HR: 1340h
AN: B13B-1188    [Abstracts]
TI: Temporal variation of carbon-13 signature of soil respiration in a beech forest ecosystem measured with a tunable diode laser spectrophotometer
AU: * MARRON, N
EM: Nicolas.Marron@scbiol.uhp-nancy.fr
AF: UMR 1137 INRA – UHP Ecologie et Ecophysiologie Forestieres (EEF), Centre INRA de Nancy, Champenoux, 54280, France
AU: PLAIN, C
AF: UMR 1137 INRA – UHP Ecologie et Ecophysiologie Forestieres (EEF), Universite Henri Poincare Faculte des Sciences BP 239, Vandoeuvre-les-Nancy, 54506, France
AU: LONGDOZ, B
AF: UMR 1137 INRA – UHP Ecologie et Ecophysiologie Forestieres (EEF), Centre INRA de Nancy, Champenoux, 54280, France
AU: BERNARD, S
AF: UMR 1137 INRA – UHP Ecologie et Ecophysiologie Forestieres (EEF), Universite Henri Poincare Faculte des Sciences BP 239, Vandoeuvre-les-Nancy, 54506, France
AU: GERANT, D
AF: UMR 1137 INRA – UHP Ecologie et Ecophysiologie Forestieres (EEF), Universite Henri Poincare Faculte des Sciences BP 239, Vandoeuvre-les-Nancy, 54506, France
AU: EPRON, D
AF: UMR 1137 INRA – UHP Ecologie et Ecophysiologie Forestieres (EEF), Universite Henri Poincare Faculte des Sciences BP 239, Vandoeuvre-les-Nancy, 54506, France
AB: Under temperate latitudes, soil respiration is responsible for the reemission of almost half of the carbon assimilated by the forest vegetation. Soil respiration is well-known to be very sensitive to environmental factors such as temperature and moisture and has been shown to widely vary during the growing season. The main difficulty when studying the impact of environment on this process is to differentiate the sources of CO₂ in the soil and their specific response to environmental factors. With regard to this drawback, high frequency measurements of ¹³C in the respiratory flux of the different compartments would help in differentiating emission compartments with short residence time (i.e. using photosynthates as respiratory carbon sources) from compartments with longer residence time (i.e. using soil organic matter as respiratory carbon sources). A tunable diode laser spectrophotometer (TDLS) was installed in the Hesse forest (northeast of France) early during the 2007 growing season in order to determine the seasonal variability in the composition in ¹³C of the CO₂ efflux released by a forest soil. This innovative method, based on the measurement of the absorption of an infrared laser at the specific wave lengths of the ¹³CO₂ and ¹²CO₂, allows the monitoring of the two isotopologues at a very high frequency. The concentrations of the two isotopologues in the soil respiration flux were continuously monitored from June to October 2007 using both chamber measurements and below canopy Keeling plots. Continuous TDLS measurements and punctual Keeling plots gave very similar values of ¹³C composition of soil respired CO₂, showing the reliability of the TDLS system in this context. Results were analysed with regard to seasonal changes in climatic and edaphic variables, in the ¹³C signatures of the potentially respiratory sources (i.e. root carbohydrates), and in water use efficiency of the canopy as inferred from eddy flux measurements of gross photosynthesis and transpiration monitored on a tower installed at the site.
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1865 Soils (0486)
DE: 1895 Instruments and techniques: monitoring
SC: Biogeosciences [B]
MN: 2007 Fall Meeting