The effect of soil and climate on the character of Sauvignon blanc wine

Il mondo del vino si è accorto che per la sua comprensione, valorizzazione e promozione è fondamentale conoscere le ragioni geologiche del vino, valutare il suo impatto sul paesaggio e acquisire il suo valore emozionale.

Right after the pouring of wine in a glass, a myriad of volatile organic compounds, including ethanol, overwhelm the glass headspace, thus causing the so-called wine’s bouquet [1]. Otherwise, it is worth noting that during wine tasting, most people automatically swirl their glass to enhance the release of aromas in the glass headspace [1]. About a decade ago, Swiss researchers revealed the complex fluid mechanics underlying wine swirling [2]. However, despite mechanically repeated throughout wine tasting, the consequences of glass swirling on the chemical space found in the headspace of wine glasses are still barely known.

Between 2002 and 2004 we studied the behaviour of two red grape varieties – Merlot and Cabernet Sauvignon – within the scope of an experimental protocol encompassing 14 plots, 7 of which had not been cultivated, situated in geographically distant locations representing different terroirs of Castilla-La Mancha.

In the last decades the growers of the Portuguese Dão winegrowing region (center of Portugal) are experiencing changes in climate that are influencing either grape phenology berry health and ripening. Aiming to study the relationships between climate indices (CI), seasonal weather and grapevine phenology, in this work long-term climate and phenological data collected at the experimental vineyard of the Portuguese Dão research centre between 1958 and 2019 (61 years) for the red variety Touriga Nacional, was analyzed. The trends over time for the classical temperature-based indices (Growing Season Temperature – GST -, Growing Degree Days – GDD, Huglin Index – HI and Cool Night Index – CI) presented a significantly positive slope while the Dryness Index (DI) showed a negative trend over the last 61 years. Regarding grapevine phenology, an average advance of 4.5 days per decade in the harvest day was observed throughout the last 61 years. Consequently, the weather conditions during the ripening period have changed, showing an increasing trend over time in the average temperature (higher magnitude in the maximum than in the minimum temperature) and a decrease in the accumulated rainfall. A regression analysis showed that ~50% of harvest date variability over years was explained by the temperature-based indices variability. These observed effects of climate change on bioclimatic indices and corresponding anticipation of harvest date can still be considered advantageous for the Dão terroir as it allows to achieve an optimal berry ripening before the common equinox rains and, therefore, avoid the potential negative impacts of the rainfall on berry health and composition.

Historical phenology records have indicated that advances in key developmental stages such as budburst, flowering and veraison are linked to increasing temperature caused by climate change. Using phenological models the timing of grapevine development in response to temperature can be characterized and projected in response to future climate scenarios.
We explore the development and use of grapevine phenological models and highlight several applications of models to characterize the timing of key stages of development of varieties, within and between regions, and the result of projections under different climate change scenarios.