Fire ecology

Fire is a vital and natural part of Canada’s forests. Many plants and animals depend on it for survival.

Understanding the interaction between fire and ecosystem health helps wildland fire management agencies balance suppression with maintaining healthy landscapes. Fire ecologists study how wildland fire:

• influences ecological patterns and processes
• impacts forest renewal
• can be used as an ecological restoration tool

The diversity of Canada’s boreal forest is mainly due to the many fires that have occurred on the landscape over a long period.

The boreal: a forest shaped by wildland fire

The Canadian boreal forest is a mosaic of tree species and stands. It ranges in composition from pure deciduous to mixed deciduous-coniferous to pure coniferous stands. Wildland fires, mostly caused by lightning, influence vegetation dynamics at all levels:

• species
• stand structure
• fuels
• landscape

In the boreal forest, wildland fires vary in frequency, intensity, severity, size, shape and season. These differences impact the regenerating vegetation. Changes in forest patterns influence the movement of wildlife populations, because of their need for food and cover. Pyrodiversity breaks up ecosystem uniformity, as well as promotes and maintains species biodiversity.

How some boreal species respond to wildland fire

Wildland fires impact the structure, growth and renewal of many of Canada’s forest and grassland ecosystems. Different species respond differently to wildland fire.

After a wildland fire, forest regeneration begins with the establishment of pioneer species such as:

• aspen (Populus spp.)
• white birch (Betula papyrifera)
• jack pine (Pinus banksiana)
• lodgepole pine (Pinus contorta var. latifolia)

All these species require full sunlight to thrive. All are well adapted to landscapes where wildland fires regularly recur.

Aspen and birch can re-establish quickly by sprouting from stumps and the roots of burned trees. These species recolonize burned sites by producing abundant seeds that can be windblown over long distances.

Jack pine and lodgepole pine depend on fire to regenerate. Both species have serotinous (protected by a waxy coating) cones that require extreme heat to release their seeds. Wildland fires produce favourable conditions for these seeds to germinate by:

• releasing nutrients in the soil
• exposing mineral soil
• eliminating competing species
• increasing the amount of sunlight on the forest floor

Black spruce (Picea mariana) has semi-serotinous cones and may become established following a wildland fire. However, it grows slowly in full sunlight. If a wildland fire does not recur within 100 years, the pioneer trees eventually die and are replaced by the black spruce growing in the understory. Other shade-tolerant tree species then establish themselves.

Species such as balsam fir (Abies balsamea), white spruce (Picea glauca) and eastern white-cedar (Thuja occidentalis) are not adapted to fire. They colonize burned areas via seeds windblown or carried by animals from unburned areas. Balsam fir and white-cedar are rare in areas repeatedly burned or where fire was large because fires make growth difficult. These tree species can take a long time to reappear after a wildland fire—in some cases, as long as 150 years.

Fire regime

Fire regime refers to the pattern, frequency and intensity of wildland fires over extended periods of time. For some ecosystems, it is a basic part of forest renewal.

Currently, climate change and increased encroachment into the wildland-urban interface are altering Canada’s fire regime.

Find out more

• Wildland fires in Canada
• Wildland fire monitoring and reporting tools
• Wildland fire behaviour

Canadian Forest Service Publications

• Val-Paradis: 25 Years After the Fire (2023)
• Restoring forest ecosystem services through trait-based ecology (2024)