Common (Translated Scientific) Name: Western Hemlock - Sitka Spruce North-Central Pacific Rainforest Group

Colloquial Name: North-Central Pacific Western Hemlock - Sitka Spruce Rainforest

Hierarchy Level:  Group

Type Concept: These rainforests are dominated by tall evergreen needle-leaved trees, and are restricted to the outer coastal hypermaritime areas of southeastern Alaska, British Columbia, Washington, Oregon and northern California. The forests are often open and scrubby but can have a closed upper canopy. Stands may be pure Picea sitchensis, Thuja plicata, or Tsuga heterophylla but are more often a mix and may occur with other conifers such as Callitropsis nootkatensis, Chamaecyparis lawsoniana, Abies grandis, Pseudotsuga menziesii, Acer circinatum, Alnus rubra, Acer macrophyllum, and Frangula purshiana. Abies amabilis is widespread (except in southern Washington) and can be common but is not dominant. In Washington, nearly pure stands of Tsuga heterophylla are common and seem to be associated with microsites where exposure to intense windstorms is likely. Wet coastal environments that support stands of Chamaecyparis lawsoniana in the absence of Tsuga heterophylla, Thuja plicata, or Picea sitchensis are also part of this group. The understory is rich with shade-tolerant shrubs and ferns, including Gaultheria shallon, Vaccinium ovatum, Menziesia ferruginea, Polystichum munitum, Dryopteris spp., and Blechnum spicant, as well as a high diversity of mosses. Oxalis oregana is important in the understory of moist sites in Washington. Oplopanax horridus and Rubus spectabilis are important understory shrubs on wet sites dominated by Picea sitchensis in the overstory canopy, these sites tend to be sub-irrigated and wet, but not saturated, soils remain well-oxygenated.

Stands are restricted to areas within 25 km of saltwater and are most abundant along coastal central British Columbia, coastal Vancouver Island, and on the Olympic Peninsula of Washington. They range from southern southeastern Alaska (approximately south of Wrangell), through British Columbia, along the southern Washington, Oregon and northern California coasts. The climate is hypermaritime, with cool summers, mild and very wet winters (coldest temperatures range 0-5°C [32-41°F), and abundant fog without a major snowpack. Annual precipitation ranges from 975 to 2399 mm (38-94 inches) with an average of 1572 mm (62 inches) with the majority falling as winter rain. Summer rains are less frequent (<10% of annual rainfall occurs in summer) which can be ameliorated by frequent, dense coastal fog and cloud cover.

Stands are found mostly below 300 m in elevation, where the terrain is mostly gentle, of low topographic relief, and often rocky. Some stands occur on stabilized dunes, others in lower toeslopes and wet sites that are also well-drained, such as sloped floodplains (but are not influenced by overbank flooding) and coarse valley bottoms. Sites occupied include the outermost coastal fringe where salt spray is prominent, riparian terraces and valley bottoms near the coast where there is major fog accumulation. Soils typically have a distinct humus layer overlying mineral horizons or bedrock. In central British Columbia the humus layers can be very thick (mean = 17-35 cm). Soils are often imperfectly drained. These forests very rarely burn, and natural disturbance is more often single tree gap-disturbance events and intense winter storms on local and regional scales. Fire becomes more of a player in the southern portions of the range, in Oregon and California.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: At its northern border this group transitions into ~Alaskan Maritime Western Hemlock - Sitka Spruce Rainforest Group (G750)$$.

Similar NVC Types: No Data Available

note: No Data Available