68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

N2O AND CO2 DYNAMICS IN A FROZEN PASTURE SOIL

Session: Permafrost (Other) / Pergélisol (autre)

Sébastien Lange, Université Laval, Dpt sol et génie agroalimentaire (Canada)
Suzanne Allaire, Université Laval, Dpt sol et génie agroalimentaire (Canada)
Mario ALberto Cuellar Castillo, Université Laval, Dpt sol et génie agroalimentaire (Canada)
Pierre Dutilleul, McGill University, Dpt. of Natural Resource Sciences (Canada)

Since gas dynamics in agricultural soils is mainly studied during plant growth, only few researches have focus on their dynamics in frozen soils covered with snow. Spatio-temporal concentrations of CO2 and N2O have been measured from the pre-freezing to the thawing period in a pasture soil during two cold seasons. Three periods related to gas dynamics were observed during both cold seasons. Both gases behaved differently during pre-freeze and thawing periods and their spatial dynamics depended on the spatial and temporal variability of soil temperature as long as the soil surface temperature was above 0°C. However, both concentrations increased and their spatial variability was independent from temperature as long as the soil was frozen, under which condition their correlation was up to 90%. Two main occurrences of gas release occurred during thawing, one related to trapped gases, similar for both gases, and the other to reactivation of microorganisms, different between both gases.