Variability in the potential effects of climate change on phenology and on grape composition of Tempranillo in three zones of the Rioja DOCa (Spain)

The objective of this research was to analyse the potential effect of climate change on phenology and berry composition of the variety Tempranillo cultivated in areas of the Rioja DOCa (Spain) with different climatic characteristics. Three zones were selected within the DOCa, which were located at elevations between 325 and 650 m a.s.l. Phenology and the evolution of berry composition during ripening was analysed for the period 2008-2018. This information included the dates of the phenological stages H (separated flowers), M (veraison) and maturity (based in a fixed value of the probable alcoholic degree (PVAD)) and as well as pH, total acidity, malic acid, total anthocyanins, total polyphenols index and colour intensity, recorded in two plots at each location. The climatic conditions recorded during the period of study were evaluated from meteorological stations located close to the vineyards. The average predicted changes in temperature (maximum and minimum) and in precipitation, under two Representative Concentration Pathway (RCP) emission scenarios (RCP4.5 and RCP8.5) and simulated using an ensemble of 10 models were analysed by 2050 and 2070 for each zone. These data were obtained using the MarkSim™ DSSAT weather file generator. The relationship found at present between climate characteristics and the phenology and grape composition were considered in order to project the changes under climate change. The results indicated projected increase of temperature higher in the warmer than in the cooler area, and changes in average precipitation, which although being small will contribute to increase water deficits. The results predict that all evaluated phenological stages will suffer an advance, which will be higher for veraison and maturity than for the stage related to flowering. The advance of the stage H, M and maturity for the three zones by 2050 could be up to 5, 8, and 12 days, respectively under the RCP4.5 emission trajectory, and up to 8, 12 and 15, respectively under the RCP8.5 emission trajectory. The predicted advances indicate that the differences in timing that already exists between zones will be maintained or even increase, which will imply reaching maturity in the second half of August in the warmer area and in earlier September in the coolest one. Grape composition could also suffer changes, reaching the required PVAD earlier with a decoupling between anthocyanins and sugars and with lower acidity caused by the increase of temperatures.