The effect of free-air ozone fumigation on photosynthesis

Most studies examining the effect of ozone on forest trees have used chamber studies with small seedlings (e. g. Reich, 1987; Sandermann et al., 1997; Matyssek and Innes, 1999). This is problematic because seedlings are uncertain surrogates given ontogenetic changes in morphological and physiological characteristics (Kolb and Matyssek, 2001). The present study makes use of a unique free-air ozone fumigation facility (Nunn et al., 2002; Werner and Fabian, 2002) to make measurements on tall trees in the field.

Two separate objectives were considered in this study. We examined 1) variation in internal conductance and photosynthetic limitations between sun and shade leaves of Fagus sylvatica, and 2) asked whether free-air ozone fumigation affects internal conductance and photosynthetic limitations. Measurements of photosynthesis (A, V_cmax), g_s and g_i were used to apportion limitations to biochemical, internal and stomatal factors.

Funding: “CASIROZ - The carbon sink strength of beech in a changing environment: Experimental risk assessment by mitigation of chronic ozone impact” (EVK2-2002-00165) funded within the 5th RTD Framework Programme of the European Union. This work was partially supported by funding from the Australian Research Council to CRW.

Partner investigators: M. Löw (Technische Universität München), R. Matyssek (Technische Universität München), M. Tausz (Karl-Franzens Universität Graz, & University of Melbourne).

Location: Free-air ozone enrichment experiment on 60-year-old beech trees at Kranzberg Forest near Munich, Germany.

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