Effects of decadal exposure to interacting elevated CO2 and/or O3 on paper birch (Betula papyrifera) reproduction

Joseph N.T. Darbah, Mark E. Kubiske, Neil Nelson, Elina Oksanen, Elina Vapaavuori, David F. Karnosky

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


We studied the effects of long-term exposure (nine years) of birch (Betula papyrifera) trees to elevated CO2 and/or O3 on reproduction and seedling development at the Aspen FACE (Free-Air Carbon Dioxide Enrichment) site in Rhinelander, WI. We found that elevated CO2 increased both the number of trees that flowered and the quantity of flowers (260% increase in male flower production), increased seed weight, germination rate, and seedling vigor. Elevated O3 also increased flowering but decreased seed weight and germination rate. In the combination treatment (elevated CO2 + O3) seed weight is decreased (20% reduction) while germination rate was unaffected. The evidence from this study indicates that elevated CO2 may have a largely positive impact on forest tree reproduction and regeneration while elevated O3 will likely have a negative impact.

Original languageEnglish (US)
Pages (from-to)446-452
Number of pages7
JournalEnvironmental Pollution
Issue number3
StatePublished - Oct 1 2008


  • Elevated tropospheric ozone and carbon dioxide
  • Flower production
  • Seed germination
  • Seed quality
  • Seedlings growth and survival
  • Seeds

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