Attenuation of Methane Oxidation by Nitrogen Availability in Arctic Tundra Soils.

CH emission in the Arctic has large uncertainty due to the lack of mechanistic understanding of the processes. CH oxidation in Arctic soil plays a critical role in the process, whereby removal of up to 90% of CH produced in soils by methanotrophs can occur before it reaches the atmosphere. Previous studies have reported on the importance of rising temperatures in CH oxidation, but because the Arctic is typically an N-limited system, fewer studies on the effects of inorganic nitrogen (N) have been reported. However, climate change and an increase of available N caused by anthropogenic activities have recently been reported, which may cause a drastic change in CH oxidation in Arctic soils. In this study, we demonstrate that excessive levels of available N in soil cause an increase in net CH emissions via the reduction of CH oxidation in surface soil in the Arctic tundra. In vitro experiments suggested that N in the form of NO is responsible for the decrease in CH oxidation via influencing soil bacterial and methanotrophic communities. The findings of our meta-analysis suggest that CH oxidation in the boreal biome is more susceptible to the addition of N than in other biomes. We provide evidence that CH emissions in Arctic tundra can be enhanced by an increase of available N, with profound implications for modeling CH dynamics in Arctic regions.