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

CH 4 emission in the Arctic has large uncertainty due to the lack of mechanistic understanding of the processes. CH 4 oxidation in Arctic soil plays a critical role in the process, whereby removal of up to 90% of CH 4 produced in soils by methanotrophs can occur before it reaches the atmosphere. Previous studies have reported on the importance of rising temperatures in CH 4 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 4 oxidation in Arctic soils. In this study, we demonstrate that excessive levels of available N in soil cause an increase in net CH 4 emissions via the reduction of CH 4 oxidation in surface soil in the Arctic tundra. In vitro experiments suggested that N in the form of NO 3 - is responsible for the decrease in CH 4 oxidation via influencing soil bacterial and methanotrophic communities. The findings of our meta-analysis suggest that CH 4 oxidation in the boreal biome is more susceptible to the addition of N than in other biomes. We provide evidence that CH 4 emissions in Arctic tundra can be enhanced by an increase of available N, with profound implications for modeling CH 4 dynamics in Arctic regions.