Proceedings of Terroir 1996

Le vigneron européen est de plus en plus à la recherche de la valorisation de son terroir par la personnalisation de la typicité de ses produits. Dans ce contexte, il est apparu depuis longtemps que la part des facteurs technologiques ou humains est d’une importance capitale face aux conditions de l’envirormement naturel. Le terroir se construit plus qu’il ne se subit.

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Research into the effects of the Terroir is of major interest for the wine sector. The study of Terroir-Vine-Grape relations, even if it is complex, is fundamental for all viticulture: indeed, the quality of the grape must be the result of the most reasoned agro-viticultural management of the vine possible, which must first, to respect a production balance. The goal sought by the winegrower is to obtain a wine, the optimized result of the interactions Terroir-Grape variety. This link to the terroir is therefore essential to establish by taking into account on the one hand the behavior of the vine (which is the cause), and on the other hand, its effects on the grapes and finally on the wine.

Franciacorta is a viticultural area which extends in the hills to the South of Iseo lake in Lombardy. It is particularly famous for the production of sparkling wines obtained mostly from Chardonnay and Pinot blanc and noir grapes. The name of this territory is of medieval origin and appeared for the first time in 1277 as “Franzacurta”, from the Latin “franchae curtes”, i.e. “tax-free” monasteries. It was geographically delimited in 1429, when it was a territory of the Republic of Venezia.

La diffusion récente et “explosive” du Chardonnay dans pratiquement toutes les zones de culture viticole du monde a fait penser, à tort, que cette variété s’adapte facilement à toutes les conditions pédo-climatiques ou presque. Cette thèse a été confirmée par la grande faculté d’adaptation dont a fait preuve le vignoble et par la popularité dont jouit le vin auprès des consommateur du monde entier.

Le manque de connaissances concernant la physiologie de la maturation du raisin a longtemps interdit d’interpréter l’effet du terroir ou du millésime sur la qualité des vendanges en termes moléculaires. L’hypothèse selon laquelle c’est la perméabilité membranaire qui contrôlerait le sens comme l’intensité du stockage des acides est pourtant déjà ancienne (1). L’étude du transport des acides organiques et de son coût énergétique permet d’avancer certaines hypothèses concemant les sites potentiels de la régulation du contenu en sucres et acides du raisin sous l’effet de paramètres environnementaux.

The Pomerol vineyard, located 35 km east of Bordeaux, covers around 800 ha on the left bank of the Isle. There is a system of fluvial terraces with more or less coarse gravel and pebble spreading, resting on a Tertiary substratum ranging from the Middle to Upper Eocene to the Lower Oligocene (Dubreuilh, 1993). This interweaving of terraces of varying thickness results in a brutal superposition of differentiated materials which give rise to various types of soil. Several site studies in this sector of the Libounais show significant morphological and analytical differences from one point to another (Guilloux et al ., 1978; Duteau, 1982; Van Leeuwen et al.., 1989). The distribution of the soils of the Pomerol vineyard was studied and resulted in a cartography at 1/25000th (Merouge, 1995).

Dans la région des Coteaux du Layon, en Maine et Loire, l’effet terroir et son déterminisme sont étudiés dans le cadre de la production des vins liquoreux.
Ces vins sont le résultat d’une maturité poussée au delà de celle prévue par la nature afin de donner aux baies une teneur en sucre et en matière sèche très forte, pour mieux valoriser ces effets de la surmaturation, les baies sont récoltées selon la méthode des tries successives (Asselin et al, 1996). Ainsi, on ne récolte à chaque passage que les grains ayant atteint le niveau de concentration requis pour obtenir des vins à fort degré d’alcool avec des sucres résiduels.

The notion of terroir covers multiple components, from geology, pedology, geomorphology and climatology (Doledec, 1995), to aspects that are less well identified but which also intervene in the “typicality” of wines. This justifies the “zoning” approach (Moncomble and Panigaï, 1990) to define homogeneous areas, under the same agro-viticultural management and also identified at the product level (Morlat and Asselin, 1992).

Face à l’enjeu d’affirmer et de mieux comprendre la spécificité des vins en relation avec leur origine, la notion de « terroir », avec la richesse de sens et la diversité des perspectives qui l’éclairent, se révèle la clef de voûte de la production et de la valorisation de vins personnalisés et typiques. Asseoir la connaissance des principaux terroirs de la Vallée du Rhône sur des bases autres que celles, jusqu’alors essentiellement empiriques, invoquées dans la seconde grande région française productrice de vins d’AOC, constitue un projet conforme à l’intérêt voué à cet enjeu d’actualité.

The diversity of potential sources of damage to the terroir of an appellation (physical, aesthetic, ecological damage, damage to the image, to collective representation or even, in a broad concept which will not be retained here, to the geographical name identifying the terroir) is accompanied by a fragmentation of the legal sources allowing its protection.

The influence of climatic conditions on the development of the vine and on the quality of the wines no longer needs to be demonstrated at the scale of the vineyard, by the regional climatic characteristics, determining on this scale the viticultural potentialities (Huglin, 1978; Branas, 1946; Riou et al ., 1994); but also on a local scale, at the level of the basic terroir unit (Morlat, 1989), by the landscape differentiation of the natural environment inducing climatic variability within the same vineyard, and partly explaining differences in functioning of the vine, in connection with the processes of maturation and the quality of the wine (Becker, 1977 and 1984; Morlat, 1989 and Lebon, 1993a). According to these authors, the climatic diversity in a wine region constitutes in addition to the edaphic component, an important component of characterization of the Basic Terroir Units (UTB).

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.

The Appellation d'Origine Contrôlée area of ​​Cahors (Lot) covers an area of ​​21,700 ha, spread over 45 municipalities, of which only 4,300 are planted with vines. The main grape variety of this AOC is the Cot noir which represents 70% of the grape varieties, thus giving their typicality to the wines of this region; but despite this importance, to our knowledge, its physiology has remained relatively unstudied.

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.