Methane oxidation in boreal peat soils treated with various nitrogen compounds

The potential methane consumption activity was examined in various plant communities of a boreal Sphagnum-dominated Bakchar bog of West Siberia. In aerobic laboratory incubations, the peat consumed methane with the maximal rates varied from 17 to 153 nmol CH4 h(-1)g(-1).The highest oxidation took place in the peat from the cotton grass and dwarf shrub-cotton grass communities. The addition of different N-compounds inhibited CH4-uptake and was not a simple influence of shift in ionic balance (`salt effect'). The introduction of sodium chloride resulted in significantly weaker inhibition effect than the same amount of nitrite and nitrate salts. The inhibition occurred at NH4+-N concentrations exceeding 100 mg kg(-1), which was more than 200 times higher native N-content in peat. Communities with high CH4-uptake activity were more sensitive to ammonium. The inhibition by ammonium was non-competitive. The inhibition by ammonium was mainly due to the toxic action of nitrite and/or nitrate produced by nitrifiers. A strong positive correlation was found between the potential nitrifying activity and inhibition of CH4-uptake in ammonium-treated peat (R-2= 0.87). The oxidized N-compounds were more strong inhibitors than ammonium and their toxicity increased in the following range: NH4+< NO2-< NO3-.