Abstract for M886

Southern Vancouverian Dry Foothill Forest & Woodland
Forêts et terres boisées sèches du piémont du sud de la région floristique de Vancouver

M886 describes the low elevation Pacific coastal forests of the rain shadow influenced maritime climate in western North America. The Canadian expression includes forests and woodlands of the southern British Columbia (BC) coast that occur in the lee of the Olympic and Vancouver Island mountain ranges. Canopies are typically evergreen coniferous, although evergreen broad-leaved and cold-deciduous broad-leaved species are often present in the tree stratum. Coast Douglas-fir (Pseudotsuga menziesii var. menziesii) is the characteristic tree species, however other diagnostic trees include Pacific arbutus (Arbutus menziesii) and Garry oak (Quercus garryana var. garryana). Western red cedar (Thuja plicata) and grand fir (Abies grandis) often co-occur with Douglas-fir on circum-mesic sites. Shore pine (Pinus contorta var. contorta) occurs occasionally on dry sites, where it can dominate some stands. The understory of conifer stands is typically dominated by evergreen broad-leaved shrubs, conifer regeneration and a well-developed moss layer. Common shrubs include ocean-spray (Holodiscus discolor), Cascade barberry (Berberis nervosa) and salal (Gaultheria shallon). The main moss species are Oregon beaked moss (Kindbergia oregana) and stairstep moss (Hylocomium splendens). Garry oak forests and woodlands have a rich understory dominated by camas (Camassia spp.) and other flowering herbs in the spring, and a variety of grasses later in the growing season. Historically, stand-replacing fire was the main natural disturbance factor but since European settlement, human-influenced disturbances predominate. Most forests were harvested many years ago and much of the range converted to agriculture, settlement and urban infrastructure; invasive non-native plant species exert a strong influence on understory composition and structure in much of the range.

In Canada, M886 forests occur between sea level and approximately 700 mASL in a cool Mediterranean climate, with moderately warm dry summers and mild wet winters. Mean annual precipitation varies between approximately 650 and 1250 mm, the majority falling as rain in winter months; snow is uncommon and ephemeral. Mean annual temperature is approximately 8° to 10° C; soils do not freeze in winter. Growing degree days above 5° C (GDD) vary between approximately 1700 and 2200 across the Canadian range. All parts of the Canadian range experienced Pleistocene glaciation; soils are mostly Brunisols developed in glacial surficial materials. Mor and moder humus forms predominate.