Soil respiration and methane flux in adjacent forest,grassland, and cornfield soils in Hokkaido,Japan

Soil respiration and methane flux from adjacent forest, grassland, and cornfield were measured by using the closed chamber method from June to November, 1999 in Shizunai, Hokkaido, Japan, where the soil was an Aquic Humic Udivitrands derived from volcanic ash. The forest soil absorbed methane, at arate ranging from -0.12 to -0.02 mg C m_-2 h_-1, while the grassland soil emitted methane, at a rate ranging from undetectable levels to 0.18 mg C m_-2 h_-1. In the cornfield soil methane flux ranged from -0.01 to 0.04 mg C m_-2 h_-1. The soil respiration rate varied from 3 to 230 mg C m_-2 h_-1, 27 to 372 mg C m_-2 h_-1, and 29 to 156 mg C m_-2 h_-1 for the cornfield, grassland, and forest soils, respectively. Linear regression analysis demonstrated that the methane flux rate was positively correlated with the soil water-filled pore space (WFPS), and negatively correlated with the relative gas diffusion coefficient (D/D _o) and air-filled pore space (AFPS). Soil respiration rates were positively correlated with the soil temperature at all the sites. The Q ₁₀ value was 4.8, 3.3, and 1.9 for the cornfield, grassland, and forest soils, respectively.