Increasing trends of soil greenhouse gas fluxes in Japanese forests from 1980 to 2009

Forest soils are a source/sink of greenhouse gases, and have significant impacts on the budget of these terrestrial greenhouse gases. Here, we show climate-driven changes in soil GHG fluxes (CO₂ emission, CH₄ uptake, and N₂O emission) in Japanese forests from 1980 to 2009, which were estimated using a regional soil GHG model that is data-oriented. Our study reveals that the soil GHG fluxes in Japanese forests have been increasing over the past 30 years at the rate of 0.31 Tg C yr⁻² for CO₂ (0.23 % yr⁻¹, relative to the average from 1980 to 2009), 0.40 Gg C yr⁻² for CH₄ (0.44 % yr⁻¹), and 0.0052 Gg N yr⁻² for N₂O (0.27 % yr⁻¹). Our estimates also show large interannual variations in soil GHG fluxes. The increasing trends and large interannual variations in soil GHG fluxes seem to substantially affect Japan's Kyoto accounting and future GHG mitigation strategies.