Abstract for M025

Vancouverian Subalpine - High Montane Forest
Forêts subalpines et des montagnes de haute altitude de la région floristique de Vancouver

M025 describes the maritime, temperate subalpine and high montane treed vegetation of western North America. The Canadian expression includes high-elevation forests and woodlands of the southern and central British Columbia (BC) coast. Most of the closed forests comprise multi-aged stands of old, medium to large trees. Canopies are typically evergreen coniferous. Stands of M025 vary from closed forests to very open short statured woodlands, becoming more open and patchy with increased elevation and seasonal longevity of snowpack, and often occurring as tree islands or ribbons in a matrix of graminoid snowbeds, meadows, heaths or shrublands at elevational treeline. Avalanches, windthrow, mass soil movement, pathogens and insect infestations are the most widespread forms of natural disturbance. In Canada, mountain hemlock (Tsuga mertensiana) is the characteristic tree species of M025 forests. Other common trees include Pacific silver fir (Abies amabilis), yellow-cypress (Callitropsis nootkatensis) and western hemlock (T. heterophylla). The understory is typically dominated by ericaceous low and dwarf shrubs, conifer regeneration and a well-developed bryophyte layer. Common shrubs include oval-leaved blueberry (Vaccinium ovalifolium), mountain huckleberry (V. membranaceum), false azalea (Menziesia ferruginea), red huckleberry (V. parvifolium) and copperbush (Elliottia pyroliflora). At higher elevations various heath species are common, including pink mountain heather (Phyllodoce empetriformis), crowberry (Empetrum nigrum) and white mountain heather (Cassiope mertensiana). Characteristic herbs and dwarf shrubs include five-leaved dwarf bramble (Rubus pedatus), twistedstalks (Streptopus spp.), deer fern (Blechnum spicant), green false hellebore (Veratrum viride), three-leaved foamflower (Tiarella trifoliata), fern-leaved goldthread (Coptis aspleniifolia) and deer cabbage (Nephrophyllidium crista-galli). Pipecleaner moss (Rhytidiopsis robusta), broom mosses (Dicranum spp.) and lanky moss (Rhytidiadelphus loreus) are the most common bryophytes on the forest floor.

In Canada, M025 forests and woodlands occur at high elevations in the coastal and insular mountain ranges of BC. Elevations extend from approximately 800 mASL to 1800 mASL, depending on location. The climate is cool, moist to wet, maritime and temperate; summers are short and cool, and winters long, cool and snowy. A deep and late-melting snowpack is characteristic of the M025 environment. Mean annual temperatures vary from 1° to 5° C and mean annual precipitation regularly exceeds 2500 mm, much of it falling as snow. All parts of the range experienced Pleistocene glaciation; soils are mostly Podzols with deep compacted Mor humus.

Two subtypes characterize regional variation in the Canadian range of M025. CM025a [Typic Vancouverian High Montane & Subalpine Forest] is the predominant condition occurring on most of the Vancouver Island and mainland ranges. CM025b [Hypermaritime Vancouverian High Montane & Subalpine Forest] describes the high elevation forests and woodlands in hypermaritime climates on Haida Gwaii and the outer coast of mainland BC.