Phenological model performance under warmer conditions: application to pinot noir in Burgundy

Aim: The current work aims to assess the performance of two phenological models - a linear model (Grapevine Flowering Véraison model, GFV) and a curvilinear model (Wang and Engel model, WE) - to warmer temperature conditions for the grapevine variety Pinot noir in Burgundy. Methods and results: Simulations using historical data from the 1973-2005 period were similar between models and consistent with observations. To mimic potential climate warming for 2050 and 2100, 3 °C and 5 °C were added to each daily average temperature of the 1973-2005 dataset. The results showed that the two models simulated similarly the véraison stage of Pinot noir in Burgundy for temperature increases up to 5 °C. However, the simulation by the GFV model was 4.7 days earlier than that by the WE model when 10 °C was added. This difference may reflect the inhibitory effect of high temperatures on plant development incorporated in the equations of the WE model. Finally, both models were tested for three other sites in Europe (Carcassonne, Cagliari and Seville) with quite contrasting climatic conditions. Results obtained showed that both models differed significantly when they were applied at latitudes below 40°N. Conclusion : In cool-climate grape growing regions and for early grapevine varieties, increased temperatures (up to +5 °C) may advance the date of véraison as predicted by heat summation models but produce little difference in predictions between the simpler GFV model and the WE model. Significance and impact of the study : Both models (GFV and WE) satisfactorily reproduce the observed véraison dates for Pinot noir in Burgundy. For the range of temperature increases expected in the future for cool temperate areas, a model that uses a curvilinear response to temperature does not improve significantly the phenological predictions compared with a simple model based on a linear response.