Impact of the Younger Dryas Cooling Event Upon Lowland Vegetation of Maritime Canada

Abstract

The aim of this research is to determine the response of the vegetation in coastal Maritime Canada to the Younger Dryas cooling event (°10 800—10 000 14 C yr BP) that interrupted the warming trend following the last glaciation. Detailed paleoecological studies were carried out on the organic, pollen, and plant macrofossil content of sediment cores recovered from six small lakes in New Brunswick and Nova Scotia. Results show that there was regional variation in the vegetation response to the cooling. Records from Splan Pond, Mayflower Lake, and Little Lake show a change from boreal forest or woodland to shrub—tundra as a result of the cooling, while Lac a Magie shows floristic changes of shrub—tundra, and Chase Pond and Main—a—Dieu Pond show replacement of shrub—tundra by herb—tundra in response to the Younger Dryas. The climate warming signifying the end of the Younger Dryas caused succession from shrub—tundra to boreal forest, or from herb—tundra to shrub—tundra. Macrofossil evidence of arctic/alpine species such as Dryas integrifolia, Salix herbacea, and Cassiope hypnoides attests to the severity of the Younger Dryas cooling. Vegetation changes in response to the climate cooling and warming, marking the onset and termination of the Younger Dryas respectively, were very rapid, taking only 50—100 yr. However, the response of some taxa, such as dwarf birch, appears to have lagged the onset of the climate change by several decades, although the duration of the lag varies between sites.