It may seem like we are beating this subject to death, which may be entirely true. But, we are dealing with a subject that is central to understanding what makes wine grapes grow into beautiful wines. It seems as if one answer leads to more questions. I am indebted to Tom Darnell for pushing me to go into far more detail than is typical of most wine blogs. Believe it or not, Tom and I are in agreement more than not.
I have read James E. Wilson’s paper that was printed in Geoscience Canada Journal in September, 2001, as Tom suggested. It was filed back when Wilson was doing book promotion tours for Terroir, etc., and is excerpted from book material.
Today, we find many different ideas about what terroir encompasses. Wilson was right when he said that terroir had become a buzzword in the world of winemaking. Over the 37 years of my involvement in the industry, I have been repeatedly surprised how a simple French term can take on so many facets. Part of the reason is technological advances, and part is owed to American winemakers and their incessant drive to differentiate their wines from the competition by whatever means possible.
What is needed now is to provide historical context to the concept of terroir.
History of Terroir
From the many published descriptions of terroir, I highly recommend pages 47-74 of the book Burgundy, written by Anthony Hanson, MW. Hanson is a British wine writer and distributor who lived in Burgundy for three years while researching the region’s wines and his book.
Hanson feels that the concept of terroir has attracted a cult following tantamount to a religion:
“In Burgundy, they love the word terroir and have virtually turned it into a religion. Indeed, if one accepts Erich Fromm’s definition of religion as ‘any group-shared system of thought and action that offers the individual a frame of orientation and an object of devotion’ then terroir in Burgundy is definitely a religion, a sort of harking back to the pagan veneration of trees, plants, hills and springs.”
– page 47, Burgundy, New Edition; Anthony Hanson, MW.
The term “terroir” originated in the Fourteenth and Fifteenth Centuries (1300-1500 AD). Producers and lovers of Burgundian wines sought the reason for the excellence of their wines over all others. They believed strongly in the importance of soil and climate, so that’s the way they defined terroir.
Almost all of the best vineyards were developed and operated by Catholic monks. Although the Benedictines, based at Cluny near Avignon, were the first, it was the Cistercians, based at Abbaye de Citeaux, eight miles east of Nuits St. George, who developed most of the great vineyard properties in Burgundy. It should be no surprise that they added a spiritual factor to the definition. You will notice, even today, the many crosses and other shrines built along the rock walls surrounding each vineyard. The monks built them, in order to provide shrines where they could take “prayer breaks” in their daily tasks of tending the vines.
St. Bernard founded the Cistercians because he felt the Benedictines lived too plush a lifestyle. So, the Cistercians lived a more Spartan existence, did not eat and drink sumptuously, and subjected themselves with greater ardor to the rigorous labors of vine tending.
The monks noticed features of the vineyards that were supported by the technological knowledge of that time. They could see differences in soil texture, but did not have any knowledge of subsurface geology, rooting depth, soil pH, clay content, soil permeability or cation exchange capacity
It was apparent to the monks that almost all of the best vineyard blocks were situated on east-to-southeast slopes (Corton Charlemagne is the only exception although part of Richebourg sweeps around to the northeast), were above the “belly” of the hill (above the most concave part of the slope), and were approximately at the same elevation above the valley floor.
The weather also seemed to influence the grapes. In warmer growing seasons, the grapes got riper. They could taste more alcohol in the wine, although they didn’t understand yet what alcohol was.
And then, they were aware that the monks worked harder than anyone else at tending the vines. So, it would have been natural to conclude that the quality of the wines reflected the monks’ dedication and hard work. Beyond that, they would have believed that God had blessed the site, because God was the central focus of their lives and they offered up their strenuous labors in praise of God and as penance for their sins. The region long ago had given up the pagan worship of trees and plants that is claimed by some historians, particularly since the rule of Charlemagne in 800 AD.
The monks gained ownership of many of the best vineyard properties at the bequest of Nobles who believed that generosity in giving to the Church would ensure their passage into Heaven.
So, the original concept of terroir was that simple and basic.
Terroir applied to a specific vineyard site. It may have been a whole vineyard, or to part of it because of changes in soils and topography.
For example, let’s take Grands Echézeaux. Its terroir is unique. Nowhere else has the same terroir. If a new American winemaker were to tell a Burgundy vigneron that he intended to make Grands Echézeaux from his new Pinot Noir vineyard, the vigneron would break out laughing. “C’est impossible!” the vigneron would exclaim, Burgundians believe, down deep, that Grands Echézeaux cannot be grown anywhere in the world other than at the real Grands Echézeaux. At first, that representation may sound arrogant, but it’s not. According to Burgundian beliefs, it is just fact.
In time, the collection of the best terroirs in Burgundy became the basis for the AOC (Appellations d”Origine Controllée) system of wine classifications adopted in 1855 and 1905. In Bordeaux, the same principle applies to the holdings of prominent chateaux. Other French regions have their own AOC systems.
In America, we have begun a very crude system of vineyard classifications, the American Viticultural Area (AVA). At this time, I feel, AVAs are too broad and ill-defined. They tend to be made more in response to political pressures than commonality of viticultural conditions. Some are multi-state. At the other end of the spectrum, the most detailed area is Yamhill County, Oregon, which embraces seven AVA’s, probably with more on the way.
As an example, Burgundy’s version of the AVA would be the area called Côte de Nuits, which is all vineyards on the Côte d’Or between Nuits St. George and Fixin.
The closest anything in America comes to the Burgundian classification of terroir is single vineyard bottlings of Pinot Noir, now quite common. Most single vineyard bottlings are a marketing tactic. There are many examples where outstanding blended “reserve” bottlings were abandoned to label the components as single vineyard wines, none of which are as good as the original blended versions..
The question arises: should we encumber ourselves with a concept of terroir from the Late Middle Ages, or should we continuously refine and define that concept to take advantage of new technology?
Major technological advances
Over the six centuries since origination of the term terroir, many technical advances have been accomplished. Soil scientists have discovered the ways to measure the soil’s characteristics and performance. Photosynthesis has been fully defined. Meteorologists and viticulturists have defined how light impinges on the vine canopy and soils. More precise measures of climate are now in common use.
Modern soil science
Now we can find data about physical and chemical properties of soils. Although not always perfect, soil origins, soil pH, horizons, depth to bedrock, clay content, cation exchange capacity, water permeability, water holding capacity, perched water tables and more are readily available in USDA’s Soil Survey series by county. The information is especially valuable in evaluation of sites for vineyard potential, and in the design of individual vineyard blocks.
Knowledge of photosynthesis is essential to understanding how the grapevine utilizes terroir in the production of grapes. The process was fully discovered by Dr. Calvin Benson at UC-Berkeley in 1947-1950, for which he received the Nobel Prize in 1961. The subject won’t be pursued in great detail here, because its complexity requires graphics and a lot of text. For more details, the reader is referred to the publications at the end of the article.
Almost all of the photosynthetic process occurs in the stroma of the grape leaves. The color pigments P-680 and P-700 (chlorophyls) absorb light (solar radiation) in two very narrow bands of the full spectrum that passes filtration and reflection by earth‘s atmosphere. Also absorbed in the first step are carbon dioxide (CO2) from the air, and water by the roots. The leaf sends hydrogen ions (H+) to the roots for ion exchange, oxygen back to the air, and NADPH and H+ ions on to the next step.
In the second step, electrons from Photosystem II run a proton pump to synthesize ATP, which then is combined with another H+ ion and an electron to yield NADPH. This is Photosystem I. The order of discovery determined which is Photosystem I or II, not their respective orders in cell processes.
The Calvin-Benson-Bassham Cycle contains the third through fifth steps. It is a complicated loop of three phases of: 1.) carbon fixation; 2.) synthesis reduction; and 3.) regeneration of RuBP. The cycle produces NADP+, phosphorous and G3P (Glyceraldehyde-3-phosphate).
G3P converts to the simple sugar, glucose. Glucose and carbon are combined with nutrient and mineral ions coming up from the roots to form other sugars (sucrose, fructose and others) in the grape. Organic acids (tartaric, malic, citric and succinic) are formed as well as fats, proteins, and anthocyanins (color pigments and tannins). Lignins (cellulose) are produced elsewhere in the vine as building blocks for the woody parts of the vine.
Dr. Winkler’s philosophy of the most important factor to grape growth is detailed in General Viticulture by Winkler, Cook, Kliewer and Lider. The concept goes back to post-WWII days. At its best, heat summation is only a crude measure of vineyard site suitability. It is not embraced by growers in France or Germany.
Light is important for this reason: photosynthesis is driven by both heat and light. More accurately, photosynthesis is driven by light, with the rate affected in part by heat energy (temperature). Photosynthesis cannot occur without both heat and light.
When Dr. Winkler developed the system, there were few sources of high quality premium wines in California. Napa Valley was almost alone at the high end, although it did not come to real prominence until Robert Mondavi built his winery in the mid-1970s. At the other end were the jug wines of the Central Valley, notably produced by Gallo. AVAs that we take for granted today developed later: Russian River Valley, Alexander Valley, Carneros, Santa Cruz, Monterey, Santa Barbara, San Luis Obispo and Santa Rita Hills among them.
California is called a “sunshine state” for a reason. Solar radiation is intense. Most of the growing time for California grapevines is spent under a light level that is in the asymptotic range, or beyond the point of diminishing returns, of carbon assimilation versus light. Therefore, in the California areas of the day, light became a constant factor in photosynthesis and temperature was the only variable worth evaluating. Hence, the heat summation system is based on degree-days during the growing season.
The several ranges of values are not much help outside of California’s warmer climates, but the system does provide useful information to differentiate among areas where there are less than 2,500 degree-days. That range is now dubbed “cool climate viticulture” by the world’s leading viticulturists. It is where “marginal climate” areas operate, such as Russian River Valley, Oregon‘s Willamette Valley, Michigan, Upper New York State, Canada, Burgundy, Alsace, the Loire, Champagne, Switzerland, Austria, and all of the German wine-producing regions. Additional information, such as solar radiation to a site, topography, prevailing wind and soil properties, is needed to adequately evaluate new vineyard sites in this range.
Another consideration relating to heat summation is that, although an average temperature over 50°F is necessary for bud break, once leaves are out, photosynthesis occurs as low as 41°F so long as light is present. Heat summation counts only the degree-days over 50°F.
Evapotranspiration Index (EpT)
EpT is a formula-derived scalar that includes temperature, precipitation, humidity, wind and specific crop. The index calculates the total inches of water per unit area that evaporate from all surfaces: soil, plants and bodies of water. Charles W. Thornthwaite developed the first, and many variations have been advanced by others. EpT could be important because it combines effects of so many climate factors.
Solar radiation is the future
During the 1960s, Richard Smart was a PhD candidate at Davis and he participated in research by P.E. Kriedemann relating to photosynthesis in grape leaves. Then, in 1991, Smart published his book, Sunlight into Wine, which analyzed how trellis design affects the amount of light reaching the leaf canopy by placing light meters at various places.
Controlled light box tests in the early 1960s at UC-Davis revealed the relationships between light, temperature and the photosynthetic rate. If temperature is held constant at 77 °F, photosynthesis (measured by carbon dioxide respiration) increases up to about 8,000 foot-candles of light, and then the rate tails off. If light is held constant at 4,000 foot-candles, photosynthesis increases with increased temperature, then it decreases beginning in the 90s (leaf surface temperature in degrees Fahrenheit) as the leaf stroma close and the leaf transpires water to survive. These observations are based on results for Shiraz and Thompson Seedless grapes. Absent further test findings on other varieties, these relationships are adopted as “typical.”
My research, with the help of a computer mathematical model of solar radiation developed in my consulting practice during 1978-93, demonstrates that light is more important than heat in photosynthesis. For example, in a VSP- trellised, north-south row, vineyard at Dundee, Oregon over the sunlit 16-hour day on an average mid-July day, solar radiation drives 81.4% of total photosynthesis. Heat energy accounts for the other 18.6%. Photosynthesis is defined by carbon dioxide respiration (mgCO2/dm2/hr).
What is the significance of these two approaches to evaluating the importance of solar radiation? Dr. Smart’s approach requires established vines, trained to the trellis system under investigation. If you want to study a new configuration, you can take the 5-7 years to develop a newly-planted vine’s canopy to maturity. That’s a lot of time. Or, you can convert an established planting to the new configuration, which may require 2-4 years to accomplish. That’s also a lot of time. The best use of his method is in the evaluation of existing trellises, with redesign based on experience.
The computer model offers the ability to estimate and compare the effects of various alternative trellis configurations and row directions in a matter of hours.
Each method has its place in vineyard design and management.
Another take on terroir
Anthony Hanson discloses another piece of information that portends the future of terroir:
“A future line of research is to quantify the proportion of soil that is vegetal, rather than mother rock, origins of Burgundy’s vineyards. Old root cells from buried, decayed vines may make up 70 per cent of some soils, so recent scannings by Claude Bourguignon suggest. So six centuries of monoculture – or more – could prove to be the real creators of these soils.”
– page 74, Burgundy, New Edition; Anthony Hanson, MW.
Claude Bourguignon is a soil scientist with his own private laboratory. Previously, he directed the government laboratory but, he says, every time he came up with a new discovery, he was met with entrenched resistance from the government and academic bureaucracy. Claude Bourguignon is definitely a “cutting edge” scientist.
So, it would appear that the grapevines are creating their own soils over time. lf the debris remaining after pressing is spread in the vineyard, as well as the vine prunings, that debris will decay, decompose and be percolated into the soil with precipitation . . . seventy percent of the soil’s composition. Wow!
As I have said before: “The vines are dining on the remains of their ancestors.”
Another effect is produced by returning the pommace from red wine fermentations to the vineyard. The yeast cells that survived fermentation will “seed” the vineyard with desirable hardy yeasts that propagate in the vineyard and expedite fermentation by “wild” yeast strains in future vintages.
Other classification questions
Soul of the vigneron. This ideas still may be appealing to the French today, but it does not stand scrutiny. Sorry to go illuminati on this one. The vigneron’s dedicated labors are man’s work, not God’s.
Soil amendments. Are adjustments to soil conditions included in terroir? How should we view liming to raise the pH, application of foliar nutrients, and even manure? Liming can be relatively long term, but it is wrought by the hand of man. The others are more clear-cut: short-term, perhaps as frequent as twice annually, and should not be considered a God-given attribute of the soil.
How should we relate to the Research Station’s attempt to rebuild entire hillsides to create the “perfect” terroir for White Riesling at Kaiserstuhl near Freiburg, Germany (1960-83)? It didn’t work, but the effort raises intriguing possibilities.
Solar radiation (light energy). The pattern of solar energy that the vine canopy “sees” (receives) is very different from the pattern presented to the vineyard just above the vine canopy, or to the bare site before planting. The French eliminate differences among topographical settings by mandating uniformity of spacing and canopy configuration, but not of row direction. But, in other countries, growers are able to take advantage of trellis differences and row direction to influence the character of the wines. Both situations, bare and post-planting, will become important to vineyard designers as they become aware of this new technology. Clearly, the bare site’s radiation is terroir, but the results of vineyard design are not.
Sources consulted in preparation of this post:
- Burgundy, 2nd Edition; Anthony Hanson, MW; faber and faber Limited; London; 1995.
- Calvin cycle; http://en.wikipedia.org/wiki/Calvin-Benson_cycle.
- Computerized Solar Radiation Model; LAMY Winery Consultants; unpublished. Developed 1978-1993.
- General Viticulture, revised edition; A.J.Winkler, J.A.Cook, W.M. Kliewer and L.A. Lider; University of California Press, Berkeley. 1974. Pp. 95-102 (Photosynthesis). First published in 1962.
- Notes: Biology 102, Chapter 7, Topic: Photosynthesis; Karen Bledsoe, Instructor; http://www.edu-bledsoek/
- PHOTOSYNTHESIS; http://www.emc.maticopa.edu/faculty/farabee/biobk/biobookps.html
- Photosystem I; http://en.wikipedia.org/wik/Photosystem_1
- Photosystem II; http://en.wikipedia.org/wiki/Photosystem_II
- Soils: An Introduction to Soils and Plant Growth, 5th Edition; Donahue, Miller and Shickluna; Prentice-Hall, Inc. Englewood Cliffs, NJ; 1958.
- Sunlight into Wine – A Handbook for Winegrape Canopy Management; Richard Smart and Mike Robinson, with guest articles by many grape research professionals; Winetitles, Adelaide, AU. 1991.
- Terroir: The Role of Geology, Climate, and Culture in The Making of French Wines; Octopus Publishing Group Ltd., London,1998; U.S. edition, University of California Press, Berkeley and Los Angeles and Wine Appreciation Guild, 1999; James E Wilson, Geologist with cooperation of the Geology Department at University of Burgundy.
- The Light Independent Reactions; http://kentsimmons.uwinnepeg.ca/cm1504/calvincycl.htm
Photo credit: http://www.estates-and-wines.com/