Time series and isotopic evidence for gaseous components (222Rn, CO2 and its carbon isotopes) of soil under a cool temperate deciduous forest in Hokkaido, Japan
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The behavior of gaseous components of forest soil was assessed by simultaneous monitoring of 222Rn, CO2 and its carbon isotopes (δ13C, Δ14C) in soil air under a semi natural forest in northern Japan. The isotope ratio of 14C (Δ14C) in soil air CO2 was found to decrease towards late summer, suggesting gradual depletion of easily decomposed soil organic matter. There was a specific case that soil air CO2 with depleted 14C appeared suddenly under snowpack in winter. It is not always appropriate to use soil 222Rn as a tracer of CO2 efflux from the soil surface to the atmosphere.
Keywords222Rn CO2 Carbon isotopes Monitoring Forest soil
The authors would like to thank Mr. Toshihiko Hatano of North One Co. Ltd. for helping instrumentation in the forest site. They also give special thanks to Dr. Claude Bertrand at Algade (France) for his useful comments and suggestions on radon monitoring. This study was supported financially by Japan Society for the Promotion of Science on Bilateral Joint Research Projects between Japan and Slovenia in 2017FY and Japan Atomic Energy Agency in 2017A-F02. Carbon isotope measurements by AMS were financially supported by the Shared Use Program of Japan Atomic Energy Agency Facility from 2008 to 2017.
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