SIMULATED RESPONSES OF ENERGY AND WATER FLUXES TO AMBIENT ATMOSPHERE AND FREE-AIR CARBON-DIOXIDE ENRICHMENT IN WHEAT

Citation
S. Grossman et al., SIMULATED RESPONSES OF ENERGY AND WATER FLUXES TO AMBIENT ATMOSPHERE AND FREE-AIR CARBON-DIOXIDE ENRICHMENT IN WHEAT, Journal of biogeography, 22(4-5), 1995, pp. 601-609
Citations number
22
Categorie Soggetti
Ecology,Geografhy
Journal title
ISSN journal
03050270
Volume
22
Issue
4-5
Year of publication
1995
Pages
601 - 609
Database
ISI
SICI code
0305-0270(1995)22:4-5<601:SROEAW>2.0.ZU;2-Y
Abstract
Increased ambient carbon dioxide has been associated with CO2-induced stomatal closure which affects growth and evapotranspiration of crop c anopies. This results in changes of the energy balance components of t he soil-plant-atmosphere system. The agroecosystem wheat model DEMETER was linked to a soil-vegetation-atmosphere-transfer module which incl udes the energy balance of the crop canopy and the energy balance of t he soil surface. Thus, it was possible to calculate evapotranspiration , canopy temperature and the changed ratio of sensible and latent heat fluxes in response to elevated atmospheric CO2 concentrations. The fr ee-air carbon dioxide enrichment (FACE) technique provided a largely u ndisturbed regime for atmospheric exchange. During the FACE wheat expe riment at Maricopa in 1992-93, the effects of elevated atmospheric CO2 concentrations on energy balance and evapotranspiration of the wheat canopy at about 350-370 mu mol/mol (control) and 550 mu mol/mol (FACE) were investigated. The recorded data were used for model validation. Diurnal trends of all energy balance components and the canopy tempera ture were simulated for FACE and control conditions using hourly weath er data. Results were compared with the observed data on 16 March 1993 . Simulated cumulative seasonal evapotranspiration was found in good a ccordance to the observed one. Consistent with observations, the simul ations suggest that there was a small reduction in evapotranspiration of about 4%. Of course, with the observed increases in growth, there w ere even larger increases in water use efficiency.