E-mail: gabriel.magnan.1@ulaval.ca

Historical fire frequencies of ombrotrophic peatlands in the Radisson Region of northern Québec
Supervisor : Martin Lavoie
Co-supervisor : Serge Payette

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Fire is the most important natural disturbance in the boreal forest. Dendrochronological techniques have been used to reconstruct the fire frequency of the forests in northern Québec for the last century. However, the fire frequency of the northern peatlands has not been well studied. While peatlands are often considered as barriers that inhibit the spread of fire, the presence of surficial and stratigraphic charcoal layers within the northern peatlands indicate that these ecosystems are in reality recurrently affected by fire. The principal aim of this project is to reconstruct the fire chronologies of three ombrotrophic peatlands in the region of Radisson (53°N; 77°W) over a several thousand year time scale. The specific objectives are: 1) to reconstruct the historical fire events that occurred during the ombrotrophic phases of the peatlands with the aid of paleobotanical indicators, 2) to calculate the fire frequency and the time intervals between successive fires, and 3) to reconstruct the post-fire vegetal succession of the peatland systems. In order to obtain these objectives, peat cores will be sampled from two points at each of the studied peatlands. A fine resolution (1 cm stratigraphic interval) paleoecological analysis of the cores will then be conducted in the laboratory. The fire chronologies of the peatlands will then be established with the aid of macroscopic charcoal analysis (>150 μm pieces, which are indicators of local fires). Post-fire vegetation succession will be determined through plant macrofossil analysis, i.e., pieces of vascular plants and sphagnum. Using a precise temporal chronology based on AMS and Pb-210 dates, it will be possible to estimate the time between consecutive fires and verify if the fire frequency varies through time as a function of peatland characteristics and environmental conditions. Finally, the fire frequencies of the peatlands will be compared with those of the regional forests as reconstructed through high resolution pollen and microscopic and wood charcoal analysis conducted on cores obtained from each of the sites.