Soil carbon dioxide fluxes to atmosphere: the role of rainfall over CO2 transport

International audienceIn order to observe the relationships between the temporal variations of CO2 surface fluxes and the CO2 soil gas transport in soil profile before and during rainfall events, two experiments were conducted in a controlled natural environment at different time periods. These experiments consisted in injecting pure CO2 in a lysimeter at 160 cm depth and simulating heavy rainfall event at its surface for 2 weeks. During the whole experiments, CO2 soil gas concentrations and surface fluxes were continuously monitored. These measurements showed that the flux measured through the flux chamber were consistent with the concentration profiles. During simulated rainfall events, the concentrations and fluxes showed a clear change linked to the presence of water on the top of the water profile. The results clearly show a significant decrease of CO2 flux to atmosphere induced by rainfall infiltration and consequential wash-out of the CO2 present in the soil