Microbial mechanisms and ecosystem flux estimation for aerobic NO y emissions from deciduous forest soils

Significance Reactive nitrogen oxides (NO y ) can negatively impact air quality, visibility, and human health. Biogenic sources of NO y are poorly understood despite their growing importance in future scenarios of decreasing anthropogenic emissions. Using soil from two forest stands that differ in plant and soil characteristics, we show that ammonia-oxidizing bacteria and to a lesser extent, heterotrophic microbes are the primary producers of NO y . Moreover, we show that ammonia-oxidizing archaea contribute little to NO y yet play a central role in determining nitrogen-cycle rates in forests. Given known relationships between tree species and soil characteristics, we conclude that NO y emissions are spatially variable, occurring in hotspots throughout the eastern United States.