Future shifts in the phenology of table grapes on Crete under a warming climate

Abstract

Climate change is expected to pose major challenges to viticulture. The projected increase in temperature in the Mediterranean region due to climate change is likely to influence the timing of grapevine phenological stages. This study developed and validated a phenological model, from budbreak to maturation phenological stages, based on the growing degree days for the Sultana grapevine cultivar on Crete Island, Greece, and used the model to assess potential changes in future phenology timing employing different climate change scenarios. A dataset of unpublished phenological observations from 20 locations spanning four decades was used to validate the phenological model. The root mean squared difference (RMSD) of the calibration-validation procedure was estimated between 5.4 and 11.5 days, depending on the phenological stage. The model outperformed for the flowering and maturity stages. The highest RMSD was found for the shoot development stages. Projections determined an earlier occurrence of the different phenological stages. Near future climate (2020–2060) projections indicate budbreak advancement by 7 to 8 days and maturity by 4 to 5 days on average. For the far future (2060–2100), the respective changes are 11 to 18 and 7 to 9 days earlier. Discussion on the underlying uncertainty sources is provided.