Biogenic nitric oxide emission of mountain soils sampled from different vertical landscape zones in the Changbai Mountains, northeastern China.

Nitric oxide (NO) is an important component in nitrogen biogeochemical cycling produced through biological processes of nitrification and denitrification in soils, but the production and the consumption processes of NO in temperate mountain soil are less understood. Through laboratory experiments focusing on NO biogenic emissions from six kinds of mountain soils sampled from different vertical landscape zones, that is, coniferous and broadleaf mixed forest (CBF), fir forest (FF), spruce forest (SF), Erman's birch forest (EBF), alpine tundra (AT), and volcanic ash (VA), in the Changbai Mountains, northeastern China, we found that the optimum water-filled pore space (WFPS) for NO production varies between 22.5% and 35% for a range of mountain soils. The optimum soil moisture for the maximum NO emission for a certain soil type, however, was constant and independent of soil temperature. The NO emission potential for forest soils was about 7-50-fold higher than tundra soil and volcanic ash, indicating that it is strongly influenced by nutrient contents in soils. On the basis of laboratory results and field monitoring data, the average NO fluxes from these mountain soils were estimated to be 0.14-29.56 ng N m(-2) s(-1) for an entire plant growth period. NO emissions mainly occur in wet season for CBF and FF, but in dry season for other soil types.