Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/2/2008
Publication Date: 5/2/2008
Citation: Hatfield, J.L., Prueger, J.H. 2008. Linkages between CO2 and H2O fluxes over corn and soybean canopies [CD-ROM}. In: 28th Agricultural and Forest Meteorology Conference, April 28 - May 1, 2008, Orlando, FL.
Technical Abstract: Measurements of CO2 and H2O vapor exchanges are becoming routine observations over many surfaces. These data are generally used to estimate the fluxes of these two critical gases as part of the energy exchanges between the plant and atmosphere. The value in these observations extends beyond that contained in the flux measurements and we have been evaluating the relationships between CO2 and H2O fluxes to determine the value of these parameters in defining canopy resistance to C and H2O exchanges and the dynamics of canopy level responses throughout the growing season. A data set has been collected since 2001 over the same field in central Iowa in which both corn and soybean are grown in rotation. The field is divided in half so that we obtain data over each crop every year. A complete energy balance and eddy covariance station is located in each field and data are collected at 20 Hz, retrieved from the data acquisition system via cell phone at night and then processed into various time intervals after screening and quality control. These data are being used to evaluate the diurnal relationships between CO2 and H2O vapor fluxes over both canopy surfaces. The diurnal relationship between CO2 and H2O vapor fluxes responds to the physiological state of the plant and there is an asymmetric relationship within a given day and these patterns change during a drydown cycle of the crop. There are different patterns for the corn versus soybean crop that relates to physiology of the crop. Use of these relationships helps to create a situation in which there is increased value in energy balance studies that can explain crop response to environmental stresses.