Methane oxidation in Japanese forest soils

Abstract

To evaluate the CH 4 uptake rate in Japanese deciduous and coniferous evergreen forest soils, the CH 4 flux and CH 4 concentration in soil gas were measured at seven sites in central Japan. The CH 4 uptake potential was calculated from incubation of soil cores. The CH 4 fluxes at all sites were negative (uptake by the soils) at every sampling time. The CH 4 uptake rate was very high (7.6 mg CH 4 m −2 d −1) in one deciduous forest soil. Fluxes were highly correlated to the air temperature except a coniferous forest site. The most active layer of CH 4 uptake in each plot differed with site: subsurface (10–15 cm) at two coniferous forest sites and topsoil (0–5 cm) at the other five sites. The potential of the subsurface layer to oxidize CH 4 made a substantial contribution to soil CH 4 uptake mechanisms, especially when the topsoil had a low ability to oxidize CH 4. Methane uptake rates were nine times higher than those of previous studies. The soil CH 4 uptake rate on a global scale may be underestimated.