Analysis of temporal variability of cv. Tempranillo phenology within Ribera del Duero Do (Spain) and relationships with climatic characteristics

The Ribera del Duero Designation of Origin (DO) has acquired great recognition during the last decades, being considered one of the highest quality wine producing regions in the world. This DO has grown from 6,460 ha of vineyards officially registered in 1985 to approximately 21,500 ha in 2013. The total grape production stands at around 90 million kg, with an average yield that approaches nearly 4,500 kg/ha. Most vineyards are cultivated under rainfed conditions. For that reason climate variability, with higher temperatures and higher water demands, may affect grape development and production. The aim of this work was to analyze the influence of the climatic characteristics on phenology within the DO. Twenty plots planted with Tempranillo (the main variety cultivated in the area) were analyzed from 2004 to 2012. The representativeness of those years was analyzed by comparing their characteristics with a longer series recorded from 1980 to 2012. The relationship between phenology and the different variables were confirmed with a multivariable analysis. While the dates during the time period showed high variability, on average, bud break was April 28th; bloom June 16th and veraison August 12th. Differences of up to 21 days in the dates were observed between years, with the earliest dates observed in dry years (2005, 2006 and to a lesser degree in 2009). On the other hand, later dates occurred in the wettest year of the period (2008). High correlations were found between veraison and temperature variables as well as with precipitation-evapotranspiration recorded during the bloom-veraison period. These effects tended to be higher in in the central part of the DO.