High-resolution pollen analysis of two lakes at the boreal forest-aspen parkland ecotone in central Saskatchewan, Canada

It is now generally accepted that the earth is experiencing changes in climate due to anthropogenic effects. These changes affect the growth and pattern of vegetation across the globe. In central and northern Saskatchewan it is believed that there will be changes in the current climate conditions that will affect the distribution and productivity of the aspen parkland and boreal forest. To assess the changes in these communities and climate in the past, sediment cores were collected from two lakes in the southern boreal forest - aspen parkland ecotone. High-resolution pollen analyses were carried out on both cores to determine the changes in pollen abundances over a period of approximately 2000 years at one lake and 500 years at the other. At high resolution it was possible to observe both short term changes in vegetation as well as changes in pollen production, and to assess the value of high-resolution pollen analyses. In addition to the sediment cores, modern pollen assemblage and environmental variable information was compiled from previously published studies and Canadian and US climate records to develop a model to reconstruct select climate variables from fossil pollen assemblages. CONISS cluster analysis, to determine patterns of similarity of samples over time, and principal components analysis, to help interpret vegetation changes over time, were also performed. Results suggest that the objectives of a study should be considered when selecting an appropriate resolution for pollen analysis work. The relatively lower resolution record from North Flat Lake was found to be appropriate for assessing changes in vegetation as well as longer term changes in climate whereas the higher resolution record from L03 was more appropriate for assessing changes in plant productivity and characterizing short term changes in climate and disturbance patterns.