The impacts of changes in snowfall on soil greenhouse gas emissions using an automated chamber system

With increasing global surface temperature, snow cover has decreased in many regions. Snow is an effective insulator, so reduced snow cover will enhance soil freezing and increase the depth of frost, and the frequency of freeze-thaw cycles is likely to increase due to reduction of snowpack thickness. Freeze thaw cycles can strongly impact soil C and N dynamics. We investigated the winter and spring response of soil greenhouse gas emissions (CO₂, CH₄ and N₂O) to changes of snow depth in a corn-soybean-wheat cropping system.

This study was established in 2010 at the Kellogg Biological Station (KBS) after wheat rotation prior to corn. The experiment is a completely randomized design (CRD) with three levels of snow depth: ambient, double snow depth, and no snow. Each level had four replicates. Twelve automated chambers were randomly assigned to treatments and greenhouse gas fluxes measured 4 times per day in each plot.

There were more freeze-thaw cycles in the no snow treatment than in the ambient and double snow treatments. Soil temperature at 5 cm depth was more variable in the no snow treatment than in the ambient and double snow treatments. CH4 fluxes were uniformly low with no significant difference across three treatments. CO2 showed expected seasonal changes with the highest emission in spring and lowest emissions through the winter. N2O peaks were higher in spring due to freeze thaw effects and cumulative N2O fluxes were substantially higher in the no snow treatment than in the ambient and double snow treatments.