Name:
Tsuga heterophylla - Pseudotsuga menziesii / Holodiscus discolor Dry Forest Alliance
Reference:
NatureServe Biotics 2019
Description:
These coniferous forests are characterized by a mixed overstory canopy of <i>Tsuga heterophylla</i> and <i>Pseudotsuga menziesii</i>. Other common tree associates include <i>Abies amabilis, Abies grandis, Picea sitchensis</i>, and <i>Thuja plicata</i>. A subcanopy of <i>Acer macrophyllum</i>, and/or <i>Taxus brevifolia</i> may also be present. The moderately dense shrub layer is commonly composed of <i>Amelanchier alnifolia, Acer circinatum, Chimaphila menziesii, Chimaphila umbellata, Gaultheria shallon, Holodiscus discolor, Linnaea borealis, Mahonia nervosa, Paxistima myrsinites, Rosa gymnocarpa, Rubus ursinus</i>, and <i>Vaccinium parvifolium</i>. The herbaceous layer is dominated by drought-tolerant and shade-tolerant forbs and ferns, including <i>Achlys triphylla, Calamagrostis rubescens, Goodyera oblongifolia, Oxalis oregana, Orthilia secunda</i>, and <i>Pteridium aquilinum</i>. An upper tree canopy dominated by <i>Tsuga heterophylla</i> and <i>Pseudotsuga menziesii</i> and dry-site conditions are diagnostic of this alliance. This coniferous forest alliance occurs at low elevations (0-1500 m) within the maritime-influenced region of the Pacific Northwest, from north coastal California to the northern coast of Vancouver Island, British Columbia. Stands are best represented on the lower slopes of the coastal ranges that feature high precipitation, long frost-free periods, and low fire frequencies. 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 of the alliance generally occur on steeper slopes and warmer aspects, on well-drained sites, and are quite dry throughout the year. The associations in this alliance are found throughout the range and represent the driest forested stands of the ~North Pacific Maritime Douglas-fir - Western Hemlock Rainforest Group (G240)$$. The associations are recognized as consistently the driest expressions of these forests throughout their range by local ecologists.
Accession Code:
urn:lsid:vegbank.org:commConcept:38666-{3305F865-4254-4CBB-9DBF-3B9043250AF6}
Plot-observations of this Community Concept:
0
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