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Montana Field Guides

Rocky Mountain Montane Douglas-fir Forest and Woodland

Provisional State Rank: S4

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General Description

In Montana, this ecological system occurs on the east side of the Continental Divide, north to about the McDonald Pass area, and along the Rocky Mountain Front. This system is associated with a dry to submesic continental climate regime with annual precipitation ranging from 51 to 102 centimeters (20-40 inches), with a maximum in winter or late spring. Winter snowpacks typically melt off in early spring at lower elevations. Elevations range from valley bottoms to 1,980 meters (6500 feet) in northern Montana and up to 2,286 meters (7500 feet) on warm aspects in southern Montana. It occurs on north-facing aspects in most areas, and south-facing aspects at higher elevations. This is a Douglas-fir (Pseudotsuga menziesii) dominated system without any maritime floristic composition. Fire disturbance intervals are as infrequent as 500 years, and as a result, individual trees and forests can attain great age on some sites (500 to 1,500 years). In Montana, this system occurs from lower montane to lower subalpine environments and is prevalent on calcareous substrates. Common understory shrubs include common ninebark (Physocarpus malvaceus), common juniper (Juniperus communis), Rocky Mountain juniper (Juniperus scopulorum), birch-leaf spiraea (Spiraea betulifolia), snowberry (Symphoricarpos species), creeping Oregon grape (Mahonia repens) and Canadian buffaloberry (Shepherdia canadensis). The Douglas-fir/pinegrass (Calamogrostis rubescens) type is the most ubiquitous association found within this system in Montana.


Diagnostic Characteristics
Forest and Woodland, aridic soils, foothill to montane elevations, moderate persistence (100-500 yr) interval

Similar Systems

Range
This system extends north into Montana on the east side of the Continental Divide to McDonald Pass and along the Rocky Mountain Front. It occurs throughout the Beaverhead Mountains.

Ecological System Distribution
Approximately 9,717 square kilometers are classified as Rocky Mountain Montane Douglas-fir Forest and Woodland in the 2016 Montana Land Cover layers.  Grid on map is based on USGS 7.5 minute quadrangle map boundaries.



Montana Counties of Occurrence
Beaverhead, Big Horn, Broadwater, Carbon, Cascade, Deer Lodge, Flathead, Gallatin, Glacier, Granite, Jefferson, Judith Basin, Lewis and Clark, Madison, Meagher, Missoula, Park, Pondera, Powell, Ravalli, Silver Bow, Stillwater, Sweet Grass, Teton, Wheatland

Spatial Pattern
Matrix

Environment
East of the Continental Divide, this ecosystem forms a forest belt on cold, dry to mesic sites in the montane zone. It is found on moderately dry mountain slopes and benches. It generally occurs on gravelly soils with good aeration and drainage and a neutral to slightly acidic pH. This system is subjected to a dry to sub-mesic continental climate. Individual trees and forests can attain great age on some sites (500-1500 years), due to mixed severity fire regimes. It often occurs at the lower treeline immediately above valley grasslands, or sagebrush steppe and shrublands.

Vegetation

This system is dominated by Douglas-fir (Pseudotsuga menziesii) forests. Limber pine (Pinus flexilis) can co-occuron calcareous substrates, and lodepole pine (Pinus contorta) is often frequent in these stands at higher elevations. Engelmann spruce (Picea engelmannii) is found in some stands within the upper montane zone, occurring just below or intergrading with whitebark pine (Pinus albicaulis) forests. Common understory shrubs include common ninebark (Physocarpus malvaceus), common juniper (Juniperus communis), Rocky Mountain juniper (Juniperus scopulorum) birch-leaf spiraea (Spiraea betulifolia), snowberry (Symphoricarpos species), creeping Oregon grape (Mahonia repens) and Canadian buffaloberry (Shepherdia canadensis). Dwarf huckleberry (Vaccinium caespitosum) or mountain huckleberry (Vaccinium membranaceum) are foundon colder, mesic sites. Common graminoids include pinegrass (Calamagrostis rubescens), Ross’ sedge (Carex rossii), and Geyer’s sedge (Carex geyeri). Bluebunch wheatgrass (Pseudoroegneria spicata) and Idaho fescue (Festuca idahoensis) are often common on sites adjacent to upper elevation montane grasslands. The Douglas-fir/pinegrass (Camogrostis rubescens) type is the most ubiquitous association found within this system in Montana. Common forbs within these forests include yarrow (Achillea millefolium), lanceleaf arnica (Arnica latifolia), pussytoes (Antennaria racemosa), wild strawberry (Fragaria virginiana), twinflower (Linnaea borealis), and beargrass (Xerophyllum tenax).


National Vegetation Classification Switch to Full NVC View

Adapted from US National Vegetation Classification

A3395 Pseudotsuga menziesii - Pinus ponderosa / Herbaceous Understory Central Rocky Mountain Woodland Alliance
CEGL000429 Pseudotsuga menziesii - Calamagrostis rubescens Woodland
CEGL000900 Pseudotsuga menziesii - Festuca idahoensis Woodland
CEGL000908 Pseudotsuga menziesii - Pseudoroegneria spicata Woodland
A3462 Pseudotsuga menziesii Middle Rocky Mountain Dry-Mesic Forest & Woodland Alliance
CEGL000439 Pseudotsuga menziesii - Juniperus communis Forest
CEGL000440 Pseudotsuga menziesii - Juniperus osteosperma Forest
CEGL000442 Pseudotsuga menziesii - Mahonia repens Forest
CEGL000457 Pseudotsuga menziesii - Spiraea betulifolia Forest
CEGL000459 Pseudotsuga menziesii - Symphoricarpos albus Forest
CEGL000462 Pseudotsuga menziesii - Symphoricarpos oreophilus Forest
CEGL000903 Pseudotsuga menziesii - Juniperus scopulorum Woodland
A3463 Pseudotsuga menziesii Middle Rocky Mountain Mesic-Wet Forest Alliance
CEGL000441 Pseudotsuga menziesii - Linnaea borealis Forest
CEGL000447 Pseudotsuga menziesii - Physocarpus malvaceus Forest
*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

Disturbances in this system are primarily caused by fire and insects. Fire return intervals generally range from 20-45 years, although fire-free periods may be longer at more mesic or higher elevation sites (Steinberg, 2002; U.S. Department of Agriculture, 2012). The majority of fires in this system are mixed-severity, although stand replacement and low-severity fires may also occur (U.S. Department of Agriculture, 2012). Douglas-fir regenerates well following fire, with higher regeneration following low-severity burns (Harvey et al., 2013). After about 40 years, trees develop fire-resistant bark that promotes tolerance low to moderate intensity surface fires (Steinberg, 2002). In the absence of disturbance, Douglas-fir will continue to regenerate under shaded conditions, and becomes dominant in undisturbed stands.

Pre-settlement fire regimes may have been characterized by frequent, low intensity ground fires that maintained relatively open stands. Under present conditions, the fire regime is mixed severity and more variable, with stand-replacing fires more common, encouraging forest homogeneity. With vigorous fire suppression, longer fire-return intervals are now common, and multi-layered stands provide fuel "ladders," making these forests more susceptible to high-intensity, stand-replacing fires. In some areas, these forests have been priorities for timber harvesting and grazing. An additional consequence of fire suppression has been the establishment of Douglas-fir in sagebrush steppe and grassland ecosystems in southwestern Montana. Historically, frequent fires confined Douglas-fir growth to particularly rocky or moist microsites. (Arno and Gruell, 1986; Heyerdahl et al., 2006).

Fire additionally interacts with biotic disturbance dynamics in this system. The Douglas-fir bark beetle (Dendroctonus pseudotsugae) causes abundant damage, and fire-affected stands tend to be more vulnerable to attack (Negron et al., 1999; Hood and Bentz, 2007; Six and Skov, 2009). A study from southwestern Montana found that large trees with high levels of crown scorch in dense stands were most vulnerable to beetle attack post-fire (Hood and Bentz, 2007). In some cases, post-fire beetle infestations may spread to nearby trees not injured by fire (DeNitto et al., 2000). Post-fire mortality may also occur as the result of Douglas-fir tussock moth (Orgyia pseudotsugata), western spruce budworm (Choristoneura occidentalis), and wood borers. Trees infected with Douglas-fir dwarf mistletoe (Arceuthobium douglasii) may be more susceptible to fire due to the accumulation of dense brooms that serve as ladder fuels (Steinberg, 2002).

In recent years, these forests have been subjected to prolonged periods of drought, creating conditions where stands are susceptible to outbreaks of Douglas-fir tussock moth and Douglas-fir bark beetle. The combination of prolonged drought and fire suppression have also contributed to an increase in the intensity and duration of western spruce budworm epidemics, increased Douglas-fir bark beetle populations, and increased dwarf mistletoe infestation (Steinberg, 2002). In addition to the effects of drought, disturbances such as snow breakage and windthrow may increase stand susceptibility to insect attack (Negron et al., 1999).


Management
In the absence of natural fire, periodic prescribed burns can be used to maintain this system. Low-severity burning decreases fuel loading, probability of stand-replacing fires, and increases available nutrients in the soil (Arno et al., 1995). Prescribed fire may additionally be useful for limiting invasion of Douglas-fir into sagebrush steppe and grassland ecosystems in southwestern Montana (Steinberg, 2002; Heyerdahl et al., 2006). It may be important to consider the consequences of prescribed burning on stand susceptibility to Douglas-fir beetles, as beetles respond quickly to available resource pulses (i.e. fire damaged trees) following fire (Negron et al., 1999; Six and Skov, 2009).

Restoration Considerations
Post-fire Douglas-fir forest restoration strategies will depend largely on the severity of the fire. Because these forests recover well following light to moderate intensity burns, restoration practices are generally not necessary. Recovery may be slow after large-scale stand-replacing fires, as seeds are wind-dispersed and rely on nearby stands to provide a seed source. Severely burned sites on steep slopes will require sediment retention and erosion control actions before and during restoration. When supplemental seeding or planting is necessitated, Douglas-fir establishment is best on mineral soil or thin organic seedbeds, and survival is greatest at relatively dry sites with partial shading (Steinberg, 2002). Prescribed fire may be an additional valuable restoration strategy in stands with high levels of dwarf mistletoe. High severity burning controls Douglas-fir dwarf mistletoe by eliminating infected trees and promoting regeneration of uninfected individuals (Alexander and Hawksworth, 1976). However, when utilizing prescribed burning as a restoration strategy, the effects of fire on local Douglas-fir beetle populations should be considered.

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: 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.

    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
1/1/2017

References
  • Classification and Map Identifiers

    Cowardin Wetland Classification: Not applicable

    NatureServe Identifiers:
    Element Global ID
    System Code CES306.959, Middle Rocky Mountain Montane Douglas-Fir Forest and Woodland

    National Land Cover Dataset:
    42: Evergreen Forest

    ReGAP:
    4266: Middle Rocky Mountain Montane Douglas-Fir Forest and Woodland


  • Literature Cited AboveLegend:   View Online Publication
    • Alexander, M.E. and F.G. Hawksworth. 1976. Fire and dwarf mistletoes in North American coniferous forests. Journal of Forestry 74(7):446-449.
    • Amo, S.F., M.G. Harrington, C.E. Fiedler, and C.E. Carlson. 1995. Restoring fire-dependent ponderosa pine forests in western Montana. Restoration and Management Notes 13:32-36.
    • Arno, S.F. and G.E. Guell. 1986. Douglas-fir encroachment into mountain grasslands in southwestern Montana. J. Range Management 39(3):272-276.
    • DeNitto, G., B. Cramer, K. Gibson, B. Lockman, T. McConnell, L. Stipe, and J. Taylor. 2000. Survivability and deterioration of fire-injured trees in the northern rocky mountains: a review of the literature. The Bark Beetles, Fuels, and Fire Bibliography 1.
    • Harvey, B.J., D.C. Donato, W.H. Romme, and M.G. Turner. 2013. Influence of recent bark beetle outbreak on fire severity and postfire tree regeneration in montane Douglas-fir forests. Ecology 94(11): 2475-2486.
    • Heyerdahl, E.K., R.F. Miller, and R.A. Parsons. 2006. History of fire and Douglas-fir establishment in a savanna and sagebrush–grassland mosaic, southwestern Montana, USA. Forest Ecology and Management 230(1):107-118.
    • Hood, S. and B. Bentz. 2007. Predicting postfire Douglas-fir beetle attacks and tree mortality in the northern Rocky Mountains. Canadian Journal of Forest Research 37(6):1058-1069.
    • Negron, J.F., W.C. Schaupp, K.E. Gibson, J. Anhold, D. Hansen, R. Their, and P. Mocettini. 1999. Estimating extent of mortality associated with the Douglas-fir beetle in the central and northern Rockies. Western Journal of Applied Forestry 14(3):121-127.
    • Six, D.L. and K. Skov. 2009. Response of bark beetles and their natural enemies to fire and fire surrogate treatments in mixed-conifer forests in western Montana. Forest Ecology and Management 258(5):761-772.
    • 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.
    • U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory. 2012. Information from LANDFIRE on Fire Regimes of Rocky Mounatin Douglas-Fir Communities. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Fo
  • 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.
    • 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:
Rocky Mountain Montane Douglas-fir Forest and Woodland — Middle Rocky Mountain Montane Douglas-Fir Forest and Woodland.  Montana Field Guide.  Retrieved on , from