HR: 08:15h
AN: B11E-02    [Abstracts]
TI: A single-substrate model to interpret high-resolution intra-annual stable isotope signals in tree ring cellulose
AU: * Ogée, J
EM: ogee@pierroton.inra.fr
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AU: Barbour, M M
AF: Landcare Research, PO Box 69, Lincoln, 8251, New Zealand
AU: Dewar, R C
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AU: Wingate, L
AF: University of Edinburgh, School of GeoSciences, Crew Building West Main Road, Edinburgh, EH9 3JN, United Kingdom
AU: Bert, D
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AU: Bosc, A
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AU: Lambrot, C
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AU: Stievenard, M
AF: CEA, LSCE, Orme des Merisiers, Gif/Yvette, 91191, France
AU: Bariac, T
AF: CNRS, BIOEMCO, Bâtiment EGER, Thiverval-Grignon, 78850, France
AU: Berbigier, P
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AU: Loustau, D
AF: INRA, EPHYSE, BP81, Villenave d'Ornon, 33883, France
AB: High-resolution measurements of the carbon and oxygen stable isotope composition of cellulose in annual tree rings (δ¹³C_cellulose and δ¹⁸O_cellulose, respectively) reveal well-defined seasonal patterns that could contain valuable records of past climate and tree function. Interpreting these signals is nonetheless complex because they not only record the signature of current assimilates, but also depend on carbon allocation dynamics within the trees. Here, we will present a single-substrate model for wood growth in order to interpret qualitatively and quantitatively these seasonal isotopic signals. We will also show how this model can relate to more complex models of phloem transport and cambial activity. The model will then be tested against an isotopic intra-annual chronology collected on a Pinus pinaster tree equipped with point dendrometers and growing on a Carboeurope site where climate, soil and flux variables are also monitored. The empirical δ¹³C_cellulose and δ¹⁸O_cellulose signals exhibit dynamic seasonal patterns with clear differences between years, which makes it suitable for model testing. We will show how our simple model of carbohydrate reserves, forced by sap flow and eddy covariance measurements, enables us to interpret these seasonal and inter-annual patterns. Finally, we will present a sensitivity analysis of the model, showing how gas-exchange parameters, carbon and water pool sizes or wood maturation times affect these isotopic signals. Acknowledgements: this study benefited from the CarboEurope-IP Bray site facilities and was funded by the French INSU programme Eclipse, with an additional support from the INRA department EFPA.
DE: 0424 Biosignatures and proxies
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 0476 Plant ecology (1851)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting