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G237 Alnus rubra - Acer macrophyllum Rainforest Group
Type Concept Sentence: This lowland hardwood or mixed hardwood-conifer forest group occurs throughout the Pacific Northwest rainforest region, on disturbed sites ranging from flat coastal areas to steep slopes subject to mass movements on a periodic basis. Alnus rubra or Acer macrophyllum are the major tree species, occurring with a variety of companion species, such as the conifers Abies grandis, Picea sitchensis, Pseudotsuga menziesii, Thuja plicata, and/or Tsuga heterophylla.
Common (Translated Scientific) Name: Red Alder - Bigleaf Maple Rainforest Group
Colloquial Name: North Pacific Red Alder - Bigleaf Maple - Douglas-fir Rainforest
Hierarchy Level: Group
Type Concept: This lowland hardwood or mixed hardwood-conifer forest group occurs in the Pacific Northwest from northern British Columbia to northern California. These forests are composed of mostly deciduous broadleaf species sometimes with varying components of conifers. Alnus rubra or Acer macrophyllum are the major tree species. Companion species are common and specific species present depend on the geographic location. Conifers, including Abies grandis, Picea sitchensis, Pseudotsuga menziesii, Thuja plicata, and/or Tsuga heterophylla, can be codominant (up to one-third relative cover). Other major dominant broadleaf species are Quercus garryana, Frangula purshiana, and Cornus nuttallii. Conifers tend to increase in abundance with time in the absence of major disturbance, although the hardwoods, particularly Acer macrophyllum, can persist in the overstory. The understory is characterized by deciduous shrubs such as Acer circinatum, Corylus cornuta, Oemleria cerasiformis, Rubus ursinus, Symphoricarpos albus, and/or Toxicodendron diversilobum, but evergreen shrubs, including Gaultheria shallon and Mahonia nervosa and forbs, such as Polystichum munitum and Oxalis oregana, can be dominant. This group occurs on valley terraces and slopes at low elevations in the mountains of the Pacific Northwest coast and interior valleys west of the high Cascade Range. It is the dominant forest and woodland surrounding cities and towns of the Pacific Northwest, and component species are indicators of recent and past disturbance, both human-induced and natural. It also occurs on steep slopes and bluffs that are subject to mass movements on a periodic basis.
Diagnostic Characteristics: These forests are composed of deciduous broadleaf forests and woodlands, sometimes with varying components of conifers. Alnus rubra and Acer macrophyllum are the major tree species. Conifers, including Pseudotsuga menziesii, Thuja plicata, Abies grandis, Tsuga heterophylla, and/or Picea sitchensis, can be codominant.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This group is conceptually a combination of two ecological systems, ~North Pacific Broadleaf Landslide Forest and Shrubland (CES204.846)$$ and ~North Pacific Lowland Mixed Hardwood-Conifer Forest (CES204.073)$$. Open shrubby and herbaceous associations that are part of the landslide system are not included in this group. British Columbia ecologists feel this group may extend over too broad a range north to south, because there are different understory species, such as the presence of Vaccinium ovalifolium and lack of Mahonia nervosa, and different overstory species, such as Acer circinatum and Acer macrophyllum throughout the range as currently defined. One option is to subdivide this type among several groups, north to south, and treat them as alliance-based successional stages. Further review is needed. Really wet areas along streams and hillslope springs that have an abundance of wet-loving shrubs in the understory, such as Rubus spectabilis, Rubus parviflorus, Ribes bracteosum, and Oplopanax horridus, are a part of ~North-Central Pacific Lowland Riparian Forest Group (G851)$$.
Should successional red alder stands that are common in coastal Del Norte and Humboldt counties be included in this group? If so, redwood should be added to the list of conifers. If redwood is present, then it is part of the ~Californian Coastal Redwood Forest Group (G235)$$.
Should successional red alder stands that are common in coastal Del Norte and Humboldt counties be included in this group? If so, redwood should be added to the list of conifers. If redwood is present, then it is part of the ~Californian Coastal Redwood Forest Group (G235)$$.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: These forests are composed of deciduous broadleaf forests and woodlands, sometimes with varying components of conifers. They are 14-20 m tall, and the canopy is generally closed to slightly open.
Floristics: Alnus rubra or Acer macrophyllum are the major tree species throughout the range of this group. Stands are often mixed with other conifers or broadleaf species. As Alnus rubra and Acer macrophyllum have a wide north-to-south coastal distribution, the companion species shift with geography. Conifer species such as Pseudotsuga menziesii, Thuja plicata, Abies grandis, Tsuga heterophylla, and/or Picea sitchensis can be codominant. Other major dominant broadleaf species are Quercus garryana, Frangula purshiana, and Cornus nuttallii. Conifers tend to increase in abundance with time in the absence of major disturbance, although the hardwoods, particularly Acer macrophyllum, can persist in the overstory. The understory is characterized by deciduous shrubs such as Acer circinatum, Corylus cornuta, Oemleria cerasiformis, Rubus ursinus, Symphoricarpos albus, and/or Toxicodendron diversilobum, but evergreen shrubs, including Gaultheria shallon and Mahonia nervosa and forbs, such as Polystichum munitum and Oxalis oregana, can be dominant.
Dynamics: This is, for the most part, an early-successional forest group. Alnus and Acer are dependent on full sunlight, and once overtopped by larger conifer species, will, without further disturbance, typically succeed to a conifer forest type. However, some stands can persist without disturbance (200 years) and remain mixed deciduous-conifer forests. When these forests are clearcut, logging companies systematically plant only conifers, causing this type to decline in heavily managed landscapes. So, it becomes an important type for conservation, especially in the Coast Ranges. In areas where it is regenerated by natural disturbances, it is not just a seral type of dry or mesic Douglas-fir - western hemlock types, but an important component of the forested landscape of the Pacific Northwest.
Environmental Description: This alliance occurs on valley terraces and slopes at low elevations in the mountains of the Pacific Northwest coast and interior valleys west of the high Cascade Range, and west of the Klamath Mountains in northwestern California. It is the dominant forest and woodland surrounding cities and towns of the Pacific Northwest, and component species are indicators of recent and past disturbance, both human-induced and natural. They also occur on steep slopes and bluffs that are subject to mass movements on a periodic basis. They are found in patches of differing age associated with different landslide events.
Soil/substrate/hydrology: In some places, hardwoods are truly only found in early-seral conditions. This is truer in the northern part of the range. In the southern regions, such as Washington state, there are a few places where hardwoods persist, outside of the dry Douglas-fir - madrone forests around the Willamette Valley, Puget Trough and the western Oregon interior valleys. In the Coast Ranges and Cascades, there are hardwoods (mostly Alnus rubra and Acer macrophyllum) found in most of the valley toeslopes. They also occur in areas with exposed talus and exposed rocks, often with Quercus garryana and Fraxinus latifolia. This mix of deciduous hardwoods and conifers can be a late-seral, relatively stable forest in many areas, while in others it is successional, with the conifers completely overtaking the hardwoods after 200 years or so without disturbance.
Soil/substrate/hydrology: In some places, hardwoods are truly only found in early-seral conditions. This is truer in the northern part of the range. In the southern regions, such as Washington state, there are a few places where hardwoods persist, outside of the dry Douglas-fir - madrone forests around the Willamette Valley, Puget Trough and the western Oregon interior valleys. In the Coast Ranges and Cascades, there are hardwoods (mostly Alnus rubra and Acer macrophyllum) found in most of the valley toeslopes. They also occur in areas with exposed talus and exposed rocks, often with Quercus garryana and Fraxinus latifolia. This mix of deciduous hardwoods and conifers can be a late-seral, relatively stable forest in many areas, while in others it is successional, with the conifers completely overtaking the hardwoods after 200 years or so without disturbance.
Geographic Range: This group occurs from northern British Columbia to northern California, in the coastal areas of the Pacific Northwest, at elevations below the Silver Fir Zone in the northern Pacific mountains and in lowlands (latter especially adjacent to coastlines), becoming less prominent in the northern half of this region.
Nations: CA,US
States/Provinces: BC, CA, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.833258
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.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.g Red Alder - Bigleaf Maple Rainforest Group | G237 | 1.B.2.Nd.3.g |
| Alliance | A0427 Red Alder - Bigleaf Maple - Douglas-fir Forest Alliance | A0427 | 1.B.2.Nd.3.g |
| Alliance | A3385 Red Alder - Bigleaf Maple Forest Alliance | A3385 | 1.B.2.Nd.3.g |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: >< Red Alder: 221 (Eyre 1980)
- Chappell, C., and J. Christy. 2004. Willamette Valley-Puget Trough-Georgia Basin Ecoregion Terrestrial Ecological System EO Specs and EO Rank Specs. Appendix 11 in: J. Floberg, M. Goering, G. Wilhere, C. MacDonald, C. Chappell, C. Rumsey, Z. Ferdana, A. Holt, P. Skidmore, T. Horsman, E. Alverson, C. Tanner, M. Bryer, P. Lachetti, A. Harcombe, B. McDonald, T. Cook, M. Summers, and D. Rolph. Willamette Valley-Puget Trough-Georgia Basin Ecoregional Assessment, Volume One: Report prepared by The Nature Conservancy with support from The Nature Conservancy of Canada, Washington Department of Fish and Wildlife, Washington Department of Natural Resources (Natural Heritage and Nearshore Habitat programs), Oregon State Natural Heritage Information Center and the British Columbia Conservation Data Centre.
- Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.
- Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
- Franklin, J. F., and C. T. Dyrness. 1973. Natural vegetation of Oregon and Washington. General Technical Report PNW-8. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR. 417 pp.