Emissions of N2O and NO and net nitrogen mineralization in a boreal forested peatland treated with different nitrogen compounds

Abstract

Fluxes of nitrous oxide (N2O) and nitric oxide (NO) were measured on a drained and forested peatland in 1992-1995. Net mineralization and nitrification were studied in situ in 1993-1994. Nitrogen additions in 1992 as KNO3, NH4Cl, or urea (100 kg N ·ha-1) were used to study the fate and transformations of N in peat. The mean N2O emissions during the growth season in 1993 were 1.9, 2.6, 3.3, and 3.5 mg N ·m-2·day-1in the control soil, KNO3, NH4Cl, and urea-treated soils, respectively. Mean NO fluxes during the growth season in 1993 averaged 0.3, 0.4, 0.7, and 0.6 mg N ·m-2·day-1in the control soil, KNO3, NH4Cl, and urea treatment, respectively. Annual net N mineralization was 87 kg N ·ha-1in the control soil and 107, 129, and 91 kg ·ha-1in the KNO3, NH4Cl, and urea-treated soils, respectively. Added N increased the fluxes of N oxides at least for a year after the treatments. The study showed that forests on drained N-rich peat soils may be significant sources of N2O and NO and that their production of nitrogenous trace gases is enhanced by additional N.