Projections of vine phenology and grape composition of Tempranillo variety In Rioja DOCa (Spain) under climate change

Aims: Some of the most direct effects of climate variability on grapevines are the changes in the onset and timing of phenological events and in the length of the growing season, which may affect grape quality. The aim of this research was to analyze the projected changes in vine phenology and on grape composition of the Tempranillo variety in Rioja DOCa under different climate change scenarios.

Methods and Results: Three zones of Rioja DOCa, located at different elevations and with different climatic conditions were compared. For the analysis, vine phenology referred to flowers separated and veraison (stage H and M, according to Baillod and Baggiolini) and maturity defined based on the date at which 13ᵒ were reached, were analysed in the three zones for the period between 2008 and 2018. Grape composition at maturity, including variables related to acidity and polyphenol content was also evaluated for the same period. The weather characteristics for the places where the plots were located were also analysed using data of different meteorological stations belonging to the Rioja government. The thermal requirements to reach each phenological stage were evaluated and expressed as the GDD accumulated from DOI=60, which were considered to predict the changes under future climatic conditions. The analysis was done for the future conditions predicted by 2050 and 2070 under two Representative Concentration Pathway (RCP) scenarios –RCP4.5 and RCP8.5-, which were simulated based on an ensemble of 10 models.

An advance of the phenological stages was predicted, higher for veraison and maturity than for floraison. 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 acidity could suffer a decrease with increasing temperature, while anthocyanins could decrease by the increase of temperature but increase due to the higher expected water deficit, and these changes could differ among zones. In addition, due to the advance in the phenology a decoupling between anthocyanins and sugars could result, which suggest the need of applying new management techniques to maintain grape quality.

Conclusion: 

The Tempranillo variety cultivated in Rioja DO may suffer significant changes in phenology and in grape composition under climate change, affected both by increasing temperatures and higher water deficits. However, differences were found between zones within the Rioja DOCa.

Significance and Impact of the Study: The study allowed quantifying the differences in the impact that climate change may produce in phenology and in grape composition in zones with different climatic conditions, which may be taken under consideration to identify potential areas in which the Tempranillo variety may suffer lower impacts under climate change.