(This chapter is based largely on information supplied by James D. Scott)
Aerial seeding has become an increasingly popular form of artificial regeneration in the provinces of Ontario and Quebec in central Canada. This is due to the success in seeding jack pine, the steadily rising cost of growing and planting nursery stock, and the relative ease of regenerating areas where rough terrain and difficult access all but preclude other procedures for reforestation.
In the northern regions of both Ontario and Quebec, aerial seeding has become a completely acceptable method of reforesting cutover areas.
The area of forest land aerially seeded in Ontario increased from 560 hectares in 1962 to 20,000 in 1978; in this same period, aerial seeding in Quebec rose to 7,000 hectares. Direct-seeding programs in the other provinces are less advanced, although Alberta, Saskatchewan, Manitoba, and Newfoundland all plan operational trials in the near future. Whereas Ontario and Quebec sow mainly jack pine, the western provinces of Alberta, Saskatchewan, and Manitoba have concentrated on white spruce (Picea glauca). Alberta seeds lodgepole pine (Pinus contorta) as well. Experiments in Newfoundland have shown some success with the seeding of black spruce. Overall, the best results have been with jack pine, with lesser success in white and black spruce and lodgepole pine.
Ontario initiated a few experimental aerial seeding projects as early as the 1930s, but not until the invention of the Brohm Aerial Seeding Unit (by the Ontario Forest Research Branch at Maple, Ontario) in 1962 did the first fully operational trials in that province take place. This device, designed specifically to distribute tree seed from both fixed-wing aircraft and helicopters, is the most commonly used seeding mechanism in the province.
Over the years aerial seeding has been a contentious issue among foresters in Ontario. Jack pine seeding is now, however, generally regarded as a viable and highly successful regeneration technique, particularly in the northeastern part of the province. This acceptance has been enhanced by research relating to seedbed receptivity as well as to rates and methods of seed application. Current research holds promise for the aerial seeding of black spruce as well.
Fixed-wing aircraft are preferred in Ontario for applying seed, whereas Quebec is partial to helicopters. Preferences seem to be determined by the individual pilot's experience rather than any inherent technical advantage of the type of aircraft.
Aerial seeding in Canada was originally used to regenerate sites that were inaccessible or difficult to plant because of topography. Now, however, it is also used to regenerate sites where the soil is too thin to plant by hand, such as the shallow rock-strewn soils in northern Ontario and Quebec. It is also used on boulder-skewn sites in Newfoundland and has become an inexpensive alternative to planting jack pine seedlings on sandy outwash plains where vegetative competition after the site has been prepared is relatively weak.
Most aerial seeding in Canada is preceded by some form of mechanical site preparation to break up the accumulated layers of undecomposed organic matter and create a suitable seedbed. This is done by scarification, using shark-finned barrels, spiked ship's anchor chains, or teeth mounted on bulldozer blades.
Most seeding takes place in late winter or early spring so that the seed will germinate as soon as possible after the snow melts. Seeding in the fall can be advantageous because it provides natural stratification, important with some tree species. Some seeding is also carried out after wildfires and after prescribed burns. Fires must be hot enough to burn away the organic surface material and expose enough mineral soil to provide a good seedbed. The thin soil of the Laurentian Shield, left after Ice Age glaciers scraped off the topsoil, has proved suitable for aerial seeding, as have the coarse sands of outwash plains.
The need to treat seed for rodent, bird, and insect control is not as well understood as it should be and seems to vary from province to province. With concern over toxic chemicals increasing, the use of endrin to control rodents has been discontinued in Ontario. There is a general impression that the smaller the seed size, the fewer the losses to predators.
In Ontario, where most aerial seeding is preceded by mechanical site preparation, it has been found that considerable control over stocking can be achieved by maintaining a balance between the amount of mineral soil exposed and the rate of seed applied. Overstocking is not considered a serious problem.