Change in climate and berry composition for grapevine varieties cultivated in the Loire Valley

Abstract

We analyzed the nature and trends of climate variables and bioclimatic indices for 6 locations situated in the Loire Valley, northwest France, along with the berry composition of the 6 main grapevine varieties cultivated there, from 1960 to 2010. Results show significant increases in mean temperature (by 1.3 to 1.8C) over the growing season (April to September) throughout the Loire Valley, with maximum temperatures increasing more strongly than minimum temperatures. Temperature variables, such as spring and summer temperatures, the number of days with maximum temperatures > 30C and bioclimatic indices increased significantly. The Huglin Index indicated that the 6 locations in the Loire Valley have shifted from a cool climate to a temperate climate between 1960 and 2010, and increases in growing degree-days were highly correlated with earlier harvest dates. The berry composition of the 6 main white and red grapevine varieties changed significantly, with higher sugar concentrations and lower titratable acidity at harvest. We conclude that these changes in berry composition were significantly influenced by the increases in temperature over the study period.