Elizabeth Wolkovich

Shifts in phenological events due to climate change have been widely studied. Yet, few studies have looked at interphenophases, the duration between two phenological events, and how they have been affected by climate change. This gap presents an opportunity to better understand both fundamental plant development and how climate change could impact it. Using hierarchical Bayesian modeling and a diverse dataset of winegrape varieties collected at Domaine de Vassal in the south of France, we determine how phenological events and interphenophases have changed since 1980. Overall event date advanced for budburst, flowering, veraison, and maturity as temperatures increased. Despite these advances, we found that most interphenophases lengthened: across all varieties budburst to flowering, veraison to maturity, and budburst to maturity lengthened while flowering to veraison remained the same. Among ripening classifications, we found no difference in change over time for budburst to flowering, veraison to maturity, or budburst to maturity, but found that for flowering to veraison, change in days per decade increased as ripening occurred later in the season. When looking at the growing degree days (GDD) of interphenophases, GDD increased for all phenological events and interphenophases. These results suggest that winegrape development may be limited by factors other than temperature, such as sugar accumulation during ripening. Moreover, we found high diversity in interphenophase rates of change among variety. While the diversity of winegrape varieties represents an important resource as vineyards prepare for changing climates, more work needs to be done to understand what characteristics are driving variety differences. Additionally, our GDD shifts indicate a need to revise GDD calculations to reflect how grapevines experience high temperatures.

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