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Contrasting responses in C allocation of beech and spruce trees to competition and
disturbance by O3
W. Ritter, R. Matyssek and T. E. E. Grams
Ecophysiology of Plants, Technische Universität München, Am Hochanger 13,
85354 Freising, Germany
Email: [email protected]
The present study examines the influence of enhanced ozone (O3) on the carbon (C)
allocation of juvenile and adult beech (Fagus sylvatica) and spruce (Picea abies). Trees were
exposed to ambient and doubled (2x) O3 concentrations, which are known to negatively affect
primary metabolism and phloem loading in leaves. Here we test the hypothesis that
enhanced O3 exposure reduces the C allocation to stem respiration. In juvenile trees, C
allocation in stem respiration of juvenile trees was assessed in a phytotron experiment at the
GSF-National Research Center for Environment and Health. A 13CO2/12CO2-label of
+ 106.4 ‰ was applied in September 2005 for five subsequent days and the isotopic signal
of stem respiratory CO2 and annual stem increment was pursued. Although standing
biomass was not yet changed, C allocation to stem respiration in beech was strongly affected
by 2xO3 and by growth in mixture with spruce, indicating early tree responses. C allocation to
stem respiration in spruce grown in mixture was only slightly increased. Overall, beech
showed higher responsiveness in allocation and stem growth to the O3- and competition
treatments than spruce. During a 12CO2/13CO2-labelling experiment of adult beech and
spruce trees at Kranzberg Forest in Aug/Sep 2006, CO2 with a δ13C of c. -47.0 ‰ was
distributed for 18 days in the canopy of adult trees via a 12CO2/13CO2 fumigation system. δ13C
of respiratory CO2 were assessed at crown base, breast height and in coarse roots. The
change in δ13C of respiratory CO2 could be followed through the trees.