WILL A DOUBLING OF ATMOSPHERIC CARBON-DIOXIDE CONCENTRATION LEAD TO AN INCREASE OR A DECREASE IN WATER-CONSUMPTION BY CROPS

Simulations with a soil/vegetation/atmosphere (SVAT) model for normal midlatitude summertime conditions corn and soybeans in order to assess the effect of doubling CO2 concentration on transpiration. A second p urpose of this short communication is to emphasize that feedback proce sses present in the plant canopy but absent in the laboratory can lead to divergence between experimental and simulated results. In contrast with results reported by Cure and Acock (1986), increases in stomatal resistance commensurate with a doubling of CO2 concentration produced negligible changes in simulated transpiration. When we take account o f the effect of biomass increases brought about by a CO2 doubling, a s mall seasonal increase in transpiration is indicated.