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Mineral soils exposed by fire are often covered by a layer of ash due to complete consumption of the forest floor (litter and duff). To assess the possible effects of ash on seed germination and viability of jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.), a laboratory experiment was conducted using ash derived from three types of forest floor samples. The samples represented areas of high conifer concentration, high aspen concentration, and mixed aspen and conifer and were collected from five mature aspen (Populus tremuloides Michx.) – conifer mixedwood stands in southeastern Manitoba. Ash derived from each forest floor type neither prohibited nor delayed conifer germination, except that of balsam fir. Balsam fir had significantly less germination on ash derived from forest floor samples with high aspen concentration. When corrected for seed viability, balsam fir had significantly less germination on all three ash types compared with jack pine, black spruce, and white spruce. However, the impact of ash on balsam fir is unlikely to have meaningful ecological implications, as balsam fir is a climax species and will establish in undisturbed mature forests. Le sol minéral exposé par le feu est souvent recouvert d’une couche de cendre due à la combustion de la couverture morte (litière et humus). Les effets de la cendre sur la viabilité et la germination des graines de pin gris (Pinus banksiana Lamb.), d’épinette noire (Picea mariana (Mill.) Britton, Sterns, Poggenb.), d’épinette blanche (Picea glauca (Moench) Voss) et de sapin baumier (Abies balsamea (L.) Mill.) ont été évalués. Une expérience en laboratoire a été réalisée en utilisant de la cendre provenant de trois types d’échantillons de couverture morte, représentatifs de zones avec une concentration élevée de conifères (HC), de peupliers (LC) et d’un mélange de peupliers et de conifères (MC) prélevés dans cinq peuplements mixtes matures de peuplier faux-tremble (Populus tremuloides Michx.) dans le sud-est du Manitoba. La cendre provenant de chacun des types de couverture morte n’a ni inhibé ni retardé la germination des conifères à l’exception du sapin baumier. Les graines de sapin baumier germaient significativement moins bien sur la cendre provenant du type de couverture morte LC. Lorsqu’elle était corrigée pour la viabilité des graines, la germination du sapin baumier était significativement plus faible sur les trois types de cendre comparativement au pin gris, à l’épinette noire et à l’épinette blanche. L’impact de la cendre sur le sapin baumier a peu de chances d’avoir des implications écologiques significatives étant donné que le sapin baumier est une espèce climacique qui s’établira dans les forêts matures non perturbées. [ABSTRACT FROM AUTHOR]

We examined jack pine (Pinus banksiana Lamb.), black spruce (Picea mariana (Mill.) BSP), and white spruce (Picea glauca (Moench) Voss) seed germination and seedling recruitment in aspen (Populus tremuloides Michx.) and conifer mixedwood stands following the 1999 Black River fire in southeastern Manitoba, Canada. Three postfire seedbed types were tested: scorched (surface litter only partially consumed), lightly burned (surface litter consumed with little or no duff consumption), and severely burned (complete consumption of litter and duff exposing mineral soil). Seeds were sown in 1999, 2000, and 2001, and each cohort was monitored for 3 years. In 1999, severely burned seedbeds had poor germination, while scorched seedbeds had the highest germination. The reverse was true in 2001. After the first growing season, continued survival of seedlings was greater on severely burned seedbeds for all three cohorts. However, better survival on severely burned seedbeds was not sufficient to overcome poor germination in 1999 and 2000. When using artificial seeding to promote conifer regeneration, we recommend a delay of one full year after a severe spring fire for jack pine and two full years for black spruce and white spruce on boreal aspen and conifer mixedwood sites. [ABSTRACT FROM AUTHOR]