Effects of inter-annual climate variability on grape harvest timing in rainfed hilly vineyards of Piedmont (NW Italy)

The current scenario of global warming impacts viticulture, influencing grape and wine quality. A study was carried out in the "Basso Monferrato" region, a rainfed hilly vine-growing area in NW Italy, to investigate the relationships between climate variables and grape harvest dates. The dates of harvest for some local wine grape varieties were recorded from 1962 to 2019 in the Vezzolano Experimental Farm and surrounding vineyards. Three series of climate data were investigated by means of trend analysis for temperature variables, Huglin index, and precipitation during the growing period. A significant trend was found for temperature variables (positive) and harvest dates (negative), indicating anticipation of harvest beginning from 11.6 to 34.2 days in the 58-years study period, depending on the variety. The influence of increasing temperature and Huglin index in anticipating the harvest period, particularly the harvest beginning, was also highly significant for all the considered varieties and vineyards in the Monferrato area. Implication under a climate warming scenario, the relevance of having available continuous and homogeneous datasets and possible future studies were also discussed.