Name:
Pseudotsuga menziesii - Tsuga heterophylla Forest Alliance
Reference:
Western Ecology Working Group of...
Description:
This coniferous forest alliance occurs at low elevations (0-1500 m) within the maritime-influenced region of the Pacific Northwest, generally west of the Cascade Mountains. Stands are best represented on lower mountain slopes of the coastal ranges with high precipitation, long frost-free periods, and low fire frequencies. Sites include upper slope and ridgetop positions, moist, rich sites such as ravines or north-facing slopes, or in depressions, swales and east- or west-facing slopes. Slopes are gentle to moderately steep. Soil types are variable, but growth is decreased on heavy soils or soils with poor drainage. These forests are characterized by a mixed canopy of Tsuga heterophylla and Pseudotsuga menziesii, often with trees exceeding 50 m in height and a complex, multi-tiered structure of multiple age classes. Thuja plicata may codominate on valley bottom sites with poorly drained soils, and Tsuga heterophylla is generally the dominant regenerating tree species. However, young stands may lack Tsuga heterophylla or Thuja plicata. Other common tree associates include Abies grandis, Picea sitchensis, Pinus monticola, and in southwestern Oregon Pinus lambertiana, Chamaecyparis lawsoniana, Calocedrus decurrens, and occasionally Pinus ponderosa. A subcanopy of Acer macrophyllum, Chrysolepis chrysophylla (= Castanopsis chrysophylla), Lithocarpus densiflorus, Umbellularia californica, and/or Taxus brevifolia may also be present. The moderately dense shrub layer is commonly composed of Acer circinatum, Mahonia nervosa, Rhododendron macrophyllum, Gaultheria shallon, Holodiscus discolor, Vaccinium ovatum, and Oplopanax horridus. The herbaceous layer is dominated by shade-tolerant forbs and ferns, including Pteridium aquilinum, Polystichum munitum, Trientalis borealis ssp. latifolia (= Trientalis latifolia), Oxalis oregana, Achlys triphylla, Chimaphila umbellata, Linnaea borealis, and many others. Diagnostic of this alliance is an upper tree canopy dominated by Tsuga heterophylla and Pseudotsuga menziesii.
Accession Code:
VB.CC.19117.PSEUDOTSUGAMENZ
Plot-observations of this Community Concept:
0
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