Nitrite transformations in an N-saturated forest soil

Nitrite dynamics could be highly associated with forest N cycles. However, they have often been overlooked mainly because of the experimental difficulties that occur owing to chemical reactive nature of NO2−. We investigated NO2− dynamics in an N-saturated forest soil with a recently developed method using 15N. Soils were aerobically incubated for 145 h after 15NO2− addition, and changes in 14N and 15N concentrations of NO2−, NO3−, NH4+, and dissolved organic N (DON) were monitored. Simultaneous production and consumption of NO2− were observed. The turnover rate of NO2− was even faster than that of NH4+ and NO3− calculated in other studies. Of the added 15NO2−, 28.5% was oxidized to NO3− and 17.8% was incorporated into the DON pool within 4 h. The remainder might be emitted as gas or fixed by insoluble soil organic matter. Our results suggested that rapid NO2− turnover could be a major driving force for N transformations in forest soil.