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Elevated Atmospheric CO2 Enhanced the Growth of Ancient Polar Forests
Beerling, D.J. and Osborne, C.P.  2002.  Physiological ecology of Mesozoic polar forests in a high CO2 environment.  Annals of Botany 89: 329-339.

What was done
The authors grew one-year old saplings related to five extant species that existed in polar forests during the Mesozoic era in environmental chambers receiving atmospheric CO2 concentrations of 400 and 800 ppm for one month to determine the effects of elevated CO2 on photosynthesis and respiration in these woody species under polar light conditions (10 and 24 hours irradiance).

What was learned
Elevated CO2 significantly enhanced rates of net photosynthesis in two of the five species by more than 40% under conditions of 24-hour irradiance; and when the saplings were exposed to 10 hours of irradiance, atmospheric CO2 enrichment increased photosynthetic rates in four of the five species by an average of more than 60%.  With respect to respiration, elevated CO2 reduced this parameter in all species in both roots and leaves by 25 to 50%.

What it means
After introducing these CO2-induced effects on photosynthesis and respiration into a coniferous forest growth model, the authors determined that historically-elevated paleo-CO2 concentrations would have increased productivity in related polar forests during the Mesozoic.  Hence, since history tends to repeat itself, it is likely that the increasing CO2 content of the air will once again stimulate the productivity and growth of these forests.  High-latitude regions consequently need to be carefully considered when calculating the strength of the terrestrial global carbon sink.

Reviewed 29 May 2002