Influences of meteorological and vegetational factors on the partitioning of the energy of a rice paddy field

Observations made in a paddy field were analysed to show the influences of meteorological and vegetational factors on the crop's energy budget. Energy budget in the paddy field was characterized by the major partitioning to latent heat flux LE and by the negative Bowen ratio B mostly in the afternoon. Canopy resistance r(c), estimated with the Penman-Monteith equation, was related to the influences of solar radiation SR, vapour pressure deficit VPD and plant height. The results demonstrated that r(c) could not directly account for B but that critical canopy resistance r(cc), defined as the canopy resistance when B = 0, could be used to standardize r(c), and that r(c) - r(c), proved to be a good parameter to account for B. Influences of bulk stomatal response on energy partitioning were assessed as follows: the Bowen ratio dropped below zero, while the bulk stomatal aperture dwindled with the increase of VPD. In addition, stomata of a big leaf acted to promote the partitioning to LE against the rise of SR in the condition of higher VPD. Copyright (c) 2005 John Wiley & Sons, Ltd.