© 2004 Heron Publishing—Victoria, Canada
Silver birch and climate change: variable growth and carbon allocation responses to elevated concentrations of carbon dioxide
and ozone
Johanna Riikonen (1, 2), Minna-Mari Lindsberg (2), Toini Holopainen (1), Elina Oksanen (1), Juha Lappi (2), Petri Peltonen (2, 3) and Elina Vapaavuori (2, 4)
1. Department of Ecology and Environmental Science, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland / 2. Finnish Forest Research Institute, Suonenjoki Research Station, 77600 Suonenjoki, Finland / 3. Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland / 4. Corresponding author (elina.vapaavuori@metla.fi) / Received October 8, 2003; accepted April 27, 2004; published online September 1, 2004
Summary
We studied the effects of elevated concentrations of carbon dioxide ([CO2]) and ozone ([O3]) on growth, biomass allocation and leaf area of field-grown O3-tolerant (Clone 4) and O3-sensitive clones (Clone 80) of European silver birch (Betula pendula Roth) trees during 1999–2001. Seven-year-old trees of Clones 4 and 80 growing outside in open-top chambers were exposed
for 3 years to the following treatments: outside control (OC); chamber control (CC); 2 × ambient [CO2] (EC); 2 × ambient [O3] (EO); and 2 × ambient [CO2] + 2 × ambient [O3] (EC+EO). When the results for the two clones were analyzed together, elevated [CO2] increased tree growth and biomass, but had no effect on biomass allocation. Total leaf area increased and leaf abscission
was delayed in response to elevated [CO2]. Elevated [O3] decreased dry mass of roots and branches and mean leaf size and induced earlier leaf abscission in the autumn; otherwise,
the effects of elevated [O3] were small across the clones. However, there were significant interactions between elevated [CO2] and elevated [O3]. When results for the clones were analyzed separately, stem diameter, volume growth and total biomass of Clone 80 were increased
by elevated [CO2] and the stimulatory effects of elevated [CO2] on stem volume growth and total leaf area increased during the 3-year study. Clone 80 was unaffected by elevated [O3]. In Clone 4, elevated [O3] decreased root and branch biomass by 38 and 29%, respectively, whereas this clone showed few responses to elevated [CO2]. Elevated [CO2] significantly increased total leaf area in Clone 80 only, which may partly explain the smaller growth responses to elevated
[CO2] of Clone 4 compared with Clone 80. Although we observed responses to elevated [O3], the responses to the EC+EO and EC treatments were similar, indicating that the trees only responded to elevated [O3] under ambient [CO2] conditions, perhaps reflecting a greater quantity of carbohydrates available for detoxification and repair in elevated [CO2].
Keywords:
Betula pendula, biomass, clone, field experiment, leaf abscission, leaf area, open-top chamber, stem volume.
