Title
Within-canopy and ozone fumigation effects on <tex>$\delta^{13}C$</tex> and <tex>$\Delta^{18}O$</tex> in adult beech (**Fagus sylvatica**) trees: relation to meteorological and gas exchange parameters Within-canopy and ozone fumigation effects on <tex>$\delta^{13}C$</tex> and <tex>$\Delta^{18}O$</tex> in adult beech (**Fagus sylvatica**) trees: relation to meteorological and gas exchange parameters
Author
Faculty/Department
Faculty of Sciences. Biology
Publication type
article
Publication
Victoria ,
Subject
Biology
Source (journal)
Tree physiology. - Victoria
Volume/pages
29(2009) :11 , p. 1349-1365
ISSN
0829-318X
ISI
000271110400005
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
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 d13C and D18O were determined under ambient (1 · O3) and twiceambient (2 · O3) atmospheric ozone concentrations during two consecutive years (2003 and 2004). We analysedthe 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. d13C was significantly lower in the shade than in the sun crown in all plant materials, whilst D18O was increased significantly in the shade than in the sun crown in bulk material and cellulose. Elevated ozone had no effect on d13C, although D18O 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 D18O between the sun and the shade crown were predominantly caused by the Pe´ clet effect. This assumption was supported by the modelled D18O 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 D18O increase with the concomitant decrease of d13C in the shade crown. The effect of doubling ozone levels on time-integrated stomatal conductance and transpiration as indicated by the combined analysis of D18O and d13C was much lower than the influence caused by the light exposure.
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