Boreal forests of Western Canada are bordered by two treelines (southern at 53°N, northern at 62°N), both of which are moving northwards with the ongoing climate change. This study of organic matter cycling in 23 lakes crossing 6 ecological regions (from tundra to Prairies) is a part of a multidisciplinary project bringing together the Dene and Inuit communities with laboratories specialising in biogeochemistry and palaeolimnology. To identify differences in greenhouse gas (GHG) production across these ecoregions, limnological data collected in situ were complimented by anoxic incubation experiments, measuring CO₂ and CH₄ production rates. Lakes with deciduous forest catchments (transition from boreal forest to Prairies) had the highest GHG production rates, possibly caused by a combination of more labile terrestrial organic matter inputs and warmer temperatures (than the lakes within coniferous forests and tundra), and a tendency to stratification (relative to more open grassland lakes). Overall, the southern lakes had higher productivity and higher CH₄ concentrations, while surface N₂O concentrations were higher in northern lakes. Surprisingly, northern boreal lakes were also prone to eutrophication – likely as a consequence of forest fires, increasingly common in these areas. Warmer water temperatures, stronger stratification, northward migration of deciduous trees and Arctic greening will likely lead to increased primary production and accumulation of GHG, followed by potentially deteriorating water quality with negative impacts on fish and northern communities.

Primary Presenter: Vilmantas Prėskienis, University of Quebec in Chicoutimi (preskienis@yahoo.com)

Authors:

Vilmantas Prėskienis, University of Quebec in Chicoutimi  (vilmantas_preskienis@uqac.ca)

Henriikka Kivilä, University of Quebec in Chicoutimi  (ehkivila@etu.uqac.ca)

Matthew Bogard, University of Lethbridge  (matthew.bogard@uleth.ca)

Jules Blais, University of Ottawa  (Jules.Blais@uottawa.ca)

Dënë Cheecham-Uhrich, Clearwater River Dene Nation  (dene.cheecham-uhrich@mltc.ca)

Milla Rautio, University of Quebec in Chicoutimi  (milla_rautio@uqac.ca)