Peatland succession and long-term apparent carbon accumulation in central and northern Ontario,Canada

Abstract

Despite their importance as globally significant carbon (C) stores, basic knowledge of post-glacial peatland history and C accumulation are lacking for the Canadian Boreal Shield and James Bay Lowland (JBL) of central and northern Ontario, Canada. Radiocarbon dates, plant macrofossil analysis, and soil C estimates from an eight-core transect of the JBL and surrounding regions are used to reconstruct the timings and patterns of fen to bog transitions, and the ranges and patterns of long-term apparent rate of C accumulation (LARCA). Peatland initiation lagged the retreat of the Laurentide ice sheet, the drainage of glacial lakes, and isostatic uplift by 810–6050 years. Transition from Carex-dominated fen to Sphagnum-dominated bog had a median timing of 3500 years following peatland establishment and ranged from 640 to 6970 years. LARCA was variable geographically and over time with median values ranging from 13.4 to 31.6 g C/m²/yr. LARCA anomalies were generally high ~6.1 kyr (kyr = 1000 calibrated years before present (cal. yr BP)) for southern sites, and ~2.5 kyr for the most northern sites, and may be associated with elevated moisture as inferred from a brief review of regional proxy reconstructions. Some sites displayed high LARCA anomalies, changes in plant ecology, or southern site initiation, which may have also been driven by a moist Hypsithermal Period occurring ~4.5 kyr. LARCA increases were not generally associated with high-temperature anomalies during the warm ‘Medieval Climate Anomaly’ compared with the cooler ‘Little Ice Age’; however, there is evidence that the establishment of modern permafrost during the late-Holocene negatively affected C accumulation.