Print Report

A3582 Tsuga heterophylla - Abies grandis Cascadian Mesic Cove Forest Alliance

Type Concept Sentence: These forests are dominated by Tsuga heterophylla often with Thuja plicata or Abies grandis. Diagnostic undergrowth species reflect Pacific Northwest and Cascadian origin with such species as Rhododendron albiflorum, Tiarella trifoliata, and Gymnocarpium dryopteris. Rocky Mountain species may be present, but the overall floristics of these forests are of Cascadian and Pacific Northwest origin. Stands occur in moist, protected coves on the eastern side of the Cascade Range, in the Blue Mountains and western slopes of the Rocky Mountains.

Common (Translated Scientific) Name: Western Hemlock - Grand Fir Cascadian Mesic Cove Forest Alliance

Colloquial Name: East Cascadian Western Hemlock Mesic Cove Forest

Hierarchy Level:  Alliance

Type Concept: These forests are dominated by Tsuga heterophylla often with Thuja plicata or Abies grandis. Diagnostic undergrowth species reflect Pacific Northwest and Cascadian origin with such species as Rhododendron albiflorum, Tiarella trifoliata, and Gymnocarpium dryopteris. Rocky Mountain species may be present, but the overall floristics of these forests are of Cascadian and Pacific Northwest origin. Stands occur in moist, protected coves on the eastern side of the Cascade Range, in the Blue Mountains and western slopes of the Rocky Mountains. Elevations range from 970-1955 m in the Blue Mountains of Oregon, to as low as 760 m in the eastern Cascades. Sites include protected coves, ravines, and valley bottoms. All aspects are represented, and slopes can be flat to steep.

Diagnostic Characteristics: Forest canopy of Tsuga heterophylla and/or Thuja plicata on the eastern slopes of the Cascade Range or western slopes of the Blue Mountains or Rocky Mountains.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This alliance is differentiated from Pacific Northwest stands by its drier nature and Cascadian understory. The eastern Cascades flora came across or up the Cascades. Maybe the Middle Rockies (Blue Mountains in Oregon) have some floristic mixing from the Sierras across Oregon. See Carstens et al. (2005) and Goward and Spribille (2005).

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Associations in this alliance are characterized by a closed tree canopy (averaging >60% cover) of tall coniferous trees which can attain 50 m in height. A subcanopy is often present, composed of broad-leaved cold-deciduous shrubs or shade-tolerant small trees. Herbaceous cover is highly variable, ranging from 0-60% cover depending on location, precipitation, fire history, and stand age. Generally the abundance of subcanopy and herbaceous cover decreases with increasing stand age and as available light decreases.

Floristics: This alliance is dominated by Tsuga heterophylla often with Thuja plicata or Abies grandis. Undergrowth species include Rhododendron albiflorum, Tiarella trifoliata, and Gymnocarpium dryopteris. Other species present include Linnaea borealis, Achlys triphylla, Clintonia uniflora and Arctostaphylos nevadensis.

Dynamics:  These forests experience a mix of high-severity and moderate-severity fires with natural return intervals of 100-600 years. Pseudotsuga menziesii colonizes vigorously and is favored with logging and/or fire disturbance to these forests. With increasing time since disturbance, Tsuga heterophylla or Thuja plicata become more abundant in the canopy, due to their ability to regenerate under closed-canopy conditions. Abies grandis forests include many sites dominated by Pseudotsuga menziesii and Pinus ponderosa which were formerly maintained by wildfire, and may now be dominated by Abies grandis (a fire-sensitive, shade-tolerant species) (Lillybridge et al. 1995, Chappell et al. 1997). Pre-European settlement fire regimes were typically of frequent, low-intensity surface fires, maintaining relatively open stands of a mix of fire-resistant species. With the advent of vigorous fire suppression, longer fire-return intervals are now the rule, and mixed-stature stands with Abies grandis in various size classes now provide fuel "ladders," making these forests more susceptible to high-intensity, stand-replacing fires (Cooper et al. 1987, Lillybridge et al. 1995)
Environmental Description:  The climate regime with which this alliance is associated is usually submesic with annual precipitation ranging from 50-100 cm, with a maximum in winter or late spring. Snowpacks typically accumulate each winter but melt off in early spring at lower elevation sites. Elevations reported for associations in this alliance range from 970-1955 m in the Blue Mountains of Oregon, to as low as 760 m in the eastern Cascades. Topographic positions are protected coves, ravines, and valley bottoms. Soils textures cover the range from excessively rocky and well-drained to silty loams with a clay pan in the B horizon.
Geographic Range: This alliance is found on the eastern side of the Cascade Range and in the Blue Mountains and western slopes of the Rocky Mountains.

Nations: US

States/Provinces:  OR, WA


Confidence Level: Low

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.3 Western Hemlock - Grand Fir - Western Larch Mesic Lower Montane Forest Macrogroup M500 1.B.2.Nb.3
Group 1.B.2.Nb.3.c Grand Fir - Douglas-fir East Cascades Forest Group G212 1.B.2.Nb.3.c
Alliance A3582 Western Hemlock - Grand Fir Cascadian Mesic Cove Forest Alliance A3582 1.B.2.Nb.3.c
Association CEGL000104 Western Hemlock / Twinflower Forest CEGL000104 1.B.2.Nb.3.c
Association CEGL000286 Grand Fir - Western Hemlock / Bride''s Bonnet Forest CEGL000286 1.B.2.Nb.3.c
Association CEGL000913 Western Hemlock / Pinemat Manzanita Woodland CEGL000913 1.B.2.Nb.3.c
Association CEGL002669 Grand Fir - Western Red-cedar / Sweet After Death Forest CEGL002669 1.B.2.Nb.3.c
Association CEGL007288 Douglas-fir - Western Hemlock / Cascade Barberry / Threeleaf Foamflower Forest CEGL007288 1.B.2.Nb.3.c
Association CEGL007305 Western Hemlock - (Douglas-fir) / Threeleaf Foamflower - Western Oakfern Forest CEGL007305 1.B.2.Nb.3.c
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: >< Douglas fir-western hemlock, # 230 (Küchler 1964)
>< Douglas-fir - Western Hemlock: 230 (Eyre 1980)
>< Grand Fir: 213 (Eyre 1980)
>< Western Hemlock Series (Lillybridge et al. 1995)
>< Western Hemlock: 224 (Eyre 1980)
>< Western Needleleaf Forests: 14: Grand Fir-Douglas Fir Forest (Abies-Pseudotsuga) (Küchler 1964)
>< Western Needleleaf Forests: 2: Cedar-Hemlock-Douglas Fir Forest (Thuja-Tsuga-Pseudotsuga) (Küchler 1964)
Concept Author(s): G. Kittel, in Faber-Langendoen et al. (2013)

Author of Description: G. Kittel

Acknowledgements: No Data Available

Version Date: 09-26-14
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