How closely does stem growth of adult beech (Fagus sylvatica) relate to net carbon gain under experimentally enhanced ozone stress?
2012
Kitao, Mitsutoshi | Winkler, J Barbro | Löw, Markus | Nunn, Angela J. | Kuptz, Daniel | Häberle, Karl-Heinz | Reiter, Ilja M. | Matyssek, Rainer
The hypothesis was tested that O₃-induced changes in leaf-level photosynthetic parameters have the capacity of limiting the seasonal photosynthetic carbon gain of adult beech trees. To this end, canopy-level photosynthetic carbon gain and respiratory carbon loss were assessed in European beech (Fagus sylvatica) by using a physiologically based model, integrating environmental and photosynthetic parameters. The latter were derived from leaves at various canopy positions under the ambient O₃ regime, as prevailing at the forest site (control), or under an experimental twice-ambient O₃ regime (elevated O₃), as released through a free-air canopy O₃ fumigation system. Gross carbon gain at the canopy-level declined by 1.7%, while respiratory carbon loss increased by 4.6% under elevated O₃. As this outcome only partly accounts for the decline in stem growth, O₃-induced changes in allocation are referred to and discussed as crucial in quantitatively linking carbon gain with stem growth.
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