POTENTIAL DENITRIFICATION AND N2O FORMATION IN DRY EUROPEAN CONIFEROUS FOREST SOILS

N2O emission from forest soils was measured in intact soil cores or in situ in seven Norway spruce and Scots pine forests. Some of the sites are associated with the CORE project. All soils had very low pH values, 3.2-4.5. The daily rate of N2O emission varied between 0.04 and 1.2 mg N2O-N m(-2) at 10-13 degrees C. After addition of nitrate and acetate the N2O emission increased. The additions corresponded to 10 mM concentrations of nitrate and acetate in the enclosed soil sample, and in some experiments, five and ten times higher concentrations were also provided, usually resulting in increased rates. Denitrification in the forest soils was limited by available nitrate. At low pH, N2O seems to be the major end product and there was no effect of adding acetylene. The annual N loss from denitrification estimated on the basis of single summer or autumn measurements was less that 4 kg N2O-N ha(-1).