Changes in the phenology and composition of wine from Franconia, Germany

While the majority of the highest quality wine-producing regions in Western and Central Europe have benefitted from an increase in quality ratings due to climate change, traditional Franconian wine is in danger of losing its unique characteristics and its traditional spatial distribution. A long-term (1949 to 2010) study was made of reference vineyard observations in Lower Franconia, Germany. This wine region in the federal state of Bavaria is one of the most northerly in the world. The current climate requires the use of adapted grape varieties and has an impact on the unique quality of traditional Franconian wine. In this research, phenological events and intervals, and composition (acid and sugar content at harvest) of white grape cultivars (Müller-Thurgau, Riesling and Silvaner) were analysed for trends over time and relationships with potential climate drivers using multiple regression. Overall, the phenology of grapevines in Lower Franconia has tended towards earlier occurrence with a shortening of phenological intervals. The relative amounts of sugar in the grapes at harvest have tended to increase. Furthermore, the findings confirm a consistent relationship between onset dates of phenological phases and corresponding climate data. The grapevines were most influenced by mean maximum temperatures preceding the event, whereas precipitation and sunshine appeared less important. The observed warmer season results in greater ripening potential in grapes; as a consequence, the sugar content increases, while the acid component decreases, resulting in an altered wine typicity and quality. Thus, the balanced ratio of sugar and acid content shifts in favour of the sugar component, which may result in a loss of the traditional character of Franconian wine.