Wine Terroir

Physical Geography and Wine Growing

The physical geography of an agricultural field, and in this case a vineyard in reference to wine grapes, exerts important controls on viticulture, with subtle differences in climate, geology, soil, and topography reflected in the wines produced from grapes grown at different sites. These site characteristics may act in a singular fashion or in tandem, such that grapes produced in adjacent vineyards on different soils, but with the same climate, produce wines with different characteristics, or soil and climate may act mutualistically to change the character of wine grapes along a gradient up valley, where both climates and soils change.

Terroir is a concept introduced by the French in their Appellation d'origine contrôlée (AOC) system and is now used by winemakers worldwide to explain the essence of place as a function of the physical geography of the vineyard where the grapes for any particular wine are grown. French viticulturalists have shown that distinct differences in wine-growing districts and vineyards in Bordeaux, for example, produce very different wines as one proceeds inland up the Garrone and Dordogne rivers across river and glaciofluvial landforms and soils of different types and ages. Winegrowers in other regions of the world, including California, New Zealand, South Africa, and Germany, have used this same concept of vineyard geography to develop vineyards and produce wines best suited to the site. Agencies that regulate the naming of agricultural regions and the labeling of wines have established similar geographically based appellation of origin systems in various countries, such as the American Viticultural Areas program in the United States.

Because of the impact of vineyard geography on fruit composition, and subsequently on the flavor and other characteristics of the wine, vintners have long been interested in the effects of climate and soils on wine. Researchers have shown that climate, that is, the surface environment of the vine (canopy zone), is an important factor that affects fruit composition and wine quality and is intimately tied to the concept of the vintage (e.g., wine quality in a given year or harvest). The length of the growing season, the intensity and duration of solar radiation, temperature extremes, growing degree-day totals, precipitation events, wind speeds, and other aspects of the vineyard climate affect vine flowering, leaf canopy development, fruit set, crop load, and grape maturation. Viticulturalists can manipulate the vine canopy (through trellising, pulling leaves and shoots, cluster thinning, and other practices) to influence the microclimate of each plant, yet the regional climate effects cannot be changed (such as excessive summer heat or late-growing-season rainfall).

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