| The objectives of this work were (1) to design a system to monitor the heat, water vapour and carbon dioxide (CO;The fluxes of heat, water vapour and CO;Two BREB systems were designed and tested for differences by establishing them over the same alfalfa (Medicago sativa L.) crop to provide half-hour flux averages of heat, water vapour and CO;The two BREB systems were separated to simultaneously provide fluxes above alfalfa and maize (Zea mays L.). Differences existed in fluxes between alfalfa and maize exposed to the same environmental conditions, which were characteristic of their C3 and C4 metabolisms, respectively. Of special interest was the effect of chilling nighttime temperatures on the CO;A simplified combined aerodynamic (SCA) method was investigated to calculate sensible heat flux using wind speed and air temperature gradients. The sensible heat flux and measurements of net radiation and soil heat flux were then used to determine latent heat flux. The sensible and latent heat fluxes calculated using the BREB method were significantly different from fluxes obtained by the SCA method. A difference of 9% existed between actual accumulated evapotranspiration values using the two methods, which was dependent on the magnitude of the Bowen ratio. |
