Determination of Methane Oxidation in the Rhizosphere of Sagittaria lancifolia Using Methyl Fluoride

Abstract

Methane oxidation in the rhizosphere of wetland plants may significantly attenuate methane losses from wetland soils to the atmosphere. Our objective was to measure the extent of methane production and oxidation in the rhizosphere of a common wetland plant (Sagittaria lancifolia L. Per.). Methyl fluoride (CH{sub 3}F), a water-soluble gas and a specific inhibitor of methane oxidation, was used in conjunction with a closed chamber technique to determine rhizospheric methane oxidation in a greenhouse study. Rhizospheric methane oxidation was also estimated using a mass balance approach. Measurements of soil methane production were made using short-term anaerobic incubations of soil. Soil methane production and plant emissions of methane were inversely related to plant biomass, presumably because larger plants transported more O{sub 2} into the rhizosphere and inhibited methanogenic activity. Methane oxidation averaged 65% (SD = 24%, n = 14) as estimated by the CH{sub 3}F technique and 79% (SD = 20%, n = 14) using the mass balance approach. Methane oxidation percentage calculated by either method was not correlated to plant biomass. Results suggest that rhizospheric methane oxidation is an important attenuator of methane emissions from vegetated wetland soils. 24 refs., 4 figs.