Department of geography
Pascale Roy-Léveillée (Regular member)
Najat Bhiry (Regular member)
Introduction: Old Crow Flats (OCF) is an arctic lowland ecosystem within the continuous permafrost zone of northern Yukon. A wetland of international significance, the region is composed of thousands of lakes, meandering rivers, and permafrost features that have evolved over the last 15,000 years. Most of the lakes are susceptible to change through erosion, expansion, and eventual drainage, leaving behind large drainage basins with remnant ponds and new vegetation growth. In recent years, residents of Old Crow have reported drastic changes to their landscape that align with climate driven landscape change in the circumpolar North. Objectives: The purpose of this case study is to investigate the evolution of drained basins older than 100 years within the forest/tundra ecotone and to compare their evolution with recently drained lakes: Characterize vegetation succession and post-drainage permafrost restoration of ancient lakes; Examine whether the rapid landscape change we see today (last 100 years) is typical or accelerated by climate change. Study sites: The study sites are located on drained lake basins in the boreal forest/tundra ecotone in Old Crow Flats, Yukon, within the Traditional Territory of the Vuntut Gwitchin First Nation. The region is characterized by a subarctic continental climate with long/cold winters, short/mild summers, and limited advective precipitation. Permafrost is 60 m thick in Old Crow Flats, with active layer thicknesses ranging from 25 to 55 cm at the study sites. The terrestrial surface of the tundra sites is dominated by a mixture of vertical shrub tundra and dwarf shrub tundra, as well as sphagnum-dominated peatlands. Spruce forests dominate forested areas adjacent to major rivers, streams, and some south-facing slopes. Remnant ponds in the basins support an abundance of aquatic macrophytes and floating mats. Material and methods: Peat samples have been collected from various basins for carbon dating, along with preliminary geophysics to determine whether permafrost is recovering within the basin since drainage. Further research includes reconstructing vegetation succession within the basins. Peat and sediment cores will be analyzed for macrofossils and pollen. References: Bandara, S., Froese, D., Porter, T. J., & Calmels, F. (2020). Holocene pore‐ice δ18O and δ2 H records from drained thermokarst lake basins in the Old Crow Flats, Yukon, Canada. Permafrost and Periglacial Processes, 1–12. Lantz, T. C. (2017). Vegetation Succession and Environmental Conditions following Catastrophic Lake Drainage in Old Crow Flats, Yukon. ARCTIC, 70(2), 177–189.
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