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| Project B 5 |
| Phase II:
Ozone effects in juvenile and adult forest trees:
Scaling between ontogenetic stages and growth conditions
Nina Koch, Helmut Blaschke, Thorsten E.E. Grams, Karl-Heinz Häberle, Alessandra Kozovits, Markus Löw, Gustavo Luedemann, Petia Nikolova, Angela J. Nunn, Ilja M. Reiter, Rainer Matyssek
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Summary
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Throughout their lifespan – from sub-canopy conditions of juvenile to closed-canopy conditions of adult stages – trees encounter significant changes during their ontogeny which are met by a wide variation in responsiveness to keep up competitiveness and individual plant fitness. One emphasis of SFB 607 is to analyse and quantify ontogeny-related responses in the ecophysiology of 3 to 60-year-old forest trees (beech and spruce) under their respective growth conditions. The project reported here refers to the central hypothesis of SFB 607: Regardless of the kind of impacting stress, plants do regulate their resource allocation in a way that stimulation of growth and competiveness leads to constraints on stress defense. Ozone is used as a tool for testing the hypothesis. Aims are to clarify the extent of common principles in structural and ecophysiological performance, irrespective of ontogenetic stage (juvenile vs adult trees) and growth conditions (field vs laboratory), and in addition, to locate those features which distinctly differ during ontogeny. This study represents a conceptual link between the SFB projects B4, B5 and B12.
Preliminary results
- Juvenile beech trees in phytotrons are more sensitive to O3 than juvenile beech trees in the field:
1. A reduction in total biomass can be observed in the phytotrons under elevated O3 (2x O3) relative to ambient O3 (1x O3). No O3-caused growth reduction was found in the field in juvenile beech.
2. Juvenile beech trees in the phytotrons display accelerated leaf shedding in fall under 2x O3 as compared with 1x O3, whereas leaf senescence does not differ between juvenile and adult trees in the field, regardless of the O3-regime.
- Juvenile spruce trees do not reduce total biomass under 2x O3.
- The length of the growing season of juvenile beech trees both in the phytotrons and in the field is shorter than of adult beech, regardless of O3-regime.
- Although juvenile beech trees on the lysimeters and in the phytotrons show decreased phototsynthetic activity during the growing season, such a trend does not substantiate at Kranzberg Forest.
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