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

抄録

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.