Nitric oxide emissions from soils: a case study with temperate soils from Saxony, Germany

Nitrogen oxides (NO x ) are involved in acid rain and ozone formation, as well as destruction. NO x are climate-relevant trace gases in the atmosphere. Atmospheric NO x originate from anthropogenic emissions (mainly combustion processes). NO from natural processes derives from thunderstorms and soil microbial processes. They may play a crucial role in soil–atmosphere feedback processes. This study aims to investigate NO x -emissions from soils under different land use, geographical and meteorological conditions. NO x -emissions were quantified in both field and laboratory experiments with a closed static chamber. Disturbed soil samples have been used for laboratory experiments. A climate chamber was used to regulate soil temperature of the samples. Field experiments showed that NO-soil emissions strongly depend on soil temperature. NO-emissions from a soil under meadow showed significant daily variations, unlike soil below spruce forest. Peak emission values were 18 μg NO–N m−2 h−1 above meadow and 1.3 μg NO–N m−2 h−1 under forest canopy. In addition, NO-emissions of meadow and forest soil were studied in a climate chamber, enhanced by an additional experiment with agricultural soil. These experiments revealed strong exponential correlations of NO-emissions and soil temperature. Maximum values reached above 400 μg NO–N m−2 h−1 from agricultural soils at soil temperatures above 50°C. This study shows that soil NO-emissions strongly depend on temperature, vegetation type and geographical position. Consequently, NO-emissions may have a positive feedback effect on climate change.