Tree Physiology Advance Access originally published online on September 4, 2009
Tree Physiology 2009 29(11):1349-1365; doi:10.1093/treephys/tpp066
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Within-canopy and ozone fumigation effects on 
13C and 
18O in adult beech (Fagus sylvatica) trees: relation to meteorological and gas exchange parameters
1 Centre for Systems Biology (ZBSA), Core Facility Metabolomics, Albert-Ludwigs-University, Habsburgerstraße 49, 79104 Freiburg, Germany
2 Centre for Plant and Food Science, University of Western Sydney, Locked Bag 1797, Penrith South DC NSW 1797, Australia
3 Bioclimatology and Air Pollution Research, Department of Ecology, Technische Universität München, Life Science Center Weihenstephan, Am Hochanger 13, 85354 Freising, Germany
4 Research Group Plant and Vegetation Ecology, Department of Biology, University of Antwerpen (CDE), Universiteitsplein 1, 2610 Wilrijk/Antwerpen, Belgium
5 Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, Albert-Ludwigs-University, Georges-Köhler-Allee 053/054, D-79110 Freiburg, Germany
6 Corresponding author (Kristine.Haberer{at}biologie.uni-freiburg.de)
7 Ecophysiology of Plants, Technische Universität München, Am Hochanger 13, 85354 Freising, Germany
8 Helmholtz Zentrum München-German Research Centre for Environment and Health, Institute of Biochemical Plant Pathology, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
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Abstract |
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In this study, the effects of different light intensities either in direct sunlight or in the shade crown of adult beech (Fagus sylvatica L.) trees on 
13C and 
18O were determined under ambient (1 x O3) and twice-ambient (2 x O3) atmospheric ozone concentrations during two consecutive years (2003 and 2004). We analysed the isotopic composition in leaf bulk, leaf cellulose, phloem and xylem material and related the results to (a) meteorological data (air temperature, T and relative humidity, RH), (b) leaf gas exchange measurements (stomatal conductance, gs; transpiration rate, E; and maximum photosynthetic activity, Amax) and (c) the outcome of a steady-state evaporative enrichment model. 13C was significantly lower in the shade than in the sun crown in all plant materials, whilst 18O was increased significantly in the shade than in the sun crown in bulk material and cellulose. Elevated ozone had no effect on 13C, although 18O was influenced by ozone to varied degrees during single months. We observed significant seasonal changes for both parameters, especially in 2004, and also significant differences between the study years. Relating the findings to meteorological data and gas exchange parameters, we conclude that the differences in 18O between the sun and the shade crown were predominantly caused by the Péclet effect. This assumption was supported by the modelled 18O values for leaf cellulose. It was demonstrated that independent of RH, light-dependent reduction of stomatal conductance (and thus transpiration) and of Amax can drive the pattern of 18O increase with the concomitant decrease of 13C in the shade crown. The effect of doubling ozone levels on time-integrated stomatal conductance and transpiration as indicated by the combined analysis of 18O and 13C was much lower than the influence caused by the light exposure.
Keywords: evaporative enrichment, light exposure, Péclet effect, seasonal and inter-annual differences
Received December 8, 2008; Accepted August 2, 2009
* Present address: Institute of Biology II-Botany, Albert-Ludwigs-University, Schänzlestraße 1, 70104 Freiburg, Germany.