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For almost a half century now, repeated failures in direct seeding operations on cutover forest lands in North America had been largely blamed on the unproven destruction of the seed supply by small mammals. In 1960, the Canadian Wildlife Service undertook a research project to ascertain the possible fate of white spruce seeds placed into the natural environment and the influence which small mammal populations may have upon such a seed supply. By equipping each seed with a microscopic radio-transmitter (radio isotopes), the seeds could be left in the field for up to one year and then recovered intact or as seed coat fragments to provide data on seed fate. Recovery success on 21,800 white spruce seeds in ten years of study has been 90%. Recoveries indicate near 50% of spring sown seeds could be destroyed by small mammals within 17 weeks in some years despite the fact that these seeds had been previously treated with the widely accepted protective coating of aluminum powder-endrin-arasan-latex. Late winter seeding reduced losses to small mammals by 2/3. No direct relationship between numbers of small mammals present and the number of seeds destroyed could be demonstrated. A critical examination of seed treatment procedures widely used has led to the development of a new seed coating formulation employing a potent rodent repellent, R-55. Under laboratory conditions, the new coating yielded improved germination and a high degree of protection against small mammals. The new coating treatment received limited field testing during 1969 and is currently undergoing refinement and more extensive laboratory and field testing in Alberta.

An index of tree growth based on the mean growth curve of black spruce shows that tree growth in the boreal forest of central Canada decreases linearly as the forest-tundra boundary is approached. A theoretical tree line is defined by black spruce growth data. The distribution of tree growth and the theoretical tree line indicate that the forest-tundra boundary is the mean summer position of the arctic front. The growth of white spruce is briefly considered, but because of a small sample size, no conclusions are drawn. [ABSTRACT FROM AUTHOR]