Mountain Mahogany Woodland and Shrubland
Global Name:
Intermountain Basins Curl-leaf Mountain-mahogany Woodland & Scrub
Global Rank:
G4G5
State Rank:
S4
(see reason below)
External Links
State Rank Reason
These dry shrublands are scattered across rocky hillsides and mountains slopes and ridges of southwest and south-central MT. They have experienced some past declines and are threatened by increased wildfires and invasive species, but these impacts are not expected to be large in both scope and severity, limiting potential impacts in the near future.
General Description
This National Vegetation Classification Group is a low to tall shrub community dominated by curl-leaf mountain mahogany. It occurs most frequently on moderately steep to very steep slopes or on ridgelines in the foothills and mountains of southwest and southcentral Montana. It extends as far north as Helena and as far east as the Wolf Mountains on the Crow Indian Reservation. It occurs primarily on south and southwestern aspects from 4,000-7,000 feet on limestone parent materials where it forms small- to large-patches on dry and rocky soils. In Montana, this shrubland group is defined solely by the dominance of curl-leaf mountain mahogany (Cercocarpus ledifolius). Rocky Mountain juniper (Juniperus scopulorum) may occur as scattered individuals in some communities and Utah juniper (J. osteosperma) may be present in some stands in the Pryor Mountains. Scattered conifers such as Douglas-fir (Pseudotsuga menziesii), limber pine (Pinus flexilis) and ponderosa pine (P. ponderosa) may also occur in some stands. This community provides important winter range for deer and elk.
This group is equivalent to the Mountain Mahogany Woodland and Shrubland Ecological System.
Diagnostic Characteristics
Shrubland; Vegetation Cover >10%; Foothill and Montane Zones; Rocky, Exposed Sites; Rocky Mountain and Intermountain Regions
Typical Dominants: Curl-leaf Mountain-mahogany (Cercocarpus ledifolius)
Similar Systems
Range
Most common in the foothills and mountain ranges of southwestern Montana and in the vicinity of the Pryor and Bighorn Mtns in Carbon and Big Horn Counties. It extends as far north as the northern foothills of the Elkhorn Range and in the vicinity of the Helena Valley. It occurs as far east as the Wolf Mountains on the Crow Indian Reservation. Small occurrences are known from the southern portion of Ravalli County in the vicinity of the Bitterroot Valley. Elsewhere in the western United States, this type occurs in hills and mountain ranges of the Intermountain West to the eastern foothills of the Sierra Nevada.
In Montana, G249 occurs within these Level III Ecoregions: 17 (Middle Rockies) and 18 (Wyoming Basin). Minor amounts also occur in 43n - Montana Central Grasslands and 43v - Pryor-Bighorn Foothills within the Northwestern Great Plains Ecoregion.
In Montana, G249 occurs within these Major Land Resource Areas: The southern half of 43B - Central Rocky Mountains, the southern portion of 46 - Northern and Central Rocky Mountain Foothills
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, Broadwater, Carbon, Cascade, Deer Lodge, Gallatin, Granite, Jefferson, Lewis and Clark, Madison, Powell, Ravalli, Silver Bow
Based on 2025 land cover layer.
Spatial Pattern
Small Patch and Large Patch
Environment
This group occurs as small- to large-patches on dry and rocky soils associated with moderately steep to very steep slopes and on ridgelines. It is most prevalent on limestone outcrops where extensive stands develop, although it also occurs on other parent materials, generally as small patches. It can occur on all aspects but is most prevalent on south and southwestern aspects. These communities range in elevation within the state from 4,000-7,000 feet. Climate within its range in Montana is typical of mid-continental regions with long severe winters and hot, dry summers.
Vegetation
This shrubland community is dominated by curl-leaf mountain mahogany (Cercocarpus ledifolius). Rocky Mountain juniper (Juniperus scopulorum) may occur as scattered individuals in some communities and Utah juniper (J. osteosperma) may be present in some stands in the Pryor Mountains. Conifers such as Douglas-fir (Pseudotsuga menziesii), limber pine (Pinus flexilis) and ponderosa pine (P. ponderosa) may also occur in some stands. Mountain big sagebrush (Artemisia tridentata ssp. vaseyana) and antelope bitterbrush (Purshia tridentata) occur in some stands. Subshrubs such as snakeweed (Gutierrezia sarothrae) and fringed sage (Artemisia frigida) are common components. Undergrowth is dominated by bunchgrasses, usually bluebunch wheatgrass (Pseudoroegneria spicata), needle and thread (Stipa comata), Indian ricegrass (Achnatherum hymenoides) or Idaho fescue (Festuca idahoensis) (Mueggler and Stewart, 1980).
Bluebunch wheatgrass (Elymus spicatus) is the dominant grass throughout this group, although Needle-and-Thread (Stipa comata) and Indian ricegrass (Oryzopsis hymenoides) may be co-dominant on more xeric sites. Mesic occurrences are frequently dominated or co-dominated by Idaho fescue (Festuca idahoensis). Prairie junegrass (Koeleria macrantha) is a minor component. Due to the rocky and shallow substrates, undergrowth cover is relatively sparse, often with less than 20% cover. Common forbs include species of pussytoes (Antennaria sp), buckwheat (Eriogonum sp), few-seed draba (Draba oligosperma), tufted fleabane (Erigeron cespitosus), and phlox (Phlox sp). Cacti such as plains pricklypear (Opuntia polyacantha) and Missouri foxtail cactus (Coryphantha missouriensis) are present on especially xeric sites. Cheatgrass (Bromus tectorum) or annual bromes may be common at some sites.
National Vegetation Classification
Download the complete NVC hierarchy for Montana
TT2 B02 Temperate-Boreal Forest and Woodland
TT2.b S92 Cool Temperate Forest and Woodland
TT2.b3 F112 Temperate Continental Conifer Forest and Woodland
TT2.b3.Na D010 Western North American Pinyon - Juniper Woodland and Scrub
TT2.b3.Na.1 M896 Intermountain Pinyon - Juniper Woodland
TT2.b3.Na.1.d G249 Intermountain Basins Curl-leaf Mountain-mahogany Woodland and Scrub
A3570 Cercocarpus ledifolius Grassy Woodland Alliance
A4710 Cercocarpus ledifolius Woodland and Scrub Alliance
*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
Curl-leaf mountain mahogany is easily killed by fire at all intensities. Some shrubs may re-sprout following low-intensity fires, but these are typically low in vigor and do not persist. Regeneration is by seedling recruitment. Post-fire regeneration may be quick unless fire intensity is severe and has destroyed the local seedbank. High-intensity fires kill all standing shrubs and may also eliminate the seed bank (Gucker 2006). However, a lack of continuous fuels, sparse undergrowth, open stand structure, and low downed woody accumulations generally results in low fire frequency within these communities. Fire return intervals currently range from 70 to 110 years with the majority of fires being mixed severity (U.S. Department of Agriculture 2012). Prior to 1900, fire return intervals are estimated to have been much shorter but have increased due to fire suppression and heavy livestock grazing, reducing fine fuel loads (Gucker 2006). The absence of fire in curl-leaf mountain mahogany habitats in central, southwestern, and southeastern Montana has in some instances increased curl-leaf mountain mahogany abundance and regeneration success (Gruell 1982).
Curl-leaf mountain mahogany provides food and cover for a variety of wildlife species such as deer and elk. Some livestock (domestic goats, sheep, and cattle) use these communities in spring, fall, and/or winter, but rarely in the summer. In other areas of this community’s geographic range, heavy grazing practices have been observed to lead to a decrease in associated grasses and an increase in the spread of cheatgrass (Bromus tectorum) (Young 1989). Thus, sites invaded by cheatgrass are changing the dynamics of this group by increasing fire potential, severity, and spread.
Management
Excessive grazing can lower the cover of the most common perennial bunchgrasses in this group and lead to an increase in the cover of prairie junegrass and needle and thread grass or invasive, annual bromes. Unpalatable subshrubs such as fringed sage or snakeweed also increase under heavy grazing pressure. Severe grazing can lead to an abundance of cheatgrass (Bromus tectorum), spotted knapweed (Centaurea stoebe), or other noxious weeds capable of colonizing dry, rocky soils.
Curl-leaf mountain mahogany is a slow-growing, drought-tolerant species that generally does not re-sprout after fire. Prolonged drought, the potential for increased fire severity and exotic species invasion are changing the dynamics of these communities. Prescribed fire exposes mineral soils which promote seedling establishment and may be used for stands in which fuel levels are low, and in which cheatgrass is absent. Fire is also recommended for sites in west-central and southwestern Montana to encourage curl-lead mountain mahogany regeneration while slowing succession by shade tolerant Douglas fir (Gucker 2006).
Restoration Considerations
Restoration strategies will depend on the type and intensity of the disturbance, and in the case of fire, on the degree of fire severity and fire recovery objectives. Light or moderately intensive burns can increase cover of native perennial bunchgrasses during the first two years following fire on sites where there was good pre-fire condition with minimal exotic cover. However, severely burned sites will require replanting with curl-leaf mountain mahogany seedlings and other co-dominant shrubs, due to the slow recovery time within this habitat and low rates of natural seedling recruitment. When planting from seed, cold, moist stratification is required to enhance germination success (Gucker 2006). Generally, larger container volume of nursery stock results in higher outplanting success; 20-cubic inch container stock is recommended for use on these sites. Curl-leaf mountain mahogany is rated as good to excellent for soil erosion control due to its ability to stabilize soils. Planting rates must be developed on a site-by-site basis to meet management objectives.
Successful restoration of native grasses within this group may be limited to sites where pre-fire cheatgrass cover was low. Fall germination and rapid elongation of roots provide cheatgrass with a competitive advantage over native perennial species (Harris 1967). Cheatgrass reduces growth of bluebunch wheatgrass seedlings and is capable of producing twice the root quantity during the first 45 days of growth (Aguirre and Johnson 1991). Prolific seed production also contributes to the competitive advantage of this species over native grasses. Thus, on sites that are heavily infested with cheatgrass prior to fire, seeding rates must be adjusted to include more competitive native grass species. Some selections of bluebunch wheatgrass that exhibit desirable growth characteristics may have promise for establishing this species on invaded sites.
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
Reptiles
Amphibians
- Diagnostic, Dominant, or Codominant Plant Species for this Community
Vascular Plants
- Other Native Species Commonly Associated with this Community
Vascular Plants
Original Concept Authors
K.A. Schulz 2015
Montana Version Authors
S. Mincemoyer, L. Vance, T. Luna, M. Hart
Version Date
12/5/2024
References
- Literature Cited AboveLegend:
View Online Publication- 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.
Gruell GE. 1982. Fires' influence on vegetative succession--wildlife habitat implications and management opportunities. In: Eustace CD, editor. Proceedings: Montana Chapter of the Wildlife Society. Billings, MT: The Wildlife Society; p 43-50.- Gucker, C.L. 2006. Cercocarpus ledifolius. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
- Harris, G.A. 1967. Some competitive relationships between Agropyron spicatum and Bromus tectorum. Ecological Monographs 37:89-111.
- 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.
- U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory. 2012. Information from LANDFIRE on Fire Regimes of Mountain-Mahogany Communities. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Serv
- Young JA. 1989. Intermountain shrubsteppe plant communities--pristine and grazed. Western raptor management symposium and workshop: Proceedings: 1987 October 26-28; Boise, ID. Scientific Technical Series No. 12. Washington DC: National Wildlife Federation; p 3-14.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Shiflet, T. N., editor. 1994. Rangeland cover types of the United States. Society for Range Management. Denver, CO. 152 pp.
- Web Search Engines for Articles on "Intermountain Basins Curl-leaf Mountain-mahogany Woodland & Scrub"
