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The Boreal Mosaic

"All things are connected. Whatever befalls the earth
befalls the children of the earth".
(Chief Seattle, 1854)

The boreal forest ecosystem is an interconnected web of life. It is a dynamic system of living organisms, plants, animals, insects and micro-organisms, interacting with the physical environment of soil, water and air. Trees are the most visible and main structural elements of the forest ecosystem. The boreal forest is dominated by a small number of needle-leaved coniferous tree species of spruce, fir, larch (tamarack) and pine. There are also several cold-hardy broadleaved tree and shrub species, in particular, birch, poplar, willow, alder and mountain ash. Even though all these species and the associated shrubs, herbs, mosses, lichens and fungi range widely through the boreal forest, there is, nevertheless, a considerable regional diversity in boreal forest makeup from south to north and from east to west.

Natural disturbances contribute to the landscape diversity of the boreal forest. Fire, insect infestation (such as the spruce budworm), disease and windthrow take place at different times and places across the forest. The result of this is a patchwork or "mosaic" of many different sized, even-aged groups of trees at different stages of growth.

In spite of the cold temperatures, a short growing season and nutrient-poor soils, the vast extent of the boreal forest results in a significant standing biomass. This accounts for its value as a forest resource as well as its influential role on global climate.

The boreal forest is divided into two great transcontinental belts of approximately equal size: the subarctic open lichen woodland and the closed crown forest. This major horizontal sectioning of the two areas reflects the steady dropping of temperature from south to north.

The more northern subarctic lichen woodland is a handsome landscape mostly unknown to Canadians because of its few settlements and roads (and also very abundant black flies !). Northern stands of scattered spruce and jack pine, accompanied by balsam fir in Quebec, form attractive open-canopied areas carpeted with yellow, green and light grey lichens. Recently burned areas are covered with birch, blueberries and other small evergreen shrubs. Larch is common in low marshy areas while shallow-rooted black spruce populates the surface of frozen and uplifted bogs known as peat plateaus.

The southern belt of closed crown forest occupies a milder climatic zone where the trees grow taller and closer together to form closed-canopies beneath which plentiful mosses, herbs and shrubs thrive. This is the commercial forest that feeds the sawmills and pulp mills. In the western part of the closed crown forest area (the northern part of British Columbia and the Rocky Mountain Foothills of Alberta) prominant tree species include white spruce, black spruce, birch and poplar. Further east in the Precambrian area of Ontario and Quebec, the predominant tree species are jack pine and black spruce. There are also large flatter areas of particularly productive forests of spruce, fir and pine.

On the southern border of the closed crown forest, fertile soil supports a richer combination of trees including white spruce and poplars. Further to the east there are sugar maple, yellow birch, red pine and white pine. These bands or areas of mixed woods show the affect of the increase in precipitation as one moves from west to east. This not only allows for greater numbers of tree species but also the greater prominence of balsam fir, a most important member of the forest from Lake Superior to Newfoundland.