DISPERSAL OF WHITE SPRUCE SEED IN MATURE ASPEN STANDS

The dispersal of white spruce (Picea glauca (Moench) Voss) seed throug h trembling aspen (Populus tremuloides Michx.) forests was investigate d by releasing artificial seed (confetti) from different heights on a meteorological tower, and, secondly, by observing the distribution of spruce regeneration along transects radiating out from small isolated patches of mature spruce seed trees. Mean dispersal distance of confet ti increased with height of release. Before leaf fall of the aspen can opy, most confetti landed close to and in all directions around the to wer. After leaf fall, no confetti was observed upwind from the tower a nd the mean dispersal distance increased, with peak densities occurrin g at a distance of 15 m in the downwind direction. The rate of decreas e in regeneration density with distance from patches of mature, seed-b earing white spruce was much less than that observed during confetti r elease experiments. Furthermore, regeneration densities were significa ntly greater in the prevailing downwind direction (toward the east). T he results indicate that stronger than average winds, primarily from t he northwest, west, and southwest, play a major role in the dispersal of white spruce seed. Simulation modelling of the observed distributio n of regeneration suggests that long-distance (>250 m) dispersal may b e an important mechanism for the persistence of white spruce in the fi re-prone boreal forest of western Canada.