Stimulating effects of snow cover on gaseous nitrogen emissions are intensified by biological soil crusts

Abstract

Winter weather patterns are changing due to global climate change, which impacts the soil nitrogen cycle and greenhouse gas flux in these ecosystems, particularly the snow cover in temperate deserts. Biological soil crusts are important soil communities of the desert ecosystem and are sensitive to environmental changes. However, knowledge of the responses of gaseous nitrogen emissions from biological soil crusts to changes in snow cover is limited. In this study, the effects of snow cover on gaseous nitrogen emissions and the abundance of nitrifier (amoA) and denitrifier (narG, nirS, nirK, nosZ) genes were investigated in three snow cover treatments (snow removal, ambient snow, and increased snow depth). Snow cover significantly affected N2O and NO emissions from bare sand and biological soil crusts in winter. The abundance of denitrifier genes in bare sand and biological soil crusts and the abundance of nitrifier genes in moss crust increased with the depths of snow addition. N2O emissions increased with the successional stages of biological soil crusts during the winter. Both N2O and NO emissions from bare sand and biological soil crusts peaked in the freeze–thaw period (March) and were lowest in mid-winter (January). The emissions of N2O increased with increasing the abundance of amoA, nirK and nosZ genes. Our findings show that N2O emissions generally increased with increasing snow cover through their effects on nitrogen cycle related functional microbial groups. These effects were regulated by the types of biological soil crust, which can increase the effect of snow cover in winter.