Abstract for M890

Rocky Mountain Intermontane Subboreal Forest
Forêts subboréales intermontagnardes des Rocheuses

M890 describes the upland subboreal forests and woodlands of the intermontane plateau areas of central British Columbia. Forest canopies can be evergreen coniferous, cold-deciduous broad-leaved, or a conifer – broad-leaved mixture. Stand-replacing fires and insect infestations are the most widespread forms of natural disturbance throughout the range of M890. Dominant tree species are interior spruce (Picea engelmannii x glauca), subalpine fir (Abies lasiocarpa) and lodgepole pine (Pinus contorta var. latifolia). Rocky Mountain Douglas-fir (Pseudotsuga menziesii var. glauca) co-occurs in warmer locations. Black spruce (Picea mariana) sometimes occurs, primarily on poor sites with cold soils. Trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera) commonly occur following disturbance and often dominate near settlements and in agricultural areas. Understories vary from dense, species-rich shrub and herb conditions to poorly developed shrub and herb layers with continuous feathermoss and/or lichen ground cover. Understory species diversity is generally high. Common understory shrubs include prickly rose (Rosa acicularis), shiny-leaved meadowsweet (Spiraea lucida), bracted honeysuckle (Lonicera involucrata), mountain huckleberry (Vaccinium membranaceum), squashberry (Viburnum edule), bristly black currant (Ribes lacustre) and soapberry (Shepherdia canadensis). Typical herb/dwarf shrub species include bunchberry (Cornus canadensis), twinflower (Linnaea borealis), one-sided wintergreen (Orthilia secunda), fireweed (Chamerion angustifolium) and arnicas (Arnica spp.). The most common moss species are red-stemmed feathermoss (Pleurozium schreberi), knight's plume moss (Ptilium crista-castrensis) and stairstep moss (Hylocomium splendens).

M890 occurs within a subhumid, mostly continental, temperate climate, with short, warm summers and cool, snowy winters. Local climatic effects significantly modify seasonal temperature extremes and annual precipitation in some portions of the range. As a result, mean annual temperatures (-0.5°C to 4.5°C) and precipitation (<350 mm to >1500 mm) are highly variable throughout the range. Up to half of the annual precipitation falls as snow. M890 forests occupy the lower elevations of the plateaux and lowlands of the southern interior system of the Cordilleran physiographic region, from the valley bottoms to the lower boundary of the high montane zone in surrounding mountain ranges (approximately 450-1500 mASL). Regional geologic and topographic features produce an array of local site conditions. All parts of the range experienced Pleistocene glaciation; soils are mostly Luvisols and Brunisols developed in glacial surficial materials.

Three subtypes distinguish regional variation within this Macrogroup. Subtype CM890a [Cool Dry Rocky Mountain Subboreal Forest] characterizes the lodgepole pine dominated forests that prevail in the dry, cool climate of the southwestern portion of the range. CM890b [Warm Rocky Mountain Subboreal Forest] characterizes the mixed lodgepole pine – interior spruce – Douglas-fir forests that occur in warmer areas of the central and southeastern portions of the range. CM890c [Cool Humid Rocky Mountain Subboreal Forest] characterizes the subalpine fir – interior spruce forests that occur in moist to wet climates primarily of the northern portion of the range.