Photosynthetic carbon isotope discrimination and its relationship to the carbon isotope signals of stem, soil and ecosystem respiration

Lisa Wingate, Jerome Ogee, Regis Burlett, Alexandre Bosc, Marion Devaux, John Grace, Denis Loustau, Arthur Gessler

Research output: Contribution to journalArticlepeer-review

Abstract

Photosynthetic carbon (C) isotope discrimination (Delta(Alpha)) labels photosynthates (delta(A)) and atmospheric CO2 (delta(a)) with variable C isotope compositions during fluctuating environmental conditions. In this context, the C isotope composition of respired CO2 within ecosystems is often hypothesized to vary temporally with Delta(Alpha).

We investigated the relationship between Delta(Alpha) and the C isotope signals from stem (delta(W)), soil (delta(S)) and ecosystem (delta(E)) respired CO2 to environmental fluctuations, using novel tuneable diode laser absorption spectrometer instrumentation in a mature maritime pine forest.

Broad seasonal changes in Delta(Alpha) were reflected in delta(W,)delta(S) and delta(E). However, respired CO2 signals had smaller short-term variations than Delta(A) and were offset and delayed by 2-10 d, indicating fractionation and isotopic mixing in a large C pool. Variations in delta(S) did not follow Delta(A) at all times, especially during rainy periods and when there is a strong demand for C allocation above ground.

It is likely that future isotope-enabled vegetation models will need to develop transfer functions that can account for these phenomena in order to interpret and predict the isotopic impact of biosphere gas exchange on the C isotope composition of atmospheric CO2.
Original languageEnglish
Pages (from-to)576-589
Number of pages14
JournalNew Phytologist
Volume188
Issue number2
Early online date20 Jul 2010
DOIs
Publication statusPublished - 1 Oct 2010

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