1. Towards flux-based ozone risk assessment – linking leaf gas exchange with biochemistry Markus Löw 1, Manuela Blumenröther 2, Karl-Heinz Häberle 1, Wolfgang Oßwald 2 and Rainer Matyssek 1 1 Ökophysiologie der Pflanzen 2 Fachgebiet Krankheiten der Waldbäume Technische Universität München, Am Hochanger 13, 85354 Freising, Germany

2. O 3 flux model at „Kranzberger Forst“ Based on Emberson et al. (2000) Extended for drought conditions Validated for adult beech under site conditions Working (2002, 2003, 2004) Nunn et al. (2005) Env. Poll. 137(3): 494-506

3. O 3 flux model at „Kranzberger Forst“ COU: cumulative stomatal ozone uptake (AF st 0) g max measured individually per tree and crown position growing season determined individually per tree and crown position modelled on a 10 minute basis soil moisture function implemented

4. O 3 flux model at „Kranzberger Forst“ Linear relationship in 2002 and 2004 = years without drought

5. End of July 2003: drought became a limiting factor No linear relationship in 2003, so AOT40 predicts misleading high risk O 3 flux model at „Kranzberger Forst“

6. Assessment of gas exchange Light saturated rate of photosynthesis (A max ) Measured during CASIROZ sampling campaigns Diagnostic test under „steady state“ conditions Licor 6400

7. Annual course of photosynthesis Overall O 3 effect on net CO 2 uptake rate: p = 0.04 (GLM, rep. meas.) 2004 means ± SD n = 4-5 trees

8. Annual course of photosynthesis No statistically significant O 3 effects in 2003 2004 2003 * ** * Significant drought effects in 2003: 1xO 3 p < 0.001; 2xO 3 p = 0.02 * * means ± SD n = 4-5 trees

9. Annual course of photosynthesis Unusual annual course 2003 (drought year) means ± SD n = 4-5 trees

10. Error bars indicate standard error sun crown *** ozone effect disappeared during drought conductance was minimal in both treatments in 2003 stomatal conductance gH 2 O 2003 - 2004

11. Annual course of photosynthesis Unusual annual course 2003 (drought year) means ± SD n = 4-5 trees

12. Annual course of photosynthesis „normal“ annual course r 2 = 0.57 p < 0.05 2004 means ± SD n = 4-5 trees

13. Ozone effect on photosynthesis means ± SD n = 4-5 trees

14. Ozone effect on photosynthesis means ± SD n = 4-5 trees (drought year)

15. Ozone effect on photosynthesis p < 0.05 senescence in October (drought year) Drought overrules ozone effect, linear correlation only during summer months

16. Ozone effect on photosynthesis means ± SD n = 4-5 trees Ozone effect on photosynthesis

17. Linear correlation only in summer months (June to September) n.s. leaf expansion in May senescence in October Ozone effect on photosynthesis

18. Pause – linking leaf gas exchange with biochemistry

19. Measured parameters Phosphoenolpyruvate-carboxylase activity (PEPc) [nkat/mg protein] in sun and shade leaves Starch content [mg glucose equivalent/g dw] in sun and shade leaves CO 2 -fixing enzyme, contributing to anaplerotic pathways, stress induced Ambivalent results for O 3 effects on carbohydrates Activity is said to increase under O 3 /stress impact (Luethy-Krause et al. 1990 (Norway spruce, Scots pine); Landolt et al. 1994, 1997 (poplar, birch); Saurer et al. 1995 (birch); Fontaine 1999 (Aleppo pine); Lütz et al. 2000 (beech); Inclam et al. 2005 (Aleppo pine)...)

20. Specific PEPc activity 2003 1xO3 sun 20032xO3 sun 20031xO3 shade 20032xO3 shade 2003 No significant annual effect of O 3 on PEPc in sun & shade leaves 2003 mv ± se

21. Significant correlations to COU in sun & shade leaves 2003 But activity in 2xO 3 leaves always lower at any given flux Specific PEPc activity vs. COU 2003 (dry year!) p < 0.05 each

22. Specific PEPc activity 2004 1xO3 sun 20042xO3 sun 20041xO3 sha 20042xO3 sha 2004 p = 0.038 Significantly decreased PEPc activity in 2xO 3 sun leaves throughout 2004 mv ± se *

23. Rising activity in shade leaves is comparable to the pattern in 2003, but is not significantly correlated to COU 2xO 3 sun leaves are not responding to COU in 2004; 1xO 3 sun leaves are significantly negative correlated to flux Specific PEPc activity vs. COU 2004 p < 0.01 Chronic effects of O 3 result in decreased PEPc activity

24. Starch concentrations in leaves 2003 (dry year) 1xO3 sun 20032xO3 sun 20031xO3 shade 20032xO3 shade 2003 Significantly decreased starch contents in 2xO 3 sun leaves throughout May, June & July p = 0.023 mv ± se * allocation processes

25. Starch concentrations in leaves 2004 1xO3 sun 20042xO3 sun 20041xO3 sha 20042xO3 sha 2004 Higher starch levels in 2004 Significantly reduced starch contents in 2xO 3 sun p = 0.009 Carbohydrates used for repair/detoxification processes in 2xO 3 sun leaves? Less photosynthetic products available under 2xO 3 ? ** allocation processes mv ± se

26. 1xO 3 = 100% Relative starch and A max vs. COU in sun leaves 2004 r 2 = 0.738 p < 0.05 Annual response patterns of A max and starch to O 3 are significantly correlated starchAmax

27. Conclusions I O 3 flux model for adult beech trees in „Kranzberger Forst“ validated & ready to use Discrepancy between O 3 exposure and uptake especially in dry year Significant O 3 effect on photosynthesis only in 2004 Significantly reduced starch concentrations in sun leaves 2003 and 2004; differences between O 3 regimes more pronounced in 2004 Significant correlation of PEPc activity and COU Biochemical parameters indicate a chronic O 3 effect Controversial results for PEPc indicate the need for more studies on adult trees….

28. Conclusions II Drought overrules O 3 impact in 2003 Different parameters (starch + A max ) show similar responses to O 3 Risk assessment does profit from the combination of several parameters from different scaling levels Thus, these parameters should be included in Flux modelling (Flux + defence)

29. Acknowledgements The present study is part of the Project "CASIROZ – The carbon sink strength of beech in a changing environment: Experimental risk assessment by mitigation of chronic ozone impact", which is supported by European Commission - Research Directorate-General, Environment Programme, "Natural Resources Management and Services" (EVK2-2002-00165, Ecosystem Vulnerability). Pierre Dizengremel, UHP Nancy, France Frank Fleischmann Tina Schmidt Angela Nunn Thorsten Grams Thomas Feuerbach...