Name:
Thuja plicata Giant Forest Alliance
Reference:
Western Ecology Working Group of...
Description:
This giant forest alliance occurs within the maritime-influenced region of the Pacific Northwest from Oregon to British Columbia, Canada, primarily west of the crest of the Cascades and outside major coastal fog influence. Climate is moderate with only mild drought and frost, generally on sites which are moist to very wet. Elevation ranges from sea level to approximately 1000 m. Soil types are variable across its range, but most commonly with fine-textured, bottomland soils, usually with low nutrient concentrations. Thuja plicata trees appear to be quite tolerant of stagnant winter water tables. These forests are characterized by a multi-tiered tree canopy of Thuja plicata that is typically codominated by Tsuga heterophylla and over 50 m in height. Pseudotsuga menziesii and Abies grandis may also be present. With increasing stand age, Thuja plicata becomes more prominent in the canopy. Most commonly the canopy includes other tree species, but can become monotypic on swampy sites. Broad-leaved cold-deciduous trees, such Acer macrophyllum, Alnus rubra, Cornus nuttallii, and Populus balsamifera ssp. trichocarpa, often form a sparse subcanopy, particularly in gaps in the upper canopy. In southern Oregon stands, additional subcanopy tree species may include Chrysolepis chrysophylla (= Castanopsis chrysophylla), Arbutus menziesii, and Lithocarpus densiflorus. The shrub layer is commonly composed of Linnaea borealis, Gaultheria shallon, Rhododendron macrophyllum, and Mahonia nervosa. The herbaceous layer is usually dominated by shade-tolerant / moisture-loving forbs and ferns such as Achlys triphylla, Oxalis oregana, Viola sempervirens, Trillium ovatum, Trientalis borealis ssp. latifolia (= Trientalis latifolia), Polystichum munitum, Blechnum spicant, and Athyrium filix-femina. Late successional stands typically have very large trees, huge amounts of woody debris, and better developed understories. Diagnostic of this forest alliance is a tree canopy over 50 m tall that is codominated by Thuja plicata.
Accession Code:
VB.CC.18283.THUJAPLICATAGIA
Plot-observations of this Community Concept:
0
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