No. 4. 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. 

H04_1.JPG (298590 bytes)Physical Setting. This habitat is typified by a moderate to deep winter snow pack that persists for 3 to 9 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.

Landscape Setting. This habitat is found adjacent to Westside Lowlands Conifer-Hardwood Forest, Eastside Mixed Conifer Forests, 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 epiphytie lichens are typically abundant in the canopy.

H04_2.JPG (251441 bytes)Composition. This forest habitat is recognized by the dominance or prominence of 1 of the following species: Pacific silver fir (Abies amabilis), mountain hemlock (Tsuga mertensiana), subalpine fir (A. lasiocarpa), Shasta red fir (A. magnific var. shastensi), 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 Mountains ecoregion, 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.

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), and 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).

H04_3.JPG (345740 bytes)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 Project 126 and Oregon Vegetation Landscape-Level Cover Types 127 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.

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 ³800 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.

H04_4.JPG (320906 bytes)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 is considered imperiled 10.

[ Top ]
[ Literature Citations ]
[ Wildlife-Habitat Types - Table 1 ]