Name:
Pseudotsuga menziesii - Arbutus menziesii / Holodiscus discolor Forest
Reference:
NatureServe Biotics 2019
Description:
This Douglas-fir forest occurs primarily in the Olympic Mountains rainshadow, including San Juan and portions of Clallam, Jefferson, Island, Skagit, and Whatcom counties, Washington. It also occurs in King and southeastern Thurston counties and in southwestern British Columbia. This forest, or less commonly woodland, is dominated or codominated by <i>Arbutus menziesii</i>, typically with <i>Pseudotsuga menziesii var. menziesii</i> codominant. <i>Arbutus menziesii</i> often forms a subcanopy below taller <i>Pseudotsuga menziesii</i>. The understory is a somewhat variable mixture of deciduous shrubs and herbs. <i>Holodiscus discolor, Lonicera hispidula</i>, and <i>Symphoricarpos albus var. laevigatus</i> are usually present and often prominent to codominant. <i>Rosa gymnocarpa</i> and <i>Festuca occidentalis</i> are usually prominent. The latter may dominate in heavily browsed stands. <i>Mahonia nervosa</i> is present in less than half the stands, but when present is prominent to codominant. <i>Mahonia aquifolium, Lonicera ciliosa</i>, and <i>Elymus glaucus</i> are also frequent. Several forbs may be present but usually not in very large amounts. These sites are typically very dry and appear to be poor to medium in relative nutrient status. It includes some of the driest sites that support forest in the ecoregion and is most frequent on sunny slopes adjacent to saltwater. This forest occurs most frequently on soils that are shallow to bedrock (outcrops often visible on plot), but also on glacial till, glacial outwash, and glacial drift sands. It is usually found on moderate to steep slopes, especially southwestern aspects, and is more frequent in dry climatic areas (Olympic Mountains rainshadow). In the pre-settlement landscape, a moderate-severity fire regime likely prevailed (variable severity, intermediate frequency). Madrone resprouts after fire or cutting, and is capable of living for a few hundred years. Madrone dominance, and Douglas-fir subordinance or even absence, is favored by repeated high-severity fires, clearcut logging followed by natural regeneration, or selective logging of Douglas-fir. Douglas-fir is likely to increase in abundance without disturbance, but does not appear to be excluding or out-competing madrone on these dry sites, even when madrone is overtopped. Fungal diseases (<i>Natrassia</i> canker, <i>Fusicoccum</i> branch dieback), which may be non-native, appear to be facilitating at least local decline in madrone. Heavy deer browsing on some islands results in dominance by grasses, especially western fescue.
Accession Code:
urn:lsid:vegbank.org:commConcept:29331-{536E24FC-589D-4D06-BA32-C5177184A5F8}
Plot-observations of this Community Concept:
0
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