HR: 0800h
AN: B11A-0997    [Abstracts]
TI: Variability in Carbon Stable Isotope Ratio of Heterotrophic Soil Respiration in a Deciduous Needle-leaf Forest
AU: * Takahashi, Y
EM: yoshiyu@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Liang, N
EM: liang@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Machida, T
EM: tmachida@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Fujinuma, Y
EM: fujinuma@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AU: Inoue, G
EM: inouegen@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AB: We investigated spatial and temporal variability in the carbon stable isotope ratio (δ¹³C) of heterotrophic soil respiration in a deciduous Japanese needle-leaf forest for 3 years. We used high-precision isotope measurement coupled with a sampling system optimized for soil respiration to capture this variability under natural conditions. The limitations of chamber-based measurements combined with spatial variation created a representation error that prevented precise estimates of flux-weighted mean δ¹³C, but we could nonetheless characterize the δ¹³C variations intrinsic to heterotrophic respiration. In the absence of root respiration, δ¹³C exhibited significant seasonal variation, with a greater range than in previous models. In a root-exclusion plot, δ¹³C was lowest at high temperatures but showed a different seasonal course from that of CO₂ efflux. A simple model explained the seasonal variation in δ¹³C using interpool differences in δ¹³C of decomposed organic matter, in the temperature dependence of decomposition rates, and in the seasonal changes in pool size. The characteristic seasonality of δ¹³C appears to be associated with the properties of the forest, including litterfall patterns.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1041 Stable isotope geochemistry (0454, 4870)
SC: Biogeosciences [B]
MN: Fall Meeting 2005