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A3747 Picea sitchensis Riparian Forest Alliance
Type Concept Sentence: This alliance consists of lowland coastal and foothill riparian forests dominated by Picea sitchensis or other conifer species such as Tsuga heterophylla or Pseudotsuga menziesii. Understory species are flood-tolerant, such as Alnus viridis, Oplopanax horridus, and Rubus spectabilis. Forests within this alliance occur in the outer coastal regions from Oregon to southeastern Alaska.
Common (Translated Scientific) Name: Sitka Spruce Riparian Forest Alliance
Colloquial Name: Sitka Spruce Riparian Forest
Hierarchy Level: Alliance
Type Concept: This alliance consists of lowland coastal and foothill riparian forests dominated by Picea sitchensis or other conifer species such as Tsuga heterophylla or Pseudotsuga menziesii. Understory species are flood-tolerant, such as Alnus viridis, Oplopanax horridus, and Rubus spectabilis. The undergrowth is typically dense with a moderate to dense short-shrub canopy dominated by Cornus sericea, Rubus spectabilis, Oplopanax horridus, Salix hookeriana, Salix sitchensis, or Vaccinium ovalifolium. The herbaceous layer is usually sparse to moderately dense with moisture-loving forbs and ferns such as Athyrium filix-femina, Blechnum spicant, Lysichiton americanus, Maianthemum dilatatum, Rubus pedatus, Streptopus lanceolatus var. curvipes, and Tiarella trifoliata var. unifoliata. Forests within this alliance occur in the outer coastal regions from Oregon to southeastern Alaska. Most stands are below 500 m elevation. The climate is strongly maritime, wet and relatively mild. Sites are typically within riparian zones and include braided stream channels, alluvial fans and footslopes. Abundant moisture is present, and substrates are typically deep, well- to moderately well-drained soils derived from alluvium with a thin organic duff layer. Stream-deposited cobbles and boulders are often present.
Diagnostic Characteristics: Sinuous pattern and understory species are diagnostic.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Deciduous trees are absent. Very difficult to differentiate remotely from aerial imagery from surrounding upland forests.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This alliance is characterized by a dense cover of needle-leaved evergreen trees from 35-50 m in height, with a subcanopy 2-35 m tall. The shrub layer is moderate to dense and is dominated by evergreen and deciduous broad-leaved shrubs. The herbaceous layer is moderately dense and is dominated by perennial forbs and ferns.
Floristics: This alliance has a canopy that is codominated by Picea sitchensis and Tsuga heterophylla. Tsuga mertensiana and Callitropsis nootkatensis (= Chamaecyparis nootkatensis) may also be codominant in the north, and Pseudotsuga menziesii in the south. Subcanopy is sparse to moderately dense and consists of Alnus rubra and young conifers. The undergrowth is typically dense with a moderate to dense short-shrub canopy dominated by Cornus sericea, Rubus spectabilis, Oplopanax horridus, Salix hookeriana, Salix sitchensis or Vaccinium ovalifolium. The herbaceous layer is usually sparse to moderately dense with moisture-loving forbs and ferns such as Athyrium filix-femina, Blechnum spicant, Lysichiton americanus, Maianthemum dilatatum, Rubus pedatus, Streptopus lanceolatus var. curvipes (= Streptopus roseus), and Tiarella trifoliata var. unifoliata.
Dynamics: Fires tend to be infrequent in stands of this alliance due to high average humidities and low lightning frequencies. When they do burn, these forests are susceptible to high-intensity crown fires. Windthrow is a common, and occasionally catastrophic, agent of disturbance, which can result in forest turnover. Following disturbance, stands of this alliance are often colonized by shade-intolerant tree species such as Pinus contorta or Alnus rubra. Shrubs such as Rubus spectabilis, Sambucus racemosa var. melanocarpa, and Vaccinium spp. can also invade. Alnus rubra and Rubus spectabilis in particular can form semi-persistent communities in disturbed forests of this alliance. Regeneration and growth of Picea sitchensis can be severely limited in such disclimax stands. In mature forests such as these, regeneration often occurs on downed "nurse logs" on the forest floor.
Environmental Description: Vegetation occurs within the maritime-influenced region of the Pacific Northwest, from Oregon to southeastern Alaska, usually within 50 km of tidewater and below 1000 m in elevation. Most stands are below 500 m elevation. The climate is strongly maritime, wet and relatively mild. Annual precipitation ranges from 100-300 cm, with the majority falling in winter as rain. Summer rain decreases to the south, but coastal fogs and drizzle are characteristic throughout the region and minimize drought stress. The vegetation of this alliance is usually associated with river floodplains near the coast. Sites are typically within riparian zones and include braided stream channels, alluvial fans and footslopes. Abundant moisture is present, and substrates are typically deep, well- to moderately well-drained soils derived from alluvium with a thin organic duff layer. Stream-deposited cobbles and boulders are often present. Adjacent stands include forests dominated by Tsuga heterophylla or Pseudotsuga menziesii.
Geographic Range: Forests within this alliance occur in the outer coastal regions from Oregon to southeastern Alaska.
Nations: CA,US
States/Provinces: AK, BC
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899799
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: >< Picea sitchensis Wetland Forests and Woodlands (Chappell et al. 1997)
>< Western Hemlock - Sitka Spruce: 225 (Eyre 1980)
>< Western Hemlock - Sitka Spruce: 225 (Eyre 1980)
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