Miller Creek Demonstration Forest
Prescribed Fire Tour
Penelope A. Latham
Raymond C. Shearer
Kevin L. O’Hara
The three stops on the Prescribed Fire Tour
show differences in forest development on clearcuts that were broadcast burned, South-1 in
May 1968, West-1 in July 1967, and East-3 in
August 1968. Next to clearcut East-3 is unburned East-2 for comparison. These are all
along the Miller Creek Road (#9650). To get
to unit South-1, drive northwesterly from the
junction of the Good Creek Road (#60) and the
Miller Creek Road 0.75 miles to the junction
with Road #2875; stay left on the Miller Creek
Road and proceed westerly 2.0 miles to Clearcut South-1. The trail uphill into the unit starts
about 200 feet from the road junction. Unit
West-1 is 0.75 miles farther on Road #9650 to
the trail (old road) that passes the Moose Pond
and goes to the bottom of unit West-1. Continue
on Road #9650 1.6 miles to units East-3 (uphill
on the left) and East-2 (downhill on the right). A trail begins at the road about 200 feet
past the boundary of East-2 and descends through the old growth forest, continues upward
through the unburned clearcut East-2, then crosses the road into burned clearcut East-3,
and continues uphill to Council Rock, then returns to Road #9650.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
1
South-1: Clearcut and Spring Prescribed Burn
South-1 sits next to clearcuts on two sides and uncut
forest on the remaining two sides. We describe site conditions and management activities on South-1 and suggest
how these events influence current and future forest development.
Vegetation Development_________
Site Conditions
Elevation (ft)
4,913
Slope (%)
22
Azimuth (degrees
clockwise from 0 or
north)
196
Size (acres)
10
Physiography
Dry slope 88%
Flat or bench 9%
Rock outcrop 3%
Habitat type,
phase
Subalpine fir/
queencup beadlily,
beargrass
Pre-disturbance
forest understory
Shrubs: blue
huckleberry
Herbs: broad-leaf
arnica, beargrass
Major disturbances such as clearcutting or wildfire
remove most of the existing vegetation. Afterwards, a
forest is in the stand initiation stage of development,
which means the reoccupation of growing space: seed
dispersal, germination and establishment of new plants,
or growth of surviving vegetation from undamaged root
systems. At Miller Creek, vegetation development after
a stand replacing disturbance primarily resembled the
species composition of the pre-disturbance forest. However, the disturbance itself, along with other forest conditions and finer scale disturbances such as browsing,
all affect the composition of the new forest stand and its
rate of development.
2
Before disturbance, the tree species composition on
South-1 closely resembled the average species composition of Miller Creek stands growing on south-facing
slopes (compare South-1: fig. 1 to South-8: fig. 1). After
disturbance, the tree community in 1984 contained more
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
Douglas-fir and subalpine fir and less of the remaining
species (fig. 2). The primary factors in the development
were the kind and intensity of disturbance. South-1 remained in the herb stage of development for 15 years.
Let’s look at some of the factors contributing to this slow
rate of development.
Tree Seed Availability ___________
Clearcutting eliminated the seed source from onsite
trees. Most natural regeneration came from offsite seed
produced in 1971, an abundant seed year. The density of
Figure 1—Composition of the old growth forest prior to harvest of South-1 is
based on basal area of trees greater than 6 inches diameter at breast height
growing there before it was clearcut, Miller Creek Demonstration Forest, 1967.
tree seedlings was greatest along the eastern and northern edges near the uncut trees. The initial patchy tree
regeneration in the middle and southwest corner of
South-1 was due to the greater distance from the seed
source rather than inadequate seed production. Since
1971, continued tree establishment has slowed because
of infrequent years of heavy cone production and development of other vegetation.
Growing Space Availability ______
Duff Reduction—Inadequate reduction of duff—the
decomposing litter layer that accumulates on the forest
Figure 2—In 1984, 16 years after fire treatment, composition of Douglasfir, Engelmann spruce, and western larch remained high on South-1 based
on the number of established seedlings and saplings.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
3
Treatments and Results
floor—greatly reduced tree establishment on South-1 (fig. 3). Many conifer
Clearcut
June 1967
Slashed
June 30, 1967
Fire treatment
Prescribed burn: May 18, 1968
Duff moisture
Upper: 41%; Lower: 135%
Average: 88%
moisture and nutrients for growth and
Fire intensity
268 g water lost from can analogs
to reduce heat or frost damage to sensi-
Fine fuel reduction
82%
tive new tissues. The mid-spring pre-
Duff reduction
16%
Ground surface
Burned duff
Bare
9/13/1968
78%
11%
Post-disturbance forest
understory (9th year)
Shrubs: blue huckleberry,
sticky currant, spirea, Scouler’s
willow
Herbs: fireweed, beargrass
sity was measured by the amount of
Succession transects
Present
gallon cans systematically distributed
Planting trial
None
Permanent plots
Present
seedlings (such as larch, pines, or
spruce) need bare mineral soil to increase the chance to obtain adequate
scribed fire reduced the duff layer an
8/15/1974
51%
37%
average of only 16 percent and exposed
little of the soil surface.
Fire Intensity—Relative fire inten-
water lost from 36 specially calibrated
within some units, including South-1
and South-8 (table 1). Initially each can
Successional vegetation development transects are marked with
white plastic pipe. The area surrounding the transects serves as a control to compare the effects of management. Corners of this area are
marked with green metal fenceposts.
Permanent tree regeneration plots are marked by iron rebar painted
red at the end. Each tree recorded is marked with metal tags and
white ribbon.
contained 2,000 grams of water. The
greater the amount of water lost during
the fire, the more intense the fire. The
prescribed fire on South-1 took place
in the spring when the lower half of
the duff layer was still saturated from
4
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
Figure 3—In the spring of 1969 flowering beargrass and charred
duff indicate lack of mineral soil for tree regeneration on South-1.
Table 1—Comparison of effects of fire intensity on seedbed preparation in
south-facing units. Data were collected the same year as the prescribed burn:
South-1 (1968); South-8, South-13, and South-14 (1967).
South
units
Fire
intensity
(g water
lost)
Duff
reduction
(%)
Soil
exposure
(%)
S-1
S-8
S-13
S-14**
268
993
NM*
NM*
16
84
100
100
14
84
100
NM
Duff moisture (%)
Average Upper Lower
88
46
40
NM
41
43
24
NM
135
48
56
NM
*Not measured
**Comparable measurements were not collected on South-14 but due to
similarity of pre-fire conditions and post-fire results, they should be similar to
those on South-13.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
5
snowmelt and rain. This resulted in relatively low fire
significant on South-1. Fire intensity was not measured
intensity. In contrast, the three Wildfire Tour units
on South-13 and South-14, as these uncut units burned
(South-8, South-13, and South-14)—previously similar
in the wildfire of August 23, 1967. However, South-8
in fuels, growing conditions, and physical characteris-
was prescribed burned 2 weeks earlier and reburned in
tics to unit South-1—burned with much greater inten-
the wildfire. Fire intensity data for South-8 were acquired
sity. Subsequent vegetation developed much differently.
after the prescribed burn and before the wildfire. As con-
While the tops of many herbs and shrubs were killed,
ditions were similar on these three units, it is reasonable
the underground parts of the plants remained undam-
to believe that fire intensity was also similar. Figure 4
aged (protected by the moist, intact duff layer) and quickly
shows the relationship between average duff moisture
resprouted following burning. Arnica and beargrass re-
and duff reduction.
appeared as abundant survivors. Fireweed also quickly
established from offsite seed sources as the small, cottony
seeds were easily carried on the wind. Tree seedlings,
more dependent on mineral soil, re-established more
Growing space for new tree seedlings was reduced on
South-1 due to inadequate duff reduction. Plants with
surviving root systems quickly reoccupied the site excluding many new tree seedlings and competing strongly
slowly, as did slow-growing blue huckleberry, the domi-
with tree seedlings that did germinate.
nant shrub on the site at the time of disturbance.
Discussion and Comparisons _____
Table 1 illustrates the effect of fire intensity on duff
reduction and preparation of growing space for the new
stand. Usually, high fire intensity combined with low
duff moisture to produce the greatest duff reduction. An
elevated lower duff moisture content was particularly
6
Figure 4—Percent duff reduction is related to water content of the
duff at the time of burning.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
The Future______________________
As a result of the low-severity burn on South-1, less
western larch have grown back than were present before
the fire. Shrub growth also responded slowly in South-1
compared to regrowth and colonization by herbs. For now,
the stand continues to develop slowly, extending the period
of stand initiation (fig. 5). It will probably not go through
a period of intense tree competition, and there will be
creation of mature forest wildlife habitat. However, vertical structure will be diverse in the mature forest as trees
will be of many ages. Broadleaf trees such as aspen and
black cottonwood, and Scouler’s willow (a tree-like shrub)
should persist for an extended period because of the openness of this unit. Many wildlife species should benefit now
and in the future from the foraging and nesting opportunities on South-1.
delayed opportunities for harvestable wood products or
You Will Find These
Species on South-1
Trees: western larch, Englemann spruce, subalpine fir, Douglas- fir, lodgepole pine, western
white pine, aspen, black cottonwood
Shrubs: Scouler’s willow, spiraea, buffaloberry,
blue huckleberry, serviceberry, Rocky Mountain
maple, fool’s huckleberry, Sitka alder
Herbs: beargrass, fireweed, broad-leaf arnica,
goldenrod
Figure 5—In summer 1994, 27 years after fire treatment, tree
regeneration is clumped and slow on South-1.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
7
Moose Pond, Clearcut West-1, and Old Riparian Forest:
Diverse Habitat for Microbes and Moose
The Moose Pond ________________
Riparian areas such as this cattail pond and the adjacent old forest provide important food, water, and shelter
source for migrating birds and resident animals. Buffaloberry is identified by the rust-colored spots on the silvery
underside of the leaves.
for forest animals. Riparian areas encompass a variety
Moose Pond and the nearby forest provide food and
of habitats from lakes, ponds, and bogs to various sized
shelter not only for birds such as blue grouse and gray
forest streams, but they all have one thing in common—
jays, but also for Miller Creek’s large moose population.
water (fig. 6). Vegetation in riparian areas is often diverse
If you are lucky enough to see a moose during your visit,
and changes both horizontally (away from the water’s
edge into the forest) and vertically. Vertical diversity
occurs because the trees, shrubs, and herbs (nonwoody
plants such as wildflowers and grass) grow in many
different layers. More diverse habitats provide greater
numbers of homes and a variety of food sources that in
turn support a wider variety of wildlife and plant species. Ecologists call these differentiated areas a “niche.”
Several tree species grow here. Their individual growth
characteristics contribute to the vertical diversity of this
forest. Fruit-producing shrubs, such as the buffaloberry
you will see along the path, provide an important food
8
Figure 6—A forest ecotone. Riparian forest surrounding a permanent bog.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
do not approach it. In protecting their young, moose can
mark a planting trial near the middle of this unit where
be aggressive. Moose are the least social of the deer species
spruce, western larch, and Douglas-fir trees were planted
and inhabit only the most northern areas of the United
yearly from 1969 through 1973. Researchers wanted to
States except for a narrow finger of habitat extending
compare the growth of planted trees with naturally regen-
along the continental divide from Montana and Idaho
erating trees to determine if planted trees subsequently
into Wyoming, Utah, and Colorado.
grew taller. The scientists also wanted to determine the
Timber harvesting around natural wetlands like you
see here may affect water levels within the pond. Some
species are susceptible to this type of disturbance. Release
of above-normal amounts of water can raise water levels,
reducing important habitat. Managers need to consider
the biological requirements of all species present at a site
when planning management activities.
time in which planted trees would have a height growth
advantage over naturally regenerated trees. Many of
the planted trees attained greater growth over that of
the natural regeneration. Shade-intolerant western larch
consistently showed greater growth if planted, while
Douglas-fir, a moderately shade-tolerant tree, showed
greater growth only if its top was able to grow above surrounding shrubs and forbs. Spruce showed little differ-
West-1 _________________________
As you round the bend in the trail skirting the end of
the pond, you will approach the old riparian forest below
the road. Above the road is a regenerating forest, West-1.
West-1 was clearcut and burned in late July 1967. It
is less comparable to the other west-facing units in the
study area as it is closely surrounded by trees that provide a seed source on three sides, and it is more moist
due to the pond and mature forest nearby. Red stakes
ence because it characteristically grows slower during
the first few years.
No trail goes into this young forest. We have provided
other opportunities to demonstrate the process of regeneration. However, if you choose to walk through it, watch
for sap-wells on some of the trees. Sap-wells are small
holes excavated by yellow-bellied sapsuckers into the
phloem (food-conducting tissue) of trees. Sap builds up in
these cavities and is used as a food source by sapsuckers.
You may also look for western gall rust, a disease on
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
9
thinned lodgepole pine trees—trees lying on the ground.
Precommercial thinning was initiated and many of the
thinned lodgepole pine show evidence of western gall rust.
Precommercial thinning treatments remove trees that
are of poorer quality from dense stands such as the trees
that were infected with western gall rust. The trees are
cut before they have any economic value and are left on
the site.
Old Riparian Forest ______________
The forest below the road is approximately 200 to 250
years old. Upon entering this older forest, notice the vertical diversity: western larch, Douglas-fir, and spruce grow
above the main tree canopy while subalpine fir, spruce,
and yew occupy the lower layers (fig. 7). We do not know
the age distribution of these trees. The forest is older,
so the trees may be of many ages. However, it is equally
Figure 7—Layering of tree canopies in a 250 year old
riparian forest.
possible that the trees are all approximately the same age
and have stratified into these vertical positions because
of differences in growth rates, shade tolerance, and structural characteristics of the tree crowns. The different
shapes of the tree crowns produce variable light patterns
opportunities for forest floor plants and tree seedlings to
grow where they previously could not.
Spruce and subalpine fir have needles and twigs designed
on the forest floor. Dense tree canopies often limit light
to withstand severe winter conditions. As they grow into
in forests. Gaps that allow light to penetrate provide
the overstory, the stiffer branches and needles abrade the
10
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
more flexible canopy of species such as Douglas-fir and
for some species in an environment where nutrients may
western larch. This causes damage to buds and branches
otherwise be limited.
of less sturdy species and creates growing space for spruce
and subalpine fir in the overstory canopy. Douglas-fir is
only moderately able to grow in the shade and does not
compete as well as subalpine fir and spruce under a continuous tree canopy. Therefore, fewer seedlings establish.
You will seldom find western larch seedlings here as they
Temperatures here differ from “outside.” The environment inside the forest is moderated by the overstory tree
canopy and decreases the amount of snow accumulating
on the forest floor. On a hot summer day, old riparian
forests provide a welcome, cooler sanctuary for wildlife—
and people.
require sunlight and mineral soil to germinate and grow.
Dying trees may create larger gaps. As growing space
becomes available, understory species may reclaim some
of it from the overstory trees. The resulting diverse habitat in turn supports a large variety of wildlife (from microbes to moose). Lichens such as the goatsbeard lichen
hanging from many of these trees provide a nutritious
supplement in the winter diet of white-tailed deer.
Another characteristic of old forests is the fallen and
rotting logs on the forest floor. Rotting logs return nutrients (tied up for a long time in trees) back to the soil to
be reused by other organisms. Decaying trees and evidence
of fungal activity such as conks on trees, mushrooms, and
root rot indicate the diversity of soil organisms that are
able to utilize this habitat. Fallen rotting trees also serve
as nurse logs that encourage tree seedling germination
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
You Will Find These Species at
Moose Pond, West-1, and the Old
Riparian Forest
Trees: spruce, subalpine fir, Douglas-fir, western larch, yew
Shrubs: blue huckleberry, twinflower, snowberry, flowering dogwood, thin-leaf alder,
Sitka alder, swamp current, buffaloberry,
Utah honeysuckle
Herbs: broad-leaf arnica, western meadowrue,
queen cup beadlily, mitrewort, coolwort foamflower, baneberry, mountain death camas, onesided wintergreen, blue wildrye
11
East-2: Clearcut with No Fire Treatment
The two adjacent east-facing units (East-2 and East-3)
Site Conditions
were similar in vegetation, growing conditions, fuels,
Elevation (ft)
5,200
Slope (%)
37
development followed clearcutting without prescribed
Azimuth (degrees
clockwise from 0 or
north)
59
fire (East-2) or with prescribed fire treatment (East-3).
Size (acres)
10
East-2 was clearcut and slashed in 1967. No additional
Physiography
Moist slope 92%
Rock outcrop 8%
Habitat type,
phase
Subalpine fir/
queencup beadlily,
fool’s huckleberry
Pre-disturbance
forest understory
Shrubs: fool’s
huckleberry,
Sitka alder, blue
huckleberry
Herbs: broad-leaf
arnica, oak fern
and physical characteristics prior to silvicultural treatment. Three decades later, a significant contrast exists
between the structure of these two stands. Vegetation
treatment was applied. Along the north boundary of
East-2 is a stand of mature forest. We describe site
conditions and management activities on East-2 and
suggest how these events influence current and future
forest development.
Vegetation Development_________
Clearcutting usually removes existing vegetation,
releases growing space, and moves a forest to the stand
initiation stage of development. Developmental processes
became available for colonization by new plants be-
associated with reoccupation of site then occur. However,
cause timber harvesting did not greatly affect shrubs
on East-2, following clearcutting, little growing space
and herbs.
12
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
Treatments and Results
Clearcut
October 1967
Slashed
November 22, 1967
Fire treatment
None
Duff moisture
Not measured but assumed
similar to E-3
Upper: 54%; Lower: 94%
Average: 74%
Relative fire intensity
Not burned
Post-disturbance
forest understory
(9th-year)
Shrubs: Sitka alder, fool’s
huckleberry, blue huckleberry
Herbs: fireweed, broad-leaf
arnica
Succession transects
Present
Planting trial
None
Permanent plots
Present
The old growth forest was mostly
Douglas-fir, subalpine fir, and Engelmann
spruce (fig. 8), with little western larch.
Following silvicultural treatment, the
1984 tree species composition was predominantly Englemann spruce and
Douglas-fir (fig. 9). By 1984, little natural regeneration established on this unit
(fig. 10). Stocking of Douglas-fir was 8 percent in 1979 but declined to 6 percent in
1984. Only Douglas-fir and Englemann
spruce (both shade-tolerant species) regeneration was present in 1984, with
only 56 seedlings and saplings per acre.
Western larch and subalpine fir did re-
Successional vegetation development transects are marked with
white plastic pipe. The area surrounding the transects serves as a
control to compare the effects of management. Corners of this area
are marked with green metal fenceposts.
Permanent tree regeneration plots are marked by iron rebar
painted red at the end. Each tree recorded is marked with metal
tags and white ribbon.
generate following clearcutting, but so
few that none occurred on the regeneration plots. Many small subalpine fir and
Engelmann spruce grew in the understory of the virgin forest and were too
small to cut. These younger trees called
“advance regeneration” grew rapidly when exposed to sunlight and are now the major tree cover. Most
early tree regeneration occurred on sites that had some of the duff layer removed during removal of cut
trees. Understory shrubs and herbs changed little from the pre-disturbance community.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
13
after logging. Without further disturbance, the understory
of Sitka alder, fool’s huckleberry, arnica, and huckleberry
will remain intact. One major exception (apparently resulting from the removal of overstory trees) was the extensive colonization by fireweed where gaps appeared in
the shrub layer (fig. 11). Let’s look at some of the factors
contributing to vegetation development on East-2.
Figure 8—Composition of the old growth forest on East-2 in 1967, prior to
being harvested and slashed, based on basal area of trees greater than
6 inches diameter at breast height, Miller Creek Demonstration Forest.
Vegetation development after clearcutting and slashing on East-2 shows how important disturbance characteristics are in determining the resulting plant community.
Characteristics such as type, severity, and frequency of
disturbances will ultimately determine what survives on
a site. Failure of the disturbance to increase sunlight or
nutrients and to reduce competition will inhibit colonization by new understory species or tree seedlings. East-2
is still in the shrub stage of development three decades
14
Figure 9—In 1984, 17 years after clearcutting, a few Douglas-fir
and Engelmann spruce seedlings made up most of the
regeneration that established on unit East-2, a great change in
composition from the old growth stand.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
development plots (fig. 12), and 11 percent of the total
cover was “advance” subalpine fir.
Growing Space Availability ______
Duff Reduction—Prior to clearcutting, vegetation,
litter, or duff completely covered the forest floor. Little
reduction of this layer followed harvesting except as a
result of scarification, mainly from logs being moved to
roads. The few western larch in East-2 probably germinated on these disturbed sites. In addition, clearcutting
Figure 10—Changes in stocking (percentage of plots on which a
species occurs) by year (1974, 1979, 1984) and species on East-2.
Tree Seed Availability ___________
Clearcutting removed the onsite conifer seed source but
left intact the seed present in the soil and duff. Although
adjacent mature trees to the north and other nearby areas
provided a plentiful offsite seed source, this seed source
did not result in abundant tree regeneration on East-2.
By 1986, tree cover was only 12 percent on the vegetation
Figure 11—In summer 1994, 26 years after clearcutting the dominant
shrubs were the same as those that dominated the uncut stand.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
15
trail one of the unused water can analogs for measuring
fire intensity.
Discussion and Comparisons _____
East-2 is now a shrubfield. Despite the presence of
a nearby conifer seed source, the retention of duff and
existing perennial vegetation (vegetation that lives for
several years) effectively excluded most conifer seedling
establishment. Regeneration was mostly from accelerated growth of understory seedlings of tolerant conifers
such as subalpine fir too small to slash after clearcutting.
Removal of the overstory released these suppressed seedlings, which then grew more rapidly than new seedlings
and maintained enough growth to rise above the shrubs.
Figure 12—Percent cover of herbs, shrubs, and trees for East-2 shows
a dramatic increase in shrub cover 19 years after clearcutting.
The other Miller Creek unit showing similar shrub development is South-8; however, an entirely different set of
circumstances contributed to that fire-generated shrubfield.
the mature stand added considerable slash and unmerchantable wood material to the forest floor. The depth
of duff and slash, and the competition from existing vegetation, permitted only limited natural regeneration of
species such as western larch and lodgepole pine.
regeneration. Competition for light is extreme, making
survival of new conifer seedlings unlikely. In 1984, 17
years after harvest, the average height of regenerating
conifers was 4.0 ft. (This height was calculated from a
Fire Intensity—East-2 was not burned following clearcutting. Before leaving the unit, you will see along the
16
Lack of site preparation has severely limited natural
survey that measured the tallest tree of each species on
each plot. Advance regeneration was not included.) Some
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
alder and fool’s huckleberry may be seeding in from
onsite seed sources.
East-2’s value for many wildlife species is low. Dense
shrubs make travel through the stand difficult for species larger than small mammals and birds. For wildlife
The Future______________________
Sitka alder and fool’s huckleberry codominate in the
shrub stage of development. While competing with tree
establishment, alder benefits this site by fixing nitrogen
in the soil and providing cover for some wildlife species.
that favor dense shrub cover, it is perfect. Species diversity may be decreasing as fewer shade-intolerant tree
species occur and early colonizing herbs such as fireweed
become less abundant. Any potential economic return
will be greatly delayed.
Development of the tree component of vegetation will be
extremely slow. This stand will probably not go through
the stem exclusion or understory reinitiation stages of
development any time in the near future. Existing trees
will just get larger as they age. As tree canopies expand,
some mortality will occur in the shrub layer, opening additional growing space, but both advance and natural regeneration may recapture it more quickly than new
seedlings can establish. This stand will remain poorly
stocked by trees for decades or longer.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
You Will Find These
Species on East-2
Trees: subalpine fire, Englemann spruce,
Douglas-fir, lodgepole pine, western larch
Shrubs: Sitka alder, fool’s huckleberry,
blue huckleberry, Rocky Mountain maple,
mountain lover, gooseberry
Herbs: broad-leaf arnica, fireweed,
oakfern
17
East-3: Clearcut and Summer Prescribed Burn
East-2 and East-3, similar in most characteristics be-
Site Conditions
fore silvicultural treatment, now show dramatically dif-
Elevation (ft)
5,425
Slope (%)
29
summer of 1968. Mature timber is on the west and south
Azimuth (degrees
clockwise from 0 or
north)
72
sides of the clearcut. We describe site conditions and
Size (acres)
10
management activities on East-2 and East-3 and suggest
Physiography
Moist slope 78%
Flat or bench 13%
Rock outcrop 9%
Habitat type,
phase
Subalpine fir/
queencup beadlily,
fool’s huckleberry
Pre-disturbance
forest understory
Shrubs: Sitka
alder, fool’s
huckleberry
Herbs: broad-leaf
arnica
ferent vegetation structure. After clearcutting, East-3
was prescribed burned whereas East-2 was not. East-3,
clearcut and slashed in 1967, was burned during the
how these early treatments precipitate marked changes
in vegetation development.
Vegetation Development_________
Reoccupation of growing space is the primary process
occurring after a stand-replacing disturbance such as
clearcutting. Colonization by new plants and regrowth
of existing plants from undamaged root systems occurred
abundantly during stand initiation on East-3. Tree density increased from 2,568 seedlings and saplings per acre
tree species on this site (fig. 14). After silvicultural treat-
in 1974 to 8,812 in 1984. This represents 15,600 percent
ment, subalpine fir and Douglas-fir substantially in-
greater regeneration than on East-2 in 1984 (fig. 13).
creased by 1974 (fig. 15). Ten years later the percentage
Vegetation development has been dynamic on East-3.
Before disturbance, Englemann spruce was the dominant
18
of western larch and Douglas-fir had increased while
subalpine fir decreased (fig. 16). Stocking of all conifers
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
Figure 15—In 1974, established natural regeneration consisted
mostly of Englemann spruce and least of western larch and
lodgepole pine.
Figure 13—Comparison of the number of naturally regenerated
trees per acre for all species over time are compared for East-2
and East-3 (data from 0.001 acre plots).
Figure 14—Composition of the old growth forest on East-3 in
1967, prior to being harvested and slashed, based on basal
area of trees greater than 6 inches diameter at breast height,
Miller Creek Demonstration Forest.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
Figure 16—During the 10 years ending in 1984, composition
of established natural regeneration increased for Engelmann
spruce, western larch, and Douglas-fir. Composition decreased
for subalpine fir, and stayed about the same for lodgepole pine.
19
Treatments and Results
Clearcut
October 1967
Slashed
November 20, 1967
Fire treatment
Prescribed burned August 7, 1968
Duff moisture
Upper: 54%; Lower: 94%
Average: 74%
Relative fire intensity
940 g average water lost from
36 cans
was 72 percent in 1974 and increased
to 100 percent by 1985. Stocking surveys record the percent of plots on which
a species occurs. Figure 17 shows the
fluctuating stocking relationships
among tree species during that decade.
By 1992, the stand was overstocked,
and Forest Service personnel thinned
designated areas.
Fine fuel reduction
92%
Duff reduction
60%
Ground surface
Burned duff
Bare
7/23/1969
54%
38%
Post-disturbance forest
understory (6th year)
Shrubs: few present
Herbs: fireweed, broad-leaf
arnica
Succession transects
Present
Planting trial
Present
Permanent plots
None
After this disturbance conifers developed
8/15/1984
72%
16%
principally from nearby seed sources.
This tree colonization combined with
reduced mortality of pre-disturbance
herbs and shrubs. Contributing factors
included a relatively hot fire treatment
and a moist duff layer combined with a
cool site. Vegetation change was meas-
Successional vegetation development transects are marked with
white plastic pipe. The area surrounding the transects serves as a
control to compare the effects of management. Corners of this area
are marked with green metal fenceposts.
Planting trials are marked with red painted metal fenceposts.
ured for only 6 years on East-3, but
significant differences occurred between
the two east-facing sites during this
short period (table 2). Herbs, primarily
arnica and fireweed, responded quickly
on East-3, covering 68 percent of the
freshly burned site by the second year. The fire treatment affected shrubs more severely, and the few survivors regrew slowly. By the sixth year, cover of herbs was five times greater than cover of shrubs.
20
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
East-3 remained in the herb stage of development
through 1974 (fig. 18), but stocking surveys show conifer
regeneration was good with 2,568 trees per acre. However,
seedling growth was slower on this cooler site. By 1995,
stand development had progressed quickly, and East-3
is in the stem exclusion stage of development. Let’s look
at some of the factors contributing to this development.
Figure 17—Changes in stocking (percentage of plots on
which a species occurs) by year (1974, 1979, 1984) and
species (western larch, Douglas-fir, Engelmann spruce,
subalpine fir, and lodgepole pine) on East-3.
Table 2—Comparison of vegetation development by life form
percent cover on East-2 and East-3 before harvest
and 6 years later.
Life form
Shrub
Herb
Pre-harvest
East-2
East-3
87
21
105
29
1974
East-2
East-3
82
60
13
61
Figure 18—During the 6 years after clearcutting and burning
treatments, herbs dominated on East-3.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
21
Tree Seed Availability ___________
layer of duff, establishment does not seem to be inhibited
for most species. As the burned duff disintegrated, addi-
Despite clearcutting the onsite conifer seed source,
conifers regenerated quickly from seed produced in the
mature forest on the south and west sides of East-3.
tional mineral soil was exposed for colonization.
Fire Intensity—The prescribed fire on East-3 took place
Most seedlings resulted from the abundant 1971 seed-
in the summer when dry conditions should have produced
fall. Subsequent cone crops provided seed for additional
an intense burn. However, the burn on this moist, east-
seedling establishment, especially Englemann spruce.
facing site was not as intense (940 grams water lost) as
Although the original old growth stand had more lodge-
the burn that occurred on South-8 (993 grams water lost).
pole pine than western larch (fig. 14), by 1984, the larch
The aerial portion of the existing vegetation was burned,
natural regeneration was eight times greater than lodgepole pine (fig. 15). Lodgepole pine was apparently not
well represented in the pre-disturbance community as it
is scarce on East-3.
Growing Space Availability ______
Duff Reduction—The prescribed fire removed the
upper 60 percent of the duff layer and substantially
reduced cover of shade-tolerant understory species, especially huckleberry, Sitka alder, and fool’s huckleberry
(fig. 19). A 1 inch layer of duff remained. On East-3, an
average duff moisture of 75 percent reflected relatively
moist conditions (54 percent upper, 94 percent lower),
which prevented the duff from being consumed by fire and
exposed mineral soil. Despite the retention of this 1 inch
22
Figure 19—White spiraea and box-myrtle regenerating from buried
rhizomes through cracks in the burned duff. Tree seedlings also
germinate on this surface because of access to mineral soil and greater
moisture.
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
but the soil was not heated enough to cause high mortal-
Site location also affects conifer growth. Western larch
ity among the pre-disturbance species on the site. In fact,
and lodgepole pine generally outgrow their associated
arnica, a rhizomatous herb, responded vigorously to fire
species, especially Englemann spruce and subalpine fir.
treatment, recovering 73 percent of its pre-disturbance
Yet, the average size of the tallest natural regeneration
cover by 1970.
shows that differences between species are not as great
on this cooler, higher elevation clearcut than on the other
Discussion and Comparisons _____
clearcuts. Lodgepole pine averaged 2 feet taller than western larch and Englemann spruce but was considerably
Despite abundant regeneration on East-3, mineral soil
smaller than on other clearcuts.
is still available. Moisture does not limit growth. Although
western larch may have continued to colonize East-3
since 1984, it occurs in smaller numbers than on some
of the west-facing or south-facing units. This may be
due to poor timing of the seed crop during the initial establishment of the stand, or it may reflect site conditions.
East-3 is 500 feet higher in elevation than the highest
south-facing unit. Western larch requires a moist but
warm site for best seedling establishment, and East-3
may not be as hospitable as other lower elevation sites.
Planting trials in the center of East-3 show the advantage in height growth obtained by planted species on this
cooler site. Statistics for all planting trials combined show
a range of survival, but trees that survive are generally
above the surrounding competition and taller than most
natural regeneration. Height of planted western larch
averaged more than twice that of the tallest natural regeneration, and the difference is nearly as great for Douglas-fir. In contrast, naturally regenerated Englemann
spruce was as tall or taller than planted spruce.
The complex interactions on East-3 include abundant
seed production (especially by Englemann spruce), moderately hot summer fire, a moist duff layer, a cool site, and
the lack of lodgepole pine seed. These combined to produce the forest community developing on East-3 today.
The Future______________________
By 1995, East-3 had progressed rapidly through early
stages of development and entered the stem exclusion
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998
23
stage (fig. 20) in many parts of the stand. Shading and
tree species contributes to the structural diversity. When
mortality of shrubs is beginning to occur. Further stud-
mature, this stand has the potential to provide abundant
ies will examine the effects of artificial thinning on accel-
wildlife cover. Wood production will be high, and under-
eration of this stand through the stem exclusion stage
story diversity should increase or remain the same due
into understory reinitiation.
to the variable canopy cover and morphology provided by
Variation in the dominance of herbs, shrubs, and trees,
and species composition contribute to the structural diversity and development rate of a stand. While Englemann
the different tree species. East-3 is an excellent example
of a forest community developing as the result of complex
abiotic and biotic interactions.
spruce dominates the stand, the presence of four other
You Will Find These
Species on East-3
Trees: Englemann spruce, subalpine fir, Douglas-fir,
western larch, lodgepole pine, western white pine,
black cottonwood
Shrubs: Scouler’s willow, Sitka alder, fool’s huckleberry, blue huckleberry, mountain lover, gooseberry
Herbs: broad-leaf arnica, fireweed, pearly everlasting, Virginia strawberry, yarrow, aster
Figure 20—In summer 1994, 26 years after prescribed burning unit
East-3, the rapidly developing natural regeneration was entering the
stem exclusion stage.
24
This publication is a supplement to USDA Forest Service Gen. Tech. Rep. RMRS-GTR-7. 1998