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A3377 Tsuga heterophylla - Pseudotsuga menziesii / Rubus spectabilis Mesic Forest Alliance

Type Concept Sentence: This is a wet-mesic coniferous forest alliance characterized by a mixed canopy of Tsuga heterophylla and Pseudotsuga menziesii and can have a complex, multi-tiered structure of multiple age classes. Thuja plicata may codominate with Pseudotsuga and Tsuga on valley bottom sites with poorly drained soils, and Tsuga heterophylla is generally the dominant regenerating tree species. It occurs at low elevations (0-1500 m) in all the maritime-influenced regions of the Pacific Northwest, from north coastal California to the northern end of Vancouver Island, British Columbia.

Common (Translated Scientific) Name: Western Hemlock - Douglas-fir / Salmonberry Mesic Forest Alliance

Colloquial Name: Western Hemlock - Douglas-fir / Salmonberry Mesic Forest

Hierarchy Level:  Alliance

Type Concept: These forests are characterized by a mixed canopy of Tsuga heterophylla and Pseudotsuga menziesii and can have a complex, multi-tiered structure of multiple age classes. Thuja plicata may codominate with Pseudotsuga and Tsuga on valley bottom sites with poorly drained soils, and Tsuga heterophylla is generally the dominant regenerating tree species. Other common tree associates include Abies amabilis, Abies grandis, Alnus rubra, Picea sitchensis, and Taxus brevifolia. Understory species are generally intolerant of drought. The shrub layer is commonly composed of Acer circinatum, Cornus sericea, Gaultheria shallon, Mahonia nervosa, Menziesia ferruginea, Oplopanax horridus, and/or Rubus spectabilis. The herbaceous layer is dominated by ferns, including Athyrium filix-femina, Blechnum spicant, Gymnocarpium dryopteris, Polystichum munitum, and /or Pteridium aquilinum. Moisture-loving forbs include Oxalis oregana, Achlys triphylla, and Tiarella trifoliata. This coniferous forest alliance occurs at low elevations (0-1500 m) in all the maritime-influenced regions of the Pacific Northwest, from north coastal California to the northern end of Vancouver Island, British Columbia. Throughout the range of this alliance, much of the annual precipitation occurs as rain. Where snow does occur, it can generally be melted by rain during warm winter storms. In all settings, this alliance occurs where environmental conditions are moderated by the marine influence, with moderate drought and frost. Stands are best represented on lower slopes of the coastal ranges of the Pacific Northwest with high precipitation, long frost-free periods, and low fire frequencies. Stands of the alliance generally occur on very moist, water-receiving slopes, usually north-facing or otherwise protected sites that are subirrigated but well-drained. Soils remain wet year-round, but are not saturated, and are not wetland or riparian in nature. Diagnostic of this alliance is an upper tree canopy dominated by Tsuga heterophylla and Pseudotsuga menziesii and moist, well-drained sites.

Diagnostic Characteristics: Tall forests dominated by Pseudotsuga menziesii and Tsuga heterophylla on poorly drained or water-receiving microsites; understory species are intolerant of drought conditions, and representative (but not constant) understory species include Rubus spectabilis, Acer circinatum, or Oplopanax horridus.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This is the wettest of the alliances within this group. As the group has a wide geographic range, this alliance is limited to sites that are well-drained but moist throughout the year, and that support not wetland plants but upland plants that do not tolerate drought or drying conditions.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation included in this alliance has a multi-layered, closed canopy of coniferous trees dominated by an overstory of old-growth trees up to over 50 m tall. Tall ferns (to 2 m height) dominate the understory. A subcanopy of deciduous and evergreen trees is often present (5-20 m tall). Also present are shrub and herbaceous layers.

Floristics: These forests are characterized by a mixed canopy of Tsuga heterophylla and Pseudotsuga menziesii and can have a complex, multi-tiered structure of multiple age classes. Thuja plicata may codominate with Pseudotsuga and Tsuga on valley bottom sites with poorly drained soils, and Tsuga heterophylla is generally the dominant regenerating tree species. Other common tree associates include Abies amabilis, Abies grandis, Alnus rubra, Picea sitchensis, and Taxus brevifolia. Understory species are generally intolerant of drought. The shrub layer is commonly composed of Acer circinatum, Cornus sericea, Gaultheria shallon, Mahonia nervosa, Menziesia ferruginea, Oplopanax horridus, and/or Rubus spectabilis. The herbaceous layer is dominated by ferns, including Athyrium filix-femina, Blechnum spicant, Gymnocarpium dryopteris, Polystichum munitum, and /or Pteridium aquilinum. Moisture-loving forbs include Oxalis oregana, Achlys triphylla, and Tiarella trifoliata.

Dynamics:  This alliance has a low fire frequency that increases from north to south across its range.
Environmental Description:  This coniferous forest alliance occurs at low elevations (0-1500 m) in all the maritime-influenced regions of the Pacific Northwest. Throughout the range of this alliance, much of the annual precipitation occurs as rain. Where snow does occur, it can generally be melted by rain during warm winter storms. In all settings, this alliance occurs where environmental conditions are moderated by the marine influence, with moderate drought and frost. Stands are best represented on lower slopes of the coastal ranges with high precipitation, long frost-free periods, and low fire frequencies. Stands of the alliance generally occur on very moist, water-receiving slopes, usually north-facing or otherwise protected sites that are subirrigated but well-drained. Soils remain wet year-round, but are not saturated, and are not wetland or riparian in nature.
Geographic Range: This alliance occurs from north coastal California to the northern end of Vancouver Island, British Columbia.

Nations: CA,US

States/Provinces:  BC, CA, 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.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.c Douglas-fir - Western Hemlock / Salal Rainforest Group G240 1.B.2.Nd.3.c
Alliance A3377 Western Hemlock - Douglas-fir / Salmonberry Mesic Forest Alliance A3377 1.B.2.Nd.3.c
Association CEGL000070 Douglas-fir / Salal / Western Swordfern Forest CEGL000070 1.B.2.Nd.3.c
Association CEGL000098 Douglas-fir - Western Hemlock / Cascade Barberry / Redwood Sorrel Forest CEGL000098 1.B.2.Nd.3.c
Association CEGL000287 Grand Fir - Western Hemlock / Western Swordfern Forest CEGL000287 1.B.2.Nd.3.c
Association CEGL000417 Douglas-fir / Vine Maple Forest CEGL000417 1.B.2.Nd.3.c
Association CEGL000497 Western Hemlock - (Douglas-fir) / Devil''s-club / Western Swordfern Forest CEGL000497 1.B.2.Nd.3.c
Association CEGL002608 Western Hemlock - Douglas Maple / Twinflower Forest CEGL002608 1.B.2.Nd.3.c
Association CEGL005534 Douglas-fir - (Red Alder, Western Hemlock) / Salmonberry Forest CEGL005534 1.B.2.Nd.3.c
Association CEGL005536 Douglas-fir - Western Hemlock / Salal / Western Swordfern Forest CEGL005536 1.B.2.Nd.3.c
Association CEGL005540 Douglas-fir - Western Hemlock / Oceanspray / Western Swordfern Forest CEGL005540 1.B.2.Nd.3.c
Association CEGL005542 Douglas-fir - Western Hemlock / (Vine Maple) / Western Swordfern Forest CEGL005542 1.B.2.Nd.3.c
Association CEGL005543 Douglas-fir - Western Hemlock / Cascade Barberry - Western Swordfern Forest CEGL005543 1.B.2.Nd.3.c
Association CEGL005559 Western Hemlock / Western Swordfern - Deer Fern Forest CEGL005559 1.B.2.Nd.3.c
Association CEGL005568 Douglas-fir - Western Hemlock / Western Swordfern - Redwood Sorrel Forest CEGL005568 1.B.2.Nd.3.c
Association CEGL005575 Western Hemlock - Douglas-fir - Pacific Silver Fir / Red Huckleberry / Sweet After Death Forest CEGL005575 1.B.2.Nd.3.c
Association CEGL005576 Western Hemlock - (Douglas-fir, Western Red-cedar) / Western Swordfern - Common Ladyfern Forest CEGL005576 1.B.2.Nd.3.c
Association CEGL005586 Western Hemlock / Western Swordfern - Redwood Sorrel Forest CEGL005586 1.B.2.Nd.3.c
Association CEGL005587 Western Hemlock / Alaska Blueberry / Redwood Sorrel Forest CEGL005587 1.B.2.Nd.3.c
Association CEGL005588 Western Hemlock - Douglas-fir / Alaska Blueberry / Redwood Sorrel Forest CEGL005588 1.B.2.Nd.3.c
Association CEGL007301 Western Hemlock / Salal / Western Swordfern - Deer Fern Forest CEGL007301 1.B.2.Nd.3.c
Association CEGL007351 Douglas-fir - (Western Hemlock) / Vine Maple - Beaked Hazelnut / Western Swordfern Forest CEGL007351 1.B.2.Nd.3.c
Association CEGL007355 Douglas-fir / Pacific Dogwood / Sweet After Death Forest CEGL007355 1.B.2.Nd.3.c
Concept Lineage: A.NCCN-044 (This replaces, in part, A.107-Pseudotsuga menziesii - Tsuga heterophylla Forest Alliance)

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: >< 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
  • Chappell, C., R. Crawford, J. Kagan, and P. J. Doran. 1997. A vegetation, land use, and habitat classification system for the terrestrial and aquatic ecosystems of Oregon and Washington. Unpublished report prepared for Wildlife habitat and species associations within Oregon and Washington landscapes: Building a common understanding for management. Prepared by Washington and Oregon Natural Heritage Programs, Olympia, WA, and Portland, OR. 177 pp.
  • Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
  • 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.
  • Kagan, J. S. 1987c. Draft species management guide for Astragalus robbinsii var. alpiniformis. Challenge grant funding with USDA Forest Service. Oregon Natural Heritage Data Base, The Nature Conservancy, Portland.
  • Parker, K. 1982. Analysis of understory vegetation of a low elevation old growth forest in the Sandy River Gorge. Unpublished undergraduate thesis, Reed College, Portland, OR. 42 pp.
  • Western Ecology Working Group of NatureServe. No date. International Ecological Classification Standard: International Vegetation Classification. Terrestrial Vegetation. NatureServe, Boulder, CO.