by Mike Allen
Written for Canadian Trees magazine Volume 1, Number 1, 2004 pp 20 -23
Canada is a country of trees. A symbolic maple tree leaf is emblazoned on the national flag. Major forest vegetation regions, across Canada can be geographically broken down for simplicity into five distinct forest regions *: Western Mountain coniferous, Prairie grasslands and Aspen parklands, Boreal, Great Lakes – St. Lawrence, Deciduous, and Acadian. Each of these forest regions has their own unique tree species along with species that are common to many areas of Canada. Each forest region has its unique and typical tree species.
* Based on J. S. Rowe. 1972. Forest Regions of Canada, Canadian Forestry Service, Ottawa
The boreal forest region is the largest extending from Yukon and B.C. to Newfoundland. Trees of the boreal forest tend to be found right across Canada. This is the forest that is naturally renewed by periodic wild fires. Surprisingly there are many tree species in the boreal forest common to all the regions of Canada. The most common large size tree species are trembling aspen, white spruce, black spruce, white birch, tamarack, and balsam poplar. The most common small sized trees found in nearly all the forest regions are choke cherry, pin cherry, Bebb willow, and pussy willow. The other prominent boreal trees are Jack pine, balsam fir, mountain maple, striped maple, and lodgepole pine in the western boreal forest. The northern fridge of the boreal forest merges with the tundra. The southern fringes of the boreal forest intermix with all of the other major forest regions. This is no more apparent than in the Canadian Shield region of eastern Manitoba, north-western Ontario, and central Ontario and Quebec. Species such as white pine, red pine, large tooth aspen, ironwood or hornbeam, eastern white cedar, black ash, silver maple, and yellow birch occur here that are normally found in the Great Lakes – St. Lawrence forest region. White spruce is the most longitudinally abundant Canadian tree species. Of all the Canadian trees only peach leaf willow has the greatest latitudinal distribution in North America as it is found in the Manitoba’s northern Interlake region and extends southward throughout United States and into Mexico.
Western Mountain Coniferous Forests
Coniferous trees dominate this region more than any other region in Canada. There are four sub-regions: Coast, Columbia, Subalpine, and Montane. The Coast rain forest is dominated by coast Douglas fir, Sitka spruce, western red cedar, western hemlock, big leaf maple, black cottonwood, and red alder and is located on the west facing side of the Cascade Mountains. Several unique but commonly seen species of the Pacific Coast forests are Garry oak, amabilis fir, mountain hemlock, yellow cypress, and arbutus. Some of Canada’s oldest trees are in the coast rain forest with western red cedar exceeding ages of 800 years The Subalpine forest which is the highest elevation forest in B.C., is uniquely comprised of Engelmann spruce and subalpine fir. Lodgepole pine is the dominant species. The Columbia forest is an interior ‘wet belt’ rain forest region merging with the other three sub-forest regions species on the coast and lower elevations. This forest consists of western red cedar, western hemlock, western white pine, grand fir, western larch, western white birch and interior Douglas fir. Lodgepole pine, interior Douglas fir, ponderosa pine and aspen occur in dry lowland hills and mountain sides throughout the dry Montane forests. These are the forests that have been burning so frequently in the last couple of years.
Prairie Grasslands and Aspen Parkland Forests
This forest and grassland region, a part of the boreal forest, has the fewest number of distinct tree species of all the Canadian forests. Trembling aspen, balsam poplar, choke cherry and willows are dominant species with mixtures of white spruce, jack pine, tamarack, and white birch. The eastern Prairies region has a richer species component with bur oak occurring abundantly in Manitoba. Bur oak thrives on the prairies to ages exceeding 300 years. Other common eastern Prairie species are black ash, American elm, peach leaf willow, eastern red cedar, and plains cottonwood. The eastern river valleys in the Prairies are extensions of the Great Lake – St. Lawrence forest region with the presence of green ash, basswood, Manitoba maple, and cottonwood. Manitoba river bottomland forests can have trees well over 200 years in age. Uniquely found on the south end sand dunes near the Lake Manitoba marshes is Delta Hackberry. Eastern hackberry is found only in south-western Ontario.
Great Lakes – St. Lawrence Forest
This forest region mixes with the boreal forest over a very large geographical area as was mentioned previously. Deciduous, broadleaved trees common to this southern region of central Canada are sugar maple, eastern hemlock, red maple, white ash, red ash, basswood, butternut, red oak, white oak, bur oak, beech, shagbark hickory, white pine, red pine, eastern white cedar, yellow birch, black willow, eastern cottonwood, and black cherry. Within recent times, it has been discovered that eastern white cedar growing on the Niagara escarpment are over 600 years in age making them the oldest trees in central and eastern Canada. In geographical pockets of eastern Ontario and southern Quebec there are unique forest areas where pitch pine, eastern red cedar (juniper) and red spruce occur. Red spruce is common to the Acadian forest region.
The unique deciduous forest occurs in south-west Ontario (Toronto to Niagara to Windsor). It has most of the species in the previous forest region plus a sub-forest region called the Carolinian forest which is an extension of the forests in the adjacent United States. There are only scattered remnants of this forest left, but tree species from this area have been planted across Canada. There are many unique species of oak and hickory, the rare pumpkin ash, blue ash, black walnut, Kentucky coffee tree, sycamore, red bud, tulip tree, red mulberry, sassafras, black gum or tupelo, pawpaw, honey locust, eastern hackberry, and others. The warm and humid temperate climate of the region fosters the large variety of tree and shrub species. Specimen red and black oaks in the Niagara area have been dated over 400 years of age. All of these tree species have been planted initially on a trial basis throughout Canada with successes being marginal and unpredictable in most areas. Many of these trees can only be seen by the public in botanical gardens although there are many enthusiastic botanists and tree people like myself that are constantly searching for new locations of rare trees and woody shrubs.
This forest region is made up a number of species from the Boreal and Great Lakes – St. Lawrence forest regions. Red, white and black spruces are common, as are balsam fir, yellow birch, eastern hemlock, trembling aspen, red oak, eastern white cedar, white pine, red maple, sugar maple, grey birch, and white birch. The proximity to so much of this forest region to the Atlantic Ocean has shaped the form, size and distribution of tree species especially those growing on shallow bedrock soils. Strong, regularly occurring winds have made the presence of large, older trees rare except in protected areas.
For me, travelling across Canada as I do frequently is a way of re-uniting with the unique character of Canadian forests in highly diverse landscapes.