Spatial and temporal variability of cv. Tempranillo response within the Toro DO (Spain) and projected changes under climate change

This work aimed to analyse the spatial and temporal variability of the response of Tempranillo variety within the Toro Designation of Origin (DO) and the potential changes under climate change scenarios. The research included the analysis of phenology (bud break, bloom, veraison and maturity) and grape composition at harvest recorded in plots located at seven locations in the DO, at elevations between 667 and 779 m above the sea level (a.s.l.). Changes in phenology and composition were projected for 2050 and 2070 under two emission scenarios (Representative Concentration Pathways RCP4.5 and RCP8.5), considering the predicted changes in climate variables using an ensemble of models. Variations in the phenological timing of up to 28 days for bud break, bloom and veraison and up to 30 days for maturity were recorded during the period analysed and titratable acidity varied between 4 and 8 gL-1. The variability in phenology and grape acidity was mainly driven by temperature and available water in different periods between phenological stages, although the effect of soil properties was also confirmed. Under warmer conditions, an advance of all phenological phases was projected (up to 6, 6, 8 and 12 days by 2050 under the RCP4.5 scenario and near double under the RCP8.5 scenario). In addition, a decrease in titratable acidity is projected (about 1.1 and 1.4 gL-1 by 2050, respectively, under the RCP4.5 and the RCP8.5 scenario and up to 2.0 gL-1 by 2070 under the warmest scenario). The results were in agreement with the variability observed in years with contrasting weather conditions.