CH4 oxidation by tundra wetlands as measured by a selective inhibitor technique

Abstract

Rates of methane (CH4) oxidation were measured in three wet sedge communities on Alaska's North Slope in 1993 and 1995 using the selective inhibitor methyl fluoride (CH3F). Comparison of CH4 flux prior to inhibition (net flux) with flux after inhibition (gross flux) enables one to infer CH4 oxidation rates by difference. Oxidation rates from Franklin Bluffs, Sagavanirktok River floodplain, Toolik Lake Inlet, and Toolik Lake Outlet averaged 24.9, 14.7 (1.6), (17.6), and 25.2 (49.8) mg CH4/m2/d in 1995 (1993), respectively. Plot level data suggest that oxidation rates vary greatly spatially and temporally down to the meter scale. As a percentage of flux, however, mean CH4 oxidation rates of 13.4, 21.7 (2.0), (16.5), and 19.4 (38.0)% at Franklin Bluffs, Sagavanirktok River, Toolik Lake Inlet, and Toolik Lake Outlet in 1995 (1993), respectively, were seen to be rather uniform over the region. The effects of temperature on CH4 production appear to be the dominant control on CH4 oxidation rates in wet sedge environments as opposed to soil moisture dependency in upland soils. Nutrient fertilization was not found to influence the fraction of CH4 lost to oxidation. This suggests that CH4 oxidation, while significant in tundra wetlands, may consume a near-constant fraction of available CH4. Copyright 1998 by the American Geophysical Union.