Efectes del canvi climàtic en els vins de carinyena en ecosistemes vulnerables. DOQ Priorat

Abstract

Grape composition and wine style are the result of the interaction of both environment (climate and soil) and human management. One of the challenges of viticulture with respect to climate change is to achieve a sustainable production that guarantees an optimum ripeness of grapes in order to obtain quality wines. The Priorat climate is hot and the soil is poor and dry, thus altering both the ripening of grapes and the final composition of wines. Today, influenced by global warming, the Priorat vineyards are an adequate site for the study of vulnerability linked to the crop and grape management. Phenology, yield, phenolic ripeness of grapes and wine composition in 5 plots of Carinyena (with different orientations and elevations), located in the municipalities of El Molar (EM, early region) and Porrera (PO, late region) were evaluated during 2009 and 2010. Significant differences within plots were found in the warm-hot vintage (2009). The climatic variability at the end of the ripening process is due mainly to the effects of high temperatures and the vapour deficit pressure. During warm years the highest phenological differences between early and late regions were recorded, which reached a maximum of one week at budbreak and veraison. The start of budbreak is delayed in years of low winter temperatures but this delay does not seem to affect the variations in the harvest date. With respect to seasonal climate variability, the temperature rises in spring and autumn shortens the phenological stages in the late region, causing advances in flowering and harvest. The warm autumn also has a noticeable effect on the elongation cycle of the vine in the early region, prolonging the period from harvest to leaf drop. In general, vineyards that develop a big canopy with high leaf area are not able to save enough water and they can not reach an optimal ripeness. In fact, the plants suffer defoliation in the fruit zone. On the other hand, the low vigour of plants leads to a critical decrease of yield, and such plants are also vulnerable to climate change. High temperatures at the end of ripening in warm vintages promotes grape-berry dehydration that reduces the quality of the grape. The differences in Brix and aciditybetween vineyards are independent of orography/vintage. Acidity remains at higher levels during the longer summers with high temperatures maintained until harvest. The accumulation of anthocyanin is favored in hot and dry years in the late region, whereas the tannin content is higher in the early regions and warm years. On the basis of the variability of plots and vintages, this study has predicted an interval of phenol content for classifying Carinyena wine qualities. Total phenol content (TPC) varies from 45 to 72 while total tannins range from 1.1 to 3 g/L. Regardless of vintage and topography (plot), the anthocyanin range is narrower, running from 441 to 526 mg/L. The style of red wines could be defined on the basis of the phenol concentration to improve winemaking techniques.