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Old-growth forests from some of Canada's forest regions

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Canadian Forest Service
Old-growth Forests in Canada

More than 40% of Canada’s 997 million hectares of land is forested. Forests form a band across the country approximately 7000 km long by 3000 km wide. The three Boreal forest regions, together with the Great Lakes–St. Lawrence region, account for over 80% of Canada’s forests.

Old-growth forests occur in all of Canada’s forest regions. Generally, the age of at least some of the trees in such a forest is at or is close to the natural longevity of the species. Old-growth forests generally have a greater abundance of dead wood, both standing and on the ground, than do younger stands. The actual age, quantity of dead wood, and other old-growth attributes vary depending on the species composition of the particular forest type. This map shows the Forest Regions of Canada, and provides examples of different old-growth forest types in some of these regions.

Forest Regions and Principal Tree Species

Boreal — Predominantly Forest
White spruce, black spruce, balsam fir, jack pine, white birch, trembling aspen
Boreal — Forest and Barren
White spruce, black spruce, tamarack
Boreal — Forest and Grass
Trembling aspen, willow
Subalpine
Engelmann spruce, subalpine fir, lodgepole pine
Montane
Douglas-fir, lodgepole pine, ponderosa pine, trembling aspen
Coast
Western red cedar, western hemlock, Sitka spruce, Douglas-fir
Columbia
Western red cedar, western hemlock, Douglas-fir
Deciduous
Beech, maple, black walnut, hickory, oak
Great Lakes and St. Lawrence
Red pine, eastern white pine, eastern hemlock, yellow birch, maple, oak
Acadian
Red spruce, balsam fir, maple, yellow birch
Grassland
Trembling aspen, willow, bur oak
Tundra

Coast (Temperate)

Age
150 years, oldest trees live 1000 years
Structure
Multi-aged, multi-layered canopy, very high biomass accumulation
Natural disturbance regime
Tree replacement
Tree species composition
Mixtures of long-lived, shade-tolerant species
Associated species
Winter wren, Pacific treefrog, fern-leaved goldthread, sword fern

Montane

Age
100 years, oldest trees live 350 years
Structure
Even-aged, single layer canopy, low biomass accumulation
Natural disturbance regime
Stand replacement
Tree species composition
Shade-intolerant species mixtures
Associated species
Northern goshawk, hoary bat, one-sided wintergreen, bearberry (kinnikinnick)

Great Lakes and St. Lawrence

Age
150 years, oldest trees live 400 years
Structure
Multi-aged, multi-layered canopy, moderate biomass accumulation
Natural disturbance regime
Tree replacement
Tree species composition
Long-lived, shade-tolerant species mixtures
Associated species
Southern flying squirrel, northern long-eared bat, red-backed
salamander, pileated woodpecker, wild leek, jack-in-the-pulpit

Boreal (dry)

Age
100 years, oldest trees live 250 years
Structure
Even-aged, single layer canopy, low biomass accumulation
Natural disturbance regime
Stand replacement
Tree species composition
Dominated by shade-intolerant species
Associated species
Three-toed woodpecker, grey jay, woodland caribou, Labrador tea, clintonia

Acadian

Age
150 years, oldest trees live 400 years
Structure
Multi-aged, multi-layered canopy, moderate biomass accumulation
Natural disturbance regime
Tree replacement
Tree species composition
Long-lived, shade-tolerant species mixtures
Associated species
Yellow-bellied sapsucker, barred owl, showy lady’s slipper, large round-leaved orchid

• Stand Structure and Reproductive Fitness Traits in White Pine
• Defining Old-Growth Forests in the Acadian Forest Region
• Old-Growth Forests as Reservoirs of Genetic Diversity and Reproductive Fitness

Boreal (wet)

Age
100 years, oldest trees live 250 years
Structure
Multi-aged, multi-layered canopy, moderate biomass accumulation
Natural disturbance regime
Tree or stand replacement
Tree species composition
Shade tolerant species, sensitive to drought
Associated species
Pine marten, black-backed woodpecker, feather moss,
New York fern

Attributes used to characterize the old-growth forests are described below.

Age - the approximate minimum age and longevity of the dominant trees in a given forest type.

Structure - the degree of vertical layering and spatial distribution of trees within a stand. Features that make up the structure of a stand include single or multiple canopy layers, distribution of different-aged trees, and amount of dead wood (biomass), either standing or on the ground.

Natural disturbance regime - falls into two categories, tree replacement or stand replacement. A tree replacement regime is characterized by small gaps in the canopy, created by the death of an individual tree or small groups of trees. A stand replacement regime may be characterized when whole stands are killed, either by fire or other major events.

Tree species composition - refers to the stand complexity and shade tolerance of the dominant species. In some forest types, the number of tree species may increase with age, but in others, the old-growth stage may be relatively simple, with low species diversity. Forest ecosystems that have reached the old-growth stage are often dominated by shade-tolerant tree
species that are able to establish under a closed forest canopy.

Associated species - are plant and animal species that occur in particular types of old-growth forests.