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Reproductive Responses of Paper Birch Trees to Elevated CO2 and O3 Concentrations
Darbah, J.N.T., Kubiske, M.E., Nelson, N., Oksanen, E., Vapaavuori, E. and Karnosky, D.F. 2008. Effects of decadal exposure to interacting elevated CO2 and/or O3 on paper birch (Betula papyrifera) reproduction. Environmental Pollution 155: 446-452.

What was done
Working at the FACE facility near Rhinelander, Wisconsin (USA), where young paper birch (Betula papyrifera Marsh.) seedlings were planted in 1997 and have been growing since 1998 in air maintained at atmospheric CO2 concentrations of either approximately 360 or 560 ppm, as well as at atmospheric O3 (ozone) concentrations of either ambient or 1.5 times ambient, the authors -- at various times over the 2004-2007 growing seasons -- collected many types of data pertaining to flowering, seed production, seed germination and new seedling growth and development.

What was learned
Giving results for O3 elevation first and CO2 enrichment second, we note (as best we can determine from Darbah et al.'s graphs and text) the following percentage changes in: (1) number of trees producing male flowers: (+86%, +140%) in 2006, (+70%, +70%) in 2007, (2) total number of male flowers produced (+58%, +260%) in 2006, (+68%, +82%) in 2007, (3) mean catkin or flower cluster mass (-8%, +12%) in 2004, (4) mean seed mass (-22%, +10%) in 2004, (-24%, +17%) in 2005, (-22%, -2%) in 2006, (5) mean seed germination success (-70%, +70%) in 2004, (-60%, +110%) in 2005, (-50%, +20%) in 2006, (6) mean seedling mortality, where the greatest reductions represent the greatest benefits, (-9%, -73%) in 2004, (7) mean seedling root length (+15%, +59%) in 2004, (8) mean seedling shoot length (-7%, +21%) in 2004, (9) mean seedling cotyledon length (-5%, +13%) in 2004, and (10) mean seedling dry mass after ~5 months growth in ambient air (-38%, +69%) in 2004.

What it means
In the one-sentence capsule summary of their work, the six researchers write that "in this study, we found that elevated CO2 enhances and elevated O3 decreases birch reproduction and early seedling growth," while in the concluding sentence of their abstract, they write that "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." Yet radical environmentalists and climate alarmists continue to brand CO2 a harmful air pollutant, with many governmental agencies the world over actually buying into this gross misrepresentation of reality.

Reviewed 22 October 2008