Print Report
A3716 Pseudotsuga menziesii - Abies grandis - Arbutus menziesii Forest & Woodland Alliance
Type Concept Sentence: This dry, mixed broadleaf-conifer forest alliance is typically dominated by a canopy of the broadleaf evergreen Arbutus menziesii. Pseudotsuga menziesii is emergent through this sclerophyllous layer, and some stands may have only Pseudotsuga menziesii. This alliance occurs along low-elevation (0-1000 m) mountain slopes and valley margins, usually on southern exposures with ample sun and seasonal drought, often adjacent to saltwater shorelines. It is found in lowland areas of the Puget Sound, including the San Juan Islands in Washington and the Gulf Islands in British Columbia, and as far south as the Klamath Mountains and northern Coast Ranges of California.
Common (Translated Scientific) Name: Douglas-fir - Grand Fir - Pacific Madrone Forest & Woodland Alliance
Colloquial Name: Douglas-fir - Grand Fir - Pacific Madrone Forest & Woodland
Hierarchy Level: Alliance
Type Concept: This dry, mixed broadleaf-conifer forest alliance is typically dominated by the broadleaf evergreen Arbutus menziesii and Pseudotsuga menziesii. Some stands may have only Pseudotsuga menziesii. Other trees present may include Abies grandis, Acer macrophyllum, Pinus contorta, and Quercus garryana. Small amounts of Tsuga heterophylla or Thuja plicata may be present. The forest understory is usually species-rich and well-developed. Common shrub species include Corylus cornuta var. californica, Gaultheria shallon, Holodiscus discolor, Lonicera hispidula, Symphoricarpos albus, and Vaccinium ovatum. The herbaceous layer is usually well-developed and dominated by xerophytic grasses and forbs. Festuca occidentalis, Elymus glaucus, and Bromus vulgaris are typical grass species. Vicia americana, Lathyrus nevadensis, and Sanicula crassicaulis are common forbs. Ferns include Polystichum munitum and Pteridium aquilinum. This alliance occurs along low-elevation (0-1000 m) mountain slopes and valley margins, usually on southern exposures with ample sun and seasonal drought, often adjacent to saltwater shorelines. It is found in lowland areas of the Puget Sound as far south as the Klamath Mountains and northern Coast Ranges of California.
Diagnostic Characteristics: Pseudotsuga menziesii with Arbutus or Abies grandis in some of the stands, and generally very dry.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This is a large alliance with forests of Pseudotsuga menziesii with or without Arbutus. We may want to separate these very dry forests into geographic or Pseudotsuga menziesii-only types.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: These forests are characterized by a diffuse broad-leaved and needle-leaved evergreen tree canopy from 35-50 m high with 50-70% cover. Often the canopy is two-tiered, with the conifers emergent through the hardwood tree layer. Some stands may have comparatively few coniferous trees. A cold-deciduous or evergreen shrub layer is often present ranging from 20-60% cover. The herbaceous understory is typically composed of a diverse and dense mixture of shade-tolerant forbs and ferns, but annual forbs and grasses can be common in light gaps.
Floristics: Communities within this alliance usually contain a diffuse canopy of Arbutus menziesii, and Pseudotsuga menziesii is emergent through this sclerophyllous layer. Other needle-leaved evergreen trees, such as Taxus brevifolia, Juniperus scopulorum, and Pinus contorta, may be present in the tree layer, depending upon location and stand history. The broad-leaved deciduous tree Quercus garryana may also be present in the upper tree stratum, or as a subcanopy. The forest understory is usually species-rich and well-developed. Common shrub species in stands of this alliance include Corylus cornuta var. californica, Gaultheria shallon, Holodiscus discolor, Lonicera hispidula, Symphoricarpos albus, and Vaccinium ovatum. The herbaceous layer is usually well-developed and dominated by xerophytic grasses and forbs. Lathyrus nevadensis, Sanicula crassicaulis, and Vicia americana are common forbs, and Festuca occidentalis, Elymus glaucus, and Bromus vulgaris are typical grass species. Ferns include Polystichum munitum and Pteridium aquilinum.
Dynamics: Vegetation types within this alliance are often comprised of second-growth stands created by fire or logging disturbance, but these are stable stands on xeric forest sites. Both Arbutus menziesii and Pseudotsuga menziesii are shade-intolerant, and these forests are dependent upon recurring disturbance for regeneration. Arbutus menziesii, which resprouts following fire, is favored over Pseudotsuga menziesii with increasing fire frequency. With increasing stand age, Pseudotsuga menziesii overtops Arbutus menziesii and assumes canopy dominance.
Environmental Description: The vegetation within this alliance occurs in relatively dry, fire-prone areas west of the Cascades. This maritime-influenced region has mild to warm winter temperatures, and receives 75-200 cm of annual precipitation, falling mostly as winter rain. However, this alliance occurs in areas with a pronounced rainshadow effect from the Olympics or Coast ranges. Vegetation within this alliance occurs along low-elevation (0-1000 m) mountain slopes and valley margins, usually on southern exposures with ample sun and seasonal drought, often adjacent to saltwater shorelines. Sites where this vegetation occurs usually have bedrock or sandy soils which drain quickly. Arbutus menziesii stump-sprouts following fire, and these communities were probably subject to a moderate-severity fire regime in presettlement times.
Geographic Range: This alliance is found in lowland areas of the Puget Sound, including the San Juan Islands in Washington and the Gulf Islands in British Columbia, and as far south as the Klamath Mountains and northern Coast Ranges of California. It is less common around the margins of the Willamette Valley, Oregon, and on the lower foothills of the Cascades in Washington and Oregon.
Nations: CA,US
States/Provinces: BC, CA, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899768
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: A.NCCN-034
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: No Data Available
- Chappell, C. 1994. Natural forests of the Puget Lowland, Washington. Northwest Science Abstract.
- Chappell, C., R. Crawford, J. Kagan, and P. J. Doran. 1997. A vegetation, land use, and habitat classification system for the terrestrial and aquatic ecosystems of Oregon and Washington. Unpublished report prepared for Wildlife habitat and species associations within Oregon and Washington landscapes: Building a common understanding for management. Prepared by Washington and Oregon Natural Heritage Programs, Olympia, WA, and Portland, OR. 177 pp.
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- Rapp, P. E. 1981. Sentinel Island, San Juan County. A survey of vegetation. Unpublished report prepared for The Nature Conservancy, Olympia, WA.