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| Titel |
Seasonal leaf and soil water isotope dynamics obtained from the δ¹⁸O signals of CO2 fluxes |
| VerfasserIn |
Lisa Wingate, Jerome Ogee, Regis Burlett, Alexandre Bosc |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053981
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| Zusammenfassung |
| The oxygen isotope composition of CO2 fluxes such as photosynthesis and respiration carry
important information on the dynamics of ecosystem water pools. Chamber-based field
measurements of total CO2 and CO18O fluxes from foliage and soil can help evaluate and
refine our models of isotopic fractionation by plants and soils and validate the extent and
pattern of isotopic enrichment within terrestrial ecosystems. This is highly desirable as the
oxygen isotope composition of atmospheric CO2 is among a very limited number of tools
available to constrain estimates of the biospheric gross CO2 fluxes, photosynthesis and
respiration at large scales. Due to sampling limitations in the past, such measurements have
been very rare and covered only a few days. In this study, we coupled automated branch
and soil chambers with tuneable diode laser absorption spectroscopy techniques to
continuously capture for the first time the oxygen isotope signals of foliage and
soil CO2 exchange at a FLUXNET site (Maritime pine forest) in southern France.
Over the growing season we observed seasonally persistent isotopic differences
between the oxygen isotope signatures of net CO2 fluxes from leaves and soils, except
during rain events when the isotopic imbalance between the two became temporarily
weaker. These variations were driven dynamically by variations in evapotranspiration
and precipitation inputs over the growing season. Variations in the oxygen isotope
composition of water pools and CO2 exchanged between leaves, soil and the atmosphere
were also modelled following theory describing changes in the oxygen isotope
composition of ecosystem water pools in response to changes in leaf transpiration
and soil evaporation. The results of this modelling and the implications for larger
scale CO2 and CO18O mass balance studies will be discussed in this presentation. |
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