Natural regeneration following disturbance
Sylvie Gauthier: My name is Sylvie Gauthier and I work for Natural Resources Canada’s Canadian Forest Service. I’m a research scientist specializing in forest ecology and forest dynamics.
David Paré: My name is David Paré, I’m a researcher at the Canadian Forest Service. I conduct research on forest soils and ecosystems.
Sylvie Gauthier: Natural regeneration is the continual process of recruitment of new stems, small trees that grow under the forest canopy or regenerate following large-scale disturbances. Seeds from nearby trees are transported to the disturbed sites by birds or by the wind, permitting stand renewal.
David Paré: Natural regeneration is the main process by which forests become re-established following disturbances. In Canada, every year, large expanses of forest are affected by natural disturbances. In most of the disturbed areas, many of which are inaccessible, renewal of the forest cover occurs through natural regeneration.
Sylvie Gauthier: Actually, natural regeneration differs from artificial regeneration in that it occurs all by itself, through natural processes. When artificial regeneration is used, seedlings are grown in greenhouses. The seedlings are then taken to the site to be planted.
David Paré: Every tree species requires certain conditions to regenerate naturally. Some species prefer to grow under the forest canopy, while others prefer large openings to regenerate. Some species require particular soil conditions, such as exposed mineral soil or decomposing woody debris.
Sylvie Gauthier: Fires are a significant disturbance agent in the boreal forest, namely because they help to renew forest ecosystems by recycling nutrients and permitting the regeneration of certain species, such as jack pine, which requires fire to regenerate. Canada’s boreal forest can be divided into two broad regions based on the fire return interval. The western boreal forest burns at a mean interval of about 100 years, which is quite frequent.
David Paré: At the eastern edge of the boreal forest, the fire cycles are very long, sometimes several centuries, and forests are adapted to these long fire cycles. In other types of ecosystems, for example in a maple forest, the most common disturbance is that of a tree falling, creating a small gap. In these forests, we find species that are well adapted to such small gaps, including the yellow birch, which regenerates on decaying stumps.
Sylvie Gauthier: Natural regeneration can’t always be depended on to ensure forest renewal. Under some conditions, natural regeneration isn’t sufficient and we need to help nature by planting trees and intervening to re-establish forest stands.
David Paré: The success of natural regeneration is generally measured through a series of inventories conducted shortly after a disturbance such as logging or fire. Provincial agencies are responsible for these inventories and the findings they entail.
Sylvie Gauthier: Natural regeneration permits the renewal of disturbed areas, helping to ensure that new forests become established there. This regeneration costs nothing. Natural disturbance events occur fairly often in large expanses of forests in Canada. When natural regeneration is successful, enough trees will grow to re-establish productive forests.