The effects of climatic variation in Europe on the yield response of spring wheat cv. Minaret to elevated CO2 and O3: an analysis of open-top chamber experiments by means of two crop growth simulation models.

摘要

In 25 open-top chamber experiments in 1994-96 at 9 locations in 8 European countries, spring wheat cv. Minaret was exposed to ambient and twice ambient CO2 and ambient and nearly twice ambient O3. Grain yields in the control treatments (ambient levels of CO2 and O3) varied greatly between sites. Yield response to elevated CO2 and O3 also showed great variation. Two simulation models were used to analyse the effects of climatic differences between sites: AFRCWHEAT2-O3 and LINTULCC. AFRCWHEAT2-O3 simulates phenology, canopy development and photosynthesis in greater detail than LINTULCC. Both models account for the effects of light and temperature on crop growth. New algorithms were developed to simulate the effects of CO2 and O3. Weather data that were measured in the experiments were used as input, and simulated growth responses to CO2 and O3 were compared with measurements. No attempt was made to merge the 2 models. Thus 2 independent tools for analysis of data related to climate change were developed and applied. The average measured grain yield in the control treatment, across all 25 experiments, was 5.9 t ha-1, with a standard deviation (SD) of 1.9 t ha-1. The models predicted similar average yields (5.5 and 5.8 t ha-1 for AFRCWHEAT2-O3 and LINTULCC, respectively), but smaller variation (SD 1.2 t ha-1 for both models). Average measured yield increase due to CO2 doubling was 30% (SD 22%). AFRCWHEAT2-O3 predicted a slightly lower value (24%, SD 9%), whereas LINTULCC overestimated the response(42%, SD 11%). The average measured yield decrease due to nearly doubled O3 levels was 9% (SD 11%). Both models showed similar results, albeit with lower variation (7% yield decrease, with SDs of 6 and 4%). Simulations accounted well for the observationthat, at elevated CO2, the percentage yield loss due to O3 was lower than at ambient CO2. The models predicted lower variation among sites and years than was measured. Yield response to CO2 and O3 was predicted to depend on the climate, with a predominant effect of temperature on the response to CO2. In the measurements, these climatic effects were indeed observed, but the greater part of the variation was not related to light intensity, temperature, CO2 or O3. This unexplained variability in the measured data set was probably caused by factors not accounted for in the models, possibly related to soil characteristics.