Climatic change in winegrowing. Effects on red grenache

Abstract

Both grape composition and wine style are the result of the environment and of viticultural management (Jackson & Lombart, 1993). Nowadays, one of the challenges of viticulture with respect to climate change is to achieve a sustainable production that ensures an optimum ripening process in order to produce high-quality wines. A vineyard reflects its immediate growing area, including the soils and climatic conditions that influence production. Variations resulting from the current climate change, especially in regions like the Mediterranean basin, should be carefully analysed and characterised for a better understanding. Such climatic changes quickly affect growing regions which possess poor coarse-textured soils with low fertility, and especially those located in areas with low and irregular precipitation that are also subject to erosive phenomena. Water stress – resulting from high evapo-transpiration, lack of summer rainfall, and well-drained soils with low retention capacity – has a significant effect on such vineyards. An understanding of vegetative growth, and of how this affects the final composition of the grapes, is essential to determining optimal harvest dates for high-quality wines. The negative effects of high temperatures, which reduce the synthesis of phenolic compounds, a factor directly related to the quality of red wines, should be noted. This paper evaluates the effect of climate variability on two different plots in the same growing area of the Priorat Protected Designation of Origin (PDO) (Catalonia, NE Spain), focusing on the grape varietal V. vinifera ‘Grenache’, in two climatically differentiated vintages, 2010 and 2011. The PDO Priorat area, situated behind the coastal mountain range of Tarragona, tends towards continentality with very little precipitation during the vegetation cycle. The soil, which is poor, dry and rocky, is largely composed of slate schist, known as “llicorella”. The two chosen plots of Grenache are referred to as: LO (in the township of Lloar) and EM (in the township of Molar), which are distinct topographic locations within the designation of origin. Grenache vines in LO are 14 years old, growing in east-south facing terraces. Grenache vines in EM are 16 years old and south-facing. Both vineyards feature a 2-wire VSP trellis system (70 cm in height). The vines are pruned as bilateral cordon. During 2010 and 2011, leaf area (LA) at the phenological stages of pea size (PS), veraison (V), final ripening (RP) and post-harvest (PH) was measured. Berry phenolic maturity was monitored and the chemical analyses of the wine were carefully evaluated. The 2010 vintage was characterized by a heterogenic distribution of rainfall and a lower vapor deficit pressure than 2011. Total leaf area (TLA) on plots did not differ significantly in the temperate year. In the drier vintage, however, vines from LO developed more leaf area than those growing in the south-facing terraces at EM. Nevertheless, the total leaf area before harvest was similar. The heterogeneity in the soil profile at the LO location could likely induce a variation in the drainage capacity, affecting the vine growth (TLA). Small berries from EM produced the highest levels of anthocyanins. EM had the highest content in ANT T, ANT E, IPT and DMACA in both years. Concerning the wines, the highest concentration of anthocyanin was found in the EM treatment, with greater differences than LO in 2010. The warming weather conditions at the end of the ripening process promote an acceleration of the sugar content that affects wine composition by increasing the alcoholic degree, whereas the colour of the wine – the phenolic concentration in anthocyanins – diminishes. Grenache vines growing under warm climate conditions (Priorat Protected Designation of Origin) in heterogeneous-stony soils showed notable variability in wine composition with respect to climate change.

Keywords: climate, stony soil, water stress, vapor pressure deficit, wine composition, anthocyanins.