Seed release from black spruce cones in logging slash

Abstract

Seed release from black spruce (Piceamariana (Mill.) BSP) cones on two clearcut sites in northwestern Ontario was evaluated over a 5-year period. Newly ripened cones were set out at seven locations on or above upland raw humus, upland mineral soil, and lowland raw humus substrates, and periodically sampled to determine the number of seeds remaining, and their germinability. Cones elevated above the substrates released 45–55% of their seeds within 1 year, and 65–75% of their seeds within 2 years. Seed release was largely confined to the growing season. Filled seeds were released more rapidly than empty seeds, and germination percent of the remaining filled seeds declined with time. Cones lying on or just above the substrates released about 25% of their seeds within 2 years, but the proportion of seeds remaining that were filled, and their germination percent, declined more rapidly with time than for elevated cones. Seed release occurred most rapidly from cones associated with upland raw humus substrates. Estimated viable seed release from cones elevated above the substrates was two to three times greater than that from cones lying on the substrates. Depending on cone location, 65–90% of all viable seed released was released within the first year after harvesting. This seed source should be considered when designing silvicultural regeneration systems for black spruce.