Taiga or Boreal Forest

The boreal forest is a continuous belt of vegetation at high latitudes that stretches from the Atlantic shoreline of central Labrador, westward across Canada to the mountains, interior and central coastal plains of Alaska.

It transitions to the tundra to the north.

Lower latitude transitions:

Subalpine forests of Alberta and British Columbia to west

Prairie grasslands to southern interior

Great Lakes/St. Lawrence mixed forest to southeast

Diversity is low

Picea glauca (white spruce) and P. mariana (black spruce) ubiquitous

Also: larch, balsam fir, jack pine, lodgepole pine

Deciduous: balsam poplar, paper birch, aspen

Climate

Cool, humid, with very cold winters

There is more precipitation than is needed for evapotranspiration

Lichen woodlands are a characteristic feature

May follow fire, or may actually be a climax community

Characteristic of the northern part of the Taiga

 

Weber, M.G. and B.J. Stocks. 1998. Forest fires and sustainability in the boreal forests of Canada. Ambio 27(7):545-550.

Fire and boreal forest ecology

Fire may have been an integral part of the ecology of this system as long ago as the Miocene or Pliocene (30-12 million years BP)

By the end of the last glaciation (15 thousand years BP), species adaptations and successional pathways were fully developed.

Climax is the culmination of forest succession.

It results in a self-perpetuating state

Strict application of this ecological concept to boreal forests is difficult

Fire is ubiquitous

Species are adapted to its regular occurrence.

Example:

Typical forest before fire is composed of jack pine, black spruce, paper birch and aspen.

After fire, recolonization is immediate, and with mostly the same species.

Fire requirement

Jack pine would disappear without fire.

Serotinous cones require fire to open

Seed needs bare mineral soil to germinate

Seedlings need absences of canopy to grow

Black spruce

Similar, but less exacting, requirements.

Other fire role

Creates a landscape mosaic

This supports plant and animal biodiversity

Fire burns in a patchy way

Return intervals and intensities are variable

Parks Canada in 1988 began reversing years of fire suppression by doing prescribed burns.

Apparently anthropogenic burning started when the land to the east of the Bering land bridge was settled 12,000 years BP

Kuuluvainen. T., et al. 2002.  Principles of ecological restoration of boreal forest ecosystems:  Finland as an example.  Silva Fennica 36(1):409-422.

Natural forest dynamics are still dominant over much of the boreal forest in Canada and Russia, but in southern Scandinavia the forests have been heavily harvested and are now mostly managed systems.

Conservation values of managed systems can be improved by modifying silvicultural techniques.

Recommendations of Finish Ministry of Environment:

Need additional conservation of rare forest types

Herb-rich forests, spruce mires

Restore forests both within protected areas and in managed areas around them

Increase conservation lands around core areas

Use bio-diversity oriented silvicultural methods

 

Management changes in practice:

Setting aside special habitats (key biotopes)

Retaining living and dead trees when harvesting

Prescribed burning

Deciduous admixture

(These all add structural features of natural forests to managed forests)

 

Most restoration in Finland has focused on drained peatlands

Filling ditches to restore hydrology

Removing trees planted in open mires

 

On mineral soil

Prescribed burns

Creates dead wood and starts succession

Girdling and felling

Imitating gap dynamics with openings in even-age stands.

Weber, M.G. and M.D. Flannigan. 1997. Canadian boreal forest ecosystem structure and function in a changing climate:  impact on fire regimes.  Environ. Rev. 5:145-166.

Boreal forest fire regime is an organizing factor of boreal forest landscapes

It includes fire intensity, frequency, seasonality, size, type (crown versus surface), and severity (depth of burn).

It is highly dependant on climate.

Models point towards unprecedented increased regional or seasonal temperatures

Projected changes most pronounced at high latitudes and there greatest in winter

Changed fire regimes could result in increased annual area burned because of an extended

                fire season, increased fire frequency, and severity.

There is potential for greatly reduced boreal forest area and increased fragmentation

Fire regime as an ecosystem process is highly sensitive to climate change because fire behavior responds immediately to fuel moisture, which is affected by precipitation, relative humidity, air temperature and wind speed.

This indirect effect of climate change has the potential to overshadow the direct effects of global warming on species distribution, migration, substitution, and extinction