Scale effect of terroir under three contrasting vintages in the Chianti Classico area (Tuscany, Italy)

Abstract

In viticulture, terroir is a concept used to explain the specific combination and interaction of natural and human factors that provides distinctive characteristics to the wine. The role of soil and geology on wine characteristics is debated and sometimes considered less important than either climate or the human component.The present study, performed on one of the largest farms of the “Chianti Classico” wine district (Tuscany, Italy), focused on the effect of terroir on wine characteristics using two different zoning scales. At a broader scale, called macro-terroir (MT), the experimental vineyards were selected based on lithology, soilscape, morphology, and mesoclimate. Each vineyard was then subdivided at a detailed scale into two homogeneous zones for soil features, the Basic Terroir Units or Unité Terroir de Base (UTB). The study was conducted during three different vintages (2012, '13 and '14), in vineyards located in four different MT, which are representative of large parts of the Chianti Classico wine district. The vineyards were surveyed by proximal sensors, namely electromagnetic induction sensor (EMI) and gamma-ray spectroscopy to characterize soil spatial variability and to define two homogeneous areas (UTB) of about 2 ha in each MT. The UTB differed for some soil features, mainly texture, gravel content, soil depth, available water capacity, and internal drainage. The weather for the three vintages was very different e during the growing season, which was very dry and hot in 2012, moderately wet and warm in 2013 and chilly and very wet in 2014. Grape harvest, wine-making and six-month ageing were carried out separately for the different UTB, using the same methodology. Mixed-design analysis of the variance of several must and wine features demonstrated that MT played the major role on must pH, as well as total acidity, glycerine content and colour intensity of the wine. The climate of the vintage played a stronger role than MT on the content of must malic acid, as well as polyphenols, anthocyanins and dry extract of the wine. Blind wine sensory analysis performed for all vintages showed significant differences between wines from the different UTB, in particular for colour intensity and wine aroma, but the differences between UTB within each MT were not stable over the three contrasting vintages, being less pronounced in the most humid vintage (summer 2014).This study demonstrates that characteristics of pedo-geological landscapes can be used for a wine district zoning, while a more detailed soil mapping, leading to UTB identification, is needed for differentiating particular wine characteristics.