A weekly census of air borne pollen grains was conducted for three years (1983-1985) at four sampling stations (from north to south: Sudbury, Peterborough, Toronto and London) in the Great Lakes region, southern Ontario, Canada. A Cour volumetric vane sampler was used at each site, located at the respective meteorological station, providing pollen spectra from an area of surrounding vegetation with an estimated radius of 40 km. Filter samples were processed by a standard, established procedure. The study area forms part of the Upper Canada Peninsula vegetation region. Two sites, Sudbury and Peterborough, occur in one of the two major vegetation zones, the Mixed-Hardwood; the others, Toronto and London, are located in the second zone, the Deciduous Forest. Previous studies of pollen-vegetation relations in this region were based on analysis of moss polsters. The pollen trap method used here provides a more sensitive registration of regional pollen and while the seven most important taxa quantitatively are found in the both data sets, such important taxa as Cupressaceae and Populus are under-represented or absent in polster data because of poor preservation, but well represented in the trap analyses (Cupressaceae at 9% and Populus at nearly 3%). Similarly, some spore taxa that are absent from previously published results occur in the present data in significant frequencies (Lycopodium at 4% from Sudbury and Sphagnaceae from all stations). The results of statistical analyses show the predictable major change in the regional pollen spectra between Sudbury and Peterborough.
