Pollen deposition in the boreal forest of west-central Canada

Abstract

Deposition of tree and tall shrub pollen was examined along a 5.5-km transect in mixed boreal forest in west-central Manitoba, Canada. Annual pollen deposition averaged ca. 6850 grains/cm2 in 1992, with jack pine contributing 67.3% and spruce 24.5% of the total. In general, flowering plant species released their pollen in early to late May, while conifer (spruce and pine) pollen release occurred in early to mid-June. Pollen deposition was poorly correlated with relative species abundance in the community, with some species (e.g., jack pine) being over-represented in the pollen rain and others (e.g., aspen poplar) being under-represented. In 1993, spruce pollen deposition was 63% of that in 1992. By contrast, total pollen deposition by jack pine showed little variation from 1991 to 1993. However, pollen release dates varied between years, occurring earlier in years with warmer spring temperatures. Jack pine pollen release exhibited diurnal variation, with the majority of pollen being released during daylight hours on warm, sunny days. Keywords: Manitoba, jack pine, black spruce, boreal forest, pollen rain, palynology.