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Macropores resulting from soil pedogenesis, biological activity, and agricultural practices play important roles in soil water, chemical and gas transport; however, seldom studies focus on the effect of soil macropores on CO2 behavior. In this study, a 150-day soil column incubation experiment was conducted to investigate the CO2 behavior in a homogeneous soil column and a soil column with an artificial macropore, which have the same total porosity. The results showed that the cumulative CO2 fluxes observed in the soil with a macropore (57.2 g m−2) were higher than those in the homogeneous soil (52.7 g m−2). The soil cumulative CO2 fluxes measured using column incubation can fit the kinetic model, and a higher carbon mineralization rate in the soil with the macropore was found. The results of the incubation experiment also suggest that macropore increased the gas diffusivities, and thus decreased the CO2 concentrations in the soil profile. This study proposed a simulation experiment and quantified the effect of macropore on soil CO2 behavior, which could help to understand the mechanism of CO2 emission from soil with macropores especially caused by agricultural practices.

Agricultural management plays an important role in the storage of carbon in soils. The behavior of soil CO2 in an Andisol in two different tillage systems (no tillage and tillage) was studied. Soil-column incubation experiments were performed for a period of 150 days to conduct this study. Soil CO2 flux, under no-tillage and tillage treatments, was observed to be 0.557 and 0.616 gCO2-C m−2 d−1, respectively. The cumulative CO2 flux under tillage treatment was observed to be higher than that under no-tillage treatment, but no distinct difference in the soil carbon stock was observed between both treatments. The soil CO2 concentration under no-tillage treatment was clearly much higher than that under tillage treatment, except at a depth of 2.5 cm. Tillage decreased soil dry bulk density and enhanced soil air-filled porosity. Soil gas diffusivity, which depends on air-filled porosity, was increased by tillage at a depth of 0–15 cm, which contributed to their lower soil CO2 concentration. CO2 flux through the soil profile, calculated from the CO2 concentration, decreased with depth. Compared to the deep soils, the surface soil (0–5 cm) showed greater variation in CO2 flux. The CO2 production at depths of 0–10 cm accounted for 62.2 and 51.7 % of the whole CO2 production of the 0–30-cm soil profile for no-tillage and tillage treatments. CO2 production was higher for soil under no tillage at depths of 0–10 cm, but contrary results were observed for soil at depths of 10–30 cm.

In this study, artificial rainfall was applied to a partially frozen Andisol soil, and the effects of the subsoil's physical conditions, prefreeze moisture condition, and soil compaction on surface runoff and soil loss were studied. The soil, an Andisol from a mountainous region of Japan, was packed into a plastic box to a thickness of 0.08 m to attain a predetermined moisture condition and dry bulk density, then stored in a freezer at -30°C overnight to create a sample representative of frozen subsoil. Twenty millimeters of unfrozen soil were added on top of the frozen subsoil to simulate a thawing surface layer. During the simulated rainfall (42 mm h ―1 ) experiment, surface runoff, soil loss, and seepage from outlets at the front wall of the downslope end of the box were sampled periodically. In the early stage of rainfall, the impermeable frozen subsoil increased surface runoff and soil loss, and seepage occurred at the downslope end of the box, indicating saturation of the near-surface, unfrozen soil. During the early stage of the rainfall, soil loss was particularly greater than during the latter half of the rainfall experiment although both showed a similar surface runoff rate. Saturation of the near-surface soil was the reason for the greater soil loss rate, while a surface seal restricted soil loss by surface runoff during the latter half of the rainfall experiment.

Recently, carbon capture and storage by soils is recognized as an important function of agricultural fields. When discussing global warming mitigation such as proper agricultural practices and/or an appropriate depth of composting in agricultural lands for soil carbon storage, not only CO2 efflux, but also profiles of CO2 concentrations in soil air, are important. This study evaluated the performance of the SOILCO2 model in predicting soil CO2 dynamics, especially CO2 concentrations at various depths in an arable bare land of Andisol. We attempted to experimentally determine two soil parameters required for the CO2 production model, the optimal CO2 production rate and the parameter of a depth-dependent CO2 production function by measuring CO2 efflux from the surface and a vertical distribution of concentration of dissolved organic carbon, respectively. Soil CO2 concentrations, water contents and temperatures were continuously monitored for approximately one year at three different depths, and simu...