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A3609 Abies grandis - Picea sitchensis - Thuja plicata Forest Alliance

Type Concept Sentence: This alliance consists of generally low-elevation forests of the Pacific Northwest located on dry well-drained sites dominated by Abies grandis and usually codominated by Picea sitchensis, Tsuga heterophylla, and/or Thuja plicata. Understory species are variable and tolerant of drought. Sites are dry and well-drained.

Common (Translated Scientific) Name: Grand Fir - Sitka Spruce - Western Red-cedar Forest Alliance

Colloquial Name: Grand Fir - Sitka Spruce - Western Red-cedar Forest

Hierarchy Level:  Alliance

Type Concept: This alliance consists of low-elevation forests of the Pacific Northwest located on dry well-drained sites dominated by Abies grandis and usually codominated by Picea sitchensis, Tsuga heterophylla, and/or Thuja plicata. These forests are characterized by a multi-tiered tree canopy and can be over 50 m in height. Understory species are variable and tolerant of drought, such as Rhododendron macrophyllum, Vaccinium ovatum, or Gaultheria shallon. Sites are dry and well-drained. These conifer forests typically occur on deep soils of alluvial terraces.

Diagnostic Characteristics: Mix of Abies grandis and other conifers on dry sites.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: These are dry but not burned areas.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Forests of this alliance are typified by a dense to moderately open multi-aged canopy of needle-leaved evergreen trees on average exceeding 50 m in height. Broad-leaved cold-deciduous trees may form a scattered subcanopy, particularly in canopy gaps.

Floristics: Sites are dominated by Abies grandis in the upper canopy and usually codominated by one or more conifers such as Picea sitchensis, Tsuga heterophylla, and/or Thuja plicata. Pseudotsuga menziesii may also be present. Understory species are variable and tolerant of drought, such as Rhododendron macrophyllum, Vaccinium ovatum, or Gaultheria shallon.

Dynamics:  Forest associations within this alliance are dominated by a moderately fast-growing, shade-tolerant, fire-intolerant conifer, which requires moist conditions and a mild temperature regime for establishment and growth. Following disturbance, a variety of other conifer species can become established and dominate sites previously supporting stands of this alliance. Pseudotsuga menziesii, in particular, can become established on these sites and dominate for many years following disturbance. Wind dominates the disturbance patterns of these forests, and fire-return intervals are very long. Fires are infrequent in these forests, due to high fuel moisture and protected topographic positions.
Environmental Description:  No Data Available
Geographic Range: This alliance occurs along coastal southern British Columbia, Washington, Oregon and northern California.

Nations: CA,US

States/Provinces:  BC, CA, OR, WA


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.Nd Vancouverian Forest & Woodland Division D192 1.B.2.Nd
Macrogroup 1.B.2.Nd.3 Western Hemlock - Sitka Spruce - Redwood Rainforest Macrogroup M024 1.B.2.Nd.3
Group 1.B.2.Nd.3.f Western Hemlock - Sitka Spruce North-Central Pacific Rainforest Group G751 1.B.2.Nd.3.f
Alliance A3609 Grand Fir - Sitka Spruce - Western Red-cedar Forest Alliance A3609 1.B.2.Nd.3.f
Association CEGL000053 Grand Fir - Sitka Spruce / Salal / Western Swordfern Forest CEGL000053 1.B.2.Nd.3.f
Association CEGL000089 Western Red-cedar / Twinflower Forest CEGL000089 1.B.2.Nd.3.f
Association CEGL000468 Western Red-cedar - (Grand Fir) / Western Swordfern Forest CEGL000468 1.B.2.Nd.3.f
Association CEGL000486 Western Red-cedar - Western Hemlock / Common Whipplea Forest CEGL000486 1.B.2.Nd.3.f
Association CEGL002846 Western Red-cedar - Bigleaf Maple - Grand Fir / (Indian-plum) / Western Swordfern Forest CEGL002846 1.B.2.Nd.3.f
Association CEGL002848 Western Red-cedar - Douglas-fir - Grand Fir / Cascade Barberry / Western Swordfern Forest CEGL002848 1.B.2.Nd.3.f
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: ? Abies grandis (Grand fir forest) Alliance (Sawyer et al. 2009) [88.100.00]
>< Picea sitchensis (Sitka spruce forest) Alliance (Sawyer et al. 2009) [83.200.00]
>< Tsuga heterophylla-Thuja plicata Coniferous Wetlands (Chappell et al. 1997)
>< Eastside Tsuga heterophylla-Thuja plicata Forests (Chappell et al. 1997)
>< Maritime Tsuga heterophylla-Thuja plicata Forests (Chappell et al. 1997)
>< Sitka Spruce Series (Henderson et al. 1989)
>< Sitka Spruce Series (Sawyer and Keeler-Wolf 1995)
>< Sitka Spruce: 223 (Eyre 1980)
>< Western Hemlock - Sitka Spruce: 225 (Eyre 1980)
>< Western Needleleaf Forests: 1: Spruce-Cedar-Hemlock Forest (Picea-Thuja-Tsuga) (Küchler 1964)
>< Western Needleleaf Forests: 2: Cedar-Hemlock-Douglas Fir Forest (Thuja-Tsuga-Pseudotsuga) (Küchler 1964)
>< Western Redcedar - Western Hemlock: 227 (Eyre 1980)
>< Western Redcedar: 228 (Eyre 1980)
>< Westside Pseudotsuga menziesii-Tsuga heterophylla Forests (Chappell et al. 1997)
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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