MODELING THE IMPACT OF CLIMATIC WARMING ON WINTER CEREAL DEVELOPMENT

Predictions of climate change suggest modification of developmental calendars for temperate crops, particularly those grown over winter. The AFRC-Wheat developmental model was used with 92 and 105 year daily temperature records from Edinburgh and Oxford, respectively, to examine the sensitivity of modelled winter wheat development to both past interannual temperature variations and arbitrary temperature changes. The model is driven by accumulated temperatures, but modified by vernalization requirement and photoperiod responses. Using the historic data, the duration from sowing to the stages of double-ridges and anthesis is approximately linearly related to mean temperature, and is more responsive at the northern site of Edinburgh than at Oxford. The duration from sowing to maturity is only weakly related to seasonal mean temperature. This is because the time course of temperatures within the season is critical in determining development rates, therefore seasons with equivalent mean temperatures can show very different wheat development calendars. This emphasizes the limitations of current climatic scenarios with little seasonal detail for agricultural impact predictions. The model does not appear to work with temperatures mom than 1-degrees-C lower than present conditions at Edinburgh. Arbitrary warming by 2 and 4-degrees-C resulted in substantial shortening of the growing season (by 30 and 49 days at Edinburgh), implying major losses of potential yield, unless varieties or sowing dates are modified so that the development calendar is fitted to the insolation pattern.