ENVIRONMENTAL-FACTORS INFLUENCING THE VARIABILITY OF METHANE OXIDATION IN TEMPERATE ZONE SOILS

The influence of organic matter and soil moisture on the spatial distr ibution of methane (CH4) oxidation was examined in temperate zone soil s by laboratory incubations. CH4 oxidation in soil cores exhibited dis tinct vertical zonation with maxima at 3 to 6 cm. The kinetic paramete rs of CH4 oxidation were measured in soil composites, The maximum rate of CH4 uptake, V-max ranged from 6.8 to 7.4 nmol hr(-1) g dry soil(-1 ) and the apparent half saturation constant, K-m, ranged from 17.4 to 19.9 (parts per million by volume) ppmv. Oxidation in random samples w as observed to be influenced by both soil moisture and organic matter contents. The rate of oxidation in each sample increased to a maximum with increasing water content and decreased with additional water. Max imum oxidation rates ranged from 2.2 to 9.0 nmol hr(-1) g dry soil(-1) at sample moisture contents of 18 to 51%. Organic matter content appe ars to explain the spatial variability of methane oxidation at optimal soil moisture contents. The oxidation maximum at this site was coinci dent with an organic matter content of 14% by weight and a gravimetric moisture content of 33%.