Biomes

Montana valley and foothill grasslands

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Choteau, Montana, USA. Photograph by David Olson

The Montana valley and foothill grasslands ecoregion occupies high valleys and foothill regions in the central Rocky Mountains of Montana in the USA and Alberta, Canada. The ecoregion, part of the Nearctic realm, occupies the Rocky Mountain Front, the uppermost flatland reaches of the Missouri River drainage involving part of the Yellowstone River basin, and extends into the Clark Fork-Bitterroot drainage of the Columbia River system. The ecoregion also extends marginally into a small part of northern Wyoming. Having moderate vertebrate species richness, 321 different vertebrate taxa have been recorded in the Montana valley and foothill grasslands. The Montana valley and foothill grasslands is deemed an element of the Temperate Grasslands, Savannas, Shrublands Biome.


The Canadian component of this ecoregion is characterized by undulating to rolling topography, and surface deposits are composed of loamy glacial till and clayey lacustrine deposits. It should be noted that there are smaller outliers of this region nested within some of the major river valleys (e.g. Bow River Valley) west of the ecoregion that are not shown on the coarse-scaled North American map.

Located in the Chinook belt, this ecoregion is characterized by dry, warm summers and mild winters. Mean annual temperature is 3.5°C, mean summer temperature is 14°C, and mean winter temperature is -8°C. Annual precipitation is approximately 425 millimeters (mm).

Biological Distinctiveness

The dominant vegetation type of this ecoregion varies somewhat, but consists mainly of wheatgrass (Agropyron spp.) and fescue (Festuca spp.). Certain valleys, notably the upper Madison, Ruby, and Red Rock drainages of southwestern Montana, are distinguished by extensive sagebrush (Artemisia spp.) communities as well. This is a reflection of semi-arid conditions caused by pronounced rain shadow effects and high elevation. Thus, near the Continental Divide in southwestern Montana, the ecoregion closely resembles the nearby Snake/Columbia shrub steppe.

caption Ruby River/ Beaverhead River confluence. Source: Mike Cline While other sites may experience similar rain-shadow effects, lower elevation, greater overall precipitation, and edaphic variations impede sagebrush growth. Along the Rocky Mountain Front, glaciated potholes in the foothills prairie create extensive wetlands and much more mesic grassland conditions than in the high valleys. The western segments of the ecoregion are within the range of moist air masses from the Pacific.

In Canada, the grassland community is dominated by rough fescue, with lesser quantities of Parry oat grass, Junegrass (Koelaria sp.) and Wheatgrass (Agropyron spp.). Forbs are also abundant, and include sticky geranium (Geranium viscosissimum), Bedstraw (Galium sp.), and Yellow Bean (Thermopsis spp.). Moist sites support shrub communities, with the most arid areas manifesting an increased amount of Needle-and-thread Grass (Stipa comata). Trees are found only in very sheltered locations along waterways.

Biodiversity

In addition to the vegetative palette, there are 321 recorded vertebrate taxa in the Montana valley and foothill grasslands.

Mammals

A number of mammalian species are found in the ecoregion, including: American Pika (Ochotona princeps), a herbivore preferring talus habitat; Bighorn Sheep (Ovis canadensis), Black-tailed Prairie Dog (Cynomys ludovicianus), who live in underground towns that may occupy vast areas; Brown Bear (Ursos arctos); Hoary Marmot (Marmota caligata), a species who selects treeless meadows and talus as habitat; and the Northern River Otter (Lontra canadensis), a species that can tolerate fresh or brackish water and builds its den in the disused burrows of other animals.

Historically, heavy grazing by native herbivores-chiefly American Bison (Bison bison)–was a major influence on most of this ecoregion. Periodic wildfires were also part of the disturbance regime. Some characteristic wildlife species of the Foothill Grasslands include White-tailed Deer (Odocoileus virginianus), Pronghorn Antelope (Antilocapra americana), Coyote (Canis latrans), rabbit (Sylvilagus sp.) and grouse (Dendragapus sp.).

Amphibians

There are six distinct anuranAn amphibian that has limbs but no tail (includes all frogs and toads) species that can be found in the Montana valleys and foothills grasslands, including: Canadian Toad (Anaxyrus hemiophrys); Western Toad (Anaxyrus boreas); Northern Leopard Frog (Lithobates pipiens); Plains Spadefoot Toad (Spea bombifrons); Columbia Spotted Frog (Rana luteiventris), an anuran that typically breeds in shallow quiet ponds; and the Boreal Chorus Frog (Pseudacris maculata).

Exactly two amphibian taxa occurr in the ecoregion: Long-toed Salamander (Ambystoma macrodactylum), a species who prefers lentic Surface waters which are essentially still, such as lakes, ponds or puddles waters and spends most of its life hidden under bark or soil; Tiger Salamander (Ambystoma tigrinum)

Reptiles

caption Yellow-bellied Racer. Source: Todd Pierson/EoL Reptilian species within the ecoregion are: Milk Snake (Lampropeltis triangulum), an adaptable taxon that can be found on rocky slopes, prairie and near streambeds; Painted Turtle (Chrysemys picta); Western Plains Garter Snake (Thamnophis radix), a taxon that can hibernate in the burrows of rodents or crayfish or even hibernate underwater; Yellow-bellied Racer (Coluber constrictor); Spiny Softshell Turtle (Apalone spinifera); Western Terrestrial Garter Snake (Thamnophis elegans); Rubber Boa (Charina bottae); Western Skink (Plestiodon skiltonianus); and the Western Rattlesnake (Crotalis viridis).

Fish

The ecoregion supports endemic and relict fisheries: Westslope Cutthroat Trout (Oncorhynchus clarki lewisi), Yellowstone Cutthroat Trout (Oncorhynchus clarkii bouvieri), and fluvial Arctic Grayling (Thymallus arcticus), a relict species from past glaciation.

The moderating effects of strong chinook winds results in a high diversity of vegetation communities in close proximity to one another. Certain sites contain relatively high levels of species richness. The Centennial Valley of southwestern Montana supports 487 vascular plant taxa. This valley supports large breeding populations of the Trumpeter Swan (Cygnus buccinator) and Sandhill Crane (Grus canadensis). Owing to its highly productive wetlands and juxtaposition to nearby montane habitats, the Centennial Valley may also be a candidate site for Grizzly Bear (Ursus arctos) recolonization of grassland habitat. This valley and other undeveloped valleys provide critical linkage habitat for grizzlies and other species moving between separate mountain ranges. Such areas also provide critical seasonal range for ungulates like Elk (Cervus elaphus) and Bighorn Sheep (Ovis canadensis).

Conservation Status

Habitat Loss and Degradation

Approximately 25 percent of the ecoregion remains as intactThe condition of an ecological habitat being an undisturbed or natural environment habitat. Less than 10 percent of the Canadian portion of this ecoregion is estimated to remain as intact habitat. Most of the ecoregion has been heavily altered. Domestic livestock overgrazing, draining of wetlands, and conversion to row crops have been major anthropogenic changes to the ecoregion. Replacement of native species with exotic grasses, and noxious weed invasions, are serious problems.

More recently, development for residential homes has been a major threat to the ecoregion. Much of the very high human population growth in the Rocky Mountains region naturally finds its way to this ecoregion, because land is largely privately-owned and lends itself to conversion to residential uses.

Long-term environmental pollution from hard rock mining is a major concern. The ecoregion contains the nation's largest national Superfund toxic waste site, stretching along the Clark Fork and Blackfoot Rivers from the Continental Divide west to Missoula, Montana.

Remaining Blocks of Intact Habitat

There are still major tracts of relatively intact habitat in the ecoregion. Along the East Front of the Rockies, from Great Falls to near Calgary, it is possible to find large tracts of grassland that have only experienced grazing. Key areas include:

  • The Pine Butte Swamp Reserve, a TNC site near Choteau, southwestern Montana
  • Extensive wetland areas on the Blackfeet Indian Homeland.
  • Whaleback, Alberta
  • In the southwestern corner of Montana, there are vast expanses of undeveloped foothills and valley bottoms. In these remote areas, homebuilding is not an immediate large-scale threat, although some key riparian areas are being subdivided and developed.
  • The Centennial Valley, the Big Hole Valley, and undeveloped parts of the Madison Valley are relatively pristine sites that are tremendously important to the health of adjacent montane systems.

Degree of Fragmentation

Rapid subdivision in some locales is contributing to wholesale fragmentation of habitat. With subdivision and homebuilding come new beachheads for exotic plant invasions, whether intentional or not. Homebuilding also leads to loss of travel routes and winter range for ungulates and other fauna. This process is most serious in the Paradise Valley, Bitterroot Valley, and the Gallatin Valley around Bozeman. Similar trends may take hold in the Madison Valley in the near future.

Possible oil and gas development on the Rocky Mountain Front in Montana and Alberta could have direct habitat impacts as well as impair connectivity between mountains and grasslands for ungulates, large predators, and other species.

Degree of Protection

The following areas are protected:

  • Red Rock Lakes National Wildlife Refuge and Wilderness, southwestern Montana
  • Pine Butte Swamp Reserve, southwestern Montana
  • National Bison Range, western Montana
  • Various BLM Wilderness Study Areas in southwestern Montana
  • Ross Lake Natural Area, Alberta - 48 km2

Types and Severity of Threats

Conversion of native habitat to homesites has been a serious localized threat in the late twentieth century, although the boom appears to be levelling off. The loss of undeveloped riparian forest linkages across valley bottoms could have severe impacts on the long-term viability of sensitive species like the grizzly bear. Spread of alien and noxious plant species could be a major long-term threat. Conversion of forest to grazing lands has a major impact on forest species; moreover, the continuing leasing of public lands at below market rates for livestock grazing produces gratuitous pressure on grassland habitat.

Suite of Priority Activities to Enhance Biodiversity Conservation

  • Priority sites need to be identified in a timely manner. Three essential components should be protected: 1) rare plant communities/associations (e.g. dune communities, fen bogs, wetlands); 2) biological corridor habitat for large carnivores and other species; and 3) seasonal range for ungulates.
  • Any opportunities to encourage or preserve the phenomenon of Grizzly Bears using grassland/wetland habitat should be a high priority. These opportunities are present on the Rocky Mountain Front and in the Centennial Valley, in particular.
  • Protection for the Whaleback holding in Alberta.

Conservation Partners

  • Alberta Wilderness Association
  • Canadian Parks and Wilderness Society, Calgary/Banff Chapter
  • Castle Crown Wilderness Coalition
  • Federation of Alberta Naturalists
  • Greater Yellowstone Coalition
  • The Nature Conservancy of Montana
  • The Nature Conservancy, Alberta
  • Waterton Natural History Association
  • The Wilderness Society
  • World Wildlife Fund Canada

Relationship to Other Classification Schemes

The ecoregion boundary closely follows Omernik. Bailey lacks a distinctive counterpart to this ecoregion, since his classification of the same geographic area amalgamates the entire elevational gradient, with the exception of M332C, corresponding the Rocky Mountain Front portion of this ecoregion. This ecoregion follows Küchler's 56 and 57; Küchler classifies the Beaverhead, Red Rock, and Big Hole drainages as 49, distinguishing it markedly from the other Montana valleys.

The Canadian portion of the Montana valley and foothill grasslands is made up of Fescue Grassland (TEC 158) along the face of the Rocky Mountain foothills. This narrow region is characterized by Grassland, Aspen Grove Boreal Forest (17), and Douglas-fir and Lodgepole Pine Montane forests (5).

References

  • Aubrey L. Haines. 2000. The Lewis and Clark Era (1805–1814). Yellowstone National Park: Its Exploration and Establishment. U.S. Department of the Interior. Washington DC
  • Verne Huser. 2004. On the river with Lewis and Clark. Texas A&M University Press.  ISBN 1-58544-344-1
  • Matthew Jaeger, Ken Frazer, Clark Nelson, Mike Vaughn, Brad Schmitz, Jim Darling. 2005. Movements and habitat use of Yellowstone native fishes and reptiles and nesting distributions of native birds. T2-25-2 Report. Montana Department of Fish, Wildlife and Parks. Miles City, MT

Disclaimer: This article contains some information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for the new information added by EoE personnel.

 

Glossary

Citation

Hogan, C., & Fund, W. (2014). Montana valley and foothill grasslands. Retrieved from http://www.eoearth.org/view/article/51cbee767896bb431f69805a

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