Development of a raised bog over 9000 years in Atlantic Canada

The chronostratigraphy of a coastal bog was studied in order to distinguish the roles of autogenic and allogenic factors in peatland development. Well-dated stratigraphical sequences from a peat cliff were used. The peatland shows three main vegetation phases: rich fen, poor fen and bog. Peat formation started around 9500 yr BP and the first expansion phase of rich fen occurred between 8550 and 7400 yr BP. The rich fen gradually changed to a poor fen through autogenic processes between 7620 and 5500 yr BP. It then became a bog in two major development phases, possibly in response to climate change, around 5250 yr BP (central part) and 2800 yr BP (margins). Expansion resumed after 5500 yr BP and terminated shortly after 2500 yr BP when the peatland had filled the basin. Although autogenic succession is the dominant process by which the peatland has evolved, climatic variability has also affected peat expansion and vegetation change. The influence of fire was very limited but topography played a major role in peat expansion. One major find is that climate change can trigger simultaneous but various responses in local vegetation, depending upon its position on the bog surface.