Les buts principaux de cet essai, sont la mise en évidence des effets traitement agroviticole et millésime, par une recherche de liens entre les données vendanges et sensorielles des vins issus.
The analysis of the distribution of natural plant populations allows an ecological characterization of cultivated environments in thermal, water and trophic terms; it guides the choice or selection of plants (or grape varieties) to cultivate (Astruc et al ., 1984, 1987; Delpoux, 1971; Jacquinet and Astruc, 1979). This approach has given good results in areas where the topography is the determining factor in the ecological differentiation of the terroirs.
The historian starts from a scientific, rigorous and recent definition of the wine-growing region. “A viticultural terroir is made up of several homogeneous units: geological and pedological elements (texture,
grain size, thickness, mineralogical nature, chemical components), geomorphological (altitude, slope, exposure), climatological (rainfall, temperature, insolation)”. Absent from this definition, the man is fortunately reintroduced a little further. By associating viticulture and winemaking, it forms a “couple” with the terroir and this couple.
The winegrowers of the intercommunal cooperative cellar of Saint Hilaire d'Ozilhan have been practicing terroir selection for ten years. Five years ago, after having equipped themselves with an efficient commercial structure, and anxious to improve knowledge of their terroirs and to better control quantitatively and qualitatively the range of typicality that they can develop, they asked the Syndicate Général des Vignerons Réunis des Côtes du Rhône and the Institut Coopératif du Vin to help them set up an approach to better judge the behavior of the Grenache and Syrah grape varieties in the different terroirs, then to enhance this work through the improving product quality.
A set of Syrah plots covering a wide range of terroirs distributed in the vineyards of the Rhone Valley and the Mediterranean South is examined through their oenological and sensory characteristics. The multidimensional analysis of data leads to the following groupings: (1) A group of unstructured wines with a simple aromatic profile dominated by fruity-floral notes; they come from plots where the ripening conditions have been disturbed by unfavorable climatic conditions, or an excess harvest.
Different “landscape unit” have been identified in Bolgheri area (a viticultural appellation in the Tirrenian coast of Tuscany) by the aid of pedological, landscape and agronomic observations in the 1992-1993 period. In all cultivar (Sangiovese, Cabernet Sauvignon and Merlot) x landscape unit combinations, experimental plots were chosen in homogeneous vineyards, single cordon trained (about 3300-4500 vines/hectare). Grape maturation was studied by weekly samples of berries from veraison to vintage in the 1992-1995 period. At harvest yield and must composition traits were measured and, from the most représentative plots, sixty kilograms of grapes were harvested each year and vinified according to a standardised scheme. Wines were evaluated by standard chemical and sensory analyses.
The maturation patterns process has been very studied. In particular the modelization of the sugars and titratable acidity during the ripening period was an important approach, in particular for the prediction of harvest date (Barillere et al., 1988; Jourion et al.,1987; Maujean et al., 1983; Scienza, 1989). In Oltrepò Pavese, the widest viticultural district of Lombardy – Northern Italy – (about 15000 hectares), grape maturation trends shows high variability, due to the large variation in environmental characteristics of vineyards (altitude, exposure, soil type, mesoclimate) and to “cultivar x environment” interaction.
In this last ten years period, there has been many integrated and interdisciplinary studies to determine the aptitude of different zones to viticulture (Lulli et al., 1989 ; Costantini, 1992 ; Fregoni et al., 1992). The researches needed some différent knowledges about environment characteristics (soil, climate), ecology, vineyard management, vine genetic, winemaking and sensory analysis. The interaction of all these knowledge produced the assessment about the environmental vocation (Scienza et al., 1992). By means of this metodology, the “viticultural vocation” joined the word “zoning”, that is the territory parting for its ecopedological and geographical characteristics in relation to adaptative answer of winegrape (Morlat, 1989).
The need to classify the vineyards of an area according to the quality of its wines is not recent, but it is only in the last ten years that studies on the suitability of different areas for the cultivation of vineyard take on an integrated and interdisciplinary character (Boselli, 1991). The definition of the suitability of the environment is thus obtained by making the climatic, pedological, topographical and cultural information interact with the vegetative, productive and qualitative expression of the grape varieties.
“The vine and the wine are great mysteries. Only the vine makes us intelligible what is the true flavor of the earth”. Colette. The notion of terroir has always been the basis of the notion of AOC from which it is inseparable. It is moreover the definition of the production zone which was at the start of the attempts to set up the designation of origin, at the beginning of the century, after the phylloxera crisis.
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In the Champagne vineyards, spring frosts are the cause of significant variations in the volume of the harvest which are very penalizing for the trade. This variability is reflected both in time (years without frost alternating with years with severe frosts) and in space. Certain sectors of the vineyard are in fact statistically more susceptible to frost than others, but each year no municipality can consider itself immune to this climatic accident. The objective of the study is precisely to analyze the spatial distribution of frost and to determine its main mechanisms, linked to the topography of the hillsides, their orientation but also to regional meteorological variables.
Temperature has a decisive influence on the growth and development of plants (Carbonneau et al., 1992). In particular, in the case of the vine, the temperature is an omnipresent variable in the climatic indices (Huglin, 1986). For reasons of convenience, these indices use the temperature of the air measured under shelter in a meteorological station, making the implicit hypothesis of a concordance between this temperature and that of the sites of perception of the thermal stimulus by the plant. However, development may be more dependent on soil temperature than air temperature (Kliewer, 1975). Morlat (1989) thus verified that the variability in the precocity of the vine, positively correlated with the quality of the harvest and of the wine in the Loire Valley, was mainly explained by differences in temperature of the root zones.
For several years, the development of computer resources, and in particular of Geographic Information Systems, have allowed the emergence of a new approach to the analysis and characterization of wine-growing areas (Morlat, 1989; Laville, 1990). These methods, which make it possible to identify homogeneous areas or units of terroir, are based on crossing, statistical analysis (in particular Principal Component Analysis: PCA) and the integration of parameters describing the natural environment in which develop the vine.
Par le fait d’une politique agricole communautaire axée sur des objectifs de qualité des produits, la recherche et l’identification des critères de cette qualité deviennent impératives. En viticulture, la notion de qualité du produit est rattachée au concept théorique de «terroir». Ce terme englobe un ensemble de paramètres du milieu (géologie, sol, climat) influant sur la récolte.