Shift from late-succession to early-succession forests

Much of the Canadian landscape was dominated by old forests when European settlement began, although natural disturbance from fires and insects ensured a range of age classes was found across the forested landscape. Old forests have greater structural diversity, complexity, and biodiversity than young forests, but the characteristics of old forests depend on the species and the site history.17, 35 The age at onset of old-growth characteristics varies with disturbance regimes, forest types, and site characteristics.35 For example, in the boreal forest, the age of old–growth stands ranges from about 80 to more than 300 years.36 In Nova Scotia, the government defines old-growth forests as over 125 years of age.35 In the B.C. interior, old-growth forests are defined as 120 to 140 years; on the coast, definitions vary from greater than 140 to greater than 250 years.17, 37, 38 A shift from old to young forests has been observed in some managed forests across the country, such as in the Atlantic Maritime,39 and Boreal Plains.36 In the Newfoundland Boreal40 and Pacific Maritime38 ecozones+ old forests still cover 40% of the forested area and it is assumed that old forests still dominate in the Hudson Plains, where human disturbance is minimal and natural disturbance regimes do not appear to have changed.

Extent of old forests

Map and graphs: extent of old forests in various locations in Canada. Click for graphic description (new window).
Note: age and size class distributions are affected by both natural and human disturbances.
Sources (clockwise, starting with Alberta): Timoney, 2003,36 Newfoundland and Labrador Department of Natural Resources, 2009,40 Pannozza and Coleman, 2008,39 Ministère des Ressources naturelles et Faune du Quebec, 2010,41 B.C. Ministry of Environment, 200638
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