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Effects of Elevated CO2 and Ozone on Ponderosa Pine Trees
Reference
Olszyk, D.M., Johnson, M.G., Phillips, D.L., Seidler, R.J., Tingey, D.T. and Watrud, L.S.  2001.  Interactive effects of CO2 and O3 on a ponderosa pine plant/litter/soil mesocosm.  Environmental Pollution 115: 447-462.

What was done
Ponderosa pine (Pinus ponderosa Laws.) seedlings were grown out-of-doors for two years in environmental SPAR units receiving atmospheric CO2 concentrations of 390 and 670 ppm in combination with low (40 ppb) and high (60 ppb) ozone concentrations to determine the effects of these two trace gasses - one beneficial and one detrimental - on this coniferous tree species.

What was learned
Elevated CO2 enhanced annual average rates of net photosynthesis by 39% and increased stem diameters by 14% and 3% at low and high ozone concentrations, respectively.  In addition, elevated CO2 increased bud lengths at the end of the second growing season by 17%.  This phenomenon led to a transitory stimulation of elongation and growth of terminal buds the following spring (+38%), but only in CO2-enriched units receiving low ozone concentrations.

What it means
As the atmospheric CO2 concentration rises, ponderosa pine trees will likely exhibit increases in photosynthesis and biomass production, in spite of potential concurrent increases in the air's tropospheric ozone concentration.  This beneficial phenomenon will likely lead to the formation of larger-sized buds at the end of each growing season; and these bigger buds will likely contribute to more robust growth rates and biomass production when growth resumes in the spring.  Thus, both growth and carbon sequestration by this species should rise in tandem with future increases in the air's CO2 content.