Temperature controls temporal variation in soil CO2 efflux in a secondary beech forest in Appi Highlands, Japan

Abstract: Forest soil is a huge reserve of carbon in the biosphere. Therefore to understand the carbon cycle in forest ecosystems, it is important to determine the dynamics of soil CO₂ efflux. This study was conducted to describe temporal variations in soil CO₂ efflux and identify the environmental factors that affect it. We measured soil CO₂ efflux continuously in a beech secondary forest in the Appi Highlands in Iwate Prefecture for two years (except when there was snow cover) using four dynamic closed chambers that automatically open after taking measurements. Temporal changes in soil temperature and volumetric soil water content were also measured at a depth of 5 cm. The soil CO₂ efflux ranged from 14 mg CO₂ m⁻² h⁻¹ to 2,329 mg CO₂ m⁻² h⁻¹, the peak occurring at the beginning of August. The relationship between soil temperature and soil CO₂ efflux was well represented by an exponential function. Most of temporal variation in soil CO₂ efflux was explained by soil temperature rather than volumetric soil water content. The Q ₁₀ values were 3.7 ± 0.8 and estimated annual carbon emissions were 837 ± 210 g C m⁻² year⁻¹. These results provide a foundation for further development of models for prediction of soil CO₂ efflux driven by environmental factors.