Poster: Global change
Abs #
17: Energy Balance and Evapotranspiration of Soybean Exposed to Free Air Gas Concentration Enrichment of carbon dioxide and ozone
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Presenter: |
Bernacchi, Carl J., bernacch@life.uiuc.edu |
Authors | Bernacchi, Carl J. (A) (B) Long, Stephen P (B) Ort, Donald R (A) (B) Kimball, Bruce A (C) | | Affiliations: |
(A): Photosynthesis Research Unit, USDA-ARS
(B): Departments of Plant Biology and Crop Sciences, Univeristy of Illinois
(C): U.S. Water Conservation Laboratory, USDA-ARS
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Tropospheric concentrations of carbon dioxide ([CO2]) and ozone ([O3]) are increasing as a result of land-use changes and fossil fuel combustion. These changes are hypothesized to have a large effect on water use for crop species. While leaf-level responses to elevated [CO2] and [O3] are well documented for crop species, few studies have addressed canopy level responses to increases in these pollutants. Evapotransporation (ET) for soybean, one of the most important agricultural crop species, was measured using an energy balance approach. Plots of soybean were exposed to a 180 µmol mol-1 increase in [CO2], a 25% increase in ambient [O3], or both. Data for the elevated [CO2] and elevated [O3] treatments were collected throughout the 2002 and 2003 growing seasons and the elevated [CO2] X [O3] treatment was collected in 2003. Measurements of air and canopy temperature, relative humidity, net radiation, soil heat flux, and wind speed were recorded in 10 minute intervals from emergence to canopy senescence for each of the four treatments. Sensible heat flux was calculated from the wind and temperature measurements. ET was determined as a residual in the energy balance from net radiation, sensible heat flux, and soil heat flux. The results show a decrease in ET for all three treatments with the largest decrease observed for the plants grown in elevated [O3]. When integrated over the entire growing season, plants grown in elevated [CO2] and elevated [O3] used 10 and 18% less water, respectively. These results suggest that future atmospheric change may influence a crops response to drought conditions and may have feedback effects on atmospheric moisture, potentially altering regional precipitation patterns.
