Vegetation dynamics in relation to late Holocene climate variability and disturbance, Outaouais, Quebec, Canada

A pollen diagram from Lac Brule in southwestern Quebec (45 degrees 4309N, 75 degrees 2632W, 270m) provides a late Holocene history of the vegetation. The presence of varved sediments permitted the development of a high-resolution (10-year), cross-dated chronology with an estimated error of approximately 1%. During the last 1400years, the forests were dominated by Tsuga, Fagus, Betula, Acer and Pinus. A peak in microcharcoal and evidence of post-fire succession suggest that the changes in the pollen assemblages around ad1375 were a consequence of a fire in the region. There was a decrease in pollen influx of several deciduous taxa and Tsuga between ad1600 and 1700, suggesting a rapid climate change that was significant enough to have affected pollen production of these taxa. This change, associated with the beginning of the Little Ice Age' in the region, affected the forest composition for the subsequent centuries. A detailed comparison of this pollen record with that from a nearby pollen diagram also prepared at high-temporal resolution shows the ability of pollen records to record short-period climate variations and disturbances.