HR: 08:30h
AN: B11E-03 INVITED    [Abstracts]
TI: Measuring carbon and oxygen isotope signals of photosynthesis and respiration: first field results from a chamber system coupled to tunable diode laser spectrometers
AU: * Wingate, L
EM: l.wingate@ed.ac.uk
AF: School of GeoSciences, University of Edinburgh, Edinburgh, UK EH9 3JN, United Kingdom
AU: * Wingate, L
EM: l.wingate@ed.ac.uk
AF: INRA, EPHYSE BP81, Villenave d'Ornon, 33883, France
AU: Burlett, R
AF: INRA, EPHYSE BP81, Villenave d'Ornon, 33883, France
AU: Bosc, A
AF: INRA, EPHYSE BP81, Villenave d'Ornon, 33883, France
AU: Cross, A
AF: School of GeoSciences, University of Edinburgh, Edinburgh, UK EH9 3JN, United Kingdom
AU: Devaux, M
AF: INRA, EPHYSE BP81, Villenave d'Ornon, 33883, France
AU: Grace, J
AF: School of GeoSciences, University of Edinburgh, Edinburgh, UK EH9 3JN, United Kingdom
AU: Loustau, D
AF: INRA, EPHYSE BP81, Villenave d'Ornon, 33883, France
AU: Seibt, U
AF: Physiological Ecology, Department of Plant Sciences University of Cambridge, Cambridge, UK CB2 3EA, United Kingdom
AU: Ogée, J
AF: INRA, EPHYSE BP81, Villenave d'Ornon, 33883, France
AB: Studying the carbon and oxygen stable isotope signals from plants and soils can help us gain insight to mechanistic processes responsible for the net exchange of CO₂ and water cycled between terrestrial ecosystems and the atmosphere. Chamber field measurements of component fluxes and their isotopic composition have been reported for a few ecosystems. These observations have revealed that isotopic signals for carbon and oxygen are dynamic over relatively short time scales (hrs and days) for both branches and soils (Seibt et al., 2006a; 2006b; Wingate et al., 2007), and not fully explained by currently available models (Seibt et al., 2006b; Wingate et al., 2007). Ecosystem isotope studies have been limited by flask sampling requirements in the past. To evaluate and refine our models of isotopic fractionation by plants and soil, we need high resolution continuous isotopic measurements over the growing season for different ecosystems. In this study, we coupled chambers with tunable diode laser spectroscopy techniques in the field to continuously capture the isotopic signals from the most important component fluxes contributing to the net ecosystem exchange of CO₂ in a Pinus pinaster forest in south-west France. We obtained profiles of the carbon and oxygen isotope content of CO₂ within and above the forest canopy. In addition, we measured branch photosynthetic ¹³C and ¹⁸O discrimination alongside the ¹³C and ¹⁸O isotopic composition of the branch, stem and soil respiration during a 6-month period in 2007. In this talk, we will present the first results from this field campaign. References Seibt, U., Wingate, L., Berry, J.A. and Lloyd, J. (2006a) Non steady state effects in diurnal ¹⁸O discrimination by Picea sitchensis branches in the field. Plant, Cell and Environment Vol 29, 928-939. Seibt, U., Wingate, L., Lloyd, J. and Berry, J.A. (2006b) Diurnally variable δ¹⁸O signatures of soil CO₂ fluxes indicate carbonic anhydrase activity in a forest soil. JGR-Biogeosciences, Vol. 111, G04005, doi:10.1029/2006JG000177. Seibt, U., Wingate, L. and Berry, J.A. (2007) Nocturnal stomatal conductance effects on the δ¹⁸O of foliage gas exchange observed in two forest ecosystems. Tree Physiology, Vol. 27, 585-595. Wingate, L., Seibt, U., Moncrieff, J.B., Jarvis, P.G. and Lloyd, J. (2007) Variations in ¹³C discrimination during CO₂ exchange by Picea sitchensis branches in the field. Plant, Cell and Environment doi: 10.1111/j.1365-3040.2007.01647.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0428 Carbon cycling (4806)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting