Response of dryland spring wheat yield to elevated CO₂ concentration and temperature by APSIM model

Global warming has become the most complicated issue facing agriculture production in the world and has received much attention in recent years. In order to determine the effect of global warming on spring wheat grain yield, field experimental results in the semiarid Dingxi region were used in APSIM model simulation and analysis. Spring wheat yield response to elevated CO₂　concentration and temperature was researched by simulating wheat yield under regular climatic conditions. The used APSIM model parameters were firstly modified and then verified based on field data. Spring wheat grain yield was stimulated by the APSIM model for a unitized design of 7 levels of temperature and CO₂ concentration. Regression equations and path analyses were also used to analyze the response of spring wheat grain yield to the changes in temperature and CO₂ concentration. The results showed that average increase in spring wheat grain yield was 4.9%, with a maximum increase of 14.6% when CO₂ concentration increased by 100 mol·mol^-1 at constant temperature. A quadratic parabola relationship was noted between spring wheat grain yield and CO₂ concentration, which indicated an increasing tendency. Spring wheat grain yield increment reduced with further increases in CO₂ concentration. Average drop in spring wheat grain yield was 6.1%, with a maximum drop of 14.2% when temperature increased by 1 ℃ at constant CO₂ concentration. Also a quadratic parabola relationship was noted between spring wheat grain yield and temperature, which suggested a declining tendency. While synergy effects of temperature and CO₂ concentration on spring wheat grain yield were positive, although negative temperature effects on grain yield were more obvious than positive CO₂ concentration effects. The study concluded that global warming with increased temperature and CO₂ concentration negatively affected dryland spring wheat grain yield in semiarid China.