The Temporal Fluctuations in Soil Respiration when Precipitation is intercepted above the Forest Floor

Soil respiration is emitted from the soil into the atmosphere and plays an important part in the carbon balance between the plant community and the atmosphere. Although soil respiration rates in forest communities have been monitored around the world, details of the process remain unknown. This is because CO2 has numerous sources, including litter, soil organic matter, soil organisms, and roots. Moreover, several factors and soil characteristics affect each source in different ways. Both soil respiration monitoring and experimental observations are necessary to clarify the process of soil respiration. Therefore, we observed soil respiration from the forest floor at a site where precipitation was intercepted in a deciduous secondary forest in Japan using an automated chamber system. The interception of the precipitation above the soil prevented the penetration of soil water into the soil, resulting in extremely dry shallow soil. The experiment examined the effect of soil moisture in the shallow layer on soil respiration. A clear diurnal fluctuation was recognized; it was at a minimum during the day and at a maximum at night. This diurnal fluctuation corresponded to the diurnal fluctuation of the soil temperature in the deep layer. Soil respiration increased rapidly after precipitation events, and the clear diurnal fluctuation disappeared 2-3 days after a precipitation event.