Montana Field Guide

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 small, gradual gradients and >50% open canopied (1st, 2nd order, avg. wetted width <2m, avg. summer temp <10°C). The (L) subclass of this ecological system denotes up or downstream connections to natural lakes which can have very different habitat for the first 100 m; lake outlets can hold some unique assemblages of aquatic insects (Newell, pers. comm. 2009). The sub class E002L are reaches connected to alpine cirque lakes and may have salmonids present if the lake has been stocked. These will usually be Yellowstone or westslope Cutthroat trout, but sometimes brook trout, golden trout or rainbows.

Many of the smallest alpine creeks are steep, shallow and fishless, containing Rocky Mountain Tailed Frogs as the only vertebrate species. The low gradient (E002) alpine streams 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 state agencies, but high mountain lakes are often still stocked with introduced salmonid 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.

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 and National Park lands, often in wilderness areas.

Linear

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 ecological systems. Long-term drought, warming temperatures and heavy recreation in fragile alpine ecosystems are the common impacts on water quantity at alpine stream sites in the north western United States.

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 ecological type may also be threatened by global warming. The communities inhabiting these streams are often 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 temperatures from diminished snow pack and glaciers, 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 biological assemblage is dictated by the fish stocking history of the high mountain lakes in the 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.