Microsite effects on first-year establishment and overwinter survival of white spruce in aspen-dominated boreal mixedwoods

First-summer establishment and overwinter survival of planted and seeded white spruce (Picea glauca (Moench) Voss) germinants were assessed in five microsites in the understory of trembling aspen (Populus tremuloides Michx.) dominated boreal mixedwood stands. Mineral soil mounds, rotten logs, large exposed patches of mineral soil, normal LFH forest floor, and small screefed patches of mineral soil were examined. The mounds and rotten logs had the highest soil temperature, lowest soil strength, and accumulated the least amount of deciduous leaf litter whereas the small screefs were at the other extreme. First-summer establishment of planted seedlings was greatest on the rotten logs, mounds, and large exposed patches; the large exposed patches had the highest establishment of seeded trees. Over 85% of the planted seedlings that were in good condition in September survived the winter. Overwinter survival of seeded trees was least on small screefed patches, but survival of these trees was increased by covering them with small plastic cups. Low soil temperature, high seedbed strength, and high vegetation cover were associated with reduced seedling establishment whereas high litter accumulation was associated with reduced overwinter survival.