Growth and water use of wheat under present and future levels of CO2

Abstract

A mechanistic simulation model was used to examine the expected responses of wheat to a doubling in atmospheric CO2 concentration in combination with a 2°C rise in temperature. The model produced satisfactory simulations of total biomass, leaf area and canopy transpiration under present climatic conditions. However, soil evaporation was underestimated by up to 35% by the simulations. Model predictions suggested that increased CO2 levels should lead to increased biomass and potential yields of wheat up to about 550ppm, after which photosynthesis under full sunlight increases only gradually with CO2. Higher temperatures are expected to decrease biomass production by shortening the growing season and by increasing plant respiration. A doubling of CO2 concentration and a temperature increase of 2°C is expected to cause only marginal changes in biomass production. Transpiration use efficiency may be enhanced by -20% with a doubling of CO2 above current levels.