N2O AND CO2 DYNAMICS IN A FROZEN PASTURE SOIL

Sébastien Lange, Suzanne Allaire, Mario ALberto Cuellar Castillo, Pierre Dutilleul

In the proceedings of: GeoQuébec 2015: 68th Canadian Geotechnical Conference & 7th Canadian Permafrost Conference

Session: Permafrost (Other) / Pergélisol (autre)

ABSTRACT: 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 these 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.

RÉSUMÉ: Peu de recherches ont porté sur la dynamique du CO2 and N2O en sols gelés et couverts de neige. La variabilité spatio-temporelle de ces gaz a été mesurée du pré-gel au dégel dans un pâturage durant deux saisons froides. Trois périodes ont été identifiées concernant leur dynamique. Leur variability spatio-temporelle était différente et dépendait de celle de -dessus de 0°C. Toutefois, leur dynamique était similaire et leur concentration a augmenté lorsque le sol était gelé, si bien que leur concentration était corrélée à 90% sous cette condition. Deux occurrences de relâchement des gaz ont été observées au dégel dans une courte période de temps. Le premier, similaire pour les deux, microorganismes.

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