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Effects of Elevated CO2 and O3 Concentrations on the Yields of Wheat and Potatoes in Europe
Fangmeier, A. and Bender, J.  2002.  Air pollutant combinations - Significance for future impact assessments on vegetation.  Phyton 42: 65-71.

What was done
The authors plotted mean grain yields of spring wheat (Triticum aestivum L. cv. Minaret) and tuber yields of potato (Solanum tuberosum L. cv. Bintje) as functions of atmospheric CO2 concentration for conditions of ambient and high atmospheric O3 concentrations.  The wheat data were derived from the ESPACE-Wheat project of the European Stress Physiology and Climate Experiment - Project 1, which was conducted for three growing seasons at eight experimental field sites across Europe (Jager et al., 1999).  The potato data were derived from a similar experiment in another trans-European study: the CHIP project (Climate Change and Potential Impact on Potato Yield and Quality).  All studies employed open-top field chambers.

What was learned
For both wheat and potato, high O3 stress at ambient CO2 concentrations significantly reduced yields, by about 12% and 9%, respectively.  As the air's CO2 concentration was increased to approximately 540 and 680 ppm, however, there were no significant reductions in the yields of either wheat or potato due to the high O3 stress.  Consequently, whereas wheat yield in ambient-O3 air increased by 34% over the entire CO2 enrichment range investigated (from approximately 380 to 680 ppm), it increased by 46% in high-O3 air; while in the case of potato, the corresponding yield increases were 17% and 28%.

What it means
Under ambient conditions (CO2 = 380 ppm; O3 = 32.5 nl l-1 for wheat and 22.2 nl l-1 for potato over 12 hours), the imposition of high ozone concentrations (60.3 nl l-1 for wheat and 57.0 nl l-1 for potato over 12 hours) significantly reduces the yields of both wheat and potato growing in the field in Europe.  Enriching the air with CO2 to approximately 545 ppm and 680 ppm, however, completely compensates for the O3-induced yield losses while boosting the yields of both crops even higher.

Jager, H.-J., Hertstein, U. and Fangmeier, A.  1999.  The European stress physiology and climate experiments - Project 1 - Wheat.  European Journal of Agronomy 10: 153-260.

Reviewed 10 September 2003