Journal Article

Tracing of recently assimilated carbon in respiration at high temporal resolution in the field with a tuneable diode laser absorption spectrometer after in situ <sup>13</sup>CO<sub>2</sub> pulse labelling of 20-year-old beech trees

Caroline Plain, Dominique Gerant, Pascale Maillard, Masako Dannoura, Yanwen Dong, Bernd Zeller, Pierrick Priault, Florian Parent and Daniel Epron

in Tree Physiology

Volume 29, issue 11, pages 1433-1445
Published in print November 2009 | ISSN: 0829-318X
Published online November 2009 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/tpp072
Tracing of recently assimilated carbon in respiration at high temporal resolution in the field with a tuneable diode laser absorption spectrometer after in situ 13CO2 pulse labelling of 20-year-old beech trees

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The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resolve the residence and transfer times of carbon in the atmosphere–plant–soil system in forest ecosystems, but it requires high frequency measurements of the isotopic composition of evolved CO2. We developed a closed transparent chamber to label the whole crown of a tree and a labelling system capable of delivering a 3-h pulse of 99% 13CO2 in the field. The isotopic compositions of trunk and soil CO2 effluxes were recorded continuously on two labelled and one control trees by a tuneable diode laser absorption spectrometer during a 2-month chase period following the late summer labelling. The lag times for trunk CO2 effluxes are consistent with a phloem sap velocity of about 1 m h−1. The isotopic composition (δ13C) of CO2 efflux from the trunk was maximal 2–3 days after labelling and declined thereafter following two exponential decays with a half-life of 2–8 days for the first and a half-life of 15–16 days for the second. The isotopic composition of the soil CO2 efflux was maximal 3–4 days after labelling and the decline was also well fitted with a sum of two exponential functions with a half-life of 3–5 days for the first exponential and a half-life of 16–18 days for the second. The amount of label recovered in CO2 efflux was around 10–15% of the assimilated 13CO2 for soil and 5–13% for trunks. As labelling occurred late in the growing season, substantial allocation to storage is expected.

Keywords: carbon allocation; Fagus sylvatica; residence time; soil CO2 efflux; trunk CO2 efflux

Journal Article.  9039 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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