Rocky Mountain Foothill Woodland-Steppe Transition
Provisional State Rank
* (see reason below)
State Rank Reason
Fire is the greatest threat, but given the proximity of this system to residential areas, fires are likely to be controlled.
This inland Pacific Northwest ecological system occurs in the foothills of the Montana Rocky Mountains, where it forms a broad ecotone between true forests ad true steppe, shrublands, or grasslands, typically on warm, dry, exposed sites too droughty to support a closed tree canopy. This is not a fire-maintained system. The "steppe" character results from a climate-edaphic interaction that results in a graminiod-dominated landscape with widely scattered trees; even in the absence of fire, a "woodland" or "forest" structure will not be obtained. Occurrences are found on all slopes and aspects; however, moderately steep to very steep slopes or ridgetops on southerly or western aspects are most common. They can be found on glacial till, glacio-fluvial sand and gravel, dune, basaltic rubble, colluvium, deep loess or volcanic ash-derived soils, with characteristic features of good aeration and drainage, coarse texture, and an abundance of mineral material. Ponderosa pine (Pinus ponderosa) or Douglas-fir (Pseudotsuga menziesii)are the predominant conifers. Limber pine (Pinus flexilis)may be present in some occurrences. In fire-protected transition areas with big sagebrush steppe systems, antelope bitterbrush (Purshia tridentata), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), big sagebrush (Artemisia tridentata ssp. tridentata), and three-tip sagebrush (Artemisia tripartita) may be common. Deciduous shrubs such as common ninebark (Physocarpus malvaceus), commonsnowberry (Symphoricarpos albus), or birch leaf spiraea (Spiraea betulifolia)may be abundant in occurrences west of the Continental Divide. Important grass species include bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg’s bluegrass (Poa secunda), needle and thread (Hesperostipa comata), needlegrass (Achnatherumspecies), and bottlebrush squirreltail (Elymus elymoides). This system is very similar to Northern Rocky Mountain Ponderosa Pine Woodland and Savanna, but with more widely scattered trees.
Woody and herbaceous, aridic and shallow soils, short disturbance interval, Pinus ponderosa, Pseudotsuga menziesii
This system is found in the foothill to montane elevations east of the Continental Divide in northwestern Montana, in the Missouri river breaks and in central Montana on soils derived from shales. Elsewhere it is found from Idaho to the Columbia Plateau region of Oregon and Washington and west along the foothills of the Modoc Plateau and eastern Cascades into southern interior British Columbia.
Ecological System Distribution
Approximately 2,325 square kilometers are classified as Rocky Mountain Foothill Woodland-Steppe Transition in the 2017 Montana Land Cover layers.
Grid on map is based on USGS 7.5 minute quadrangle map boundaries.
Montana Counties of Occurrence
Blaine, Carbon, Carter, Cascade, Chouteau, Fallon, Fergus, Garfield, Golden Valley, Hill, Judith Basin, Lewis and Clark, Liberty, Mccone, Meagher, Musselshell, Park, Petroleum, Phillips, Pondera, Prairie, Rosebud, Stillwater, Sweet Grass, Teton, Toole, Treasure, Valley, Wheatland, Wibaux, Yellowstone
In Montana, this system is found at scattered locations throughout northwestern and west central Montana, at elevations of 914-1,829 meters (3,000-6,000 feet) (Pfister et al, 1977; Mueggler and Stewart, 1980). Occurrences are found on all slopes and aspects; however, moderately steep to very steep slopes or ridgetops on southerly or western aspects are most common. This system can occur in association with cliff and canyon systems. It generally occurs on glacial till, glacio-fluvial sand and gravel, and loamy soils derived from a variety of parent materials. Soils are coarse with good aeration, often thin, and with slightly acidic to slightly basic pH. There is usually an abundance of mineral material consisting of fine and coarse rocks. Consequently, this system is subjected to droughty soil conditions during the growing season. Annual precipitation ranges from 36 to 56 centimeters (14 to 20 inches).
Ponderosa pine (Pinus ponderosa) or Douglas-fir (Pseudotsuga menziesii) are the most common conifers. Limber pine (Pinus flexilis) may be present in some occurrences. In transition areas with sagebrush steppe systems, antelope bitterbrush (Purshia tridentata), Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis), big sagebrush (Artemisia tridentata ssp. tridentata), and three-tip sagebrush (Artemisia tripartita) may be common in fire-protected sites such as rocky areas. Common ninebark (Physocarpus malvaceus), common snowberry (Symphoricarpos albus), or birch leaf spiraea (Spiraea betulifolia) can be abundant in occurrences on northern or eastern aspects, or sites west of the Continental Divide in northwestern Montana. Important grass species include bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg’s bluegrass (Poa secunda), needle and thread (Hesperostipa comata), needlegrass (Achnatherum species), prairie junegrass (Koeleria macrantha) and bottlebrush squirreltail (Elymus elymoides).
Common forbs include yarrow (Achillea millefolium), nodding onion (Allium cernuum), rosy pussytoes (Antennaria rosea), hairy golden aster (Heterotheca villosa), elk thistle (Cirsium undulatum), fleabane (Erigeron species), buckwheat (Eriogonum species), Indian blanket flower (Gaillardia aristata), stoneseed (Lithospermum ruderale), silky lupine (Lupinus sericeus), silky crazyweed (Oxtropis sericea), and Hood’s phlox (Phlox hoodii). Arrowleaf balsamroot (Balsamorhiza sagittata) can be abundant in some occurrences.
National Vegetation Classification Switch to Full NVC View
Adapted from US National Vegetation Classification
A3392 Pseudotsuga menziesii - Pinus ponderosa / Shrub Understory Central Rocky Mountain Forest & Woodland Alliance
A3446 Pinus ponderosa / Shrub Understory Central Rocky Mountain Woodland Alliance
CEGL005648 Pinus ponderosa - Purshia tridentata Central Rocky Mountain Woodland
A3447 Pinus ponderosa / Herbaceous Understory Central Rocky Mountain Open Woodland Alliance
CEGL000865 Pinus ponderosa - Pseudoroegneria spicata Woodland
A3462 Pseudotsuga menziesii Middle Rocky Mountain Dry-Mesic Forest & Woodland Alliance
CEGL000909 Pseudotsuga menziesii - Purshia tridentata Woodland
A3464 Pinus ponderosa Dry-Mesic Black Hills Forest & Woodland Alliance
CEGL000878 Pinus ponderosa Scree Woodland
*Disclaimer: Alliances and Associations have not yet been finalized in the National Vegetation Classification (NVC) standard.
A complete version of the NVC for Montana can be found here
Dry conditions and droughty soils that limit tree establishment are the driving factors in this system. Tree growth is likely episodic, with regeneration episodes in years with available moisture. Tree density is limited in some areas by available growing space due to the rocky conditions of the site. Disturbances in this system include fire, soil erosion, and biotic vectors. This system burns occasionally, although it does not require fire to prevent succession to a closed canopy forest structure due to the interaction of climate and edaphic factors. Fire frequency is estimated to be 30 to 50 years (Landfire, 2007). While tree seedlings may be killed by fire, tree species in this system exhibit moderate to high fire resistance (Steinberg, 2002; Howard, 2003), and fuel loads are generally light due to open rocky terrain. Fires are consequently typically of low severity and cause minimal damage. Frequent low-intensity surface fires promote grass production (Howard, 2003), but may also encourage invasion by non-native species (Symstad et al., 2014). Consequently, invasion of non-native cheatgrass (Bromus tectorum) is changing fire frequency, spread, and severity, and cheatgrass invasion risk in Montana is expected to increase under future climatic conditions (Bradley, 2009).
Increasing drought frequency and severity subjects conifers in this system to increased incidence of biotic disturbance. Drought affects Douglas-fir susceptibility to Douglas-fir tussock moth (Orgyia pseudotsugata), Douglas-fir bark beetle (Dendroctonus pseudotsugae), and western spruce budworm (Choristoneura occidentalis) outbreaks (Steinberg, 2002). Both drought-stressed ponderosa pine and limber pine have an increased likelihood of attack by the mountain pine beetle (Dendroctonus ponderosae) (Graham and Jain, 2005; Jackson et al., 2010). However, outbreaks may be less likely to reach epidemic levels as stands in this system exhibit extremely low stand densities (Howard, 2003). White pine blister rust (Cronartium ribicola) additionally infects limber pine in this system, causing reduced regeneration and mortality (Jackson et al., 2010). Trees that occupy this edge environment and exhibit resistance to abiotic and biotic stressors are important genetic resources to maximize adaptive potential to current and continued environmental change.
In the absence of natural fire, periodic prescribed burns can be used to maintain and restore this system to similar pre-settlement conditions, although results may be variable due to insufficient ground fuels and the rocky terrain typical of this system. Periodic burning is used to expose mineral soils, provide nutrient availability, reduce competition, and stimulate native grass and forb production. When insect outbreaks are active, a combination of control actions including thinning, removal of infested trees, and application of targeted insecticides can be used, although control efforts are best utilized at small scales and for high-value individuals (Howard, 2003). In light of blister rust prevalence, stands can be managed to maintain limber pine forest composition, and to diversify age structure to include regeneration, thereby encouraging natural selection of rust resistant individuals (Jackson et al., 2010).
Excessive grazing can result in the depletion of the most common perennial grasses and lead to an abundance of exotic grasses in this system. In some cases, especially on sites heavily infested with cheatgrass, frequent prescribed burning at low intensities may stimulate greater cheatgrass cover following fire, especially if the burn fails to eliminate the seed bank. Controlling invasive species like cheatgrass prior to prescribed burning may help to reduce post-burn outbreaks (Symstad et al., 2014), and increasing the time between prescribed fires may inhibit cheatgrass by increasing surface fuels (both herbaceous and litter) which directly inhibit cheatgrass establishment (Keeley and McGinnis, 2007). On sites with slopes and forage that support domestic livestock, use can be monitored to maintain soil integrity.
Successful restoration of native grasses within this system may be limited to sites where pre-fire cheatgrass (Bromus tectorum) cover was low. Because recovery of lightly burned areas is quite quick, reseeding is usually not necessary, especially if an intact native herbaceous understory was present before the fire. However, to offset invasion of exotics such as cheatgrass, re-seeding with competitive native grasses may be desirable after low-intensity or prescribed surface fires. Cheatgrass establishment in this system is enhanced by disturbance that opens the understory, removes litter, or both. (Mack and Pyke, 1983; Gundale et al., 2008). Fall germination and rapid elongation of roots provide cheatgrass with a competitive advantage over native perennial species (Harris, 1967). Prolific seed production also contributes to the competitive advantage of this grass over native grasses and associated perennial forbs. For areas in which blister rust is prevalent, augmenting natural limber pine regeneration with seed sources that exhibit some resistance to blister rust or, in some cases, with nursery stock, may be necessary.
Species Associated with this Ecological System
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state 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, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system 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 ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system 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, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems 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 (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems 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 ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- 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.
- 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.
- Native Species Commonly Associated with this Ecological System
- Native Species Occasionally Associated with this Ecological System
Original Concept Authors
Montana Version Authors
- Classification and Map Identifiers
Cowardin Wetland Classification:
National Land Cover Dataset:
|Element Global ID
||CES306.958, Northern Rocky Mountain Foothill Conifer Wooded Steppe
42: Evergreen Forest
5426: Northern Rocky Mountain Foothill Conifer Wooded Steppe
- Literature Cited AboveLegend: View Online Publication
- Bradley, B.A. 2009. Regional analysis of the impacts of climate change on cheatgrass invasion shows potential risk and opportunity. Global Change Biology 15(1): 196-208.
- Graham, R.T. and T.B. Jain. 2005. Ponderosa pine ecosystems. pp. 1-32. In: Proceedings of the Symposium on Ponderosa Pine: Issues, Trends, and Management, Gen. Tech. Rep. PSW-GTR-198. Albany CA: Pacific Southwest Research Station, Forest Service, US Department of Agriculture, Klamath Falls, OR.
- Gundale, M.J., S. Sutherland, and T.H.DeLuca. 2008. Fire, native species, and soil resource interactions influence the spatio-temporal invasion pattern of Bromus tectorum. Ecography 31(2):201-210
- Howard, J. L. 2003. Pinus ponderosa var. scopulorum. In: Fire Effects Information System, [Online}. U. S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- Jackson, M., A. Gannon, H. Kearns, K. Kendall. 2010. Current Status of Limber Pine in Montana. Report 10-06. Missoula, MT: U.S. Department of Agriculture, Forest Service, Northern Region. 14 p.
- Keeley, J. E., and T. W. Mcginnis. 2007. "Impact of Prescribed Fire and Other Factors on Cheatgrass Persistence in a Sierra Nevada Ponderosa Pine Forest". International Journal of Wildland Fire. 16 (1): 96-106.
- Landfire. 2007. Northern Rocky Mountain Foothill Conifer Wooded Steppe. BPS:0111650. In: Landfire Biophysical Setting Descriptions.
- Steinberg, P. D. 2002. Pseudotsuga menziesii var. glauca. In: Fire Effects Information System, [Online}. U. S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- Symstad, A.J., W.E. Newton, and D.J. Swanson. 2014. Strategies for preventing invasive plant outbreaks after prescribed fire in ponderosa pine forest. Forest Ecology and Management 324:81-88.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Aguirre, Lucrecia, and Douglas A. Johnson. 1991. "Influence of Temperature and Cheatgrass Competition on Seedling Development of Two Bunchgrasses". Journal of Range Management. 44 (4): 347-354.
- Harris, G.A. 1967. Some competitive relationships between Agropyron Spicatum and Bromus tectorum. Ecological Monographs 37:89-111.
- Mack, Richard N., and David A. Pyke. 1983. "The Demography of Bromus Tectorum: Variation in Time and Space". The Journal of Ecology. 71 (1): 69-93.
- Mueggler, W. F. and W. L. Stewart. 1980. Grassland and shrubland habitat types of western Montana. USDA Forest Service Gen. Tech. Rep. INT-66, Intermountain Forest and Range Exp. Sta., Ogden, Utah. 154 pp.
- 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.