Comparison of ozone uptake and sensitivity between a phytotron study with young beech and a field experiment with adult beech (Fagus sylvatica)

Chamber experiments on juvenile trees have resulted in severe injury and accelerated loss of leaves along with reduced biomass production under chronically enhanced O-3 levels. In contrast, the few studies conducted on adult forest trees in the field have reported low O-3 sensitivity. In the present study, young beech in phytotrons was more sensitive to O-3 than adult beech in the field, although employed O-3 regimes were similar. The hypotheses tested were that: (1) differences in O-3 uptake were caused by the ontogenetically higher stomatal conductance of young compared to adult trees, (2) the experimental settings in the phytotrons enhanced O-3 uptake compared to field conditions, and (3) a low detoxification capacity contributes to the higher O-3 sensitivity of the young trees. The higher O-3 sensitivity of juvenile beech in the phytotrons is demonstrated to relate to both the experimental conditions and the physiological responsiveness inherent to tree age. (c) 2005 Elsevier Ltd. All rights reserved.