Mineralization of nitrogen and N2O production potentials in acid forest soils under controlled aerobic conditions

Some acid surface mineral soils from different forest vegetations and sites in central Japan were taken during April and October in 2003 to study the net N mineralization and N2O production potentials in the laboratory. Under the controlled aerobic conditions, 50 Pa C2H2 in the headspace can be used to study total gaseous-N losses during the aerobic mineralization and heterotrophic N2O production in acid forest soils. The net N mineralization of these acid forest soils and N2O-N production was variable with forest stands and with seasons, probably because of the quality of the litters and the variations of soil attributes. Three deciduous forest soils during two sampling reveal a higher potential for the total gaseous-N loss during the aerobic mineralization as compared with two coniferous forest soils. Heterotrophic nitrification among these acid forest soils accounted for the range from 37.0 to 76.3% of the total N2O production under the experimental conditions, and was variable with forest stands and with seasons. Some factors regulating the net N mineralization and N2O-N production were discussed in these acid forest soils.