04 – Montane Mixed Conifer Forest
Christopher B. Chappell
Geographic Distribution. These forests occur in mountains
throughout Washington and Oregon, excepting the Basin and Range
of southeastern Oregon. These include the Cascade Range, Olympic
Mountains, Okanogan Highlands, Coast Range (rarely), Blue and Wallowa
mountains, and Siskiyou Mountains.
Physical Setting. This habitat is typified by a moderate
to deep winter snow pack that persists for three to nine months.
The climate is moderately cool and wet to moderately dry and very
cold. Mean annual precipitation ranges from about 40 inches (102
cm) to >200 inches (508 cm). Elevation is mid- to upper montane,
as low as 2,000 ft (610 m) in northern Washington, to as high as
7,500 ft (2,287 m) in southern Oregon. On the westside, it occupies
an elevational zone of about 2,500 to 3,000 vertical feet (762 to
914 m), and on the eastside it occupies a narrower zone of about
1,500 vertical feet (457 m). Topography is generally mountainous.
Soils are typically not well developed, but varied in their parent
material: glacial till, volcanic ash, residuum, or colluvium. Spodosols
are common.
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Landscape Setting. This habitat is found adjacent to Westside
Lowlands Conifer-Hardwood Forest, Eastside Mixed Conifer Forest,
or Southwest Oregon Mixed Conifer-Hardwood Forest at its lower elevation
limits and to Subalpine Parkland at its upper elevation limits.
Inclusions of Montane Forested Wetlands, Westside Riparian-Wetlands,
and less commonly Open Water or Herbaceous Wetlands occur within
the matrix of montane forest habitat. The typical land use is forestry
or recreation. Most of this type is found on public lands managed
for timber values and much of it has been harvested in a
dispersed-patch pattern.
Structure. This is a forest, or rarely woodland, dominated
by evergreen conifers. Canopy structure varies from
single- to multi-storied. Tree size also varies from small to
very large. Large snags and logs vary from abundant to
uncommon. Understories vary in structure: shrubs, forbs,
ferns, graminoids or some combination of these usually
dominate, but they can be depauperate as well. Deciduous
broadleaf shrubs are most typical as understory
dominants. Early successional structure after logging or
fire varies depending on understory species present.
Mosses are a major ground cover and epiphytic lichens
are typically abundant in the canopy.
Composition. This forest habitat is recognized by the dominance
or prominence of one of the following species: Pacific silver fir
(Abies amabilis), mountain hemlock (Tsuga mertensiana),
subalpine fir (A. lasiocarpa), Shasta red fir (A. magnifica
var. shastensis), Engelmann spruce (Picea engelmannii),
noble fir (A. procera), or Alaska yellow-cedar (Chamaecyparis
nootkatensis). Several other trees may co-dominate: Douglas-fir
(Pseudotsuga menziesii), lodgepole pine (Pinus contorta),
western hemlock (Tsuga heterophylla), western redcedar (Thuja
plicata), or white fir (A. concolor). Tree regeneration
is typically dominated by Pacific silver fir in moist westside middle-elevation
zones; by mountain hemlock, sometimes with silver fir, in cool,
very snowy zones on the westside and along the Cascade Crest; by
subalpine fir in cold, drier eastside zones; and by Shasta red fir
in the snowy mid- to upper-elevation zone of southwestern and south-central
Oregon.
Subalpine fir and Engelmann spruce are major species
only east of the Cascade Crest in Washington, in the Blue
and Wallowa mountains, and in the northeastern Olympic
Mountains (spruce is largely absent in the Olympic
Mountains). Lodgepole pine is important east of the
Cascade Crest throughout and in central and southern
Oregon. Douglas-fir is important east of the Cascade Crest
and at lower elevations on the westside. Pacific silver fir
is a major species on the westside as far south as central
Oregon. Noble fir, as a native species, is found primarily
in the western Cascades from central Washington to
central Oregon. Mountain hemlock is a common dominant
at higher elevations along the Cascade Crest and to the
west. Western hemlock, and to a lesser degree western
redcedar, occur as dominants primarily with silver fir at
lower elevations on the westside. Alaska yellow-cedar
occurs as a co-dominant west of the Cascade Crest in
Washington, rarely in northern Oregon. Shasta red fir and
white fir occur only from central Oregon south, the latter
mainly at lower elevations.
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Deciduous shrubs that commonly dominate or co-dominate
the understory are oval-leaf huckleberry
(Vaccinium ovalifolium), big huckleberry (V. membranaceum),
grouseberry (V. scoparium), dwarf huckleberry (V.
cespitosum), fools huckleberry (Menziesia ferruginea),
Cascade azalea (Rhododendron albiflorum), copperbush
(Elliottia pyroliflorus), devil’s-club (Oplopanax horridus), and,
in the far south only, baldhip rose (Rosa gymnocarpa), currants
(Ribes spp.), and creeping snowberry (Symphoricarpos
mollis). Important evergreen shrubs include salal (Gaultheria
shallon), dwarf Oregongrape (Mahonia nervosa), Pacific
rhododendron (Rhododendron macrophyllum), deer oak (Quercus
sadleriana), pinemat manzanita (Arctostaphylos nevadensis),
beargrass (Xerophyllum tenax), and Oregon boxwood (Paxistima
myrsinites).
 Graminoid
dominants are found primarily just along the Cascade Crest and to
the east and include pinegrass (Calamagrostis rubescens),
Geyer’s sedge (Carex geyeri), smooth woodrush (Luzula
glabrata var. hitchcockii), and long-stolon sedge (Carex
inops). Deerfern (Blechnum spicant) and western oakfern
(Gymnocarpium dryopteris) are commonly co-dominant. The most
abundant forbs include Oregon oxalis (Oxalis oregana), single-leaf
foamflower (Tiarella trifoliata var. unifoliata),
rosy twisted-stalk (Streptopus roseus), queen’s cup
(Clintonia uniflora), western bunchberry (Cornus unalaschkensis),
twinflower (Linnaea borealis), prince’s pine (Chimaphila
umbellata), five-leaved bramble (Rubus pedatus), dwarf
bramble (R. lasiococcus), sidebells (Orthilia secunda),
avalanche lily (Erythronium montanum), Sitka valerian (Valeriana
sitchensis), false lily- of-the-valley (Maianthemum dilatatum),
and Idaho goldthread (Coptis occidentalis).
Other Classifications and Key References. This habitat
includes most of the upland forests and their successional stages,
except lodgepole pine dominated forests, in the Tsuga mertensiana,
Abies amabilis, A. magnifica var. shastensis,
A. lasiocarpa zones of Franklin and Dyrness.88
Portions of this habitat have also been referred to as A. amabilis-Tsuga
heterophylla forests, A. magnifica var. shastensis
forests, and Tsuga mertensiana forests.87 It
is equivalent to Silver fir- Douglas-fir forest No. 3, closed portion
of Fir-hemlock forest No. 4, Red fir forest No. 7, and closed portion
of Western spruce-fir forest No. 15.136
The Oregon Gap II Project126 and Oregon
Vegetation Landscape-Level Cover Types127 that
would represent this type are mountain hemlock montane forest, true
fir-hemlock montane forest, montane mixed conifer forest, Shasta
red fir-mountain hemlock forest, and subalpine fir-lodgepole pine
montane conifer; also most of the conifer forest in the Silver Fir,
Mountain Hemlock, and Subalpine Fir Zones of Washington Gap.37
A number of other references describe this habitat.13,
15, 17, 25, 26, 36, 38, 90, 108, 111, 114, 115, 118, 144, 148, 158,
212, 221
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Natural Disturbance Regime. Fire is the major natural
disturbance in this habitat. Fire regimes are primarily of the high-severity
type,1 but also include the moderate-
severity regime (moderately frequent and highly variable) for Shasta
red fir forests.39 Mean fire-return intervals
vary greatly, from [.greaterequal]800 years for some mountain hemlock-silver
fir forests to about 40 years for red fir forests. Windstorms are
a common small-scale disturbance and occasionally result in stand
replacement. Insects and fungi are often important small-scale disturbances.
However, they may affect larger areas also, for example, laminated
root rot (Phellinus weirii) is a major natural disturbance,
affecting large areas of mountain hemlock forests in the Oregon
Cascades.72
Succession and Stand Dynamics. After fire, a typical stand
will briefly be occupied by annual and perennial ruderal forbs and
grasses, as well as predisturbance understory shrubs and herbs that
resprout. Stand initiation can take a long time, especially at higher
elevations, resulting in shrub/herb dominance (with or without a
scattered tree layer) for extended periods.3, 109 Early
seral tree species can be any of the potential dominants for the
habitat, or lodgepole pine, depending on the environment, type of
disturbance, and seed source. Fires tend to favor early seral dominance
of lodgepole pine, Douglas-fir, noble fir, or Shasta red fir, if
their seeds are present.1 In some areas,
large stand-replacement fires will result in conversion of this
habitat to the Lodgepole Pine Forest and Woodland habitat, distinguished
by dominance of lodgepole. After the tree canopy closes, the understory
typically becomes sparse for a time. Eventually tree density will
decrease and the understory will begin to flourish again, but this
process takes longer than in lower elevation forests, generally
at least 100 years after the disturbance, sometimes much longer.1
As stand development proceeds, relatively shade-intolerant trees
(lodgepole pine, Douglas-fir, western hemlock, noble fir, Engelmann
spruce) typically decrease in importance and more shade-tolerant
species (Pacific silver fir, subalpine fir, Shasta red fir, mountain
hemlock) increase. Complex multi-layered canopies with large trees
will typically take at least 300 years to develop, often much longer,
and on some sites may never develop. Tree growth rates, and therefore
the potential to develop these structural features, tend to decrease
with increasing elevation.
Effects of Management and Anthropogenic Impacts. Forest
management practices, such as clearcutting and plantations, have
in many cases resulted in less diverse tree canopies with an emphasis
on Douglas-fir. They also reduce coarse woody debris compared to
natural levels, and truncate succession well before late-seral characteristics
are expressed. Post-harvest regeneration of trees has been a perpetual
problem for forest managers in much of this habitat.16,
97 Planting of Douglas-fir has often failed at higher
elevations, even where old Douglas-fir were present in the unmanaged
stand.115 Slash burning often has negative
impacts on productivity and regeneration.186
Management has since shifted away from burning and toward planting
noble fir or native species, natural regeneration, and advance regeneration.16,
103 Noble fir plantations are now fairly common in
managed landscapes, even outside the natural range of the species.
Advance regeneration management tends to simulate wind disturbance
but without the abundant downed wood component. Shelterwood cuts
are a common management strategy in Engelmann spruce or subalpine
fir stands.221
Status and Trends. This habitat occupies large areas of
the region. There has probably been little or no decline in the
extent of this type over time. Large areas of this habitat are relatively undisturbed
by human impacts and include significant old-growth stands. Other areas have been extensively affected by
logging, especially dispersed patch clearcuts. The habitat is stable
in area, but is probably still declining in condition because of
continued logging. This habitat is one of the best protected, with
large areas represented in national parks and wilderness areas.
The only threat is continued road building and clearcutting in unprotected
areas. None of the 81 plant associations representing this habitat
listed in the National Vegetation Classification are considered
imperiled.10
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