Responses of wheat and rice to factorial combinations of ambient and elevated CO2 and temperature in FACE experiments

Elevated CO₂ and temperature strongly affect crop production, but understanding of the crop response to combined CO₂ and temperature increases under field conditions is still limited while data are scarce. We grew wheat (Triticum aestivum L.) and rice (Oryza sativa L.) under two levels of CO₂ (ambient and enriched up to 500 μmol mol^?1) and two levels of canopy temperature (ambient and increased by 1.5–2.0 °C) in free‐air CO₂ enrichment (FACE) systems and carried out a detailed growth and yield component analysis during two growing seasons for both crops. An increase in CO₂ resulted in higher grain yield, whereas an increase in temperature reduced grain yield, in both crops. An increase in CO₂ was unable to compensate for the negative impact of an increase in temperature on biomass and yield of wheat and rice. Yields of wheat and rice were decreased by 10–12% and 17–35%, respectively, under the combination of elevated CO₂ and temperature. The number of filled grains per unit area was the most important yield component accounting for the effects of elevated CO₂ and temperature in wheat and rice. Our data showed complex treatment effects on the interplay between preheading duration, nitrogen uptake, tillering, leaf area index, and radiation‐use efficiency, and thus on yield components and yield. Nitrogen uptake before heading was crucial in minimizing yield loss due to climate change in both crops. For rice, however, a breeding strategy to increase grain number per m² and % filled grains (or to reduce spikelet sterility) at high temperature is also required to prevent yield reduction under conditions of global change.