24 – Montane Coniferous Wetlands
Christopher B. Chappell & Jimmy Kagan
Geographic Distribution. This habitat occurs in mountains throughout much of Washington
and Oregon, except the Basin and Range of southeastern Oregon, the Klamath Mountains of southwestern
Oregon, and the Coast Range of Oregon. This includes the Cascade Range, Olympic Mountains, Okanogan
Highlands, Blue and Wallowa mountains.
Physical Setting. This habitat is typified as
forested wetlands or floodplains with a persistent winter snow pack, ranging from moderately to very deep.
The climate varies from moderately cool and wet to moderately dry and very cold. Mean annual precipitation
ranges from about 35 to >200 inches (89 to >508 cm). Elevation is mid- to upper montane, as low as
2,000 ft (610 m) in northern Washington, to as high as 9,500 ft (2,896 m) in eastern Oregon. Topography is
generally mountainous and includes everything from steep mountain slopes to nearly flat valley bottoms.
Gleyed or mottled mineral soils, organic soils, or alluvial soils are typical. Subsurface water flow
within the rooting zone is common on slopes with impermeable soil layers. Flooding regimes include
saturated, seasonally flooded, and temporarily flooded. Seeps and springs are common in this habitat.
Landscape Setting. This habitat occurs along stream courses or as patches, typically
small, within a matrix of Montane Mixed Conifer Forest, or less commonly, Eastside Mixed Conifer Forest or
Lodgepole Pine Forest and Woodlands. It also can occur adjacent to other wetland habitats: Eastside
Riparian-Wetlands, Westside Riparian- Wetlands, or Herbaceous Wetlands. The primary land uses are forestry
and watershed protection.
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Structure. This is a forest or woodland (>30% tree canopy
cover) dominated by evergreen conifer trees. Deciduous broadleaf trees are occasionally co-dominant. The
understory is dominated by shrubs (most often deciduous and relatively tall), forbs, or graminoids. The
forb layer is usually well developed even where a shrub layer is dominant. Canopy structure includes
single-storied canopies and complex multi-layered ones. Typical tree sizes range from small to very large.
Large woody debris is often a prominent feature, although it can be lacking on less productive sites.
Composition. Indicator tree species for this habitat, any of which can be dominant or
co-dominant, are Pacific silver fir (Abies amabilis), mountain hemlock (Tsuga mertensiana),
and Alaska yellow-cedar (Chamaecyparis nootkatensis) on the westside, and Engelmann spruce
(Picea engelmannii), subalpine fir (Abies lasiocarpa), lodgepole pine (Pinus
contorta), western hemlock (T. heterophylla), or western redcedar (Thuja plicata) on the
eastside. Lodgepole pine is prevalent only in wetlands of eastern Oregon. Western hemlock and redcedar are
common associates with silver fir on the westside. They are diagnostoc of this habitat on the east slope
of the central Washington Cascades, and in the Okanogan Highlands. Douglas-fir (Pseudotsuga
menziesii) and grand fir (Abies grandis) are sometimes prominent on the eastside. Quaking aspen
(Populus tremuloides) and black cottonwood (P. balsamifera ssp. trichocarpa) are in
certain instances important to co- dominant, mainly on the eastside. Dominant or co-dominant
shrubs include devil’s-club (Oplopanax horridus), stink currant (Ribes bracteosum),
black currant (R. hudsonianum), swamp gooseberry (R. lacustre), salmonberry (Rubus
spectabilis), red-osier dogwood (Cornus sericea), Douglas’ spirea (Spirea
douglasii), common snowberry (Symphoricarpos albus), mountain alder (Alnus incana),
Sitka alder (Alnus viridis ssp. sinuata), Cascade azalea (Rhododendron albiflorum),
and glandular Labrador- tea (Ledum glandulosum). The dwarf shrub bog blueberry (Vaccinium
uliginosum) is an occasional understory dominant. Shrubs more typical of adjacent uplands are
sometimes co-dominant, especially big huckleberry (V. membranaceum), oval-leaf huckleberry (V.
ovalifolium), grouseberry (V. scoparium), and fools huckleberry (Menziesia ferruginea).
Graminoids that may dominate the understory include bluejoint reedgrass (Calamagrostis
canadensis), Holm’s Rocky Mountain sedge (Carex scopulorum), widefruit sedge (C.
angustata), and fewflower spikerush (Eleocharis quinquiflora). Some of the most abundant forbs
and ferns are ladyfern (Athyrium filix-femina), western oakfern (Gymnocarpium dryopteris),
field horsetail (Equisetum arvense), arrowleaf groundsel (Senecio triangularis), two-
flowered marshmarigold (Caltha leptosepala ssp. howellii), false bugbane (Trautvetteria
carolinensis), skunk-cabbage (Lysichiton americanus), twinflower (Linnaea borealis),
western bunchberry (Cornus unalaschkensis), clasping- leaved twisted-stalk (Streptopus
amplexifolius), singleleaf foamflower (Tiarella trifoliata var. unifoliata), and five-
leaved bramble (Rubus pedatus). Other Classifications and Key References. This
habitat includes nearly all of the wettest forests within the Abies amabilis and Tsuga
mertensiana zones of western Washington and northwestern Oregon and most of the wet forests in the
Tsuga heterophylla and Abies lasiocarpa zones of eastern Oregon and
Washington.88 On the eastside, they may extend down into the Abies grandis
zone also. This habitat is not well represented by the Gap projects because of its
relatively limited acreage and the difficulty of identification from satellite images. But in the Oregon
Gap II Project126 and Oregon Vegetation Landscape-Level Cover
Types127 the vegetation types that include this type would be higher elevation
palustrine forest, palustrine shrubland, and NWI palustrine emergent. These are primarily palustrine
forested wetlands with a seasonally flooded, temporarily flooded, or saturated flooding
regime.54 They occur in both lotic and lentic systems. Other references describe
this habitat.36, 57, 90, 101, 108, 111, 114, 115, 118, 123, 132, 221
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Natural Disturbance Regime. Flooding, debris flow, fire, and wind are the major natural
disturbances. Many of these sites are seasonally or temporarily flooded. Floods vary greatly in frequency
depending on fluvial position. Floods can deposit new sediments or create new surfaces for primary
succession. Debris flows/torrents are major scouring events that reshape stream channels and riparian
surfaces, and create opportunities for primary succession and redistribution of woody debris. Fire is more
prevalent east of the Cascade Crest. Fires are typically high in severity and can replace entire stands,
as these tree species have low fire resistance. Although fires have not been studied specifically in these
wetlands, fire frequency is probably low. These wetland areas are less likely to burn than surrounding
uplands, and so may sometimes escape extensive burns as old forest refugia.1
Shallow rooting and wet soils are conducive to windthrow, which is a common small-scale disturbance that
influences forest patterns. Snow avalanches probably disturb portions of this habitat in the northwestern
Cascades and Olympic mountains. Fungal pathogens and insects also act as important small- scale natural
disturbances. Succession and Stand Dynamics. Succession has not been well studied in this
habitat. Following disturbance, tall shrubs may dominate for some time, especially mountain alder, stink
currant, salmonberry, willows (Salix spp.), or Sitka alder. Quaking aspen and black cottonwood in
these habitats probably regenerate primarily after floods or fires, and decrease in importance as
succession progresses. Lodgepole pine is often associated with post-fire conditions in eastern
Oregon,131 although in some wetlands it can be an edaphic climax species.
Pacific silver fir, subalpine fir, or Engelmann spruce would be expected to increase in importance with
time since the last major disturbance. Western hemlock, western redcedar, and Alaska yellow-cedar
typically maintain co-dominance as stand development progresses because of the frequency of small-scale
disturbances and the longevity of these species. Tree size, large woody debris, and canopy layer
complexity all increase for at least a few hundred years after fire or other major disturbance.
Effects of Management and Anthropogenic Impacts. Roads and clearcut logging practices can
increase the frequency of landslides and resultant debris flows/ torrents, as well as sediment loads in
streams.198, 199, 229 This in turn alters hydrologic patterns and the composition and
structure of montane riparian habitats. Logging typically reduces large woody debris and canopy structural
complexity. Timber harvest on some sites can cause the water table to rise and subsequently prevent trees
from establishing.221 Wind disturbance can be greatly increased by timber
harvest in or adjacent to this habitat. Status and Trends. This habitat is naturally
limited in its extent and has probably declined little in area over time. Portions of this habitat have
been degraded by the effects of logging, either directly on site or through geohydrologic modifications.
This type is probably relatively stable in extent and condition, although it may be locally declining in
condition because of logging and road building. Five of 32 plant associations representing this habitat
listed in the National Vegetation Classification are considered imperiled or critically
imperiled.10 Back to Top
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