[N2O emission by trees under natural condition].

The sources of N2O, one of the major greenhouse gases in the atmosphere, are still unclear till now. It was previously thought that only soil microbial process produced N2O. The aim of this study was to provide evidences that plant can emit N2O under the natural condition. The measurement of aboveground vertical profiles of N2O concentrations were conducted within coniferous-deciduous mixed forests in Changbai Mountain, China. Significant high N2O concentrations were found at or near the height of canopy. High concentrations in profiles were 3.03% to 64.9% higher than the "normal concentrations". Differences between the high concentrations and the "normal concentrations" were statistically significant. The simultaneous occurrence of high concentrations at/nearby the canopy height and normal concentrations at the trunk space height indicated an efflux of N2O from foliage to atmosphere. This study afforded evidences supporting that plant per se, besides forest soil, was an important source of atmospheric N2O in a forest ecosystem.