FLUXES OF NITROUS-OXIDE FROM BOREAL PEATLANDS AS AFFECTED BY PEATLANDTYPE, WATER-TABLE LEVEL AND NITRIFICATION CAPACITY

Feat soils with high nitrogen content are potential sources of nitrous oxide (N2O). Fluxes of nitrous oxide were measured in situ on nine vi rgin and ten drained peatlands of different hydrology and nutrient sta tus. Numbers of nitrifying bacteria were estimated in different layers of the peat profiles with a most-probable-number technique. Nitrifica tion potentials were determined in soil slurries of pH 4 and 6 from th e profiles of six peat soils. Many virgin peatlands showed low N2O upt ake. Lowering of the water table generally increased the average fluxe s of N2O from the soils, although more in minerotrophic (nutrient rich ) than in ombrotrophic (nutrient poor) sites. Ammonium oxidizing bacte ria were found on only two sites but nitrite oxidizers were detected i n almost all peat profiles. More nitrite oxidizers were found in drain ed than in virgin pear profiles. Nitrification was enhanced after lowe ring of the water table in minerotrophic peat but not in ombrotrophic peat. The N2O fluxes correlated positively with the numbers of nitrite oxidizers, nitrification potential, N, P and Ca content and pH of the soil and negatively with the level of water table (expressed as negat ive values) and K content of the soil.