Prolongation of soil frost resulting from reduced snow cover increases nitrous oxide emissions from boreal forest soil

Emission rates of the greenhouse gas, nitrous oxide (N 2 O), from northern upland forest soils are generally low. According to recent climate scenarios, the snow cover in the boreal region is predicted to decrease and which will result in lower soil temperatures. In this study, we investigated whether lower soil temperatures during winter can also trigger N 2 O emissions from boreal forest soils with originally low N 2 O emissions, as has earlier been shown for northern agricultural soils with higher N 2 O emissions. We measured the N 2 O emissions from a spruce forest in eastern Finland where the soil temperature was changed by manipulating snow-pack thickness and using insulating covers. The effects of the treatments on methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes were also studied for comparative purposes. The results show that there can be an increase in N 2 O emissions and CO 2 production rate from boreal upland forest soils resulting from a thinner snow cover that causes a prolongation of soil frost. Reducing the snow pack thickness had only minor effects on the CH 4 fluxes.