title: Bias in estimated online leaf carbon isotope discrimination due to woody tissues.
abstract: Branch or shoot chamber measurements integrate over both foliar and woody tissue carbon dioxide (CO2) fluxes and their associated influences on the carbon isotopic composition of atmospheric/headspace CO2. Here, we quantified the bias introduced by woody tissue carbon isotope fluxes on apparent leaf (13)C discrimination (Δ(13)Capparent) estimates, using laser spectroscopy under controlled conditions. CO2 efflux from woody tissues of defoliated beech saplings in the dark was strongly related to temperature (R(2) = 0.78), which served as the basis to model light-dependent woody tissue photosynthesis (R(2) = 0.72). We then quantified the contributions of leaf and woody tissues to leaf Δ(13)Capparent of foliated beech saplings in the light. Unbiased foliar Δ(13)C was 1.1 to 4.9‰ lower than leaf Δ(13)Capparent, depending on photosynthetic rates of woody tissues. Therefore, we strongly recommend accounting for isotope-related bias due to woody tissues when estimating leaf Δ(13)Capparent based on branch or shoot chamber measurements.
authors: a Institute of Agricultural Sciences, ETH Zürich , Zürich , Switzerland.
authors: Carola H
authors: CH
authors: Blessing
authors: Matti
authors: M
authors: Barthel
authors: Nina
authors: N
authors: Buchmann
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis* / Q000378:metabolism; D029964:Fagus / Q000737:chemistry* / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018547:Plant Stems / Q000737:chemistry / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D002245:Carbon Dioxide
keywords: assimilation; branch chamber; carbon isotope fractionation; carbon-13; isotope ecology; laser spectroscopy; shoot chamber; stem CO2 efflux; woody tissue