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Montana Field Guides

Rocky Mountain Conifer Swamp

Provisional State Rank: S1
(see reason below)

External Links

State Rank Reason
This is a system with limited occurrence in Montana. Drought and climate change are the major stressors; increased fire frequency or intensity, or loss of overstory vegetation, may also alter dynamics.

General Description

In northwestern Montana, conifer swamps occur from 865 to 1485 meters (2,838-5,200 feet). This is a minor system with infrequent occurrences on valley bottoms, lower benches, toeslopes, stream terraces, and flat sites, often adjacent to lakes, fens or wet meadows with low gradient, meandering streams. Water tables are typically within 50 centimeters (20 inches) of the soil surface throughout the year, with standing water in surface depressions. These swamps are dominated by conifers growing on poorly drained soils that are saturated year-round or have seasonal flooding in the spring. This system is indicative of poorly drained, mucky areas, and areas are often a mosaic of moving water and stagnant water. Soils can be woody peat, muck or mineral but tend toward mineral. Vegetation includes wetland phases of western red cedar (Thuja plicata), western hemlock (Tsuga heterophylla), subalpine fir (Abies lasiocarpa) and Engelmann spruce (Picea engelmannii) forests. These wetland forests are generally distinguishable from other upland forests and woodlands by shallow water tables and mesic or hydric undergrowth vegetation. Some of the most typical understory species include American ladyfern (Athyrium filix-femina), woodfern (Dryopterisspecies), skunk cabbage (Lysichiton americanus), field horsetail (Equisetum arvense), arrowleaf groundsel (Senecio triangularis), and bluejoint reedgrass (Calamagrostis canadensis). This system frequently borders fens and wet to mesic coniferous forests.

Diagnostic Characteristics
Woody wetland, Forest and Woodland, saturated soils, depressional, seepage fed slopes, mineral soil w/ A horizon <10 cm

Similar Systems

This system occurs in the northern Rocky Mountains from northwestern Wyoming and central Montana, north into the Canadian Rockies and west into eastern Oregon and Washington. In northwestern Montana, this uncommon system is represented in the Flathead, Kootenai and Yaak river drainages. Montane spruce- and subalpine fir dominated swamps also occur east of the Continental Divide.

Ecological System Distribution
Approximately 6 square kilometers are classified as Rocky Mountain Conifer Swamp in the 2017 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.

Montana Counties of Occurrence
Beaverhead, Broadwater, Carbon, Cascade, Deer Lodge, Flathead, Gallatin, Granite, Jefferson, Judith Basin, Lake, Lewis and Clark, Lincoln, Meagher, Mineral, Missoula, Park, Pondera, Powell, Ravalli, Sanders, Silver Bow, Teton

Spatial Pattern
Large or Small Patch


This system is dominated by coniferous trees on poorly drained soils that are saturated year-round or are subjected to seasonal flooding during spring months. These forests are found on flat to gently sloping lowlands, but also occur up to the lower limits of continuous forest. In northwestern Montana, these uncommon wetland forests occur most frequently in depressions on valley bottoms. However, they can occur on steeper slopes where soils are shallow over unfractured bedrock. Soils in these systems are poorly drained and can be organic peat or muck, but are more commonly mineral soils with an A horizon of 10 centimeters (4 inches) or less. Surface horizons usually have high organic matter, and redox depletions are found in moist subsoil. Water tables are typically within 50 centimeters (20 inches) of the soil surface throughout the year, with standing water in surface depressions. Generally, there is both moving and stagnant water within these forests. The system is often seen as an ecotone gradient between fens, wet meadows or marshes and mesic, upland coniferous forests. Some occurrences develop in spring-fed areas adjacent to lakes and ponds, but the system is most often found on benches, toeslopes or valley bottoms along mountain streams. At higher elevations, subalpine fir-bluejoint reedgrass (Abies lasiocarpa- Calamagrostis canadensis) forests are found along sub-irrigated stream terraces, pond margins and wet meadows (Pfister et al 1977).


In conifer dominated swamps, the understory vegetation is characterized by high cover of ferns and fern allies such as American ladyfern (Athyrium filix-femina), woodfern (Dryopteris species), and horsetail (Equisetum species). Common graminoids include bluejoint reedgrass (Calamagrostis canadensis), beaked sedge (Carex utriculata) and softleaf sedge (Carex disperma).

In spruce- (Picea species) dominated swamps in the Flathead Valley, skunk cabbage (Lysichiton americanus) can form a nearly continuous cover in the understory. American ladyfern is often co-dominant on these sites. In other spruce-dominated occurrences, field horsetail (Equisetum arvense) or common horsetail (Equisetum hyemale) and American ladyfern are frequently the dominant species in the understory. Other forbs include arrowleaf groundsel (Senecio triangularis), Brewer’s miterwort (Mitella breweri), five stamen miterwort (Mitella pentandra), bunchberry dogwood (Cornus canadensis), dwarf red blackberry (Rubus pubescens), twisted stalk (Streptopus amplexifolius), and Canada violet (Viola canadensis) (Hansen et al., 1995). Orchids such as one leaf orchid (Ameorchis rotundifolia), sparrow’s egg ladyslipper (Cypripedium passerinum) and small yellow ladyslipper (Cypripedium parviflorum) may occur on hummocks formed around base of trees and shrubs, especially in spruce swamps occurring adjacent to extremely rich fens. The shrub canopy may include thinleaf alder (Alnus incana), water birch (Betula occidentalis), dwarf birch (Betula nana) and redoiser dogwood (Cornus sericea).

In northwestern Montana, swamps of western redcedar (Thuja plicata) and western hemlock (Tsuga occidentalis) are largely confined to toeslopes and valley bottoms below 1,280 meters (4,200 feet). In these swamps, devil’s club (Oplopanax horridum) is the dominant shrub. Pacific yew (Taxus brevifolia) is often present. The herbaceous understory includes American skunk cabbage, American ladyfern, oak fern (Gymnocarpium dryopteris), wild ginger (Asarum caudatum), foam flower (Tiarella trifoliata), starry solomon’s seal (Maianthemum stellatum), and fragrant bedstraw (Galium triflorum).

Subalpine fir (Abies lasiocarpa) swamps are infrequently represented in Montana, but floristically, they are very similar to western red cedar swamps. This minor type occurs in colder areas between 1,188 to 1,324 meters (3,900 to 5,000 feet) in northwestern Montana (Pfister et al., 1977). However, subalpine fir-bluejoint reedgrass systems are common throughout Montana up to the subalpine elevations. Shrub cover is low and is usually represented by alder (Alnus species). Bluejoint reedgrass dominates the understory vegetation. Associated forbs include lanceleaf arnica (Arnica latifolia), Canadian horseweed (Conyza canadensis), Idaho licorice root (Ligusticum tenuifolium), and brook saxifrage (Saxifraga arguta).

National Vegetation Classification Switch to Full NVC View

Adapted from US National Vegetation Classification

A3613 Tsuga heterophylla - Thuja plicata Warm-Mesic Central Rocky Mountain Forest & Woodland Alliance
CEGL000473 Thuja plicata - Athyrium filix-femina Forest
A3756 Tsuga heterophylla - Picea sitchensis / Lysichiton americanus Swamp Forest Alliance
CEGL002670 Thuja plicata / Tsuga heterophylla - Lysichiton americanus Swamp Forest
A3757 Abies lasiocarpa - Picea engelmannii Swamp Forest Alliance
CEGL000322 Abies lasiocarpa / Picea engelmannii - Oplopanax horridus Swamp Forest
CEGL000336 Abies lasiocarpa / Picea engelmannii - Streptopus amplexifolius Swamp Forest
CEGL000357 Picea engelmannii - Caltha leptosepala Swamp Forest
CEGL002678 Picea engelmannii - Calamagrostis canadensis Swamp Forest
CEGL005927 Picea engelmannii - Equisetum arvense Swamp Forest
A3770 Salix wolfii - Salix brachycarpa - Betula glandulosa Wet Shrubland Alliance
CEGL001079 Betula glandulosa - Carex utriculata Wet Shrubland
CEGL005887 Betula glandulosa - Carex spp. Wet Shrubland
A3775 Picea engelmannii Swamp Forest Alliance
CEGL000405 Picea (engelmannii x glauca, engelmannii) - Carex disperma Swamp Forest
CEGL000412 Picea (engelmannii x glauca, engelmannii) - Lysichiton americanus Swamp Forest
A3776 Thuja plicata - Tsuga heterophylla Rocky Mountain Swamp Forest Alliance
CEGL000479 Thuja plicata / Tsuga heterophylla - Oplopanax horridus Rocky Mountain Swamp Forest
CEGL005931 Thuja plicata - Carex disperma Swamp Forest
*Disclaimer: Alliances and Associations have not yet been finalized in the National Vegetation Classification (NVC) standard.  A complete version of the NVC for Montana can be found here.

Dynamic Processes
Due to the high water tables, trees are very susceptible to windthrow. Fire is very infrequent. Mortality from spruce budworm outbreaks in adjacent upland forests may affect this system.

Adjacent roads, trails, logging and other activities present problems due to poor drainage, organic soils, and high water tables. Wet and moist soils are very vulnerable to compaction, even during winter months. All development, travel and equipment use should be diverted away from these forested swamps to suitable, adjacent upland sites. Timber harvesting is very problematic. Increased land use within 100 meters (328 feet) has been correlated with increased nutrient levels in peatlands in Montana, so setbacks should be 100 meters or greater to adequately protect these systems (Jones, 2003).

Restoration Considerations
The prerequisite for restoration of this system is to restore original hydrology on sites where water has been drained or altered. Remedial restoration work may be needed on sites where timber was harvested.

Species Associated with this Ecological System
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2012.  Mammals of Montana.  Second edition.  Mountain Press Publishing, Missoula, Montana.  429 pp.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Original Concept Authors
Natureserve Western Ecology Group

Montana Version Authors
T. Luna, C. McIntyre, L.K. Vance,

Version Date

  • Classification and Map Identifiers

    Cowardin Wetland Classification:
    System Palustrine
    Class Forested
    Water Regime Saturated or seasonally flooded
    Geographically Isolated Wetland Usually

    NatureServe Identifiers:
    Element Global ID 28639
    System Code CES306.803, Northern Rocky Mountain Conifer Swamp

    National Land Cover Dataset:
    90: Woody Wetlands

    9111: Northern Rocky Mountain Conifer Swamp

  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Hansen, P. L., R. D. Pfister, K. Boggs, B. J. Cook, J. Joy, and D. K. Hinckley. 1995. Classification and management of Montana's riparian and wetland sites. Montana Forest and Conservation Experiment Station, School of Forestry, University of Montana, Miscellaneous Publication No. 54. 646 pp. + posters.
    • Jones, W.M. 2003. Kootenai National Forest peatlands: Description and effects of forest management. Report to the Kootenai National Forest, Montana. Montana Natural Heritage Program, Helena. 14 pp. plus appendices.
    • Pfister, R. D., B. L. Kovalchik, S. F. Arno, and R. C. Presby. 1977. Forest habitat types of Montana. USDA Forest Service. General Technical Report INT-34. Intermountain Forest and Range Experiment Station, Ogden, UT. 174 pp.

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Citation for data on this website:
Rocky Mountain Conifer Swamp — Northern Rocky Mountain Conifer Swamp.  Montana Field Guide.  Retrieved on , from