Line Source Carbon Dioxide Release. I. Field Experiment
- L. H. Allen,
- R. L. Desjardins and
- E. R. Lemon
Carbon dioxide gas was released from one northeastsouthwest line in a corn (Zea mays L.) field during several days in August and September, 1969. CO2 concentration profiles were measured at 15 and 45 m downwind. The purposes of the releases were: (1) to study the micrometeorological transport processes in plant canopies using CO2, as a tracer, and (2) to determine the micrometeorological feasibility of CO2 enrichment under field conditions. The study showed that vertical turbulent diffusion and horizontal mass flow quickly diminished the concentration of CO2, downwind from the line source. High concentrations of CO2 could be maintained in the canopy only under a stable temperature stratification of the air which reduced vertical wind fluctuations. Short-term eddies with CO2 concentrations in excess of 1,000 ppm were observed 30 m downwind from the release line at an analyzer height of 530 cm, but these were very infrequent. CO2 concentration profiles showed that CO2 tended to be turbulently diffused upward and wafted downwind, with some of the CO2 being again transported into the canopy. Turbulent diffusion in the canopy was usually too active to maintain a high CO2 concentration; however, this same effectiveness of turbulence assures an adequate supply of CO2 to plant canopies under typical field conditions. This study showed, from a micrometeorological viewpoint, that CO2 enrichment would not be practical under most natural field and crop conditions because of rapid gaseous exchange with the bulk atmosphere.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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