The FACE approach was developed jointly by scientists from ARS and Brookhaven National Laboratory and has provided essential knowledge regarding the potential effects of anticipated increases in atmospheric CO2 on crop production. This particular paper identified a limitation in the original design, which has since led to improvements in FACE operating strategies in the US and around the world. The paper also clarified our original findings with respect to wheat phenology and yield.

Below is an interpretive summary of the paper in layman's terms.

Free-air CO₂ enrichment (FACE): Blower effects on wheat canopy microclimate and rates of plant development. Agricultural and Forest Meteorology, 2000, 103(4): 319-333. by P.J. Pinter, Jr., B.A. Kimball, G.W. Wall, D.J. Hunsaker, F.J. Adamsen, K.F.A. Frumau, H.F. Vugts, G.R. Hendrey, K.F. Lewin, J. Nagy, H.B. Johnson, F. Wechsung, S.W. Leavitt, T.L. Thompson, A.D. Matthias, and T.J. Brooks. 2000.

Conducting realistic field experiments to confirm hypotheses regarding the potential effects of global change on productivity of crops has been problematic for agricultural research scientists. Results from experiments conducted in growth chambers and glasshouses are often confounded by microclimatic artifacts caused by the enclosures themselves. Plant response is sometimes affected by restricted rooting volume and/or unnatural competition for light, water, and nutrients. Therefore, results from enclosure studies are not always scalable to the real world. An innovative experimental approach, developed jointly by Brookhaven National Laboratory and the USDA Agricultural Research Service, has resolved many of these problems. Commonly referred to by its acronym, "FACE", for Free Air Carbon dioxide Enrichment, this approach has provided a realistic and cost-effective method for evaluating the effects of elevated atmospheric CO₂ concentrations on growth, yield, and water requirements for important food and fiber crops, as well as for many natural plant species.

With current FACE technology, CO₂-enriched air is released around the perimeter of circular plots, and natural patterns of wind disperse the CO₂ across the experimental area. Our research showed that the blowers used to inject CO₂ exerted subtle effects on the microclimate similar to the way that wind machines protect orchards from frost. Under relatively calm conditions found at night in our area, the FACE blowers were found to increase air and leaf temperatures slightly and to change patterns of dewfall. Our research quantified the magnitude of these effects and explored their biological significance. The advantages of the FACE approach still outweigh disadvantages of doing elevated CO₂ research in enclosures or open-topped chambers. However, our findings emphasize the importance of evaluating even minor environmental perturbations caused by experimental equipment.

These published results have helped scientists formulate appropriate strategies for conducting global change research using similar and improved technologies at more than 20 locations around the world. This manuscript also provided us with an opportunity to demonstrate that elevated CO₂ by itself had no measurable effect on the length of the growing season or grain filling period of wheat. The extent to which rising levels of atmospheric CO₂ will affect agricultural production depends on the amount of water and nutrients provided to the crops. FACE has been an important new methodology for providing this information.

Paul J. Pinter, Jr.
Research Biologist
USDA, ARS, US Water Conservation Laboratory