Terroir is one of the most commonly used words when it comes to describing wine, though many struggle with the exact definition of the word and what effect terroir has on wine.

What is Terroir?

Terroir can be described as the combined influence that climate, soil and topography have on a wine. The term is derived from the French word terre, meaning “land,” and can be used in the context of both large regions (such as Bordeaux) as well as smaller zones within a vineyard. While terroir itself has no defined flavor, its influence can be tasted through different characteristics of a wine such as alcohol, acidity etc.

How Terroir Affects Wine

When considering the effects of terroir on a wine, it’s necessary to look at how the following factors contribute to a wine’s flavor profile:

Climate

Climate is a term used to describe the average weather a grape experiences during its growing cycle. In relation to terroir, the most significant climatic factor to take into account is temperature.

The climate of a region is determined by geographical location and latitude; climates can be classified as cool, moderate, warm or hot. In warm or hot regions, grapes produce higher levels of sugar and wines are subsequently higher in alcohol. In cool or moderate regions, grapes produce lower levels of sugar while at the same time retaining acidity. Resulting wines are lower in alcohol and more acidic.

Smaller sub-regions or even individual vineyards can also experience unique microclimates. In such instances, the vineyard or subregion is subject to different climatic conditions, resulting in unique or remarkable wines. Examples of climate categories include Maritime Climate, Mediterranean Climate, Continental Climate and Temperate Climate. Climate and temperature is often measured by Albert J. Winkler's Degree Day system . (Learn more in "Albert J. Winkler and His Contributions to Viticulture.")

Soil

The type of soil of a region has a profound effect on the flavor of a wine. Soils provide the nutrients required by vines to prosper, though somewhat counterintuitively, it is poor soils that are unsuitable for almost all other types of agriculture that are perfect for growing quality grapes.

It is believed that soils also add a certain minerality to wines, though scientists are still unsure as to exactly how this occurs.

The type and composition of soil can alter the ambient temperature within a vineyard. Darker soils absorb sunlight and increase the temperature while lighter soils are reflective. Large rocks and boulders within the ground store heat, warming vines during the night when air temperature drops.

Finally, soil directly the supply of water to grapes. Water is stored in soil by binding to clay particles; the higher percentage of clay within a soil, the more water is retained. Grapes require a delicate balance of water and either too much or too little can result in poor quality grapes, and subsequently, poor quality wine. (Read on in "Soil Types and the Grapes That Grow Best in Them.")

Topography

Terrain and topography refers to the location of a vineyard and its surrounding properties. When discussing terrain, we’re shouldn’t just think about the vineyard’s position on the map, instead we must also take into account slope, altitude and nearby physical features.

Slope, or aspect, of a vineyard affects the amount of sunlight grapes receive. As with temperature, sunlight is essential for grapes to ripen. If grapes receive insufficient sunlight, wines will display harsh, unwanted, "green" characteristics; too much sunlight, on the other hand, and grapes become cooked, producing bitter jammy flavors.

Altitude, on the other hand, impacts the temperature of a vineyard. As altitude increases, temperature of the vineyard decreases, allowing viticulture in regions that would otherwise be far too hot to produce quality wines. High-altitude vineyards also experience a high diurnal range (difference in day and night-time temperatures). This helps grapes maintain acidity, providing balanced wines. (Read on in "Salta, Argentina: Land of the Highest Vineyards in the World.")

Physical features such as lakes or mountains can be vital to the the success of vines. Lakes or large bodies of water provide a moderating influence (warming in winter, cooling in summer), while mountain ranges can offer protection against elements such as a wind or rain.

Combined Effect = Terroir

No two winemaking regions are the same, yet the idea that each individual region can display its own, unique, terroir is only comprehensible because of the enormity of variables that affect it. Understanding terroir and its effect on wine is more straightforward than most people imagine. Detecting its influence during wine tasting, however, is much more complicated and can require years of practice. (Learn more in "Wine Tasting 101.")