Print Report

A3463 Pseudotsuga menziesii Middle Rocky Mountain Mesic-Wet Forest Alliance

Type Concept Sentence: This forest and woodland alliance is dominated by Pseudotsuga menziesii without the maritime floristic composition. It occurs on relatively moist, cool to warm 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 Mesic-Wet Forest Alliance

Colloquial Name: Middle Rocky Mountain Douglas-fir Mesic-Wet Forest

Hierarchy Level:  Alliance

Type Concept: Stands are Pseudotsuga menziesii-dominated forests and woodlands; occasionally Populus tremuloides may codominate on disturbed sites ,and Pinus contorta may be present 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 relatively mesic species such as the shrubs Acer glabrum, Amelanchier alnifolia, Linnaea borealis, and Physocarpus malvaceus, and herbs and grasses such as Achillea millefolium, Bromus carinatus, Eucephalus engelmannii, Fragaria vesca, Geranium viscosissimum, Lathyrus spp., Osmorhiza berteroi, and Piptatheropsis micrantha. This alliance is restricted to mesic to wet sites in 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 occurs 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. Stands typically occupy cooler northern exposures in relatively moist sites such as lower slopes, benches and valley bottoms. Lower elevation stands occupy mesic ravines and canyons on northerly aspects. 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 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 mesic-wet site indicator species in the understory such as Acer glabrum, Amelanchier alnifolia, Linnaea borealis, Osmorhiza berteroi, Physocarpus malvaceus, and Piptatheropsis micrantha.

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: These forests and woodlands are characterized by a multi-tiered needle-leaved evergreen tree canopy up to 50 m high, with between 25-100% cover. A sparse subcanopy of cold-deciduous or evergreen trees is often present, particularly in northwestern coastal stands. Downed wood may also be abundant in older stands. Shrub cover is dominated by cold-deciduous species and can be dense. A sparse to dense perennial herbaceous layer is usually present and composed of either shade-tolerant forbs and ferns in the Central Rockies or mesophytic forbs and grasses.

Floristics: Stands of this alliance are Pseudotsuga menziesii-dominated forests and woodlands. Occasionally Populus tremuloides may codominate on disturbed sites, and Pinus contorta may be present 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 relatively mesic species such as the shrubs Acer glabrum, Amelanchier alnifolia, Holodiscus dumosus, Linnaea borealis, Paxistima myrsinites, Physocarpus malvaceus, Rosa woodsii, and Salix scouleriana, and herbs and grasses such as Achillea millefolium, Bromus carinatus, Eucephalus engelmannii (= Aster engelmannii), Fragaria vesca, Galium boreale, Geranium viscosissimum, Lathyrus spp., Osmorhiza berteroi, and Piptatheropsis micrantha (= Piptatherum micranthum).

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 is restricted to mesic to wet sites in 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 occurs 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. Stands typically occupy cooler northern exposures in relatively moist sites such as lower slopes, benches and valley bottoms. Lower elevation stands occupy mesic ravines and canyons on northerly aspects. 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 can be derived from moderately deep colluvium or shallow-jointed bedrock, and are usually gravelly or rocky.
Geographic Range: This alliance occurs on relatively moist, cool to warm 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


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.2 Cool Temperate Forest & Woodland Formation F008 1.B.2
Division 1.B.2.Nb Rocky Mountain Forest & Woodland Division D194 1.B.2.Nb
Macrogroup 1.B.2.Nb.2 Ponderosa Pine - Douglas-fir - Limber Pine Central Rocky Mountain Dry Forest Macrogroup M501 1.B.2.Nb.2
Group 1.B.2.Nb.2.c Douglas-fir Middle Rocky Mountain Montane Forest & Woodland Group G215 1.B.2.Nb.2.c
Alliance A3463 Douglas-fir Middle Rocky Mountain Mesic-Wet Forest Alliance A3463 1.B.2.Nb.2.c
Association CEGL000418 Douglas-fir / Rocky Mountain Maple Forest CEGL000418 1.B.2.Nb.2.c
Association CEGL000420 Douglas-fir / Saskatoon Serviceberry Forest CEGL000420 1.B.2.Nb.2.c
Association CEGL000441 Douglas-fir / Twinflower Forest CEGL000441 1.B.2.Nb.2.c
Association CEGL000445 Douglas-fir / Mountain Sweet-cicely Forest CEGL000445 1.B.2.Nb.2.c
Association CEGL000447 Douglas-fir / Mallow Ninebark Forest CEGL000447 1.B.2.Nb.2.c
Association CEGL000543 Quaking Aspen - Douglas-fir / Saskatoon Serviceberry Forest CEGL000543 1.B.2.Nb.2.c
Association CEGL000905 Douglas-fir / Little-seed Ricegrass Woodland CEGL000905 1.B.2.Nb.2.c
Concept Lineage: This alliance includes five 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 one association 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 / Amelanchier alnifolia Community Type (Mueggler 1988)
> Pseudotsuga menziesii / Acer glabrum Habitat Type (Steele et al. 1981)
> Pseudotsuga menziesii / Acer glabrum Habitat Type, Pachistima myrsinites Phase (Steele et al. 1983)
> Pseudotsuga menziesii / Amelanchier alnifolia Habitat Type (Roberts 1980)
> Pseudotsuga menziesii / Osmorhiza chilensis Habitat Type (Steele et al. 1983)
> Pseudotsuga menziesii / Physocarpus malvaceus Habitat Type (Cooper et al. 1987)
>< Interior Douglas-fir: 210 (Eyre 1980)
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: K.A. Schulz and M.S. Reid

Acknowledgements: We have incorporated significant descriptive information previously compiled by Marion Reid.

Version Date: 01-08-14
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