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Montana Field Guides

Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest

Provisional State Rank: S3

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General Description

This ecological system, composed of highly variable montane conifer forests, is found throughout Montana. It is associated with a submesic climate regime with annual precipitation ranging from 250 to 1,000 millimeters (10-39 inches), with most precipitation occurring during winter, and April through June. Winter snowpacks typically melt off in early spring at lower elevations. Elevations range from valley bottoms to 1,676 meters (5,500 feet) in northwestern Montana and up to 2,286 meters (7,500 feet) on warm aspects in southern Montana. In northwestern and west-central Montana, this ecosystem forms a forest belt on warm, dry to slightly moist sites. It generally occurs on gravelly soils with good aeration and drainage and a neutral to slightly acidic pH. In the western part of the state, it is seen mostly on well drained mountain slopes and valleys from lower treeline to up to 1,676 meters (5,500 feet). Immediately east of the Continental Divide, in north-central Montana, it occurs at montane elevations. Douglas-fir (Pseudotsuga menziesii) is the dominant conifer both as a seral and climax species. West of the Continental Divide, occurrences can be dominated by any combination of Douglas-fir and long-lived, seral western larch (Larix occidentalis), grand fir (Abies grandis), ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta). Aspen (Populus tremuloides) and western white pine (Pinus monticola) have a minor status, with western white pine only in extreme western Montana. East of the Continental Divide, larch is absent and lodgepole pine is the co-dominant. Engelmann spruce (Picea engelmannii), white spruce, (Picea glauca)or their hybrid, become increasingly common towards the eastern edge of the Douglas-fir forest belt.


Diagnostic Characteristics

montane elevations, mixed coniferous forests, Abies grandis, ustic soils


Similar Systems

Range
Douglas-fir and grand fir are the climax species in a broad forest belt at montane elevations throughout the western Montana Rocky Mountains. East of the Continental Divide, including the mountain island ranges of west-central and south-central Montana, Douglas-fir is the climax species. Elsewhere, this forest system is a low to montane elevational forest in the interior Pacific Northwest, ranging from southern interior British Columbia, eastern Washington, eastern Oregon and northern Idaho east to Montana, and south along the eastern slope of the Cascade Range in Washington and Oregon.

Ecological System Distribution
Approximately 10,827 square kilometers are classified as Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest 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, Blaine, Carbon, Cascade, Chouteau, Deer Lodge, Fergus, Flathead, Gallatin, Glacier, Golden Valley, Granite, Hill, Judith Basin, Lake, Lewis and Clark, Liberty, Lincoln, Madison, Mineral, Missoula, Musselshell, Park, Phillips, Pondera, Powell, Ravalli, Sanders, Stillwater, Sweet Grass, Teton, Toole, Wheatland

Spatial Pattern
Matrix

Environment
In northwestern and west-central Montana, this ecosystem forms a forest belt on warm, dry to moist sites. It is associated with a submesic climate regime with annual precipitation ranging from 250 to 1,000 millimeters (10-39 inches), with most precipitation occurring during winter, and April through June. Winter snowpacks typically melt off in early spring at lower elevations. Elevations range from valley bottoms to 1,676 meters (5,500 feet) in northwestern Montana and up to 2,286 meters (7,500 feet) on warm aspects in southern Montana. In northwestern and west-central Montana, this ecosystem forms a forest belt on warm, dry to slightly moist sites. It generally occurs on gravelly soils with good aeration and drainage and a neutral to slightly acidic pH. In the western part of the state, it is seen mostly on well-drained mountain slopes and in valleys from lower treeline to up to 1,676 meters (5,500 feet). Immediately east of the Continental Divide, in north-central Montana, it occurs at montane elevations.

Vegetation

Douglas-fir is the dominant conifer; west of the Continental Divide, occurrences are dominated by a mix of Douglas-fir and long-lived, seral western and other species, including lodgepole pine and western white pine. East of the Continental Divide, larch is absent and lodgepole pine is the co-dominant. Engelmann spruce or white spruce, or their hybrid, becomes increasingly common towards the eastern edge of the Douglas-fir forest belt. Grand fir may occur in this forest type, but is typically confined to relatively warm and moister sites in northwestern and west-central Montana.

Undergrowth is dominated by graminoids, such as bluebunch wheatgrass (Pseudoroegneria spicata), Columbia brome(Bromus vulgaris),blue wildrye (Elymus glaucus), pinegrass (Calamagrostis rubescens), Geyer’s sedge (Carex geyeri), and Ross’ sedge (Carex rossii). Common forbs that occur in the understory include American pathfinder (Adenocaulon bicolor), heartleaf arnica (Arnica cordifolia), queen’s cup beadlily (Clintonia uniflora), twinflower (Linnaea borealis), and beargrass (Xerophyllum tenax). The shrub understory contains a variety of shrubs, such as Rocky mountain maple (Acer glabrum), kinnikinnick (Arctostaphylos uva-ursi), common juniper (Juniperus communis), oceanspray (Holodiscus discolor), mallow ninebark(Physocarpus malvaceus), common snowberry (Symphoricarpos albus), birch leaf spiraea (Spiraea betulifolia), dwarf bilberry (Vaccinium caespitosum) or mountain huckleberry (Vaccinium membranaceum)on colder, more mesic sites. In the western part of the state, the Douglas-fir/mountain huckleberry association is the most common type found in the Lolo, Bitteroot and Flathead Mountain ranges on relatively cold sites up to 2,073 meters (6,800 feet) (Pfister et al, 1977).


National Vegetation Classification Switch to Full NVC View

Adapted from US National Vegetation Classification

A3362 Abies grandis - Pseudotsuga menziesii Central Rocky Mountain Forest & Woodland Alliance
CEGL000176 Pinus monticola - Clintonia uniflora Forest
CEGL000275 Abies grandis - Linnaea borealis Forest
CEGL000277 Abies grandis - Physocarpus malvaceus Forest
CEGL000281 Abies grandis - Spiraea betulifolia Forest
CEGL000461 Pseudotsuga menziesii - Symphoricarpos occidentalis Forest
CEGL000465 Pseudotsuga menziesii - Vaccinium caespitosum Forest
CEGL000916 Abies grandis - Calamagrostis rubescens Woodland
CEGL005850 Pseudotsuga menziesii - Clintonia uniflora Forest
CEGL005851 Pseudotsuga menziesii - Menziesia ferruginea - Clintonia uniflora Forest
CEGL005852 Pseudotsuga menziesii - Vaccinium membranaceum - Xerophyllum tenax Forest
CEGL005853 Pseudotsuga menziesii - Heracleum maximum Forest
CEGL005854 Pseudotsuga menziesii - Clintonia uniflora/ Xerophyllum tenax Forest
A3392 Pseudotsuga menziesii - Pinus ponderosa / Shrub Understory Central Rocky Mountain Forest & Woodland Alliance
A3395 Pseudotsuga menziesii - Pinus ponderosa / Herbaceous Understory Central Rocky Mountain Woodland Alliance
CEGL000429 Pseudotsuga menziesii - Calamagrostis rubescens Woodland
CEGL000430 Pseudotsuga menziesii - Carex geyeri Forest
A3454 Pseudotsuga menziesii Southern Rocky Mountain Forest & Woodland Alliance
CEGL000424 Pseudotsuga menziesii - Arctostaphylos uva-ursi Forest
A3462 Pseudotsuga menziesii Middle Rocky Mountain Dry-Mesic Forest & Woodland Alliance
CEGL000427 Pseudotsuga menziesii - Arnica cordifolia Forest
CEGL000462 Pseudotsuga menziesii - Symphoricarpos oreophilus Forest
A3463 Pseudotsuga menziesii Middle Rocky Mountain Mesic-Wet Forest Alliance
CEGL000441 Pseudotsuga menziesii - Linnaea borealis 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

Douglas-fir and all associated seral species in this system regenerate well following fire, and all, with the exception of lodgepole pine, tolerate repeated low intensity surface fires due to thick bark and deep roots. In the absence of disturbance, the longevity and fire resistance of western larch and Douglas-fir lead to their co-dominance in many areas of western Montana. Douglas-fir and grand fir continue to regenerate under shaded conditions, and these too may become dominant in undisturbed stands. In eastern Montana, lodgepole pine is most often co-dominant with Douglas fir. Presettlement fire regimes may have been characterized by frequent, low-intensity ground fires that maintained relatively open stands of a mix of fire-resistant species. Under present conditions, the fire regime is mixed severity and more variable with stand-replacing fires more common, resulting in increasing forest homogeneity. Fire return intervals vary between approximately 40 and 80 years, with intervals being shortest in stands in which Douglas-fir and western larch are co-dominant, and longest where Douglas-fir and lodgepole pine are co-dominant (U.S. Department of Agriculture, 2012). In Glacier National Park, this forest type historically experienced fire return intervals of 36 years at dry sites, and 46 years at relatively mesic sites, with stand replacing fires occurring at intervals of approximately 140-180 years (Barrett et al., 1991). With vigorous fire suppression, longer fire-return intervals are now common, and multi-layered stands of conifers provide fuel "ladders," making these forests more susceptible to high-intensity, stand-replacing fires. Both western larch and lodgepole pine are aggressive colonizers after major disturbances. These are very productive forests which have been priorities for timber production.

The species in this system vary in their susceptibility to biotic vectors. Western larch is generally resistant to damage from pathogens and insects (Scher, 2002). However, in western larch stands in the Bitterroot Mountains of western Montana where fire has been suppressed and regeneration is limited, dwarf mistletoe infects trees and impacts stand persistence (McCune, 1983). In contrast to western larch, grand fir, Douglas-fir, lodgepole pine, and ponderosa pine are susceptible to a variety of insects and pathogens. Both grand fir and Douglas-fir are affected by western spruce budworm (Choristoneura occidentalis) and Douglas-fir tussock moth (Orgyia pseudotsugata), while the western balsam bark beetle (Dryocoetes confuses) and fir engraver beetles (Scolytus ventralis) further affect grand fir (Howard and Aleksoff, 2000; Steinberg, 2002). The Douglas-fir bark beetle (Dendroctonus pseudotsugae) causes abundant damage to Douglas-fir in this system and fire-affected stands tend to be more vulnerable to attack (Negron et al., 1999; Hood and Bentz, 2007; Six and Skov, 2009). Both lodgepole pine and ponderosa pine are highly susceptible to mountain pine beetles. Elevated temperature and increasing drought severity combine to favor beetle population growth and weaken lodgepole and ponderosa pine defense mechanisms, increasing susceptibility to beetle attack (Raffa et al., 2008).


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 is particularly important when management goals include the maintenance of western larch and/or ponderosa pine within this system (Habeck, 1992; Scher, 2002). Burning exposes a mineral seedbed which is preferred for germination by all species in this system. The timing of prescribed burning in this system is important and fall burning following dry summers is typically most effective. Removing seedlings and duff from the bases of western larch and ponderosa pine may be necessary to prevent fire damage to roots and the spread of surface fires to tree crowns (Scher, 2002; Kolb et al., 2007). The varying vulnerability of species in this system to windthrow should be considered when thinning is applied to reduce fire risk. Western larch has deep roots and moderate to high windthrow resistance, ponderosa pine and douglas fir are moderately susceptible, and lodgepole pine is highly susceptible to windthrow due to its shallow root system (Scher, 2002; Anderson, 2003).


Restoration Considerations

Restoration strategies will depend largely on the severity of the fire. Early successional stages may be dominated by fireweed (Chamerion angustifolium) and other forbs, graminoids and understory shrubs. Dominant species such as Douglas-fir, lodgepole pine and western larch regenerate well following fire and mineral soil seedbeds that result from burning favor germination by these species. However, prolonged drought conditions and high soil temperatures on bare mineral soils can impede natural regeneration and may require supplemental planting post-disturbance (Scher, 2002).

Intense fires that occur during summer months cause considerable damage to native perennial grasses, forbs and shrubs, and may completely destroy existing seed banks, especially on steep facing slopes and ridgetops. Steep slopes may require reseeding with native grasses to prevent soil erosion. In some cases, severely burned sites will require replanting with conifer seedlings. Generally, larger container volume of nursery stock results in higher outplanting success than bareroot nursery stock, especially where spring and early summer precipitation patterns are unpredictable, or where exposed mineral soil temperatures are high during the first year of establishment. Generally, 6-8 cubic inch container stock types are used on milder sites with good site preparation, and 10, 15 or 20 cubic inch container stock is used on the hotter, drier aspects or sites. Conifer stocking rates must be developed on a site-by-site basis and to meet management objectives.

Prescribed fire may be an additionally valuable restoration strategy in stands with high levels of dwarf mistletoe if all infected individuals are eliminated (Hawksworth et al., 2002). High severity burning controls 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 insect populations should be considered as vulnerability to attack may increase post fire (e.g. Hood and Bentz, 2007).


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
R. Crawford, C. Chappell, and 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 28641
    System Code CES306.805, Northern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest

    National Land Cover Dataset:
    42: Evergreen Forest

    ReGAP:
    4232: Northern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest


  • 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.
    • Anderson, M.D. 2003. Pinus contorta var. latifolia. In: Fire Effects Information System, [Online}. U. S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).
    • Barrett, S.W., S.F. Arno, and C.H. Key. 1991. Fire regimes of western larch-lodgepole pine forests in Glacier National Park, Montana. Canadian Journal of Forest Research 21(12):1711-1720.
    • Hawksworth, F.G., D. Wiens, and B.W. Geils. 2002. Arceuthobium in North America. Mistletoes of North American conifers 29-56.
    • 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.
    • Howard, J.L. and K.C. Aleksoff. 2000. Abies grandis. 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.
    • McCune, B. 1982. Fire frequency reduced two orders of magnitude in the Bitterroot Canyons, Montana. Canadian Journal of Forest Reaseach 13:212-218.
    • 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.
    • Scher, J.S. 2002. Larix occidentalis. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.
    • 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 Northern Rocky Mounatin Montane Mixed-Conifer Communities. In: Fire Effects Information System, [Online]. U.S. Department
  • Additional ReferencesLegend:   View Online Publication
    Do you know of a citation we're missing?
    • Arno, S. 1979. Forest regions of Montana. Research paper Int-218, USFS Intermountain and Range Experiment Station, Ogden, Utah.
    • 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 Dry-Mesic Montane Mixed Conifer Forest — Northern Rocky Mountain Dry-Mesic Montane Mixed Conifer Forest.  Montana Field Guide.  Retrieved on , from