HOLOCENE HISTORY OF FOREST TREES ON THE BRUCE PENINSULA, SOUTHERN ONTARIO

Two new pollen sequences from the Bruce Peninsula. southern Ontario. d emonstrate the Holocene history of forests in the area. During the mid - and late Holocene, the southern portion of the peninsula supported a rich deciduous forest, dominated by Acer saccharum and Fagus grandifo lia, while the northern portion was dominated by a forest with a much higher proportion of conifers. These two sites are compared numericall y with a third site, on Manitoulin Island, by means of principal compo nents analysis. Despite similar bedrock, soils, climate, and topograph y, the three pollen sequences show a remarkable divergence of Holocene forest history. The role of historical factors in determining forest composition may be much greater than previously appreciated. This stud y emphasises the need to understand the magnitude of variation between pollen sequences within uniform terrain before ascribing the differen ces in pollen sequences from contrasting environments (because of clim ate, soils or topography) to the factors causing the obvious contrast.