Geology and wine 8. Modeling viticultural landscapes: a GIS analysis of the terroir potential in the Umpqua Valley of Oregon

Geoscience Canada, Dec, 2004 by Gregory V. Jones, Nicholas Snead, Peder Nelson

SUMMARY

Terroir is a holistic concept that relates to both environmental and cultural factors that together influence the grape growing to wine production continuum. The physical factors that influence the process include matching a given grape variety to its ideal climate along with optimum site characteristics of elevation, slope, aspect, and soil. While some regions have had hundreds and even thousands of years to define, develop, and understand their best terroir, newer regions typically face a trial and error stage of finding the best variety and terroir match. This research facilitates the process by modeling the climate and landscape in a relatively young grape growing region in Oregon, the Umpqua Valley appellation. The result is an inventory of land suitability that provides both existing and new growers greater insight into the best terroirs of the region.

SOMMAIRE

Le terroir est un concept holiste de facteurs environnementaux et culturels agissant sur un continuum s'etendant de la croissance de la vigne a la vinification. Dans le domaine des facteurs physiques, il faut trouver la combinaison ideale entre la variete du raisin d'une part, et le climat et les caracteristiques du site de culture comme l'elevation, la pente, l'aspect et le type de sol, d'autre part. Alors qu'en certaines regions, on a eu des centaines, voire des milliers d'annee pour definir, developper et definir le terroir ideal, dans les regions nouvelles, on dolt proceder par essais et erreur pour trouver le meilleur appariement raisin et terroir. La recherche decrite ci-contre entend faciliter ce processus de mariage ideal en modelisant les facteurs du climat et du paysage dans une region viticole relativement jeune de l'Oregon, celle de la vallee de Umpqua. Le resultat obtenu est un inventaire des terrains propices, ce qui fait aussi bien l'affaire des vignerons etablis que des nouveaux vignerons dans leur quete des meilleurs terroirs de la region.

INTRODUCTION

Overall, the quality of wine produced in any viticultural region comes primarily from the high quality of the grapes, which are carefully vinified through often long-held cultural practices in the winery. The quality of the grape, however, is the result of the combination of five main factors: the climate, the site or local topography, the nature of the geology and soil, the choice of the grape variety, and how they are together managed to produce the best crop (Fig. 1). The French have named this interaction between cultural practices, the local environment, and the vines, the "terroir." While there will always be some disagreement over which aspects of the terroir are most influential, it is clear that the prudent grape grower must understand their interactions and controls on grape growth and quality (for a good review of the concept of terroir see Vaudour, 2002).

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Numerous researchers have examined various aspects of terroir at different spatial scales providing insights into the complex inter-relationships between grape growing, quality wine production, and the site. In a comprehensive book on terroir, Wilson (1998) discusses the debate of which terroir factor is more important--nature or the winemaker's art--with the general conclusion that the debate may never be scientifically understood enough to differentiate the component contributions, but that its discourse has provided greater recognition of the influence that geology and geological processes have relative to wine quality traits. Haynes (1999) further discusses the importance of the interrelationships of all the terroir-related factors in the production of quality of wine, however the author makes a sound case of the soil and subsoil being the "determining factor controlling the taste and bouquet of a wine" by examining vineyard designation differences in the Cote d'Or region of France. Applied terroir-related research has resulted in examinations of individual elements such as soil (Becket, 1988), plant growth (Tesic et al., 2002a), viability of specific varieties (De Villars, 1997), cultural practices (Jordan et al., 1980), climate (Smart and Dry, 1980; Jackson and Cherry, 1988), and the zoning of viticultural environments (Carey, 2001; Carey et al., 2001). Others have addressed site suitability issues as a collection of factors that allow insights into a region's unknown potential (Tukey and Clore, 1972; Sayed, 1992; Boyer and Wolf, 2000; Jones, 2001) or as a measure of prediction for new areas to plant in existing regions (Davis et al., 1984; Margary et al., 1998; Tesic et al., 2002b). From a geology perspective, applied research has helped redefine sub-appellations in the Niagara Peninsula of Canada based on a combination of bedrock geology, soil, and climate, not simple climate zones as originally delineated (Haynes, 2000). In addition, two detailed studies by Meinert and Busacca (2000 and 2002) in the Walla Walla and Red Mountain appellations of Washington have yielded great insight into how, over a relatively small area, geology combines with climate to yield a broad range of wine styles and consistently high-rated wines.