Under the Crown Forest Sustainability Act, site specific harvest, renewal and maintenance prescriptions are required to be implemented to ensure that the forest is renewed and maintained. All areas harvested are required to be regenerated, excluding roads, landings and slash piles. These areas typically occupy approximately 2-4% of the harvested area.
The forest can regenerate naturally from root sprouts (suckers), stump sprouts (shoots) or seeds. It can also be regenerated artificially by direct seeding or by planting trees. In either case, the method of regeneration and any associated treatments must be described in an approved forest management plan before the work can begin.
Regeneration Methods
Natural Regeneration
Natural regeneration can be an effective means of regenerating the forest when conditions are right. Although natural regeneration is usually reliable and ensures that only the trees suited to the site (i.e. the species already on the site) are established, the time delays in achieving regeneration can be long. As well, the opportunities for genetic enhancement are limited.
Effective natural regeneration from seed depends on the harvest being conducted the year after
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Naturally regenerating red pine seedlings. |
Alternatively, some species can regenerate from suckers and shoots. Aspen can be effectively regenerated naturally by ensuring that the roots growing near the surface of the soil are sufficiently scraped, bruised and/or cut into sections to promote dense sucker development. Similarly, red maple, sugar maple, and silver maple can be regenerated from shoots growing from stumps after a clearcut harvest.
Natural regeneration is low in cost, but entails a considerable risk of failure if other undesirable plant species take hold.
This form of regeneration can prolong the rotation – “the period of years required to establish and grow even-aged timber crops to a specified condition of maturity” (Haddon, 1988) – delaying the next harvest. Since one of the functions of silviculture is to shorten the rotation, natural regeneration is not usually the preferred option for more intensive levels of forest management.
With natural regeneration, there is a higher probability of developing mixed stands, those that are “…composed of two or more prominent species” (Helms, 1998). This may occur even when the original stand was pure, “a stand composed principally of one species, conventionally at least 80% based on numbers, basal areas or volumes” (Helms, 1998). Both mixed and pure stands occur naturally and the forest manager may want to grow either type, depending on the objectives for the forest.
Direct (artificial) Seeding
Direct (artificial) seeding is usually carried out from the ground or from the air on sites that have been prepared for seed germination. While it is a more expensive procedure than natural regeneration, there is a greater likelihood of establishing the desired species. The limitations of this procedure are that:
- the seeds must have a high germination potential
- soil, light, and moisture conditions must be appropriate for germination
- large volumes of seed must be applied (typically, 10 seeds must be dispersed on a site for each successful germination)
Planting
Planting is the most reliable regeneration option, and often the most expensive. The 
advantages of planting are:
- the establishment is more predictable and controllable
- seedlings can be germinated in greenhouses before stands are even harvested, thereby resulting in a “head start” on regeneration and shortening rotations
- seedling density and stocking are controlled and allow for the best utilization of the sites
The limitations of planting are:
- the planning and organization for seeds to be collected, processed, stored, and germinated in greenhouses well in advance (one to three years) of planting
- seedlings must be matched to the site, with respect to their species, size, and relative vigour in order to ensure successful establishment
- sites must normally be prepared for seedlings to take hold and grow
It is often necessary to prepare the ground for planting, seeding, or even natural regeneration. This type of operation, referred to as site preparation, may consist of raking or pushing most of the logging slash (foliage, branches, decaying logs, etc. left after harvest) into mounds or windrows, tilling the forest floor, burning the woody debris and undesirable vegetation, killing undesirable competing vegetation with herbicides, or a combination of these treatments. The intent is to provide growing sites that will establish and develop the next generation of trees under the best possible conditions.
References
Haddon, B.D., 1988. Forest Inventory Terms in Canada, 3rd Ed. For. Can., Petawawa Nat. For. Inst., Chalk River, ON.
Helms, J.A., ed., 1998. The Dictionary of Forestry. Soc. Amer. For., Bethesda, MD, 210 p.
