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www.biogeosciences-discuss.net/7/1345/2010/
doi:10.5194/bgd-7-1345-2010
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Continuous measurement of soil CO2 efflux in a larch forest by automated chamber and concentration gradient techniques
1Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
2Graduate School of Agriculture, Hokkaido University, Sapporo 060-0809, Japan
3East China Normal University, Shanghai 200062, China
4The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA
5Tottori University of Environmental Studies, Tottori 689-1111, Japan
Abstract. Winter measurements of soil CO2 effluxes are few because such measurements are difficult when the ground is snow-covered, limiting the ability of chamber systems to characterize soil CO2 effluxes accurately year-round. In this study, we used two systems for continuous measurements of soil CO2 effluxes in a larch forest in northern Japan: (1) a 16-channel automated soil chamber system with eight chambers for measuring soil CO2 efflux and eight chambers for measuring heterotrophic respiration during snow-free periods, and (2) a soil CO2 concentration gradient system used year-round, including when the ground was snow-covered. During the warm season, the gradient approach yielded systematically higher CO2 effluxes than the automated chamber technique, whereas it yielded lower CO2 effluxes during the cold season. As a result of this bias (p<0.001), the annual soil CO2 efflux estimated by the automated chamber was 959 g C m−2 (of which 57% was contributed by heterotrophic respiration), whereas the efflux estimated by the gradient approach was 1040 g C m−2. Because of the fast-response infrared gas analyzer adopted for the chamber technique, the soil CO2 efflux response to the onset of rain was detected immediately and the efflux returned to pre-rain values several hours after the rain had stopped. Rain events accounted for about 24 g C m−2 (about 2% of the annual soil CO2 efflux). The gradient system successfully measured the soil CO2 effluxes when the ground was snow-covered (9 December to 17 April), when they ranged from 0.40 to 0.70 μmol m−2 s−1. Total CO2 efflux from the snowpack estimated by the gradient technique approached 73 g C m−2, corresponding to about 7% of the annual soil CO2 efflux. The Q10 coefficient of the soil CO2 efflux showed large seasonal variation, mainly because of the large temperature sensitivity of root respiration.
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Citation: Liang, N., Hirano, T., Zheng, Z.-M., Tang, J., and Fujinuma, Y.: Continuous measurement of soil CO2 efflux in a larch forest by automated chamber and concentration gradient techniques, Biogeosciences Discuss., 7, 1345-1375, doi:10.5194/bgd-7-1345-2010, 2010. Bibtex EndNote Reference Manager XML
