Linking changes in snow cover with microbial nitrogen cycling functional gene abundance and expression in agricultural soil

Agricultural fields are responsible for significant production of the greenhouse gas nitrous oxide (N2O), especially at spring-thaw. In eastern Canada, climate change is predicted to result in warmer winter temperatures that may affect snow depth. Less snow might change soil temperature and moisture with potential consequences to the soil microbes, called denitrifiers and nitrifiers, involved in nitrogen cycling and N2O emissions. This study’s objective was to see how snow removal, passive snow accumulation (snow fence), and ambient snow influence the abundance and activity of denitrifier and nitrifier communities in a potato field over two winters. In the first winter, the greatest N2O emissions were observed in the snow removal plots, although the abundance of microbial communities was not affected. Changes in abundance of specific groups of denitrifiers and nitrifiers were observed, however, in passive snow accumulation . In the second winter, the largest N2O spring thaw emissions as well as the greatest denitrifier and nitrifier abundances were observed in the ambient snow treatment, suggesting a link between soil microbial communities and nitrogen cycling. The activity of denitrifier and nitrifier communities was not affected by snow depth, but was at its greatest during warmer conditions, indicating that microbial activity was promoted by freeze-thaw and summer conditions. Overall, changes in snow depth affected the abundance of denitrifier and nitrifier communities but not their activity. This suggests a greater role of the abundance of denitrifier and nitrifiers in spring thaw N2O emissions than was previously understood.