Lethal and Nonlethal Effects of the Organic Horizons of Forested Soils on the Germination of Seeds from Several Associated Conifer species of the Rocky Mountains

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Canadian Journal of Forest Research

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Describes laboratory tests to determine whether the lethal effect of the O horizon of Picea engelmannii stands on overwintering P. engelmannii seeds (demonstrated in a previous report) also affects seeds of Abies lasiocarpa, Pinus contorta var. latifolia and Pseudotsuga menziesii var. glauca, and whether the O horizons of these associated species have a similar effect. Untreated seeds and seeds treated with a 10% slurry of 50% captan or powdered 75% captan were stratified in Petri dishes in the pure O horizon (unsterilized or autoclaved). In unsterilized P. engelmannii O horizon, the germination of untreated and powder-treated seeds respectively was: P. engelmannii 3.5 and 77.3%; A. lasiocarpa.1.3 and 20.8; P.m. var. glauca 9.5 and 84.8; and P.c. var. latifolia 11.9 and 85.7. O horizons of A. lasiocarpa and P.m. var. glauca were lethal to seeds of the species from which they were derived but only moderately harmful to seeds of other species. The O horizon of P.c. var. latifolia was almost neutral to all seeds. Autoclaving of the O horizons and powder treatment of seeds produced similar results.