Forested Ecozones

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Abstract

In Canada, there are 20 ecozones, consisting of 15 terrestrial and 5 marine units. The vegetation varies from one ecozone to another. Forests cover totally or partially nine ecozones: Pacific Maritime, Montane Cordillera, Boreal Cordillera, Taiga Plains, Boreal Plains, Prairie, Boreal Shield, Mixedwood Plains, and Atlantic Maritime.

Canada has defined a hierarchical system of ecosystems. At a simple level there are 20 ecozones ecozones, consisting of 15 terrestrial and 5 marine units. Each unit is distinguished from others by its unique mosaic of plants, wildlife, climate, landforms and human activities.

Forests of Canada cover in total about nine ecozones. The vegetation that covers each of them is briefly described below.

• Pacific Maritime: The combination of heavy rainfall and mild temperature during all year support temperate rain forests. This ecozone has the most productive forests and the biggest and oldest trees of Canada. In low-lying coastal areas, western hemlock forests dominate; in higher elevations subalpine mountain hemlock forests are more common.
• Montane Cordillera: The relief and the vegetation vary a lot through this ecozone. In the alpine environments there are various herbs, lichen and shrubs. In the subalpine regions dominant tree species include the alpine fir and Englemann spruce. As the elevation decreases the vegetation is divided into three forest groups: the upper elevations are characterized by Engelmann spruce, alpine fir and lodgepole pine; the second zone is characterized by ponderosa pine, Interior Douglas-fir, lodgepole pine and trembling aspen; and the third one contains western hemlock, western red cedar, Interior Douglas-fir, and western white pine in the southeast.
• Boreal Cordillera: Forests cover 62% of this ecozone. Lower elevations are generally forested by white spruce, black spruce, alpine fir, lodgepole pine, trembling aspen, balsam poplar and white birch. Upper elevations near treelines are dominated by deciduous shrubs, mainly scrub birch and willows.
• Taiga Plain: The territory of this ecozone is 80% forested. The forest in the Taiga Plain is a transition between tundra and dense coniferous forests. Tree species include black spruce, white spruce, jack pine, tamarack, paper birch, trembling aspen, and balsam poplar. Along the alluvial flats of the larger rivers where soils contain richer nutrients, white spruce and balsam poplar grow to a size comparable to the largest in the boreal forest. In this ecozone, forest fire occurs frequently and destroys several thousand hectares each year.
• Boreal Plains: The Boreal Plains contain part of the Boreal Forest and timber covers 84% of the ecozone. Forestry is the primary industry. Tree species include white and black spruce, balsam fir, jack pine, tamarack, and lodgepole pines. Most common broadleaf trees are aspen and poplar, and birch exists in some areas. The distribution and growth rates of trees are mostly determined by fire, but native insect pests and disease also affect these forests.
• Prairies: Agriculture is the dominant land use in the prairie landscape, but 16% of the prairies are forested. In this ecozone, vegetation consists of grasslands and limited forests in the Aspen Parkland in the northern portion of the ecozone. The Aspen Parkland is a transition zone between the boreal forest in the north and the grasslands to the south. Few deciduous trees and shrubs grow in the ecozone. In the eastern regions, there are trembling aspen and shrubs, whereas the southwest displays a mixed montane-type open forest of Lodgepole Pine.
• Boreal Shield: More than 80% of the ecozone is forested but tree growth and timber volume are lower than in many of the forested ecozones in Canada. In fact, much of the ecozone remains in a wilderness condition. Black spruce, white spruce, jack pine and balsam fir grow in this ecozone. Black spruce is the most common species. In the southern part of the ecozone, there is a wider distribution of hardwood trees such as white birch, trembling aspen and balsam poplar along with white, red and jack pine. Fire suppression and harvesting practices in this ecozone resulted in a shift from conifers to hardwoods. Throughout the Boreal Shield, forests are mixed with numerous wetlands.
• Mixedwood Plains: This ecozone surrounds the Great Lakes and the St. Lawrence River Valley. It is the most densely populated part of Canada and also the most intensely used area. Once heavily forested, very little of the original forest remains today. Centuries of agriculture, logging, and urbanization have fragmented the landscape into isolated pockets of forests. Originally, eastern white pine, eastern hemlock, yellow birch, red pine, sugar maple, red oak, basswood, and white elm were widely distributed. There was also a small portion of the deciduous or Carolinian forest in southwestern Ontario. Today, the remaining forests in this ecozone consist of 12.8% mixedwood, 2.1% deciduous, and 0.2% coniferous trees.
• Atlantic Maritime: The Atlantic Maritime Ecozone is 76% covered with forests. It is the third most forested ecozone in Canada. There are three distinct forest regions: Boreal characterized by fir and spruce; Great Lakes-St. Lawrence with eastern white pine, red pine, yellow birch, and eastern hemlock; and Acadian which is covered by mainly red spruce, sugar maple, beech, and yellow birch.