Profile

Julien Arsenault
Postdoctoral fellow
Department of Applied Geomatics
University of Sherbrooke
julien.arsenault2@usherbrooke.ca

Supervised by:

Frédéric Bouchard (Regular member)

Research project description

Effects of Permafrost Degradation on the Biogeochemical Cycle Dynamics of Peatland Pools of the Hudson Bay Lowlands

Introduction: The permafrost that characterizes the wetlands of northern regions around the globe is thawing at an increasingly rapid pace due to climate change. The decomposition of organic matter (OM) in these soils, which contains large quantities of carbon (C), nitrogen (N), and phosphorus (P) stored sometimes for millennia, leads to the emission of greenhouse gases and the release of nutrients essential for plant growth. Permafrost thaw also leads to the formation of ponds in peatlands. These ponds have different physical characteristics than the surrounding soils, allowing certain biological and chemical processes to occur at higher rates than in the soils. The increasing number of ponds in northern peatlands could accelerate the pace at which these processes take place. However, the impacts of pond development on peatlands and the fate of soil OM remain understudied.Objectives: The main objective of my research project is to assess the effects of permafrost degradation on the biogeochemistry of C, N, and P in subarctic peatland ponds of the Hudson Bay lowlands. The project specifically aims to i) characterize the state of permafrost degradation in peatland ponds located at the ecotone between boreal forest and tundra, and at the intersection of continuous and discontinuous permafrost zones; ii) quantify the concentrations and forms of C, N, and P in peatland ponds and in the water, ice, and peat of surrounding soils, along a permafrost degradation gradient; and iii) determine the influence of permafrost degradation on the accumulation and export of C, N, and P from the studied peatlands.Study sites: My work is conducted in the Churchill region (Manitoba) and Wapusk National Park. This area encompasses continuous permafrost zones (to the north and near the coasts), discontinuous and sporadic permafrost (in the central and southern areas), forming the second-largest peatland complex globally, storing approximately 30 Gt of carbon (Packalen et al., 2014). However, it is susceptible to rapid pond development in the coming years (Dyke & Sladen, 2022).Material and methods: The studied peatlands follow a gradient of permafrost degradation, from low to high, extending from the southern boundary of Wapusk National Park to the vicinity of the town of Churchill. To assess the impact of permafrost degradation on the biogeochemistry of C, N, and P in the peatlands of the region, at each site, I am investigating the composition, age, and origin of the organic matter found in the water, ice, and peat.References: Packalen, M. S., Finkelstein, S. A., & McLaughlin, J. W. (2014). Carbon storage and potential methane production in the Hudson Bay Lowlands since mid-Holocene peat initiation. Nature Communications, 5, 1–8. Dyke, L. D.,

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