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G241 Abies amabilis - Tsuga heterophylla Rainforest Group
Type Concept Sentence: This forested group occurs in the lower and montane regions of the central Pacific Northwest rainforest region, primarily west of the Cascade Crest, dominated by Tsuga heterophylla, Abies amabilis, and/or Callitropsis nootkatensis, in maritime and submaritime climatic zones from northwestern Oregon, coastal British Columbia, and possibly extreme southeastern Alaska.
Common (Translated Scientific) Name: Pacific Silver Fir - Western Hemlock Rainforest Group
Colloquial Name: North-Central Pacific Maritime Silver Fir - Western Hemlock Rainforest
Hierarchy Level: Group
Type Concept: This forested group occurs in the Pacific Northwest mountains primarily west of the Cascade Crest. Tsuga heterophylla and/or Abies amabilis dominate the canopy of late-seral stands, and Callitropsis nootkatensis can be codominant, especially at higher elevations or moister sites. Thuja plicata is also common and sometimes codominates in British Columbia. Major dominant understory species are Vaccinium alaskaense, Blechnum spicant, and/or Rubus pedatus. In drier settings, Pseudotsuga menziesii is usually also common. Abies procera forests (usually mixed with silver fir) are included in this group, as well as stands where Abies lasiocarpa can occur as a codominant on the east side of the Cascades. Dry-setting understory species may include Achlys triphylla, Mahonia nervosa, Xerophyllum tenax, Vaccinium membranaceum, and/or Rhododendron macrophyllum. This group occurs at mid-montane elevations in dry to moist maritime, some hypermaritime and some submaritime climatic zones from northwestern Oregon, coastal British Columbia to extreme southeastern Alaska. It generally occurs in an elevational band above Pseudotsuga menziesii - Tsuga heterophylla and hypermaritime zone forests and below Tsuga mertensiana forests. It is known to occur on windward and leeward sides of Vancouver Island and on the Olympic Peninsula. In the Cascade Range of northern Washington (north of Snoqualmie River) and in the Coast Mountains of mainland British Columbia, it occurs in the wettest portions, including inland to the mountain crest. A somewhat variable winter snowpack that typically lasts for 2-4 months is characteristic. The climatic zone within which it occurs is sometimes referred to as the "rain-on-snow" zone because of the common occurrence of major winter rainfall on an established snowpack.
Diagnostic Characteristics: This group contains full-statured, continuous forests dominated by Tsuga heterophylla and Abies amabilis.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Abies amabilis in southeastern Alaska is an extreme outlier, occurring in only a few stands in the extreme southern part of the panhandle (T. DeMeo pers. comm. 2013). Therefore, Abies amabilis associations in Alaska need to be further documented and determined if they belong to this group or another.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This group contains tall (15-45 m) evergreen coniferous forests with thick low to tall shrub undergrowth.
Floristics: Tsuga heterophylla and/or Abies amabilis dominate the canopy of late-seral stands, and Callitropsis nootkatensis (= Chamaecyparis nootkatensis) can be codominant, especially at higher elevations. Thuja plicata is also common and sometimes codominates in British Columbia. In Alaska, Abies amabilis occurs in nearly pure stands and in mixture with Picea sitchensis and Tsuga heterophylla. In more mesic settings, Pseudotsuga menziesii is relatively rare to absent, and a major understory dominant species is Vaccinium ovalifolium. Other mesic-setting understory species include Oxalis oregana, Blechnum spicant, and/or Rubus pedatus.
In drier settings, Tsuga heterophylla and/or Abies amabilis dominate the canopy of late-seral stands, though Pseudotsuga menziesii is usually also common because of its long lifespan and because it regenerates after fires and therefore is frequent as a codominant, and indeed its prevalence is an important indicator for dry climate alliances within this group. At the highest elevations, Callitropsis nootkatensis can be codominant. Abies procera forests (usually mixed with silver fir) are included in this group and occur in the Cascades from central Washington to central Oregon and rarely in the Coast Ranges of Oregon. Abies lasiocarpa sometimes occurs as a codominant on the east side of the Cascades and at higher elevations in British Columbia. Dry-setting understory species may include Achlys triphylla, Mahonia nervosa, Xerophyllum tenax, Vaccinium membranaceum, and/or Rhododendron macrophyllum.
In drier settings, Tsuga heterophylla and/or Abies amabilis dominate the canopy of late-seral stands, though Pseudotsuga menziesii is usually also common because of its long lifespan and because it regenerates after fires and therefore is frequent as a codominant, and indeed its prevalence is an important indicator for dry climate alliances within this group. At the highest elevations, Callitropsis nootkatensis can be codominant. Abies procera forests (usually mixed with silver fir) are included in this group and occur in the Cascades from central Washington to central Oregon and rarely in the Coast Ranges of Oregon. Abies lasiocarpa sometimes occurs as a codominant on the east side of the Cascades and at higher elevations in British Columbia. Dry-setting understory species may include Achlys triphylla, Mahonia nervosa, Xerophyllum tenax, Vaccinium membranaceum, and/or Rhododendron macrophyllum.
Dynamics: Fire regime is significantly different at regional scale between dry and mesic stands of this forest. Mesic stands occur within a very wet climate that is more coastal, less continental, with cooler summers, and warmer winters on average. The major disturbance process within these coastal mesic forests are small-scale gap dynamics where windthrow is common, causing gap creation that starts the successional process. These mesic stands rarely, if ever, burn and are dominated by trees that run from 700 to over 1000 years in age. In British Columbia, coastal rainforests may burn an average of once every 2000 years. Extreme, stand-replacing fires are infrequent to absent, with return intervals of several hundred or more years.
In drier stands, the dominant natural process is stand-replacing fires which occur on average every 200-500 years. Where old-growth does exist, it is mostly "young old-growth" 200-500 years in age. Natural-origin stands less than 200 years old are also common. Mixed-severity fires occur in the drier more interior and often southern parts of this group, so that forest structure, patch size and proportions can be different from northern, more mesic stands. In Oregon, there are more mixed-severity fires.
In drier stands, the dominant natural process is stand-replacing fires which occur on average every 200-500 years. Where old-growth does exist, it is mostly "young old-growth" 200-500 years in age. Natural-origin stands less than 200 years old are also common. Mixed-severity fires occur in the drier more interior and often southern parts of this group, so that forest structure, patch size and proportions can be different from northern, more mesic stands. In Oregon, there are more mixed-severity fires.
Environmental Description: Climate: This forested group occurs at mid-montane elevations in dry to moist maritime and some submaritime climatic zones from northwestern Oregon, coastal British Columbia to extreme southeastern Alaska. It generally occurs in an elevational band above Pseudotsuga menziesii - Tsuga heterophylla and hypermaritime zone forests and below Tsuga mertensiana forests. It is known to occur on windward and leeward sides of Vancouver Island and on the Olympic Peninsula. In the Cascade Range of northern Washington (north of Snoqualmie River) and in the Coast Mountains of mainland British Columbia, it occurs in the wettest portions but does not extend all the way inland to the mountain crest. A somewhat variable winter snowpack that typically lasts for 2-4 months is characteristic. The climatic zone within which it occurs is sometimes referred to as the "rain-on-snow" zone because of the common occurrence of major winter rainfall on an established snowpack.
Geographic Range: This forested group occurs only in the Pacific Northwest mountains, primarily west of the Cascade Crest. It dominates mid-montane dry to mesic maritime and some submaritime climatic zones from northwestern British Columbia to northwestern Oregon. In the Olympic Mountains, this group occurs on the leeward side of the mountains only. In British Columbia and the Washington Cascades, it occurs on both windward and leeward sides of the mountains. It occurs very sporadically in the Willapa Hills of southwestern Washington and in the northern Oregon Coast Range. This type may also occur on the east side of the Oregon Cascades north of 45°N latitude (Mount Hood National Forest - Hood River and Barlow ranger districts, and possibly the northern edge of Warm Springs Reservation in part of the McQuinn Strip). It is restricted in Washington''s eastern Cascades to a few miles of the crest, primarily between the upper Naches drainage and Lake Wenatchee, finally dwindling to scattered stands in the upper Methow drainage in the northern Cascades (Lillybridge et al 1995). It may also extend north to about 56°N latitude in southeastern Alaska. Abies amabilis has a limited distribution in Alaska, and is confined to the extreme southern mainland and a few islands south of 56°N latitude.
Nations: CA,US
States/Provinces: AK, BC, CA?, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.833262
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.d Pacific Silver Fir - Western Hemlock Rainforest Group | G241 | 1.B.2.Nd.3.d |
| Alliance | A3386 Pacific Silver Fir - Western Hemlock / Sweet After Death Forest Alliance | A3386 | 1.B.2.Nd.3.d |
| Alliance | A3387 Pacific Silver Fir - Western Hemlock / Thinleaf Huckleberry Cold Forest Alliance | A3387 | 1.B.2.Nd.3.d |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = I.A.1.h - Silver fir-western hemlock (Viereck et al. 1992)
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