06 – Lodgepole Pine Forest and Woodlands
Rex C. Crawford
Geographic Distribution. This habitat is found along the eastside
of the Cascade Range, in the Blue Mountains, the Okanogan Highlands and ranges
north into British Columbia and south to Colorado and California. With
grassy undergrowth, this habitat appears primarily along the eastern slope of
the Cascade Range and occasionally in the Blue Mountains and Okanogan Highlands.
Subalpine lodgepole pine habitat occurs on the broad plateau areas along the
crest of the Cascade Range and the Blue Mountains, and in the higher elevations
in the Okanogan Highlands. On pumice soils this habitat is confined to the
eastern slope of the Cascade Range from near Mt. Jefferson south to the vicinity
of Crater Lake.
Physical Setting. This habitat is located mostly
at mid- to higher elevations (3,000-9,000 ft [914-2,743 m]). These environments
can be cold and relatively dry, usually with persistent winter snowpack. A few
of these forests occur in low-lying frost pockets, wet areas, or under edaphic
control (usually pumice) and are relatively long-lasting features of the
landscape. Lodgepole pine is maintained as a dominant by the well-drained, deep
Mazama pumice in eastern Oregon. Landscape Setting. This habitat
appears within Montane Mixed Conifer Forest east of the Cascade crest and the
cooler Eastside Mixed Conifer Forest habitats. Most pumice soil lodgepole pine
habitat is intermixed with Ponderosa Pine Forest and Woodland habitats and is
located between Eastside Mixed Conifer Forest habitat and either Western Juniper
Woodland or Shrub-steppe habitat.
Structure. The lodgepole pine
habitat is composed of open to closed evergreen conifer tree canopies. Vertical
structure is typically a single tree layer. Reproduction of other more
shade-tolerant conifers can be abundant in the undergrowth. Several distinct
undergrowth types develop under the tree layer: evergreen or deciduous
medium-tall shrubs, evergreen low shrub, or graminoids with few shrubs. On
pumice soils, a sparsely developed shrub and graminoid undergrowth appears with
open to closed tree canopies.
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Composition. The tree layer of this
habitat is dominated by lodgepole pine (Pinus contorta var.
latifolia and P. c. var. murrayana), but it is usually
associated with other montane conifers (Abies concolor, A. grandis, A.
magnifica var. shastensis, Larix occidentalis, Calocedrus decurrens,
Pinus lambertiana, P. monticola, P. ponderosa, Pseudotsuga menziesii).
Subalpine fir (Abies lasiocarpa), mountain hemlock (Tsuga
mertensiana), Engelmann spruce (Picea engelmannii), and whitebark
pine (Pinus albicaulis), indicators of subalpine environments, are
present in colder or higher sites. Quaking aspen (Populus tremuloides)
may occur in small numbers. Shrubs can dominate the undergrowth. Tall
deciduous shrubs include Rocky Mountain maple (Acer glabrum),
serviceberry (Amelanchier alnifolia), oceanspray (Holodiscus
discolor), or Scouler’s willow (Salix scouleriana). These tall
shrubs often occur over a layer of mid-height deciduous shrubs such as baldhip
rose (Rosa gymnocarpa), russet buffaloberry (Shepherdia
canadensis), shiny-leaf spirea (Spiraea betulifolia), and snowberry
(Symphoricarpos albus and/or S. mollis). At higher elevations, big
huckleberry (Vaccinium membranaceum) can be locally important,
particularly following fire. Mid-tall evergreen shrubs can be abundant in some
stands, for example, creeping Oregongrape (Mahonia repens), tobacco brush
(Ceanothus velutinus), and Oregon boxwood (Paxistima myrsinites).
Colder and drier sites support low-growing evergreen shrubs, such as
kinnikinnick (Arctostaphylos uva-ursi) or pinemat manzanita (A.
nevadensis). Grouseberry (V. scoparium) and beargrass (Xerophyllum
tenax) are consistent evergreen low shrub dominants in the subalpine part of
this habitat. Manzanita (Arctostaphylos patula), kinnikinnick, tobacco
brush, antelope bitterbrush (Purshia tridentata), and wax current
(Ribes cereum) are part of this habitat on pumice soil. Some
undergrowth is dominated by graminoids with few shrubs. Pinegrass
(Calamagrostis rubescens) and/or Geyer’s sedge (Carex geyeri)
can appear with grouseberry in the subalpine zone. Pumice soils support grassy
undergrowth of long-stolon sedge (C. inops), Idaho fescue (Festuca
idahoensis) or western needlegrass (Stipa occidentalis). The latter
two species may occur with bitterbrush or big sagebrush and other bunchgrass
steppe species. Other nondominant indicator graminoids frequently encountered in
this habitat are California oatgrass (Danthonia californica), blue
wildrye (Elymus glaucus), Columbia brome (Bromus vulgaris) and
oniongrass (Melica bulbosa). Kentucky bluegrass (Poa pratensis),
and bottlebrush squirreltail (Elymus elymoides) can be locally abundant
where livestock grazing has persisted. The forb component of this
habitat is diverse and varies with environmental conditions. A partial forb list
includes goldthread (Coptis occidentalis), false solomonseal
(Maianthemum stellata), heartleaf arnica (Arnica cordifolia),
several lupines (Lupinus caudatus, L. latifolius, L. argenteus
ssp. argenteus var. laxiflorus), meadowrue
(Thalictrum occidentale), queen’s cup (Clintonia
uniflora), rattlesnake plantain (Goodyera oblongifolia), skunkleaf
polemonium (Polemonium pulcherrimum), trailplant (Adenocaulon
bicolor), twinflower (Linnaea borealis), Sitka valerian (Valeriana
sitchensis), western starflower (Trientalis latifolia), and several
wintergreens (Pyrola asarifolia, P. picta, Orthilia secunda).
Other Classifications and Key References. The Lodgepole Pine Forest and
Woodland habitat includes the Pinus contorta zone of eastern Oregon and
Washington.88 The Oregon Gap II
Project126 and Oregon Vegetation Landscape-Level Cover
Type127 that would represent this type is lodgepole
pine forest and woodlands. Quigley and Arbelbide181
referred to this habitat as Lodgepole pine cover type and as a
part of the Dry Forest potential vegetation group. Other references detail plant
associations with this habitat.117, 118, 122, 123, 144, 212, 221
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Natural Disturbance Regime. This habitat typically
reflects early successional forest vegetation that originated with fires. Inland
Pacific Northwest lodgepole pine has a mean fire interval of 112
years.22 Summer drought areas generally have low to
medium-intensity ground fires occurring at intervals of 25-50 years, whereas
areas with more moisture have a sparse undergrowth and slow fuel build-up that
results in less frequent, more intense fire. With time, lodgepole pine stands
increase in fuel loads. Woody fuels accumulate on the forest floor from insect
(mountain pine beetle) and disease outbreaks and residual wood from past fires.
Mountain pine beetle outbreaks thin stands that add fuel and create a drier
environment for fire or open canopies and create gaps for other conifer
regeneration. High-severity crown fires are likely in young stands, when the
tree crowns are near deadwood on the ground. After the stand opens up,
shade-tolerant trees increase in number. Succession and Stand
Dynamics. Most Lodgepole Pine Forest and Woodlands are early- to mid seral
stages initiated by fire. Typically, lodgepole pine establishes within 10-20
years after fire. This can be a gap phase process where seed sources are scarce.
Lodgepole stands break up after 100-200 years. Without fires and insects, stands
become more closed-canopy forest with sparse undergrowth. Because lodgepole pine
cannot reproduce under its own canopy, old unburned stands are replaced by
shade-tolerant conifers. Lodgepole pine on pumice soils is not seral to other
tree species; these extensive stands, if not burned, thin naturally, with
lodgepole pine regenerating in patches. On poorly drained pumice soils, quaking
aspen sometimes plays a mid-seral role and is displaced by lodgepole when aspen
clones die. Serotinous cones (cones releasing seeds after fire) are uncommon in
eastern Oregon lodgepole pine (P. c. var. murrayana). On the
Colville National Forest in Washington, only 10% of lodgepole pine (P. c.
var. latifolia) trees in low-elevation Douglas-fir habitats had
serotinous cones, whereas 82% of cones in high-elevation subalpine fir habitats
were serotinous.4 Effects of Management and
Anthropogenic Impacts. Fire suppression has left many single-canopy
lodgepole pine habitats unburned to develop into more multilayered stands.
Thinning of serotinous lodgepole pine forests with fire intervals <20 years
can reduce their importance over time. In pumice-soil lodgepole stands, lack of
natural regeneration in harvest units has lead to creation of “pumice
deserts” within otherwise forested habitats.47
Status and Trends. Quigley and
Arbelbide181 concluded that the extent of the
lodgepole pine cover type in Oregon and Washington is the same as before 1900
and in regions may exceed its historical extent. Five percent of Pacific
Northwest lodgepole pine associations listed in the National Vegetation
Classification are considered imperiled.10 At a finer
scale, these forests have been fragmented by roads, timber harvest, and
influenced by periodic livestock grazing and altered fire regimes. Back to Top
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