Abstract for M495

Eastern North American Boreal Forest
Forêts boréales de l'Est de l'Amérique du Nord

M495 describes upland boreal forests and woodlands in eastern Canada, ranging from southeastern Manitoba to Atlantic Canada. Forest canopies can be coniferous, broad-leaved cold-deciduous or a conifer–broad-leaved mixture. Stand-replacing fires and insect infestation (primarily by spruce budworm [Choristoneura fumiferana]) are the most widespread forms of natural disturbance throughout the range of M495. In general, the relative frequency of fire decreases eastward as maritime climatic influences create more humid environmental conditions. Forests that are characteristic of a longer fire cycle with periodic insect perturbations become more prevalent on the landscape in the eastern part of the range. Dominant tree species include trembling aspen (Populus tremuloides), paper birch (Betula papyrifera), black spruce (Picea mariana), white spruce (Picea glauca), balsam fir (Abies balsamea) and jack pine (Pinus banksiana). Balsam poplar (Populus balsamifera) occurs on moist, nutrient-rich sites. Understories range from dense, species-rich shrub and herb conditions to sparse and open with continuous feathermoss and/or lichen ground cover. Common understory species include common Labrador tea (Rhododendron groenlandicum), sheep laurel (Kalmia angustifolia), velvet-leaved blueberry (Vaccinium myrtilloides), early lowbush blueberry (V. angustifolium), mountain ashes (Sorbus spp.), mountain maple (Acer spicatum), creeping snowberry (Gaultheria hispidula), yellow clintonia (Clintonia borealis), northern starflower (Lysimachia borealis), wild sarsaparilla (Aralia nudicaulis) and red-stemmed feathermoss (Pleurozium schreberi).

The M495 range is characterized by a humid, mostly continental boreal climate, with long, cold winters and short, mild summers. Maritime influences become pronounced in the eastern part of the range, where seasonal temperature extremes are mitigated and annual precipitation is higher. High elevation areas and colder more exposed coastal environments of otherwise temperate southern Quebec and the Maritime Provinces also support boreal forests described by M495. Mean annual temperature varies from <0°C at the northern limit of the range to >3.5°C in insular Newfoundland. Annual precipitation generally increases eastward from approximately 640 mm in southeastern Manitoba and northwestern Ontario to >1800 mm in parts of insular Newfoundland and Cape Breton Island. Elevations are mostly <500 mASL although parts of the Laurentian Region of the Precambrian Shield and the Chic-Choc Mountains of the Gaspé region reach 1000 mASL or higher. Regional geologic and topographic features of the Precambrian Shield and Appalachian physiographic regions produce an array of local site conditions. All parts of the range experienced Pleistocene glaciation; soils are mostly Podzols, Brunisols and Luvisols developed in surficial glacial materials.

Two subtypes distinguish boreal forests characteristic of maritime climatic influences (CM495a [Atlantic Boreal Forest]) from forests characteristic of shorter fire cycles in a more continental climate (CM495b [Ontario-Quebec Boreal Forest]).