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Montana Field Guides

Great Plains Ponderosa Pine Woodland and Savanna

Provisional State Rank: S4
(see reason below)

External Links

State Rank Reason
The system is at risk from insects and fire, but somewhat less so than its counterpart in the western part of the state.

General Description

These ponderosa pine (Pinus ponderosa) occurrences differ from the Rocky Mountain Ponderosa Pine Woodland and Savanna systems in that they are typically found within the matrix of the Great Plains grassland systems east of the Continental Divide on sites that are relatively dry and nutrient-poor (Howard, 2003). They are often surrounded by mixed-grass prairie, in places where available soil moisture is comparatively higher or soils are more coarse and rocky. Soils in this system are typically derived from both igneous and sedimentary parent materials including volcanic cinder, basalt, sandstone, and limestone (Howard, 2003). This system occurs at elevations that range from 1,189 meters (3,900 feet) in southeastern Montana to 1,646 m (5,400 feet) in north-central Montana. At the upper elevational portion of its range in central Montana, this system merges with Rocky Mountain Foothill Limber Pine-Juniper Woodlands, while in southeastern Montana, ponderosa pine is the only forest tree species (Howard, 2003; Arno, 1979). Occurrences are usually on east- and north-facing aspects.

Common overstory associates of this system include Douglas-fir (Pseudotsuga menziesii), limber pine (Pinus flexilis), and Rocky Mountain juniper (Juniperus scopulorum). Understories are commonly comprised of shrubs such as western snowberry (Symphoricarpos occidentalis) and skunkbush sumac (Rhus trilobata), and grassland species such as blue grama (Bouteloua gracilis), side-oats grama (B. curtipendula), and prairie Junegrass (Koeleria macrantha) (Howard, 2003; Arno, 1979). These woodlands can be physiognomically variable, ranging from very sparse patches of trees on drier sites, to nearly closed-canopy forest stands on north slopes or in draws where available soil moisture is higher. On sites with greater available soil moisture understories may be dense and support species commonly associated with ponderosa pine woodlands west of the Continental Divide. Fire suppression of the past century, increasingly severe drought and insect outbreaks have altered the natural processes of this system.

Diagnostic Characteristics

Ridge-summit-upper slope, aridic-sand soil texture, organic A horizon less than 10 cm, Pinus ponderosa with graminoid understory, Pinus ponderosa with shrub understory

Similar Systems

This system is found in northern, central and eastern Montana. It occurs along the Missouri River breaks, around the Little Belts and Snowy Mountains, in south-central Montana between the Bighorns and the Black Hills (along the Tongue and Powder Rivers), and in other areas of eastern Montana. In extreme south-eastern Montana into north-eastern Wyoming, it potentially occurs in the foothills of the Bear Lodge Mountains. In north-central Montana, it occurs in the Bear Paw mountains.

Ecological System Distribution
Approximately 8,214 square kilometers are classified as Great Plains Ponderosa Pine Woodland and Savanna in the 2017 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.

Montana Counties of Occurrence
Big Horn, Blaine, Carbon, Carter, Cascade, Chouteau, Custer, Dawson, Fallon, Fergus, Garfield, Golden Valley, Hill, Judith Basin, Mccone, Meagher, Musselshell, Park, Petroleum, Phillips, Powder River, Prairie, Rosebud, Sheridan, Stillwater, Sweet Grass, Toole, Treasure, Valley, Wheatland, Wibaux, Yellowstone

Spatial Pattern
Large patch

This system occurs primarily on gentle to steep slopes along escarpments, buttes, canyons, rock outcrops, or ravines and can grade into one of the Great Plains canyon systems or the surrounding prairie system. Elevation ranges from 1,189 meters (3,900 feet) in southeastern Montana to 1,646 meters (5,400 feet) in north-central Montana. In the eastern Little Belts and Snowy Mountains, these woodlands can occur on the upper slopes. Soils typically range from well-drained loamy sands to sandy loams formed in colluvium, weathered sandstone, limestone, scoria, or eolian sand. The understory may be shrub or graminoid dominated, depending on aspect or site.


Along the Missouri Breaks in north-central Montana, woodlands dominated by Douglas-fir (Pseudotsuga menziesii) are found in the same ecological settings as ponderosa pine, and so are included in this system. In the breaks where it occurs, Douglas-firhas a very open canopy over graminoid undergrowth, predominantly composed of bluebunch wheatgrass (Pseudoroegneria spicata), with few to no shrubs present. In most of the Missouri Breaks, however, ponderosa pine dominates and Rocky Mountain juniper (Juniperus scopulorum) is a common associate. Shrubs associated with ponderosa pine dominated forests include bearberry (Arctostaphylos uva-ursi), creeping Oregon grape (Mahonia repens), soapweed yucca (Yucca glauca), snowberry (Symphoricarpos species), chokecherry (Prunus virginiana), common juniper (Juniperus communis), horizontal juniper (Juniperus horizontalis), serviceberry (Amelanchier alnifolia), skunkbush sumac (Rhus trilobata) and ninebark (Physocarpus species). The herbaceous understory can range from a sparse to a dense layer of species typical of the surrounding prairie system. Mixed-grass species are usually common, such as big bluestem (Andropogon gerardii), sideoats grama (Bouteloua curtipendula), sun sedge (Carex inops ssp.heliophila), threadleaf sedge (Carex filifolia), poverty oatgrass (Danthonia intermedia), prairie junegrass (Koeleria macrantha), green needlegrass (Nassella viridula), roughleaf ricegrass (Oryzopsis asperifolia), and western wheatgrass (Pascopyrum smithii). Common herbaceous forbs include yarrow (Achillea millefolium), pussytoes (Antennaria species), boreal sagewort (Artemisia frigida), arrowleaf balsamroot (Balsamorhiza sagittata), Indian blanket flower (Gaillarida aristata), silky lupine (Lupinus argenteus), crazyweed (Oxytropis species), alpine sweetvetch (Hedysarum alpinum), penstemon (Penstemon species), prairie cinquefoil (Potentilla gracilis), goldenrod (Solidago species) and smooth aster (Symphyotrichum laeve).

National Vegetation Classification Switch to Full NVC View

Adapted from US National Vegetation Classification

A3398 Pinus ponderosa Southern Rocky Mountain Forest & Woodland Alliance
CEGL000849 Pinus ponderosa - Carex inops ssp. heliophila Woodland
A3464 Pinus ponderosa Dry-Mesic Black Hills Forest & Woodland Alliance
CEGL000860 Pinus ponderosa - Juniperus horizontalis Woodland
A3465 Pinus ponderosa Mesic Black Hills Forest Alliance
CEGL000192 Pinus ponderosa - Prunus virginiana Forest
CEGL000204 Pinus ponderosa - Symphoricarpos occidentalis Forest
A3466 Pinus ponderosa Northwest Great Plains Open Woodland Alliance
CEGL000201 Pinus ponderosa - Schizachyrium scoparium Open Woodland
CEGL000873 Pinus ponderosa - Quercus macrocarpa Open 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.

Dynamic Processes

Frequent low-intensity surface fires are common within this system due to generally sparse understories and the accumulation of litter at the base of mature trees (Graham and Jain, 2005; Pfister et al., 1977). Fire return intervals average approximately 15 years, although infrequent mixed- to high-severity fires may also occur at longer time scales (U.S. Department of Agriculture, 2012). More mesic sites, as well as higher elevation stands are typically more dense and experience infrequent higher severity fires (every 100-200 years). The thick, insulating bark and deep rooting habit characteristic of ponderosa pines allows individuals to withstand low-severity fires, although younger trees with thinner bark may be more vulnerable (Graham and Jain, 2005). Individuals in low density stands have a better likelihood of surviving surface fires than trees in higher density stands (Howard, 2003).

Comparatively fewer insects attack ponderosa pines in this system than those occurring west of the Continental Divide (Howard, 2003), although the mountain pine beetle (Dendroctonus ponderosae) is the most damaging insect to ponderosa pine throughout Montana. Mountain pine beetles generally occur at endemic levels and target trees with weakened defenses due to drought, lightning strikes, pathogen infections, and old age (Graham and Jain, 2005). Outbreaks may reach epidemic levels when stands are characterized by high densities of large, stressed trees, a common attribute of stands in which low-intensity fires have been suppressed (Negron et al., 2008; Howard, 2003).

Grazing by domestic livestock may reduce associated grasses, and in cases of extreme overgrazing, cheatgrass (Bromus tectorum) may become established. Frequent low-intensity surface fires promote grass production (Howard, 2003), but may also encourage invasion by non-native species (Symstad et al., 2014). Wind, ice, and snow also cause infrequent disturbance resulting in the formation of canopy openings where regeneration can occur, creating multi-aged stands (Graham and Jain, 2005). In the absence of canopy-opening disturbance events, seedling establishment is discontinued approximately 70 years after a stand-replacing event (Lundquist and Negron, 2000).


In the absence of natural fire, periodic prescribed burns, selective thinning, and reduction of ladder and basal fuels to prevent crown fires can be used to maintain and restore this system to similar pre-settlement conditions. Thinning understory trees and manually removing ladder fuels and heavy fuels from the base of large trees may be necessary in order to prevent old growth mortality during prescribed burning (Kolb et al., 2007). An additional benefit of thinning is to reduce the probability of insect and disease outbreaks, as these are more common in high density stands (Graham and Jain, 2005). 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 smaller scales and for high-value stands (Howard, 2003).

Periodic burning is used to expose mineral soils, increase nutrient availability, reduce competition, stimulate native grass and forb production, increase basal diameter growth of overstory ponderosa pine, and provide favorable seedbeds. In some cases, especially on sites heavily infested with cheatgrass, frequent prescribed burning at low intensities may stimulate greater cheatgrass cover following the fire, especially if the burn did not 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 inhibits cheatgrass establishment (Keeley and McGinnis, 2007). Minimizing the extent of high severity burning by pre-fire thinning, or by applying prescribed burns in cooler, wetter conditions may also reduce the probability of post-burn outbreaks as higher burn intensity may correspond to greater probability of invasion by non-native species (Symstad et al., 2014).

Excessive grazing can result in the loss of the most common perennial grasses and lead to an abundance of exotic grasses in this system. Cheatgrass establishment in low-elevation ponderosa pine forests is enhanced by disturbance that opens the understory, removes litter, or both. (Mack and Pyke 1983). Fall germination and rapid elongation of roots provides 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.

Restoration Considerations

Restoration strategies for this system will depend on fire severity or grazing impacts. Fire generally creates favorable conditions for ponderosa pine regeneration as surface fires remove litter and duff that inhibit seedling establishment and reduce competition with understory species (Howard, 2003). Because lightly burned areas recover quite quickly from fire, 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. Intense fires that occur during summer months cause considerable damage to native perennial grasses. Ponderosa pine seeds are typically only viable in the seed bank for the year after dispersal (Howard, 2003). Therefore, in cases where severe, stand replacing fires occur, reseeding or replanting efforts may be necessary. Severe mountain pine beetle outbreaks may also necessitate restoration efforts as ponderosa pine does not establish well on unburned soils (Graham and Jain, 2005). In order to slow the rapid loss of the oldest age classes of ponderosa pine in this system, mechanical thinning and the restoration of historic fire return intervals to restore nutrient cycling, and reduce the probability of beetle attack and stand replacing fires is 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:
    1. 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);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. 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: 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.

    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.
    • 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.

Original Concept Authors
M.S. Reid

Montana Version Authors
L.K. Vance, T. Luna

Version Date

  • Classification and Map Identifiers

    Cowardin Wetland Classification: Not applicable

    NatureServe Identifiers:
    Element Global ID
    System Code CES303.650, Northwestern Great Plains - Black Hills Ponderosa Pine Woodland and Savanna

    National Land Cover Dataset:
    42: Evergreen Forest

    4280: Northwestern Great Plains - Black Hills Ponderosa Pine Woodland and Savanna

  • Literature Cited AboveLegend:   View Online Publication
    • Arno, S. 1979. Forest regions of Montana. Research paper Int-218, USFS Intermountain and Range Experiment Station, Ogden, Utah.
    • 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.
    • 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.
    • Kolb, T.E.,J.K. Agee, P.Z. Fule, N.G. McDowell, K. Pearson, A.Sala, and R.H. Waring. 2007. Perpetuating old ponderosa pine. Forest Ecology and Management 249(3):141-157.
    • Lundquist, J.E. and J.F. Negron. 2000. Endemic forest disturbances and stand structure of ponderosa pine (Pinus ponderosa) in the Upper Pine Creek Research Natural Area, South Dakota, USA. Natural Areas Journal 20(2):126-132.
    • 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.
    • U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory. 2012. Information from LANDFIRE on Fire Regimes of Northern Rocky Mountain Ponderosa Pine Communities. In: Fire Effects Information System. Missoula, MT: USDA Forest Servic
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Arno, S. F. 1980. Forest fire history in the northern Rockies. Journal of Forestry 78(8):460-465.
    • Harris, G.A. 1967. Some competitive relationships between Agropyron spicatum and Bromus tectorum. Ecological Monographs 37:89-111.
    • 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.
    • 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.
    • 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.

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Citation for data on this website:
Great Plains Ponderosa Pine Woodland and Savanna — Northwestern Great Plains - Black Hills Ponderosa Pine Woodland and Savanna.  Montana Field Guide.  Retrieved on , from