Montane Forested Wetland
Global Name:
Rocky Mountain-Great Basin Swamp Forest
Global Rank:
G4G5
State Rank:
S4?
(see reason below)
External Links
State Rank Reason
These forested wetland habitats are widespread but somewhat uncommon. They have been relatively stable but are likely to experience threats from increases in fire severity and frequency, increased temperatures and drought as well as from invasive species.
General Description
This National Vegetation Classification Group encompasses wetlands dominated by coniferous or deciduous trees growing on poorly drained soils that are saturated year-round or have seasonal flooding in the spring. Sites are poorly drained, mucky areas, and have standing water at least early in the growing season often with a mosaic of moving water and stagnant water. Sites may be dominated or co-dominated by one or more species including Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii and Picea, x albertiana), Lodgepole Pine (Pinus contorta), Paper Birch (Betula papyrifera), Quaking Aspen (Populus tremuloides), Western Redcedar (Thuja plicata), and Western Hemlock (Tsuga heterophylla). Many sites occupied by these species are upland communities, but these forested sites are typified by soils that are saturated year-round and/or are seasonally flooded with an obligate wetland herbaceous understory. These forests are typically found on flat to gently sloping bottomlands often adjacent to low gradient, montane streams. They also occur adjacent to ponds, fens, wet meadows or marshes and may be found from valley bottoms to the lower subalpine. In Montana, this group occurs in mountainous areas on both sides of the Continental Divide.
This group includes the Rocky Mountain Conifer Swamp Ecological System and portions of the Rocky Mountain Subalpine-Montane Riparian Woodland Ecological System.
Diagnostic Characteristics
Wetland Forest; Rocky Mountain Region; Montane and Subalpine Zones; Deciduous and Coniferous Trees; Seasonally, Vernally or Permanently Saturated Soils.
Typical Dominants: Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii and Picea, x albertiana), Lodgepole Pine (Pinus contorta), Paper Birch (Betula papyrifera), Quaking Aspen (Populus tremuloides), Western Redcedar (Thuja plicata), Western Hemlock (Tsuga heterophylla)
Similar Systems
Range
In Montana, this group occurs in mountainous areas on both sides of the Continental Divide. East of the Divide in the island ranges of central Montana, it is likely restricted to the Belts, Snowies and Crazy Mtn and may be absent from drier ranges like the Bear’s Paw and Little Rocky Mountains.
In MT, G505 occurs within these Level III Ecoregions: 15 (Northern Rockies), 16 (Idaho Batholith), 17 (Middle Rockies) and 41 (Canadian Rockies).
In Montana, G505 occurs within these Major Land Resource Areas: 43A-Northern Rocky Mountains, 43B-Central Rocky Mountains, and 44A - Northern Rocky Mountain Valleys.
Density and Distribution
Based on 2025 land cover layer. Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Mapped Distribution by County
Beaverhead, Big Horn, Broadwater, Carbon, Deer Lodge, Flathead, Gallatin, Glacier, Granite, Jefferson, Judith Basin, Lake, Lewis and Clark, Lincoln, Madison, Meagher, Mineral, Missoula, Park, Powell, Ravalli, Sanders, Silver Bow, Teton
Based on 2025 land cover layer.
Spatial Pattern
Small Patch
Environment
This group 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 often adjacent to low gradient montane streams. These wetland forests occur from valley bottoms to the lower subalpine. They can also occur on steeper slopes where soils are shallow over unfractured bedrock. Soils in these groups 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. There may be both moving and stagnant water within these forests. These communities may occur as an ecotone between fens, wet meadows or marshes and mesic, upland coniferous forests. Some occurrences develop in spring-fed areas adjacent to lakes and ponds, but they are most often found on benches, toeslopes or valley bottoms along mountain streams.
Vegetation
This group is dominated by conifers or deciduous trees with an obligate wetland herbaceous understory on poorly drained soils that are saturated year-round or that have seasonal flooding in the spring. Sites may be dominated or co-dominated by Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii and Picea, x albertiana), Lodgepole Pine (Pinus contorta), Paper Birch (Betula papyrifera), Quaking Aspen (Populus tremuloides), Western Redcedar (Thuja plicata), or Western Hemlock (Tsuga heterophylla). The understory is dominated by obligate wetland, herbaceous species. In many conifer-dominated swamps, the understory vegetation is characterized by a 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 Rough Horsetail (Equisetum hyemale) and American ladyfern are frequently the dominant species in the understory. 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 Round-leaved Orchis (Amerorchis 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 Red-osier 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 4,200 feet. In these swamps, Devil’s-club (Oplopanax horridus) is the dominant understory. Pacific Yew (Taxus brevifolia) is often present. The herbaceous understory includes Skunk Cabbage, American Ladyfern, Wild Ginger (Asarum caudatum), Foam Flower (Tiarella trifoliata), Starry False Solomon's-seal (Smilacina stellata), and Sweet-scented Bedstraw (Galium triflorum).
Subalpine Fir (Abies lasiocarpa) swamps are infrequent in Montana, but floristically, they are very similar to western red cedar swamps. This minor type occurs in colder areas between 3,900 to 5,000 feet in northwestern Montana (Pfister et al. 1977). However, subalpine fir-bluejoint reedgrass communities 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.
In Montana, this group includes 4 Alliances and 13 Associations within the National Vegetation Classification, which likely encompasses the diversity of these habitats within this group in the state.
National Vegetation Classification
Download the complete NVC hierarchy for Montana
TP1 B08 Palustrine Wetland
TP1.a S69 Forested Wetland
TP1.a2 F136 Temperate-Boreal Forested Wetland
TP1.a2.Nd D195 Rocky Mountain-Great Basin Montane Flooded and Swamp Forest
TP1.a2.Nd.1 M034 Rocky Mountain-Great Basin Montane Riparian and Swamp Forest
TP1.a2.Nd.1.b G505 Rocky Mountain-Great Basin Swamp
A3758 Pinus contorta var. murrayana - Pinus contorta var. latifolia Swamp Forest Alliance
CEGL000138 Pinus contorta / Calamagrostis canadensis Swamp Forest
CEGL005929 Pinus contorta / Cornus sericea Swamp Woodland
A3775 Picea engelmannii Swamp Forest Alliance
CEGL000300 Abies lasiocarpa - Picea engelmannii / Calamagrostis canadensis Swamp Forest
CEGL000322 Abies lasiocarpa - Picea engelmannii / Oplopanax horridus Swamp Forest
CEGL000357 Picea engelmannii / Caltha leptosepala Swamp Forest
CEGL000405 Picea (x albertiana, engelmannii) / Carex disperma Swamp Forest
CEGL000412 Picea (x albertiana, engelmannii) / Lysichiton americanus Swamp Forest
CEGL002678 Picea engelmannii / Calamagrostis canadensis Swamp Forest
CEGL005927 Picea engelmannii / Equisetum arvense Swamp Forest
A3776 Thuja plicata - Tsuga heterophylla Rocky Mountain Swamp Forest Alliance
CEGL000473 Thuja plicata / Athyrium filix-femina Swamp Forest
CEGL000479 Thuja plicata - Tsuga heterophylla / Oplopanax horridus Rocky Mountain Swamp Forest
CEGL005931 Thuja plicata / Carex disperma Swamp Forest
A4431 Populus tremuloides - Betula papyrifera Swamp Forest Alliance
CEGL000574 Populus tremuloides / Calamagrostis canadensis Swamp Forest
*Disclaimer: Some Alliances and Associations are considered provisional. Some require further documentation to verify their occurrence in the state
and some may be modified or deleted in future revisions after collection of additional data and information.
Dynamic Processes
Due to the high-water tables, the shallowly-rooted trees are susceptible to windthrow.
Management
Sites should be managed to maintain hydrologic function. Wet soils are very vulnerable to compaction. 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 communities (Jones 2003).
Restoration Considerations
Restoring hydrology on sites where water has been drained or the hydrology altered is critical for proper functioning and maintenance of the habitats.
Species Associated with this Community
- How Lists Were Created and Suggested Uses and Limitations
Animal Species Associations
Please note that while all vertebrate species have been systematically associated with vegetation communities, only a handful of invertebrate species have been associated with vegetation communities and invertebrates lists for each vegetation community should be regarded as incomplete. Animal species associations with natural vegetation communities that they regularly breed or overwinter in or migrate through were made by:
- 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, Werner et al. 2004, Adams 2003, and Foresman 2012);
- Evaluating structural characteristics and distribution of each vegetation community relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each vegetation community;
- Calculating the percentage of observations associated with each vegetation community relative to the percent of Montana covered by each vegetation community 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. Species that only migrate through Montana were only evaluated for migratory habitat use. In general, species are listed as associated with a vegetation community if it contains structural characteristics known to be used by the species. However, species are not listed as associated with a vegetation community if we found no support in the literature for the species’ use of structural characteristics of the community even if point observations were associated with it. If you have any questions or comments on animal species associations with vegetation communities, please contact the Montana Natural Heritage Program's Senior Zoologist.
Plant Species Associations
Please note that while diagnostic, dominant, or codominant vascular plant species for a vegetation community have been systematically assigned to those communities and vascular plant Species of Concern were systematically evaluated for their associations with vegetation communities, the majority of Montana’s vascular plant species have not been evaluated for their associations with vegetation communities and no attempt has been made to associate non-vascular plants, fungi, or lichens with vegetation communities. Plant species associations with natural vegetation communities were made in a manner similar to that described above for animals, but with review of Lesica et al. (2022) and specimen collection data from the Consortium of Pacific Northwest Herbaria. If you have any questions or comments on plant species associations with vegetation communities, please contact the Montana Natural Heritage Program's Program Botanist.
Suggested Uses and Limitations
Species associations with vegetation communities 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 or predicted habitat suitability models (this information can be requested at: https://mtnhp.mt.gov/requests/), or systematic surveys for species and onsite evaluations of habitat by trained biologists. Users of this information should be aware that the land cover data used to generate species associations is based on satellite imagery from 2016 and was only intended to be used at broader landscape scales. Land cover mapping accuracy is particularly problematic when the vegetation communities 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 vegetation community within its known geographic range, portions of that vegetation community 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.
- Consortium of Pacific Northwest Herbaria. https://www.pnwherbaria.org/ Last accessed May 30, 2025.
- 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.
- Lesica P., M. Lavin, and P.F. Stickney. 2022. Manual of vascular plants, 2nd Edition. Brit Press. 779 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.
- Species of Concern Associated with this Community
Vascular Plants
Mammals
Birds
Amphibians
Invertebrates
- Diagnostic, Dominant, or Codominant Plant Species for this Community
Vascular Plants
- Other Native Species Commonly Associated with this Community
Vascular Plants
Original Concept Authors
G. Kittel and M.S. Reid (2015)
Montana Version Authors
S. Mincemoyer, T. Luna, C. McIntyre, L. Vance
Version Date
12/6/2024
References
- Literature Cited AboveLegend:
View Online Publication- 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.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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.
- Web Search Engines for Articles on "Rocky Mountain-Great Basin Swamp Forest"
