitat. There was no maximum residual diameter; instead, a
maximum harvested diameter was set at 52.5 cm dbh (except
for trees that had to be removed to clear skid trails). This was
done because the largest trees carry lichen loading and wildlife
tree values proportionately far greater than their contribution
of 6% of the total stand basal area, and were expected to be
relatively windfirm compared to codominant and intermediate trees. To determine residual stand diameter distribution,
we compared the diameter distributions that would result from
various q-values. The q-value of 1.2 was selected because it
allows relatively high retention of larger diameter classes.
Marking rules for the STS unit followed the principle
of “cutting the worst first”, and at a minimum, maintaining or
increasing the proportion of spruce relative to subalpine fir in
the residual stand.
Treatment layout
Designated skid trails
Layout of cut and leave trees in the GS and STS units
was carried out by Northwood Inc.’s consultants in the summer of 1996. The first step for both units was laying out
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designated skid trails by flagging the routes and recording
GPS locations. A minimum
distance between skid trails of
40 metres was used to provide a maximum long-line distance of 20 metres. In the
GS treatment, “speed trails”
at distances of 70 to 100
metres apart were laid out to
provide a series of fast skidding corridors between skid
trails attached to the group
harvest openings and landings. Trees or groups of trees
to be logged were marked only
after the locations of designated skid trails were known.
Single-tree selection
Marking rules provided to the marking crews were
developed co-operatively by licensee foresters and researchers (Crampton 1996).
The marking crew covered the entire STS treatment
unit in a series of systematic transects. Along each transect,
initial prism sweeps determined the pre-harvest basal area and
the number of trees available to be cut, based on the target
basal area. The target basal area determines the minimum
number of trees to be kept in a given area. The crew kept a
continuous tally of the number of trees marked and not marked
in each diameter class.
The decision to mark an individual tree was based not
only on the marking rules, but also on practical falling issues
and the location of a tree in relation to a skid trail. As well,
trees immediately adjacent to natural openings were not cut.
After the crew finished marking in an area, they took final
prism sweeps to ensure that the target basal area range was
achieved.
Group selection
The GS openings were designed to have a minimum
width of one tree length (about 30 metres) and a maximum
width of about two tree lengths (about 60 metres). These size
limits were achieved by harvesting aggregations of one or more
adjacent natural clumps up to the prescribed area size limits.
In planning the GS unit, the implications of current
harvest decisions for future harvest entries were considered.
Harvest openings were spread more or less uniformly throughout the entire block. Their spatial distribution was planned so
that future harvests could be similarly distributed and not have
their access compromised by poor skid trail layout. Where
possible, openings were at least 50 metres apart and were
designed to resemble a parallelogram or a teardrop oriented at
35 to 45 degrees to the skid road. This angle was planned to
allow a straight line skid from the upper to lower end of the
opening and onto the skid trail.
Trees on the outside perimeter of the planned opening
were marked with orange paint above the level of the
snowpack, and with orange dots at the base. All marked trees
and unmarked trees within the opening were to be cut. To
facilitate layout and future tracking of harvested areas, GPS
locations were recorded for boundaries of marked groups.
Although this latter procedure may not be required by regulations at time of writing, it is recommended.
The Silviculture Prescription for the GS unit indicates that the openings accounted for 24% of the total area of
the unit, with skid trail area making up an additional 3%.
Harvesting
The GS and STS units were harvested in March and
April, 1998, by the forest licensee, Northwood Inc. under a
single cutting permit, CP 377. Snow depth at that time was about
one metre of settled spring snowpack in a low-snow year.
A Timbco 455C feller-buncher with a 22" (56 cm)
diameter “hot saw” was used in both units. One feature of this
type of feller-buncher particularly suited to partial-cutting in
Marking rules for the Single Tree Selection (STS) Harvest Unit
1.
2.
3.
Retain all trees greater than 52.5 cm dbh.
Leave all trees where the pre-harvest live basal area is less than 25 m2/ha. (A range of basal areas from 15 to 55 m2/ha existed in the pre-harvest stand);
Mark trees for cutting according to the following marking rules for each diameter class:
Diameter class
17.5-22.4
22.5-27.5
27.5-32.4
32.5-37.5
42.5-52.5
4.
Marking rule
Cut 4 trees of every 7
Cut 2 trees every 5
Cut no trees
Cut 1 tree of every 5
Cut 2 trees of every 6
Percent removal
57%
40%
0%
20%
33 %
(The marking rules were determined by the number
of stems in the pre-harvest stand in excess of the target
J curve.)
Select individual trees for cutting according to the following specifications:
a) Tree species Subalpine fir = first choice for cutting ; Engelmann spruce = second choice (Retention of spruce was encouraged as it is
currently less abundant than subalpine fir, and an increase in the relative proportion of subalpine fir is not desired.)
b) Tree class / quality Take the worst, leave the best (Wherever possible, the marking objective is to cull the poorer grades of trees from the
stand to establish a vigorous stand of trees capable of using the increased growing space available after the partial cut.)
c) Lichen Loading If a choice is to be made between two trees of equal status, the one with the least amount of lichen is to be marked-to-cut.
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confined stand conditions is its “zero tail-swing” — that is, its
rotating chassis does not extend beyond the dimensions of its
tracks. This feature allows a reasonably experienced operator
to cut selected trees, and to turn and manoeuvre in close proximity to leave-trees, without striking or damaging their boles.
Generally, this machine was able to move on the spring
snowpack and harvest trees throughout the spruce-fir stand
with little evidence of its passage off the skid trails other than
the cut stumps of selected marked-to-cut trees.
The Timbco feller-buncher was used to fell trees both
on and off designated skid trails. Trees selected for cutting up
to 20 metres away from designated skid trails were not dropped
at the stump after cutting and oriented at an angle to the skid
trail as they would be in traditional hand-falling. Rather, the
buncher was able to hold a cut tree upright, back up to the skid
trail, and place the tree on the skid trail in the intended skidding direction.
Logs were skidded to the landings and roadsides by
two D6 tracked grappled skidders. Cut trees were delimbed
at roadside and cut to truck length by a button-top processor
(stroke delimber) and stacked for log hauling three months
later, in July 1998.
The on-site logging supervisor considered the designated skid trails to be an advantage to logging productivity. In
his recent experience with randomly-skidded selection cutting
elsewhere, he had observed that fallers and skidder operators
spent much time locating marked trees and manoeuvring cut
trees around leave-trees. Designated skid trails seemed to solve
this problem and made the falling and skidding more orderly
and efficient.
Regeneration Methods
In August 1998 an excavator with a five-tine site
preparation rake and mechanical thumb attachment was used
to pile logging debris in roadside accumulations and landings.
In the GS unit, harvested openings were mounded with a
small excavator bucket to create warmer micro-sites for planting of spruce seedlings. The STS unit was not mounded due
to limitations on summer equipment access, and risk of machine damage to advance regeneration.
Both units were planted by Northwood Inc. in September 1998 with 1+0 PSB 415 Engelmann spruce stock.
The GS openings were planted to a target stocking standard of
1000 sph. Both spruce and subalpine fir are preferred species,
so quality subalpine fir natural regeneration will also be
silviculturally acceptable. The STS unit was planted to an
estimated 100 to 150 sph outside the drip line of leave trees, in
order to augment the spruce composition of understorey layers.
Acceptable inter-tree spacing was modified to 1.0
metre in the GS unit to facilitate cluster planting. The Silviculture Prescription did not include reforestation of naturally
unstocked wet openings or microsites, but rather, concentrated
on regenerating areas in the vicinity of harvested trees.
Studies of stand dynamics
In partial-cut silvicultural systems, structural elements
of the original forest, including living trees, standing dead
trees, and fallen trees, are carried forward into the post-harvest
stand. Stands resulting from partial cutting will
be structurally complex along both horizontal
and vertical dimensions. However, the longterm effects of various patterns and scales of
partial cutting on stand dynamics and biodiversity are poorly known. At Pinkerton Mountain we are investigating the effects of single
tree selection and group selection on post-harvest stand attributes, dynamics, and structural
biodiversity.
Stand development and growth
and yield study
A network of 24 permanent growth
and yield sample plots (8 per treatment, including the control unit) have been established to
examine medium to long-term stand response
to the different treatments. Response variables
being examined include future stand basal area
and volume growth, regeneration abundance
and vigour, regeneration growth rates and species composition, and damage and mortality
patterns for all sizes of trees.
FIGURE 7. The “zero tail-swing” fellerbuncher was able to harvest trees in
confined spaces without damaging
leave trees.
Wildlife trees and coarse woody debris
Along with the tree measurements that will allow interpretations about stand dynamics, we are collecting a variety
of assessments that will allow us to make interpretations about
habitat for wildlife. Disturbances in the forest, whether they
are caused by humans or other disturbance agents, affect both
forest productivity and biodiversity. Most of the structures
and attributes that distinguish a wildlife tree from
a tree with no special habitat value result from
damage agents, such as disease, insects, wind,
snow, lightning, sudden temperature changes,
and mechanical damage. The processes that
transform a live standing tree into a log on the
forest floor are also processes of damage and
mortality. The information we are collecting
allows us to assess the immediate impact of partial cutting on wildlife trees and coarse woody
debris, and provides baseline data for the longterm monitoring of biodiversity structures.
All the sample trees in our plots are
assessed for the presence of Wildlife Tree Types
(Keisker 1999) – configurations of habitat
features that appear to be required by one of
more wildlife species. For example, Wildlife
Tree Type 1 (WT1) – hard outer wood surrounding decay-softened inner wood – is
needed by Three-Toed Woodpeckers and other
strong cavity excavators as a substrate for the
excavation of nestholes. WT4 – large excaFIGURE 8. Partial cutting may have
vated or natural cavities – is commonly used
both short-term and long-term effects on
by various small owls, bats, squirrels, and memthe occurrence of wildlife trees and
bers of the weasel family for nesting, denning
coarse woody debris.
or resting. Wildlife Tree Types may occur in
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living or dead trees, and are not mutually exclusive. A given
tree may have zero, one, or more Types. We used the number
of Types associated with each sample tree as a single variable
to characterize the habitat value of that tree.
Although 30% removal of basal area was planned for
both harvest treatments, we expected partial cutting to affect
the abundance of wildlife trees differently in the two treatment units. Any trees that can be dangerous to workers —
which includes many of the dead and dying trees — must be
removed in a harvesting area. In a single tree selection unit,
harvesting can potentially take place throughout the unit, and
a high proportion of the dead and dying trees are subject to
removal. In a group selection unit, worker activity is concentrated in the harvest openings, and fewer of the potentially
dangerous trees are likely to affect the work areas.
In the group selection area, the proportion of sample
trees with one or more Wildlife Tree Types that remained after
harvesting was about the same as the overall proportion of
sample trees that remained in the residual stand. Relatively
few trees with Wildlife Tree Types were removed outside the
group selection openings. In the single tree selection area,
71.3% of the sample trees in general were still present after
logging, but only 56.8% of the sample trees with one or more
Wildlife Tree Types were still present. The removal of trees
having value to wildlife was disproportionately greater than
the overall level of removal – but not by as much as we had
expected.
All the Wildlife Tree Types that were present in the
stand before harvesting were still present after harvesting. The
most conspicuous reduction was in WT6 (cracks, loose bark,
or deeply furrowed bark), an attribute that occurs most often
in the study area in subalpine fir that have been dead long
enough to have loose, peeling bark, but still have most of
their full height. Because they often have butt-rot, and are tall
enough to make a large area hazardous, they are likely to be felled.
One of the objectives of the study is to monitor the
effects of damage agents, including logging damage, on wildlife tree attributes. Very few damaged trees were located in the
sample plots. In the group selection area eight (3.9%) of 205
sample trees had minor damage and the rest were undamFIGURE 9. Duration of wetting of Alectoria and
aged. Of the 237 sample trees
Bryoria at two canopy heights, June - September
in the single tree selection area
1998.
four (1.7%) had major damage, five (2.1%) had minor
damage and the rest were undamaged.
Coarse Woody Debris Types
have also been identified
(Keisker 1999). Examples of
Coarse Woody Debris Types
are CWD1 — large concealed spaces used for denning
and escape cover by grouse,
hares, some mustelids, and
other mammals; and CWD5
– large or elevated, long material clear of dense vegeta-
tion used as travel lanes by tree squirrels and chipmunks. The
partial cut harvesting had very little immediate effect on either
the occurrence of Coarse Woody Debris Types in the study
area or on Coarse Woody Debris volume. Estimated volume
of coarse woody debris in the group selection area was 270
+ 49 (SE) m3/ha before logging and 293 + 40 m3/ha after
logging. In the single tree selection area, pre-harvest volume
was 295 + 34 m3/ha and post-harvest volume was 286 +
24 m3/ha. Neither of those changes was statistically significant.
Canopy studies
Partial cutting affects the microclimate in the canopy
and its architecture – the size and shape of tree crowns, the
overlap of branches of different trees, the spatial relationships
between old trees and young trees. Our research examines
which elements of canopy microclimate and architecture are
most important to the productivity of the arboreal lichens
eaten most by mountain caribou – the dark brown beard
lichens, Bryoria spp., and the light green beard lichen, Alectoria
sarmentosa.
Canopy microclimate
As non-vascular plants, lichens do not have access to
groundwater or water from their host tree. Their metabolic
activity depends on direct exposure to precipitation, or in
some cases, delayed exposure, as from snowmelt in the canopy.
The main factor controlling lichen growth rates is thus the
length of time that the thallus — the body of the lichen —
remains moist during and after precipitation. This is controlled primarily by regional climate. Lichens are most abundant
in areas with high rain and snowfall and in areas with frequent
fog and mist. Once lichens have absorbed water from rainwater or snowmelt, the length of time they can remain wet then
becomes important. The effect of air movement on water
vapour changes dramatically from the top to the bottom of a forest
canopy. Near the ground surface the air is comparatively still and
humid. In the upper canopy average wind speed is higher, resulting in more removal of water vapour away from lichen thalli. At
the same time lichens in the upper canopy are exposed to more
sunlight, which also increases drying rates.
These interacting profiles of air movement and sunlight create unique environments for lichen growth in subalpine
spruce-fir forests. In the upper canopy lichens dry rapidly
after each precipitation event (Figure 9). In contrast, lichens in
the lower canopy remain moist much longer, increasing the
length of time they have for growth and reproduction. Our
measures of lichen thallus wetting in intact old-growth forest
show the cumulative impact of these different growth environments. For both Alectoria and Bryoria, the total duration
of wetting in the lower canopy is almost twice that of the same
lichen species growing in the upper canopy. The removal of
trees by selection harvesting shifts these gradients of moisture
and light downwards in the remaining canopy, exposing lower
canopy lichen communities to microclimate conditions more
like that of undisturbed upper canopy forest. Our microclimate
measurements set the stage for understanding the changes we
observe in the growth, distribution, and biomass of the lichens.
Arboreal lichen studies
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FIGURE 10. Abundance of Alectoria, Bryoria and foliose lichens at different
heights in the canopy.
The abundance of forage lichens for caribou reflects the combined influence of several factors: the availability of lichen
fragments to colonize trees, the availability of suitable surfaces
for the lichens to grow on, and favourable microclimatic conditions. The canopy structure of large old-growth trees provides both long-lasting surfaces for colonization by lichens
and a microclimate that promotes continued lichen growth.
Managers need to know at what point changes in stand structure influence this complex of interacting factors such that
lichen growth and colonization are no longer adequate to meet
management objectives. We are examining this question by
studying three parts of the system in natural forest stands
and in stands modified by partial cutting. These system
components are:
Biomass
The biomass of lichens in the canopy affects forage
availability for caribou as well as other ecological processes,
such as nutrient cycling. Ours is one of the first research
studies to measure lichen abundance by directly accessing the
upper canopy using rope-based climbing techniques. We have
found marked height-dependant zonation of canopy lichen
species (Figure 10; Campbell 1998), presumably in response
to microclimate gradients.
Litterfall
The rate at which lichens are removed from the canopy
interacts with biomass to determine the long-term persistence
of lichens in forest stands. The long strands of lichens are
easily fragmented by wind action during storms, some falling
onto lower branches, and some falling to the forest floor. Increased exposure brought about by partial cutting may alter
litterfall rates. In extreme cases, residual lichens can be scoured
from forest stands after partial cutting. We are monitoring
lichen litterfall to determine how partial cutting affects the
removal of lichens from the canopy.
Growth rates
Lichens that remain in the canopy after harvesting
must show continued high growth rates to balance normal
litterfall and other mortality. We are measuring the growth
rates and fragmentation rates of Alectoria and Bryoria in the
lower canopy and mid-canopy of trees in the partially cut and
unharvested areas. By monitoring the growth rates of the
lichens in combination with microclimate measurements, we
expect to have a better understanding of the short-term responses of the lichens to partial cutting, and a better basis for
predicting longer-term responses.
Conclusion
This project has been set up to provide both shortterm and long term benefits. One of our goals in establishing
a silvicultural systems trial at Pinkerton Mountain was to increase operational experience with the kind of partial cutting
that is currently recommended in mountain caribou habitat.
Several key points have emerged from our experience at
Pinkerton Mountain.
•
Detailed pre-harvest planning is essential. While it may
appear to increase overall costs, it is better seen as an investment that will be repaid by increased efficiency of harvesting and silviculture operations, less damage to the residual
stand, and a layout that allows for future stand entries.
•
Designated skid trails laid out on the ground before trees
were marked for cutting made logging operations more
orderly and efficient than in selection harvested blocks
without an overall skidding plan.
•
The small, “zero tail-swing” feller-buncher used in both
the group selection and single tree selection areas allowed
the operator to manoeuvre close to the leave-trees without striking their boles and to carry a harvested tree upright from the stump to the skid trail.
•
To maintain the naturally clumpy structure of the stand,
group selection openings were laid out so that pre-existing clumps of trees were either retained or harvested as a
unit. Use of GPS technology made it practical to create
openings that were irregular rather than geometric in shape.
Another goal was to determine the immediate impact
of partial cutting on the structure of the residual stand. While
not all the data have been analyzed yet, our preliminary results
show that:
•
Fewer than 4% of the sample trees in the residual stand
sustained logging damage. Fewer than 1% were rated as
having major damage.
•
Group selection harvesting had little effect on wildlife
trees outside the harvest openings. Single tree selection
had a greater impact on wildlife trees in the residual stand,
but not as much as expected – 57% of the sample trees
with wildlife habitat attributes were still present after the
single tree selection harvest.
•
Partial cutting had very little immediate effect on either
the volume of coarse woody debris or its wildlife habitat
attributes.
Since maintaining habitat for mountain caribou is part
Ministry of Forests, 5th Floor, 1011 - 4th Avenue, Prince George, BC V2L 3H9 Telephone: (250) 565-6100 Fax: (250) 565-4349
of the rationale for partial cutting in the ESSF, it is important to
evaluate its success. Over the next few years, we expect to
learn more about how partial cutting affects the microclimate
in the canopy and the productivity of the caribou forage lichens that grow there. This information will help managers
decide whether selection silvicultural systems are in fact appropriate in mountain caribou habitat, and what type of prescription is most effective in promoting the abundance of forage lichens.
To make informed decisions about what silvicultural
systems to use to meet resource objectives, managers need to
know the implications of their decisions for a variety of resource values. In the long term, the stand structural information we have collected at Pinkerton Mountain before and
after harvesting will become the baseline for continued monitoring of a variety of stand dynamics processes, and continued
reporting of our results to managers.
References
Alexander, R.R. and C.B. Edminster. 1977. Uneven-aged management of old-growth spruce-fir forests: cutting methods and stand structure goals for the initial entry. USDA
For. Serv., Rocky Mtn. For. Range Exp. Sta., Res. Pap. RM186.
Armleder, H.M. and S.K. Stevenson. 1996. Using alternative
silvicultural systems to integrate mountain caribou and timber management in British Columbia. Rangifer Special Issue No. 9:141-149.
Campbell, J. 1998. Canopy research in north-central British
Columbia: an exploration of lichen communities. MSc
thesis. Univ. of Northern BC, Prince George, BC.
Crampton, D. 1996. Operational comparison of group and single-tree selection systems in mountain caribou habitat. Unpublished contract report, ArborEcos Forest Management
and Research Consulting Ltd, Invermere BC. Submitted to
the Prince George Forest Region, British Columbia Ministry of Forests, Prince George, BC. 7 pages.
Guildin. 1990. BDq Regulation of Sierra-Nevada mixed conifers. J. Forestry 6(2):27-32.
Jull, M., C. DeLong, A. Eastham, R.M. Sagar, S. Stevenson and
R.L. DeLong. 1996. Testing silvicultural systems for the
ESSF: early results of the Lucille Mountain Project. Prince
George Forest Region Research Note # PG-01. Prince
George, BC.
FIGURE 11. Rope-based
climbing techniques
allow access to the
canopy for studies of
microclimate, lichen
abundance, and lichen
growth rates.
Keisker, D.G. 1999. Types of wildlife trees and coarse woody
debris required by wildlife of north-central British Columbia. Unpubl. Report. BC Ministry of Environment,
Lands and Parks, Williams Lake, BC and BC Ministry of
Forests, Prince George, BC.
Smith, D.M. 1986. The practice of silviculture. 2nd Edition.
McGraw-Hill, New York.
Stevenson, S.K., H.M. Armleder, M.J. Jull, D.G. King, E.L. Terry,
G.S. Watts, B.N. McLellan, and K.N. Child. 1994. Mountain caribou in managed forests: preliminary recommendations for managers. Technical Working Group for the
Mountain Caribou in Managed Forests Program. Research
Branch, BC Ministry of Forests, Victoria, BC.
Disclaimer
Acknowledgements
The Northern Rockies Wet-belt ICH/ESSF Silvicultural Systems Research Project and Forest Canopy Processes and Partial-Cutting Silvicultural Systems in Northern Wet-belt Forests
are funded by the Forest Renewal Plan of British Columbia. We appreciate the participation
of our industrial partners: the licensee, Northwood Inc.; the Silviculture Prescription/layout
contractor, Forey Management Ltd.; and the harvesting contractor, Warmac Ventures Ltd.
We acknowledge the contributions of many colleagues, especially D. Crampton (planning the
prescription and training the layout crew), R. Sagar (microclimate data), and J. Clements and K.
Jordan (canopy access). The Borealis Communications Group designed and produced the
publication.
Any mention of product or commercial names is purely
for descriptive purposes and is not intended as an endorsement or approval by the authors or any other party, of any
product or service to the exclusion of other products that
may be equivalent or suitable.
For further information contact:
Susan Stevenson
Silvifauna Research
101 Burden Street, Prince George, BC V2M 2G8
Telephone: (250) 564-5695
Fax: (250) 562-8419
email: [email protected]
Ministry of Forests, 5th Floor, 1011 - 4th Avenue, Prince George, BC V2L 3H9 Telephone: (250) 565-6100 Fax: (250) 565-4349