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Why not let the forest regenerate naturally, and not use herbicides at all?

Category: Vegetation Management

Across Canada, approximately 45% of all harvested areas are left to regenerate naturally, without using herbicides. Many of these sites are intended to grow hardwood species (e.g., aspen, birch, maple), which readily regenerate by natural means. However, most conifer species, require very specific conditions to regenerate naturally. To maintain a healthy and productive forest, it is usually necessary to assist conifer establishment and growth through direct seeding, planting, herbicide treatments, and continued tending.

A photo sequence showing a young white spruce seedling 1 day (left) and 3 growing seasons (right) after planting (note the person standing amidst the pin cherry and other brush that have overgrown the seedling, reducing its available light, soil moisture, nutrients and space). This photo sequence is typical of the competitive nature of many productive forest sites. (Photos: Doug Pitt).

Good forest management strives to maintain a mosaic of different stand types (hardwood, conifer and mixed), in different age classes, emulating as closely as possible the expected natural spatial distribution of these features on the landscape. In Canada, just under half of the area harvested each year is left to regenerate naturally (http://nfdp.ccfm.org/). The expectation is that hardwoods and mixedwoods occupy these sites with little or no tending. Hardwood species, particularly in the boreal forest, regenerate from both coppice growth (root and stump suckering) and seed, allowing them to rapidly colonize disturbed areas on their own. Most conifer species, however, rely solely on seed for natural regeneration. Without rather exacting stand and soil conditions at time of harvest (e.g., those that often occur with natural fire events), conifer establishment can be difficult and variable without our help; through planting or direct seeding. An overreliance on natural regeneration, coupled with inadequate tending, can precipitate a substantive loss in the abundance and dominance of conifer on a landscape, resulting in both economic and ecological repercussions (Armson et al. 2001, Hearnden et al. 1992, OMNR 1986; 1988). The loss of pine and spruce dominated stands across the landscape continues to be recognized as a major challenge for the forest sector.

Armson, K.A., Grinnell, W.R., Robinson, F.C. 2001. History of reforestation in Ontario. Pages 3-22 In: R.G Wagner and S.J. Colombo eds. Regenerating the Canadian Forest: Principles and Practice for Ontario. Markham, ON.

Hearnden, K.W., Millson, S.C., Wilson, W.C. 1992. A report on the status of forest regeneration. Ontario Ministry of Natural Resources. Independent Forest Audit Committee, Sault Ste. Marie, ON, 117 p.

Ontario Ministry of Natural Resources (OMNR). 1986. Survey of artificial regeneration in northern Ontario: Summary report for Northwestern, North Central and Northern Regions, based on field sampling, 1984-1986. Ministry of Natural Resources files (as cited by Armson et al. 2001).

Ontario Ministry of Natural Resources (OMNR). 1988. Survey of artificial regeneration in northern Ontario: Summary report for Northestern and Algonquin regions, based on field sampling, 1987-1988. Ministry of Natural Resources files (as cited by Armson et al. 2001).

Ontario Ministry of Natural Resources. 2008. Annual report on forest management 2005/2006. Queen’s Printer for Ontario.