Montane - Subalpine Riparian Forest
Global Name:
Rocky Mountain-Great Basin Montane Riparian Forest
Global Rank:
G4G5
State Rank:
S4
(see reason below)
External Links
State Rank Reason
These riparian, forested habitats are widespread but face several potential threats from invasive species, livestock grazing, increased severity/frequency of wildfires and climate change, all of which may reduce the condition and extent of these forests. Some past declines have also occurred from many of these same factors and from logging and roadbuilding. Overall, this riparian forest group is relatively secure.
General Description
This National Vegetation Classification Group of forested riparian communities is extensive in Montana, occurring in mountainous areas across the state on both sides of the Continental Divide. West of the Divide it occurs in some of the forested valley bottoms and foothills up to the subalpine zone. East of the Divide it occurs in all the island ranges, and from the southwest mountains to the hills near Ashland in southeast Montana. It encompasses the majority of forested riparian sites occurring in the mountainous areas of the state excluding the Black Cottonwood/Balsam Poplar communities of G796 and the swampy forested sites of G505. Sites may be dominated or co-dominated by a wide range of coniferous trees, Narrowleaf Cottonwood (Populus angustifolia) and/or Quaking Aspen (Populus tremuloides). Coniferous species that may form riparian communities within this group include Grand Fir (Abies grandis), Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii), Ponderosa Pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), and Rocky Mountain Juniper(Juniperus scopulorum). As a result, this group spans a large elevational range from a low of approximately 2,500ft in northwest Montana to almost 9,000ft in the southern mountains. Other environmental and site characteristics also vary widely. Communities in this group are confined to riparian environments occurring on floodplains or terraces of rivers and streams, in V-shaped, narrow valleys and canyons (where there is cold-air drainage). Less frequently, occurrences are found on large floodplains along rivers in moderately wide valley bottoms, on pond or lake margins, and along seeps on gentle to moderate slopes.
This group is similar to the Rocky Mountain Subalpine-Montane Riparian Woodland Ecological System.
Diagnostic Characteristics
Riparian & Wetland Forest; Rocky Mountain Region; Montane and Subalpine Zones; Deciduous and Coniferous Trees
Typical Dominants: Grand Fir (Abies grandis), Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii), Ponderosa Pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii) Narrowleaf Cottonwood (Populus angustifolia), Quaking Aspen (Populus tremuloides), Rocky Mountain Juniper(Juniperus scopulorum)
Similar Systems
Range
This group has an extensive range in Montana occurring in mountainous areas across the state on both sides of the Continental Divide. West of the Divide it occurs in some of the forested valley bottoms and foothills up to the subalpine zone. East of the Divide it occurs in all the island ranges, and from the southwest mountains to the hills near Ashland in southeast Montana.
In MT, G506 occurs within these Level III Ecoregions: 15 (Northern Rockies), 16 (Idaho Batholith), 17 (Middle Rockies), 41 (Canadian Rockies) and portions of 42 (Northwestern Glaciated Plains) and 43 (Northwestern Great Plains).
In Montana, G506 occurs within these Major Land Resource Areas: 43A - Northern Rocky Mountains, 43B - Central Rocky Mountains; 44A - Northern Rocky Mountain Valleys, 44B - Central Rocky Mountain Valleys, 46 - Northern and Central Rocky Mountain Foothills, and portions of 52 - Brown Glaciated Plains, 58A,B - Northern Rolling High Plains.
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, Blaine, Broadwater, Carbon, Cascade, Chouteau, Deer Lodge, Fergus, Flathead, Gallatin, Glacier, Golden Valley, Granite, Hill, Jefferson, Judith Basin, Lake, Lewis and Clark, Liberty, Lincoln, Madison, Meagher, Mineral, Missoula, Musselshell, Park, Phillips, Pondera, Powell, Ravalli, Sanders, Silver Bow, Stillwater, Sweet Grass, Teton, Toole, Wheatland
Based on 2025 land cover layer.
Spatial Pattern
Small Patch and Large Patch
Environment
This group of forested riparian communities occurs in mountainous areas across the state on both sides of the Continental Divide from forested valley bottoms and foothills up to the subalpine zone. Communities in this group are confined to riparian environments occurring on floodplains or terraces of rivers and streams, in V-shaped, narrow valleys and canyons (where there is cold-air drainage). Less frequently, occurrences are found on large floodplains along rivers in moderately wide valley bottoms such as the South Fork of the Flathead River, on pond or lake margins, and along seeps on gentle to moderate slopes. It encompasses the majority of forested riparian sites occurring in the mountainous areas of the state and spans a large elevational range from a low of approximately 2,500ft in northwest Montana to almost 9,000ft in the southern mountains. Other environmental and site characteristics also vary widely.
Vegetation
Riparian sites in this group may be dominated or co-dominated by a wide range of coniferous trees, Narrowleaf Cottonwood (Populus angustifolia) and/or Quaking Aspen (Populus tremuloides). Coniferous species that may form riparian communities within this group include Grand Fir (Abies grandis), Subalpine Fir (Abies lasiocarpa), Engelmann Spruce (Picea engelmannii), Ponderosa Pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), and Rocky Mountain Juniper (Juniperus scopulorum). Mature stands may be open to dense and of medium-stature (Rocky Mountain Juniper) or more commonly tall trees. Sites range from relatively dry, riparian habitats such as in Rocky Mountain Juniper or Ponderosa Pine communities to more mesic sites with lush, shrubby or herbaceous undergrowth. Due to the wide variety of riparian sites encompassed within this group and the large elevational range, the shrub and herbaceous component may be comprised of a very wide range of species. Individual plant community descriptions should be consulted for species associated with particular riparian habitats.
In Montana, this group includes 7 Alliances and 20 Associations within the National Vegetation Classification. However, 1 Alliance and Association, the Thuja plicata - Tsuga heterophylla Rocky Mountain Riparian Forest Alliance (A4432) and the Thuja plicata / Gymnocarpium dryopteris Riparian Forest Association (CEGL000476) are essentially identical to the Tsuga heterophylla / Gymnocarpium dryopteris Forest Association (CEGL000494) in G217 Cedar - Hemlock Forest and likely should be grouped with it. They are probably best treated within G217 as they both occur on lower to mid slopes or in the drier portions of the riparian zone.
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.a G506 Rocky Mountain-Great Basin Montane Riparian Forest
A3757 Abies lasiocarpa - Picea engelmannii Wetland Forest Alliance
CEGL000297 Abies lasiocarpa - Picea engelmannii / Alnus viridis ssp. sinuata Riparian Forest
CEGL000314 Abies lasiocarpa / Ledum glandulosum Riparian Forest
CEGL000336 Abies lasiocarpa - Picea engelmannii / Streptopus amplexifolius Riparian Forest
CEGL000414 Picea (x albertiana, engelmannii) / Packera streptanthifolia Riparian Forest
CEGL002663 Abies lasiocarpa - Picea engelmannii / Mertensia ciliata Riparian Forest
CEGL002677 Picea engelmannii / Cornus sericea Riparian Woodland
CEGL005843 Picea engelmannii / Salix drummondiana Riparian Woodland
A3759 Populus angustifolia Riparian Forest Alliance
CEGL002648 Populus angustifolia / Symphoricarpos (albus, occidentalis, oreophilus) Riparian Woodland
CEGL002664 Populus angustifolia / Cornus sericea Riparian Woodland
CEGL003749 Populus angustifolia / Invasive Perennial Grasses Ruderal Riparian Woodland
A3760 Populus tremuloides Riparian Forest Alliance
CEGL000582 Populus tremuloides / Cornus sericea Riparian Forest
CEGL000609 Populus tremuloides / Symphoricarpos albus Riparian Forest
A3761 Picea pungens - Pseudotsuga menziesii - Abies concolor Riparian Forest Alliance
CEGL000899 Pseudotsuga menziesii / Cornus sericea Riparian Woodland
A3762 Abies grandis Rocky Mountain Riparian Forest Alliance
CEGL000270 Abies grandis / Athyrium filix-femina Riparian Forest
CEGL000280 Abies grandis / Senecio triangularis Riparian Forest
A3797 Pinus ponderosa - Mixed Conifer Riparian Forest Alliance
CEGL000746 Juniperus scopulorum / Cornus sericea Riparian Woodland
CEGL000853 Pinus ponderosa / Cornus sericea Riparian Woodland
CEGL000855 Pinus ponderosa / Crataegus douglasii Riparian Woodland
A4432 Thuja plicata - Tsuga heterophylla Rocky Mountain Riparian Forest Alliance
CEGL000476 Thuja plicata / Gymnocarpium dryopteris Riparian 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
These mostly streamside and floodplain communities are often subject to periodic flooding and fluctuating water tables. Accumulation of winter snowpack, sometimes far upstream and the associated spring runoff are vitally important to the hydrology of these systems.
Management
Grazing along narrow, low order streams can result in increased erosion and channel downcutting (Mitsch and Gosellink 2000). Sites that are subjected to heavy grazing practices may transition to an herbaceous understory consisting of introduced grasses and forbs such as Kentucky bluegrass (Poa pratensis) and Canadian thistle (Cirsium arvense). In addition, fire suppression, timber harvest and reduced flood frequency can affect the succession of riparian communities.
Restoration Considerations
Restoration strategies are dependent on the degree and type of disturbance event. Restoration efforts must first concentrate on restoring the stream's hydrology, if that has been adversely impacted. In-stream habitat enhancement (e.g., additions of logs or boulders) can be employed after restoring natural processes or where short-term improvements in habitat are needed (e.g., for species in recovery).
Removing or strictly limiting grazing by livestock will allow the community to recover if hydric soils have not been lost due to extensive soil compaction, pugging, or down cutting of stream channels, and if there are existing populations of herbaceous, native species (Carex, Juncus, and native grasses) that possess rhizomatous root systems capable of re-colonizing bare soils. Rhizomatous, highly adaptable exotic grasses such as Kentucky bluegrass, common timothy and smooth brome and pasture forbs such as clovers (Trifolium species) and common dandelion (Taraxacum officinale) may persist on the site and compete with existing populations of native graminiods and forbs. Grazing should be excluded for several years to allow adequate re-growth and recovery of existing shrubs and the herbaceous understory.
Most shrub species within these riparian habitats are capable of re-sprouting and typically possess extensive, spreading root systems, minimizing additional restoration needs. Vigor, health and degree of vegetative regeneration of existing trees and shrubs must be evaluated to determine if these components of the community are capable of recovery in an acceptable time frame. Intensive revegetation efforts should be limited to sites where catastrophic wildfire or prolonged heavy grazing has destroyed existing trees, shrubs and the seed bank.
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 (2015)
Montana Version Authors
S. Mincemoyer, L. Vance, C. McIntyre, T. Luna
Version Date
12/6/2024
References
- Additional ReferencesLegend:
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Ellis, Janet H., and Jim Richards. 2003. A planning guide for protecting Montana's wetlands and riparian areas. Bozeman, MT: Montana Watercourse.
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.
Malanson, George P., and David R. Butler. 1991. "Floristic Variation among Gravel Bars in a Subalpine River, Montana, U.S.A.". Arctic and Alpine Research. 23 (3): 273-278.
Mitsch WJ, Gosselink JG. 2000. Riparian Ecosystems. In: Wetlands. 3rd Edition. John Wiley and Sons, Inc. 920 p.
- Web Search Engines for Articles on "Rocky Mountain-Great Basin Montane Riparian Forest"