Relative importance of climatic and autogenic controls on Holocene carbon accumulation in a temperate bog in southern Ontario, Canada

Abstract

Peat cores from Wylde Lake Bog in temperate southern Ontario, Canada, were examined to determine factors affecting Holocene ecological change and long-term rate of carbon accumulation (LORCA). By 10,250 cal. BP, a marsh was established, characterized by sediments with higher bulk density, highly decomposed material in the macrofossil record, and lower LORCA. By 8100 cal. BP, the marsh was replaced by a peat-accumulating fen dominated by herbaceous taxa and non- Sphagnum mosses. Around 4000 cal. BP, transition to a Sphagnum-dominated bog took place. These directional changes suggest a strong role for autogenesis, although periodic fluctuations in macrofossil assemblages and in LORCA suggest an important secondary role for climatic change and disturbance in explaining Holocene changes. LORCA remained fairly stable through the fen and bog zones, ~18 g C/m2/yr. In the high-resolution record spanning the most recent 1800 years, relatively higher values for LORCA and macrofossils associated with wetter conditions were recorded around 1400 cal. BP, partially coincident with the ‘Medieval Climate Anomaly’. LORCA decreases to minimum values for the record during part of the ‘Little Ice Age’ as woody macrofossils increase, suggesting a drier peat surface. The most recent portion of the record shows significant changes in LORCA and in bog vegetation associated with anthropogenic land clearance and damming. The charcoal record suggests that fire did not play an important role in peatland dynamics in the pre-industrial Holocene; however, a major anthropogenic fire in ad 1870 significantly altered the peatland, affecting surface vegetation heterogeneously.