2011 Volume 46 Issue 1 Pages 30-36
At elevated atmospheric CO2 concentrations, the soil CH4 flux may be mediated by plant physiology, including the transpiration rate and water use efficiency. To investigate the effect of elevated CO2 on atmospheric CH4 consumption by well-drained forest soil, we measured the soil CH4 flux at the Free Air CO2 Enrichment (FACE) site of Hokkaido University during two growing seasons (2008 and 2009). Fumigation with CO2 began in June 2003, since when the plots have either been exposed to ambient levels or enriched with CO2 at 130 μL L-1. We also studied two soil types, brown forest soil and volcanic ash soil, which are widely distributed in northern Japan. The soil CH4 flux and soil water content were measured simultaneously on four occasions at monthly intervals during each growing season. In both types of soil, the elevated CO2 plot experienced an approximately 50 % lower soil CH4 consumption rate than in the ambient CO2 plot. However, there was no significant difference in soil CH4 consumption between two soil types. Regardless of the soil type, soil CH4 consumption was observed at all measurement points in the ambient CO2 plot, but approximately 13 % of all sampling points in the elevated CO2 plot experienced net CH4 production, suggesting that increases in soil moisture influence CH4 oxidation at elevated CO2 concentrations.