Chen Chen, McGill University - MacDonald Campus, Ste. Anne de Bellevue, QC, CANADA and Joann Whalen, Dept. Natural Resource Sciences, Mcdonald Campus, McGill University, Ste-Anne-de-Bellevue, QC, Canada
Nitrous oxide (N2O) is a greenhouse gas that is released from both aerobic nitrification and anaerobic denitrification processes. Soil moisture content is a key controller of the biochemical pathways leading to N2O emission, causing a switch between nitrification and denitrification processes. Earthworms increase N2O emissions from soil, but how earthworm activities are affected with fluctuations in soil moisture and the impact on soil N2O emission is unknown. The objectives of this study were to (1) evaluate the soil moisture effects on earthworm activities, and (2) link these effects to earthworm-induced N2O emissions under three soil moisture regimes (constant aerobic, constant anaerobic and fluctuating anaerobic-aerobic conditions). During a two month mesocosm study, earthworms from endogeic and anecic functional groups were kept in PVC tubes (10 cm diam. by 20 cm tall) with 5 replicates of each soil moisture regime. In each cycle, earthworm growth rate was measured and N2O flux were quantified every 1-2 d. From the preliminary results, N2O was emitted at a relatively constant rate from soil under constant anaerobic conditions, with and without earthworms. Nevertheless, earthworms significantly enhanced the N2O emission rate in the soil that was constantly aerobic. In the fluctuating soil moisture regime, soil without earthworms had higher N2O rate when the soil was wet, while the soil with earthworms had a high N2O emission rate even when the soil was dry. Our results will relate earthworms and N2O emissions under constant and fluctuating soil moisture conditions, which provide insights into N2O emission in riparian areas.