Quantifying field-scale effects of elevated carbon dioxide concentration on crops

Climate change will affect crop growth and agricultural production worldwide. Crop production will be affected not only by modified rainfall patterns, increased air temperatures and changes in evaporative demand, but also elevated atmospheric CO 2 concentrations ([CO 2]). This study used meta-analytic techniques to quantify field-scale effects of elevated [CO 2] (mainly 541 to 620 μmol mol -1) on agricultural crops in free air CO 2 enrichment (FACE) conditions. Overall, crops benefit from elevated [CO 2] by improving water productivity (+23% for biomass production and +27% for yield production), which is achieved through production increases in biomass (+15% for aboveground biomass) and yield (+16%), in combination with a decrease in seasonal evapotranspiration (-5%). Increased root:shoot ratios (+24%) indicate a more than proportional stimulation of belowground biomass production. Less critical, yet statistically significant are changes in canopy development rate and in phenology. Certain statistically significant differences existed between C3 and C4 crops, and between levels of environmental stress (nitrogen and water availability). Once the effect of elevated [CO 2] is well understood and quantified, crop modellers can investigate the interactions with other climatic factors, providing better estimates of potential impacts on food production. © Inter-Research 2012.