AOBPreview originally published online on February 20, 2003
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Annals of Botany 91: 559-569, 2003
© 2003 Annals of Botany Company
Influence of Elevated CO2 and O3 on Betula pendula Roth Crown Structure
1 Institute of Botany and Ecology, University of Tartu, Lai 40, 51005 Tartu, Estonia, 2 Institute of Ecology, Tallinn Pedagogical University, Kevade 2, 101376 Tallinn, Estonia and 3 Finnish Forest Research Institute, Suonenjoki Research Station, 77600 Suonenjoki, Finland
* For correspondence. Institute of Botany and Ecology, University of Tartu, Lai 40, 51005 Tartu, Estonia. Fax: +372 7 376222, e-mail: olevi{at}ut.ee
Received: 19 July 2002; Returned for revision: 4 October 2002; Accepted: 14 December 2002 Published electronically: 20 February 2003
Elevated CO2 and ozone effects were studied singly and in combination on the crown structure of two Betula pendula clones. Measurements were made at the end of the second fumigation period in an open-top-chamber experiment with 9-year-old trees. Shoot ramification (number of long and short daughter shoots), shoot length, and number of metamers, leaves and buds were measured at four positions in every tree. As a result of increased temperature, trees in chambers had longer shoots and more frequent shoot ramification than control trees not enclosed in chambers. Ozone treatment decreased shoot ramification significantly. Additionally, ozone treatment resulted in an increased number of metamers in one clone. There was no statistically significant interaction between ozone effect and crown position; however, there was a slight tendency for the lower crown to be more affected by ozone. Elevated CO2 caused a significant increase in the number of long-shoot metamers. Therefore, 2x ambient CO2 concentration partly ameliorated the negative effect of ozone because the increased number of leaves per shoot counteracted the decreased branching. Although the main effects of elevated ozone and CO2 were similar in the two clones, slight, statistically insignificant, differences appeared in their responses when interactions with crown position were considered.
Key words: Betula pendula Roth, silver birch, ozone, CO2, open-top chambers, clones, shoot growth, ramification, metamers, crown structure, shoot dimorphism, sylleptic shoots.