|Free Air CO2 Enrichment (FACE) Project|
Determination of the effects of elevated CO2 and interacting environmental variables on agronomic crops.
Numerous CO2-enrichment studies in greenhouses and growth chambers have suggested that growth of most plants should increase about 30% on the average with a projected doubling of the atmospheric CO2 concentration. However, the applicability of such work to the growth of plants outdoors under less ideal conditions has been seriously questioned. The only approach that can produce an environment as representative of future fields as possible today is the free-air CO2-enrichment (FACE) approach.
A computer-control system uses the wind speed and CO2 concentration information to adjust the CO2 flow rates to maintain the desired CO2 concentration at the center of the FACE ring. The system uses the wind direction information to turn on only those pipes upwind of the plots, so that CO2-enriched air flows across the plots, no matter which way the wind blows. When wind speeds are low (< 0.4 m/s) and direction is difficult to detect, the CO2-enriched air is released from every other vertical pipe around the ring. The CO2 flow rate is updated every second, and the choice of which vertical pipes to release from is updated every 4 seconds.
1989 cotton at ample water
1990 and 1991 cotton at ample and limited supplies of water
1993 and 1994 wheat at ample and limited supplies of water
1996 and 1997 wheat at ample and limited supplies of nitrogen
1998 and 1999 sorghum at ample and limited supplies of water
More than a hundred papers have been published on various aspects of these experiments, including: leaf area, plant height, above- and below-ground biomass, apical and morphological development, canopy temperature, reflectance, chlorophyll, light use efficiency, energy balance, evapotranspiration, soil and plant elemental analyses, soil water content, sap flow, root biomass from soil cores, leaf and canopy photosynthesis, respiration, stomatal conductance, leaf water potential, carbohydrates, photosynthetic proteins, antioxidants, stomatal density and anatomy, digestibility, decomposition, grain quality, soil CO2 fluxes, and changes in soil C storage from soil and plant C isotopes. In addition, more than a dozen papers have been written by wheat growth modelers who utilized our data for validation of their models.
Hendrey, G.R. (Ed.) 1993. Free-air Carbon Dioxide Enrichment for Plant Research in the Field. C.K. Smoley, Boca Raton, FL, USA.
IPCC. 2001. [Houghton. J.T., Ding. Y/, Griggs. D.J., Noguer, M., Van der Linden, P.J., Dai, X., Maskell, K., Johnson, C.A. (Eds)] Climate Change 2001: The Scientific Basis, Contribution from Working Group I to the Third Assessment Report, Inter-governmental Panel for Climate Change.
Kimball, B.A., R.L. LaMorte, P.J. Pinter Jr., G.W. Wall, D.J. Hunsaker, F.J. Adamsen, S.W. Leavitt, T.L. Thompson, A.D. Matthias, and T.J. Brooks. 1999. Free-air CO2 enrichment (FACE) and soil nitrogen effects on energy balance and evapotranspiration of wheat. Water Resources Research 35(4): 1179-1190.
Kimball, B.A., K. Kobayashi, and M. Bindi. 2002. Responses of agricultural crops to free-air CO2 enrichment. Advances in Agronomy 77:293-368.
Ottman, M.J., B.A. Kimball, P.J. Pinter Jr., G.W. Wall, R.L. Vanderlip, S.W. Leavitt, R.L. LaMorte, A.D. Matthias, and T.J. Brooks. 2001. Elevated CO2 increases sorghum biomass under drought conditions. New Phytologist 150(2):261-273.
Triggs, J.M., B.A. Kimball, P.J. Pinter Jr., G.W. Wall, M.M. Conley, T.J. Brooks, R.L. LaMorte, N.R. Adam, M.J. Ottman, A.D. Matthias, S.W. Leavitt, and R.S. Cerveny. 2004. Free-air carbon dioxide enrichment effects on energy balance and evapotranspiration of sorghum. Agricultural and