抄録
Many streams of Kureha Hill, Toyama, Japan, are believed to suffer from nitrogen saturation because of their extremely high concentration of nitrate. The enhanced nitrification by nitrogen saturation would accelerate an emission of N2O to the atmosphere. We measured the N2O flux to the atmosphere both from a nitrogen-saturated forest floor and from a non-nitrogen-saturated forest floor in order to determine the effect of nitrogen saturation on the emission of N2O.
As a representative of a nitrogen-saturated stream, Hyakumakidani was selected because it contains a high concentration of nitrate as 164μmol/l. Sannokuma Stream on Imizu Hill, adjacent to Kureha Hill, was selected as a non-nitrogen-saturated stream because it contains no more than 9μmol/l of nitrate. Both forested watersheds are covered mainly by hardwood. Their vegetation, soil types, and nitrogen deposition are similar.
The average N2O flux from the nitrogen-saturated watershed, Hyakumakidani, was 2.42μg-N/m2/h from October 2004 to May 2005, while it was only 0.21μg-N/m2/h from the non-nitrogen-saturated watershed.This result clearly shows that nitrogen saturation could accelerate N2O emission to the atmosphere.
