Middle Rockies Small Alpine and Subalpine Stream - Draft Account
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General Description
This system is found in the high elevation (usually >2000m) mountainous streams of the Northern and Middle Rockies Ecoregions, including the isolated moutain ranges. Elevation ranges from as low as 6,600 ft in northwestern Montana to 10,500 feet in southwestern Montana. Streams are steep, small and >50% open canopied (1st, 2nd order, avg. wetted width <3m, avg. summer temp <10°C). The sub class E001L are reaches connected to alpine cirque lakes and may have salmonids present if the lake has been stocked. These will generally be Yellowstone or westslope Cutthroat trout, but sometimes brook trout, golden trout or rainbows.
Diagnostic Characteristics
The smallest E001 alpine creeks are steep, shallow and fishless, containing Rocky Mountain Tailed Frogs as the only vertebrate species. The E002 alpine creeks are more gradual gradient, shallow and fishless. If fish are present in the drainage or have access to the streams from a lake outlet, they will typically be members of a single species assemblage dominated by westslope or Yellowstone cutthroat trout depending on the drainage, or by the introduced golden or brook trout. This assemblage is dictated by the fish stocking history of the high mountain lakes in the area. Native species management plans have been developed by management agencies, but high mountain lakes are often still stocked with introduced species. Sufficient downstream barriers (waterfalls, boulder step-drops) usually exist to prevent the dispersal of mottled sculpin into this system and impede the colonization of introduced species (brook trout) into the pure cutthroat trout areas. The (L) subclass of this ecological system denotes up or downstream connectors to alpine lakes. These can have very different habitat within 100m of the lake. The diverse Macroinvertebrate community of coldwater stenotherms consists primarily of the Mountain Stream and Medium Mountain Stream Assemblages. The community indicator species are characterized by intolerant, shredder, and scraper mayfly, stonefly and caddisfly species (Drunella spinifera, Epeorus grandis, Yoraperla, Soliperla, Zapada frigida, many Leuctridae and Capniidae species, Oligophlebodes, and numerous predatory Rhyacophila spp. and the cold-water dipterans (Thaumalidae, Bibiocephela, and Glutops). At more downstream occurrences, where the alpine mountain streams begin to lose elevation/gradient and warm (>10 °C), a dominance shift occurs to the Medium Mountain Stream Assemblage.
Range
This system occurs at or above treeline throughout the Rocky Mountain ranges, and east into the mountain island ranges of central and south-central Montana. In Montana, the Alpine Stream community is described from ~30 sites within the Northern and Middle Rockies, including the isolated ranges. These include streams in the Beartooths, Absorokas, Elkhorns, Big Belts, Little Belts, Crazys, Gallatin-Madison-Bridgers, Anaconda-Pintlers, Pioneers and in Glacier National Park. These ecosystems typically fall within the boundaries of US Forest Service, National Park lands and are often within wilderness areas.
Density and Distribution
Spatial Pattern
Linear
Dynamic Processes
Alpine ecosystems are tied to snowpack, climate, groundwater discharge, and water quality. Impacts to these parameters, as well as their natural variability, will have a corresponding effect on alpine biological and ecological systems. Long-term drought, warming temperatures and recreational disturbances in fragile alpine ecosystems are the common impacts on water quantity at alpine stream sites in the northwestern United States.
Management
Due to the high altitude nature of these streams anthropogenic disturbances are usually minimal, but may include high impact recreational use (e.g. stock use, campsites, stream crossings). This stream type may be most threatened by climate change. The communities inhabiting these streams are glacial relicts taking refuge from the last ice age and are confined to these high elevations due to temperature requirements. If these cold-water dependent communities experience increased unsuitable temperatures from snow pack and glacier reductions they have nowhere to go. Due to the inherent inaccessibility of these systems few have been inventoried, but some may contain Species of Concern, like the Lednian Meltwater stonefly (G1S1) and the western glacier stonefly (G2S1) from the glacier-fed streams of Glacier Park. The fish assemblage is dictated by the fish stocking history of the high mountain lakes in the adjacent area. Native species management plans are in place by management agencies, but high mountain lakes are often still stocked with introduced species. Sufficient downstream barriers (waterfalls, boulder step-drops) usually exist to prevent the dispersal of mottled sculpin into this system and impede the colonization of introduced species (brook trout) into the pure cutthroat trout areas.
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
Amphibians
References
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