Methane consumption in temperate and subarctic forest soils: rates, vertical zonation, and responses to water and nitrogen.

Rates of methane consumption were measured in subarctic coniferous and temperate mixed-hardwood forest soils, using static chambers and intact soil cores. Rates at both sites were generally between 1 and 3 mg of CH(4) m day and decreased with increasing soil water contents above 20%. Addition of ammonium (1 mumol g of soil) strongly inhibited methane oxidation in the subarctic soils; a lesser inhibition was observed for temperate forest samples. The response to nitrogen additions occurred within a few hours and was probably due to physiological changes in the active methane-consuming populations. Methane consumption in soils from both sites was stratified vertically, with a pronounced subsurface maximum. This maximum was coincident with low levels of both nitrate and ammonium in the mixed-hardwood forest soil.