Methane consumption and soil respiration by a birch forest soil in West Siberia

Methane and carbon dioxide fluxes were measured in a birch forest soil in West Siberia, in August 1999, June 2000 and September 2000. The study site had a very thick organic horizon that was subject to drought during the observation periods. The soils always took up CH₄, while CO₂ was released from the surface to the atmosphere. CH₄ consumption and CO₂ emission rates ranged from 0.092 to 0.28 mg C m⁻² h⁻¹ and from 110 to 400 mg C m⁻² h⁻¹ respectively. The CH₄ consumption rate and soil temperatures showed significant relationships for individual measurements. The soil respiration rate was weakly correlated with individual soil temperatures. This study examined the effect of current and lagged soil temperatures at a depth of 5 cm on CH₄ consumption and soil respiration. The variation in the correlation coefficient between CH₄ consumption and lagged soil temperature was greatest at a 4-h lag, whereas that for soil respiration showed a gentle peak at lags from several hours to half a day. This difference in the temperature-related lag effect between CH₄ consumption and soil respiration results from differences in the exchange processes. Neither flux showed any correlation with soil moisture. The limited variation in soil moisture during our observation period may account for the lack of correlation. However, the droughty soil conditions resulted in high gas diffusion and, consequently, high CH₄ consumption.