Modelling predicts that heat stress, not drought, will increase vulnerability of wheat in Europe

Abstract

New crop cultivars will be required for a changing climate characterised by increased summer drought and heat stress in Europe. However, the uncertainty in climate predictions poses a challenge to crop scientists and breeders who have limited time and resources and must select the most appropriate traits for improvement. Modelling is a powerful tool to quantify future threats to crops and hence identify targets for improvement. We have used a wheat simulation model combined with local-scale climate scenarios to predict impacts of heat stress and drought on winter wheat in Europe. Despite the lower summer precipitation projected for 2050s across Europe, relative yield losses from drought is predicted to be smaller in the future, because wheat will mature earlier avoiding severe drought. By contrast, the risk of heat stress around flowering will increase, potentially resulting in substantial yield losses for heat sensitive cultivars commonly grown in northern Europe.

Figure 1. (A) Anthesis, and (B) maturity.

Mean simulated day of anthesis and maturity for the baseline (black rectangles) and for the 2055(A1B) scenario (box plots) at nine European sites: TR (Tylstrup, Denmark), WS (Warsaw, Poland), WG (Wageningen, the Netherlands), RR (Rothamsted, UK), MA (Mannheim, Germany), DC (Debrecen, Hungary), CF (Clermont-Ferrand, France), MO (Montagnano, Italy) and SL (Seville, Spain) (see Table SI.1 for details). Box plots are constructed from 15 predictions of mean day of anthesis (and maturity) for climate scenarios (each consists of 300 yrs of daily weather) based on 15 individual GCMs from the CMIP ensemble. Box boundaries indicate the 25 and 75-percentiles, the line within the box marks the median, whiskers below and above the box indicate the 10 and 90-percentiles.

Figure 2. Grain yield.

Mean simulated grain yield for the baseline (black rectangles) and for the 2055(A1B) climate scenario with no change in [CO₂] of 338 ppm (considering effect of change in climate only, open box plots) and increased [CO₂] of 541 ppm (gray box plots) corresponding to the A1B emission scenario. All wheat cultivars were assumed to be tolerant to heat stress around anthesis.

Figure 3. (A) 95-perccentiles of DSI, and (B) soil water deficit at anthesis.

For the baseline (black rectangles) and for the 2055(A1B) climate scenarios (box plots).

Figure 4. Probability of maximum temperature exceeding temperature thresholds.

Thresholds of 27°C (A,B) or 30°C (C,D) within 3 days of anthesis (A,C) or consecutively with 3 days of anthesis and within 3 days of five days after anthesis (B,D) for the baseline (black rectangles) and for the 2055(A1B) climate scenarios (box plots). Sirius was used to calculate anthesis dates for each individual year of baseline and 2055(A1B) climate scenarios for 15 GCMs from the CMIP3 ensemble.