Print Report
A3462 Pseudotsuga menziesii Middle Rocky Mountain Dry-Mesic Forest & Woodland Alliance
Type Concept Sentence: This forest and woodland alliance is dominated by Pseudotsuga menziesii and occurs on relatively dry to mesic sites throughout the middle Rocky Mountains of central and southern Idaho, the Greater Yellowstone region, and the Wind River, Gros Ventre and Bighorn ranges of Wyoming and in Montana on the east side of the Continental Divide.
Common (Translated Scientific) Name: Douglas-fir Middle Rocky Mountain Dry-Mesic Forest & Woodland Alliance
Colloquial Name: Middle Rocky Mountain Douglas-fir Dry-Mesic Forest & Woodland
Hierarchy Level: Alliance
Type Concept: Stands of this alliance are Pseudotsuga menziesii-dominated forests and woodlands occasionally with Juniperus osteosperma, Juniperus scopulorum, Pinus flexilis (on calcareous substrates), Populus tremuloides (on disturbed sites), and Pinus contorta (at higher elevations). True firs, such as Abies concolor, Abies grandis, and Abies lasiocarpa, are absent, but occasional Picea engelmannii can occur in some stands. Pinus ponderosa is also not common in this group. Understory components include shrubs such as Cercocarpus ledifolius, Juniperus communis, Mahonia repens, Purshia tridentata, Spiraea betulifolia, Symphoricarpos albus, and Symphoricarpos oreophilus. Common graminoids include Calamagrostis rubescens, Carex rossii, Leucopoa kingii, and Pseudoroegneria spicata. Forbs are variable, but typical taxa include Arnica cordifolia, Thalictrum occidentale, Viola adunca, and species of many other genera, including Antennaria, Arenaria, Erigeron, Eriogonum, Lathyrus, Lupinus, Penstemon, and Vicia. This alliance occurs on relatively dry to mesic sites throughout the middle Rocky Mountains of central and southern Idaho, the Greater Yellowstone region, and the Wind River, Gros Ventre and Bighorn ranges of Wyoming. It extends north into Montana on the east side of the Continental Divide, to the McDonald Pass area, and also into the Rocky Mountain Front region and central "sky island" ranges of Montana. This alliance often occurs at the lower treeline immediately above valley grasslands, or sagebrush steppe and shrublands. Stands are found on all aspects in the Central Rockies where the southern monsoon influence is less and maritime climate regime is not important. Climate is drier and more continental than at higher elevations or in the Pacific Northwest. Annual precipitation ranges from 50-100 cm with moderate snowfall and a greater proportion falling during the growing season. Monsoonal summer rains can contribute a significant proportion of the annual precipitation in the southern portion of the range. Elevations range from less than 1000 m in the central Rocky Mountains to over 2400 m in the Wyoming Rockies. Lower elevation stands typically occupy cooler, less xeric northern exposures often on steep slopes. At higher elevations, these forests occur primarily on southerly aspects or ridgetops and plateaus. Soils are highly variable and derived from diverse parent materials, including extrusive volcanics in the Yellowstone region, and sedimentary rocks elsewhere in the Rockies. The soils are typically well-drained and well-aerated. They can be derived from moderately deep colluvium or shallow-jointed bedrock, and are usually gravelly or rocky.
Diagnostic Characteristics: Open to closed-canopy woodlands and forests dominated by Pseudotsuga menziesii with a variety of dry-mesic site indicator species in the understory such as the shrubs Cercocarpus ledifolius, Juniperus communis, Mahonia repens, Purshia tridentata, Spiraea betulifolia, Symphoricarpos albus, Symphoricarpos oreophilus, and several herbaceous species, including Arnica cordifolia, Calamagrostis rubescens, Carex rossii, and Leucopoa kingii.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Several associations included in this alliance are broadly defined and may occur outside the central Rocky Mountains. More review of similar groups and the associations in this alliance is needed to clarify the classification.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation included in this alliance is characterized by open stands of evergreen needle-leaved trees 15-50 m tall. There may be sparse cover of broad-leaved and scale-leaved trees in the subcanopy (5-15 m tall). Shrubs are typically sparse, but may be moderately dense on some sites and are typically dominated by broad-leaved, cold-deciduous shrubs <2 m tall. The herbaceous layer is sparse under denser tree canopies and on rock substrates, but is typically a moderately dense layer that is usually dominated by perennial, medium-tall bunch grasses with forbs. Occasionally perennial forbs are dominant. Annual grasses and forbs are seasonally present.
Floristics: Stands are Pseudotsuga menziesii-dominated forests and woodlands occasionally with Juniperus osteosperma, Juniperus scopulorum, Pinus flexilis (on calcareous substrates), Populus tremuloides (on disturbed sites), and Pinus contorta (at higher elevations). True firs, such as Abies concolor, Abies grandis, and Abies lasiocarpa, are absent, but occasional Picea engelmannii can occur in some stands. Pinus ponderosa is also not common in this group. Understory components include shrubs such as Cercocarpus ledifolius, Cercocarpus montanus, Holodiscus dumosus, Juniperus communis, Mahonia repens, Purshia tridentata, Spiraea betulifolia, Symphoricarpos albus, and Symphoricarpos oreophilus. Common graminoids include Calamagrostis rubescens, Carex rossii, Festuca idahoensis, Leucopoa kingii, and Pseudoroegneria spicata. Forbs are variable, but typical taxa include Arnica cordifolia, Thalictrum occidentale, Viola adunca, and species of many other genera, including Antennaria, Arenaria, Erigeron, Eriogonum, Lathyrus, Lupinus, Penstemon, and Vicia. This alliance often occurs at the lower treeline immediately above valley grasslands, or sagebrush steppe and shrublands. Sometimes there may be a "bath-tub ring" of Pinus ponderosa at lower elevations or Pinus flexilis between the valley non-forested and then solid Pseudotsuga menziesii forest. In the Wyoming Basins, this alliance occurs as isolated stands of Pseudotsuga menziesii with Artemisia tridentata, Carex rossii, Leucopoa kingii, and Pseudoroegneria spicata. Annual grasses and forbs may be present, especially on disturbed sites.
Dynamics: Successional relationships in this alliance are complex. Pseudotsuga menziesii is less shade-tolerant than many northern or montane trees such as Abies concolor, Picea engelmannii, Thuja plicata, or Tsuga heterophylla, and seedlings compete poorly in deep shade. At drier locales, seedlings may be favored by moderate shading, such as by a canopy of Pinus ponderosa, which helps to minimize drought stress. In some locations, much of these forests have been logged or burned during European settlement, and present-day stands are second-growth forests dating from fire, logging, or other stand-replacing disturbances (Mauk and Henderson 1984). Pseudotsuga menziesii forests were probably subject to a moderate-severity fire regime in presettlement times, with fire-return intervals of 30-100 years.
Environmental Description: This alliance occurs on relatively dry to mesic sites throughout the middle Rocky Mountains of central and southern Idaho, the Greater Yellowstone region, and the Wind River, Gros Ventre and Bighorn ranges of Wyoming. It extends north into Montana on the east side of the Continental Divide, to the McDonald Pass area, and also into the Rocky Mountain Front region and central "sky island" ranges of Montana. Stands are found on all aspects in the Central Rockies where the southern monsoon influence is less and maritime climate regime is not important. Climate is drier and more continental than at higher elevations or in the Pacific Northwest. Annual precipitation ranges from 50-100 cm with moderate snowfall and a greater proportion falling during the growing season. Monsoonal summer rains can contribute a significant proportion of the annual precipitation in the southern portion of the range. Elevations range from less than 1000 m in the central Rocky Mountains to over 2400 m in the Wyoming Rockies. Lower elevation stands typically occupy protected northern exposures and canyons, often on steep slopes. At higher elevations, these forests occur primarily on southerly aspects or ridgetops and plateaus. Substrates are typically shallow, lithic, course-textured soils derived from colluvium and residuum. Soil texture ranges from gravelly sand to loam. There is typically high surface cover of rock, as well as coarse fragments within the soil. Soil pH varies from acidic to alkaline depending on parent material. Parent materials are extremely varied and may include andesite, basalt, dolomite, gneiss, granite, lava, limestone, mudstone, rhyolite, sandstone and tuff. Extrusive volcanics are common in the Yellowstone region, and sedimentary rocks elsewhere in the Rockies. Pseudotsuga menziesii forests are reported by most studies (Pfister et al. 1977, Steele et al. 1981, Mauk and Henderson 1984) to show no particular affinities to geologic substrates. These rocky, shallow soils have so little moisture-holding capacity that these sites are effectively very dry for plant growth even where there is substantial precipitation. In some cases, these sites are exposed to high winds. Wind detracts from soil moisture status by blowing off snow, directly desiccating plants, and eroding soil.
Geographic Range: This alliance occurs on relatively dry to mesic sites throughout the middle Rocky Mountains of central and southern Idaho, the Greater Yellowstone region, and the Wind River, Gros Ventre and Bighorn ranges of Wyoming. It extends north into Montana on the east side of the Continental Divide, to the McDonald Pass area, and also into the Rocky Mountain Front region and central "sky island" ranges of Montana.
Nations: CA,US
States/Provinces: ID, MT, WY
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899585
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: This alliance includes seven associations from Old Alliance I.A.8.N.c. Pseudotsuga menziesii Forest Alliance (A.157), one association from Old Alliance I.C.3.N.a. Populus tremuloides - Pseudotsuga menziesii Forest Alliance (A.426), and five associations from And Old Alliance II.A.4.N.b. Pseudotsuga menziesii Woodland Alliance (A.552). A.157 (in part), A.426 (in part), and A.552 (in part)
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: > Populus tremuloides - Pseudotsuga menziesii / Symphoricarpos oreophilus Community Type (Mueggler 1988)
> Pseudotsuga menziesii - Pinus flexilis / Hesperochloa kingii Association (Cooper 1975)
> Pseudotsuga menziesii / Arnica cordifolia Habitat Type (Pfister et al. 1977)
> Pseudotsuga menziesii / Berberis repens Habitat Type (Hoffman and Alexander 1976)
> Pseudotsuga menziesii / Cercocarpus ledifolius Community Type (DeVelice 1992)
> Pseudotsuga menziesii / Juniperus communis Habitat Type (Steele et al. 1983)
> Pseudotsuga menziesii / Spiraea betulifolia Habitat Type (Cooper et al. 1987)
> Pseudotsuga menziesii / Symphoricarpos albus Habitat Type (Steele et al. 1981)
> Pseudotsuga menziesii / Symphoricarpos oreophilus Habitat Type (Steele et al. 1981)
< Interior Douglas-fir: 210 (Eyre 1980)
> Pseudotsuga menziesii - Pinus flexilis / Hesperochloa kingii Association (Cooper 1975)
> Pseudotsuga menziesii / Arnica cordifolia Habitat Type (Pfister et al. 1977)
> Pseudotsuga menziesii / Berberis repens Habitat Type (Hoffman and Alexander 1976)
> Pseudotsuga menziesii / Cercocarpus ledifolius Community Type (DeVelice 1992)
> Pseudotsuga menziesii / Juniperus communis Habitat Type (Steele et al. 1983)
> Pseudotsuga menziesii / Spiraea betulifolia Habitat Type (Cooper et al. 1987)
> Pseudotsuga menziesii / Symphoricarpos albus Habitat Type (Steele et al. 1981)
> Pseudotsuga menziesii / Symphoricarpos oreophilus Habitat Type (Steele et al. 1981)
< Interior Douglas-fir: 210 (Eyre 1980)
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