A late-glacial-Holocene palaeoecological record from Pye Lake on the eastern shore of Nova Scotia, Canada

Pollen and chironomid analyses and radiocarbon dating at Pye Lake on the eastern shore of Nova Scotia are used to outline the vegetation and climatic history of the area. The coast was deglaciated prior to approximately 12 200 (super 14) C BP (14 300 cal BP), and herbaceous tundra vegetation invaded the area. Midge-inferred maximum summer surface-water temperatures in the lake ranged between 9 and 11 degrees C. Subsequent gradual warming to approximately 18 degrees C by 10 800 (super 14) C BP (12725 cal BP) favoured the migration of a variety of herbaceous and shrub taxa into the region. Rapid cooling to approximately 10 degrees C saw vegetation revert to herbaceous tundra communities. This interval, related to the Younger Dryas cold interval of the North Atlantic and Europe, lasted until approximately 10 000 (super 14) C BP (11630 cal BP). The climate then warmed again to conditions similar to those that prevailed immediately before onset of Younger Dryas cooling. Further warming saw successive tree species migrate into the area until, by the mid-Holocene, the forests contained most of the taxa prevalent today. Since approximately 3500 years ago, cooling of the climate has favoured conifer species over broad-leaved taxa. Agriculture and logging practices in the last 150 years have altered the forest composition, but pollen analysis of the most recent sediments cannot resolve these changes adequately.