Understanding The Terroir of Burgundy part 4.4: Erosion: a challenge to the authenticity of terroir

Erosion Vosne wider implications

Our best understanding of soils of the Côte de Nuits:

In trying to grasp the relationship of the wines made soil from particular crus, many writers, myself included, had come to fundamentally incorrect conclusions regarding terroir. My version, could be summarized into this:

I believed that chemical and mechanical weathering of the limestone bedding naturally created soil types that were dictated by their position on the slope. Highest on the slope, the compact limestone soils were produced by the simultaneous production of clay and erosion clay. Lower on the slope, where transported clay enriched the otherwise arid, colluvial soils, I believed that if farmed carefully, clay production could remain in a relative of a state equilibrium with clay erosion. While, it most of these vineyards may not absolutely been in their natural state as when the Romans arrived, of many mid-slope Burgundy vineyards, I felt were relatively authentic in their terroir.  

A challenge to the authenticity of terroir:

Vosne-Romanée Les Damaudes, sitting upon the upper-most slope, with a 12% grade had equal parts clay and gravel in 2004. This is despite already having lost 54mm depth of clay sized particle since 1952. In the foreground, Vosne Malconsorts is allowed to grow it's grass in June of 2012. photo: googlemaps

Vosne-Romanée Les Damaudes, sitting upon the upper-most slope, with a 12% grade had equal parts clay and gravel in 2004. This is despite already having lost 54mm depth of clay-sized particle since 1952. In the foreground, Vosne Malconsorts is allowed to grow its grass in June of 2012. photo: googlemaps

The data of the 2008 paper by Quiquerez, Brenot, Garcia, Petit and Catena however, presented far wider implications than the study’s intended focus, being the impact of the erosion upon the soil. The study’s plot site, high up on the hillside, with a long, 12% grade, would challenge the perception that upper-slope Burgundian soils do not have high percentages of clay and silt. This vineyard, with its 40% clay content, at the onset of the study, is doubly surprising, given that the data showed these materials exhibit a high erosional rate out of the plot area. 

This study not only gives us a prophetic view of this vineyard’s future soil but also clearly illuminated a much more fertile soil in the past. Just as this vineyard once had an exceptionally high clay content, there is every reason to believe this was also true across the breadth of Burgundy vineyards, indicating a very different erosional story played out regarding the ‘arid’ soils of elite mid-slope vineyards. This information directly challenges the authenticity of the terroir vineyards as they exist in Burgundy today.

What the study of this vineyard tells us is that, at least on this site, there has been a relatively tight erosional timeline, with much of the damage occurring over the past half century. Additionally, the erosion is projected to finish its ‘third act’ in Les Damaudes, over the next 25 years, at which point it will have a classic Burgundian compact limestone soil.  While it would appear that mechanized farming as the most erosive in this vineyard’s largely unreported history, we know that there was massive erosion in other vineyards over the centuries. The remaining question is: What about the historical farming of this vineyard allowed its clay to remain in this parcel of Les Damaudes?

*This article is based on the findings a pair of studies chronicled in Part 4.3, and centers upon the upper hillside plot of Vosne-Romanée’s village cru of Les Damaudes.

Why is this study so important to our understanding of Burgundy?

It has slowly become apparent that the problem in talking about the terroir of Burgundy is this: We really don’t know what the wines of Burgundy might have naturally been, had men had both the knowledge and forethought to do what it would take to preserve these vineyards centuries ago. However, a study like this (click here) gives us the ability to hypothetically see both where this vineyard is going, and what it might have been like before man caused so much erosion upon the hillsides. We were lucky that the researchers chose this particular vineyard at the top of VosneRomanée for their study. Les Damaudes is a steep hillside vineyard (in the most revered of villages) that is only midway through its journey of erosional destruction.  A study of a vineyard from any of the other lesser appellations could easily be dismissed as not being applicable to les grands villages de Bourgogne. But with a vineyard within VosneRomanée, there is no doubt as to the applicability of the information, as this vineyard is in the immediate vicinity of some of the greatest vineyards in the world, including La Tache and Romanée-Conti.

soil projection

The projected future soil composition of Les Damaudes over the next 5 storms (roughly 25 years) Click to enlarge.

It has become increasingly clear through the research in preparing this series of articles, that vineyards like Ruchottes-Chambertin have been so seriously degraded by the techniques of the farming employed there, that the terroir we talk about today is one that wears immense repercussions of the farming practices of the past centuries. However, it seemed plausible, that the upper slopes could naturally have developed a compact limestone soil, (one that is 85 to 90% crushed limestone and only 10 to 15 % clay). But these studies re-orient our thinking, forcing us to realize that this is not a soil type that is natural to Burgundy. Because of that, it is not a terroir that is natural to Burgundy.

It is not to say that these vineyards, with their degraded soils, do not produce beautiful or interesting wines, but we must realize that this is a vineyard condition that has been inflicted by man. In the truest sense, Burgundy now has a terroir that has been drastically altered, metamorphosed by the actions of man.

Note: at the bottom of this article I discuss data gaps and the certain information the study might have provided which would have been key to a more complete understanding of the soil of Vosne Les Damaudes. 

2004: Establishing a soil base-line

Although the changes to the soil makeup after the 2004 storm were covered in-depth the latter half of Part 4.3, it is the basis for projecting what the soil make up was in 1952, so it bears a brief retelling now.

Click to enlarge. Adapted from the paper "Soil degradation caused by a high-intensity rainfall event : implications for medium-term soil sustainability in Burgundian vineyards" Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008

Click to enlarge. Adapted from the paper “Soil degradation caused by a high-intensity rainfall event: implications for medium-term soil sustainability in Burgundian vineyards” Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008

In June of 2004, a storm, which was unusually large for Burgundy, dropped 40 mm of water on Vosne Romanee over a 24 hour period. The effects of that storm were studied, and the researchers determined that the vineyard plot had irrevocably lost between 1.8 mm and 4 mm soil due to erosion, a vast majority of which were very fine particles under 63 μm in size.  The material lost was clay and silt since erosion most efficiently targets these tiny particles. (1)

To the right is a graphic I adapted from the study to show the grain size distribution of the soil after the 2004 storm. Each rectangle represents a range of particle size. I also included the before level of clay and silt sized particles to illustrate the loss of those materials, which was shown as 25% in a graph in the study.

 

1952: the soil content of the past

Given the study’s data, we can extrapolate, at least conceptually, what the clay content on these slopes the vineyard was planted in 1952.(2)  Starting with the fact 2004 the hillside contained roughly equal parts clay and gravel at 40+% each; the balance being sand, that we can add 54 mm more super-fine material (smaller than 63 μm) that it did in 2004.  If we assume that past soil loss rates were similar to that of the 2004 storm, we can postulate how much clay would have been present in 1952.  This figure would be much easier to arrive at if the researchers had given us the soil depth, which would allow us to estimate the volume of gravel (colluvium) and allow us a much more accurate estimate, but that information was not within the scope of the study.

Click to enlarge. Adapted from the paper "Soil degradation caused by a high-intensity rainfall event : implications for medium-term soil sustainability in Burgundian vineyards" Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008

Click to enlarge. Adapted from the paper “Soil degradation caused by a high-intensity rainfall event: implications for medium-term soil sustainability in Burgundian vineyards” Quiquerez/Brenot/Garcia/Petit, Catena 73, 2008

The soil loss projections of the next five large storms, predicts that erosion will remove up to 20 mm in-depth in places. The lost material, it is expected would continue to consist of primarily be smaller than 63 μm in size. 

However, would it not be logical assume soil losses of previous storms were similar to that of the 2004 storm? If so, it would not be unreasonable to apply the projected soil loss, in order to estimate the vineyards clay percentage in the past.  If these big storms (of 40+mm rainfall per event) happen every 5 or so years, we can estimate that thirty years ago this same hillside may have had as much as a 70% clay content. How much clay existed before the plot was planted in 1952 can not readily be determined without establishing a rough estimate of the volume of gravel in the vineyard, but it is likely that the vineyard, may have had clay content 85%.  Such a high percentage suggests that either this plot was either not farmed before it was planted in 1952, or was farmed quite differently in the past than it is now. 

In Retrospect

We should not have been surprised that the soils of Burgundy are not as nature created them. We should have suspected something was amiss long ago because the soil type in Burgundy today is one of an arid climate. France, and the surrounding Burgundian countryside, however, do not have an arid climate at all. Rather the climate is classified as semi-continental, where rain is frequent and happens virtually year around. These soils would naturally have at least some petrogenetic development, which it is doubtful that any vineyard in the Côte d’Or does. We were told and simply wanted to believe that the wines of Burgundy are naturally and uniquely sparse of nutrients and clay. Additionally, we have not wanted to believe that, in the course of making these great wines, man has precipitously hastened the decline of the greatest vineyards of the world, though poor farming decisions that have been made throughout the centuries. This has never been truer since the organization of vineyards for the mechanization of farming.


 

Gaps in the data: deficiencies in quantification

As transformative as this study is to our understanding of the wines of Burgundy, the paper, unfortunately, omits some fairly important information. First and foremost, it is unclear how the samples for the data were collected, and secondly how well the data actually represents the soil of the slope in the root zone. The report does say that the soil of the vineyard was homogeneous in its makeup, and no petrogenetic development was observed; meaning the entire vineyard was the same, with no observable generation of new soil. This indicates that what little organic deterioration may develop was washed away by erosion, and no soil horizons (layering) could develop  Lack of soil development and soil horizons would be caused the dual soil disruptions created by regular tilling and erosion.

However, the problem lies in the word “homogeneous”. Even if at some point the soil was homogeneous from topsoil to bedrock, erosional changes to the soils would primarily affect only the material nearest to the surface, and then most acutely in the rill affected inter-rows. Now, even after one storm, the soil is no longer homogeneous in its makeup, because the soil at a certain (unknown) depth would contain more clay and silt sized particles than the topsoil. Now there would be two soil types.

Because of this, we must assume that the researchers collected a shallow soil collection for the sample in order to determine particle size.(3)  Quantifying the depth of this sample is critical, was this a  sample from the first 25mm (1 inch) or 50mm  (2 inches) or from deeper, say 200 mm (8 inches) of depth which is the deepest that most tilling reaches? Further, when the samples were collected: ie before or after anthropogenic resupply of the sediment was returned to the slope, and before or after the soil was tilled, are both important factors in understanding the distribution of soil.  Additionally, knowledge samples at various depths of the sample would be instructive as the effective depth of the erosional change. This is ever truer after workers had returned the sediment to the hillside, and tilled back into the soil.

Root development through soil

The root zone on a hillside vineyard is often restricted to no more than 300mm (12in) to 460mm (18in) represented by the brown strip in the graphic above.  Original graphic of unknown origin.

It would appear that the study only represents changes to the surface soil: those that would most be affected by erosion, and anthropogenic resupply of the sediment to the hillside. it is possible but less likely, that the soil sample may have been taken down to a 200mm depth (8in), which is the standard reach of a plow shear. But even if samples were taken from the 200mm depth, that is only 2/3s of the minimum depth required by a vine for its root zone.

Despite questions and any doubts these numerical omissions might create regarding the validity of the numbers and projections from the study, the value of this information far exceeds reaches far into the black hole of understanding that existed before. For this reason, I accept these numbers and build in a fairly wide mental fudge-factor when considering the above.

 

 

Puligny Folatieres after a rain

A tractor moves on the road between Paul Pernot’s “Clos des Folatières” and Les Clavillons in Puligny-Montrachet photo source: googlemaps

 

Musigny anthopogenic resupply

“Anthropogenic resupply” of redepositing the sediment back upslope is now done with heavy machinery at Comte de Vogüé. photo: Steen Öhman

Musigny anthopogenic resupply 2

Heavy machinery at Comte de Vogüé. Given a major cause of erosion is compression, it’s hard to imagine this is really helping the situation much. photo: Steen Öhman

*Special thanks to Steen Ohman, sleuth, and vineyard historian who writes the excellent winehog.org, for providing me with the 1827 cadastre Map show above.

 


(1) The variance between the 1.8mm figure and the 4mm figure was not explained, but it is likely that lower sections of the vineyard, which were subject to a higher volume of rainwater runoff, and had developed rill erosion, were subject to greater levels of erosional loss.

(2) While the study lumps both clay and silt into a grouping of material by size under 63 μm, according to Wikipedia, as well as other sources, say that silt is primarily made up of the parent materials feldspar or quartz. Feldspar is prone to chemical erosion, just as is limestone, both of which metamorphose into clay (phyllosilicate minerals + water and air), while quartz will not erode due the same contact with the carbonic acid in rainwater.  Although granite (the major source of quartz-silt) is common in the areas surrounding the Cote, like in Beaujolais, it is not found near the surface in the immediate area. Although silt has been washed onto the Cotes by alluvial action and transported to the soils of the Cote by wind erosion, I have to assume that silt-sized quartz fragments are a very small minority in the area’s soil makeup. For that reason, I often refer to the study’s grouping of material under 63 μm, simply as clay. Clay, of course, is actually smaller than silt. Although the size definition varies between disciplines 1–5 μm, the metamorphological change that occurs upon clay is the ultimately defines clay, not its size.  * an underlying reason that I identify this material may also be that — no wine writer has ever attributed any of Burgundy’s success to silt. Am I cowering in conformity?

 

(3) How else could one explain a 15% change in a clay content?  The planting bed must be at least 30cm  (12 inches) for vines to be viable. Most vineyards have this with a much lower clay content, often to 30% less. If we were to use 30cm depth as a baseline, it stands to reason that the depth is likely 30% more than 30cm, being at a minimum 40cm of soil over the base rock though there is likely more. So, if the soil is 400mm deep, and 240mm of that are clay minerals, a 4mm decrease in the clay represents only a 1.7% decrease in clay content in the soil.

 

 

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Understanding the Terroir of Burgundy Part 4.3 Erosion and Rills: Studies in Vosne-Romanée and Monthélie

Erosion in Vosne Romanee

In the water’s path

Erosion comes in two forms: the seen and the unseen.

Rill erosion is the most obvious form of erosion and typically occurs in heavier downpours of more than 30 mm (1.2 inches) over a 24 hour period. They begin in spots where soil aggregates are weakened, and will collapse with weight and friction of the water above it, forming the aqueduct-like channels into which the runoff will funnel. Rills often generate in flow zones,  gathers in the depressions between rows. Here water can consolidate, growing in volume and velocity as moves with increasing rapidity down the hillside. With the water growing in mass and speed, larger and larger soil particles are pulled with it, releasing from both the bottom and sides of the rill, developing their typically U-shaped trough. As rills go unrepaired, they can grow substantially,  that can be difficult to control, if measures are not already in place to prevent them.

Sheet erosion (aka surface erosion) is a precursor to, and happens simultaneously with, rill erosion. In this case, rainwater runoff moves in sheets across the surface of the vineyard, but between and through the vines in places where rills won’t, or have not yet, formed. Surface runoff has a less concentrated volume of water than the runoff that travels through rills, so it yields a lower speeds and less velocity. Because of this limited velocity, the water of surface runoff is capable of carrying particles with a lower suspension velocity than rills are capable. These may include sands, but unless the downpour was heavy, would primarily include clays and silts. In less intense storms (< 20mm) surface runoff can cause sheet erosion, but these actions are considered slightly erosive, typically transporting finer materials in weak aggregates. From year to year, soil loss to sheet erosion goes largely unnoticed as the topsoil loss directly beneath the vines disappears down the hillside forever.

  • For an explanation of erosional factors and concepts click here for part 4.2
  • For history of erosion and vineyard restoration in Burgundy click here for Part 4.1
  • For the history of erosion and man in Burgundy click here for Part 4.

 

2006 Study of erosion in Vosne-Romanée, Aloxe-Corton, and Monthélie

Two sibling studies, preformed by the same research team, illustrates very well the processes of erosion (detailed in part 4.2), and how it affects the wine we drink. These are multi-discipline studies by conducted by the team of Amélie Quiquerez, Jean-Pierre Garcia, and Christophe Petit from the Université de Bourgogne, and Jérôme Brenot from Géosciences Université de Rennes.

The first of the two studies was published in the Bolletino della Società Geologica Italiania 2006, with contributions by Philippe Davy, Université de Rennes. Entitled “Soil erosion rates in Burgundian vineyards (link).” It examined the erosion rates in the villages of Vosne-Romanée, Aloxe-Corton, and Monthélie. I highly encourage you to look at these important studies to get their analysis, which in some ways is limited by the rigors of science which require the researcher to prove what they already know to be true. My overview of the information revealed by their study applies my own perspective and insights.

The researchers selected three steep, upper-hillside vineyards from which to gather data, all which carried essentially the same average grade, with a mean of 10.5% for Vosne and Aloxe-Corton, with Monthelie the steepest, with a mean slope of 10.7%.  Additional selection criteria were all three were they must meet these three (very traditional Burgundian) vineyard practices.

  1. The rows ran vertically down the hillside.
  2. None of the plots were allowed to have grass grow between the vines.
  3. Frequent plowing or tractor crossings (up to 15 times per year)

However, I note two marked differences between the vineyards. 

  1. How much the slope changed within the plot boundaries.
  2. The length of the slope. 
Vosne Damodes

Vosne Damaudes photo: google earth

The study’s most uniform slope was a vineyard in Vosne, with a fairly consistent 10% to 12% grade. It also had, by far, the longest slope studied, at 130 meters.(1)  This longer slope length, one might expect, would allow water to gain volume, speed, and velocity. These three factors all increase the runoff’s ability to carry larger and heavier particles with higher suspension velocities. Conversely, it was the only slope studied which had a murger (stone wall) at its base, slowing the runoff enough to allow sedimentation to occur, and it would appear to be the only plot with a level spot for sedimentation to rest. 

Although unnamed by the study’s author, I have concluded this vineyard is Les Damaudes on the Nuit-St-Georges border. Clues to its identity include a maximum elevation of 345 meters – the highest in Vosne, and uniform slope of 10-12%. Identifying the parcel location is possible as well, as only one location in Les Damaudes is long enough to fit the 130-meter plot length of this study. When subtracting in the dirt roads at the top and bottom of the vineyard, which are natural erosional breaks, the total length is 126 meters. This vineyard was studied in-depth, over a multi-year period, and spawned the two studies I will detail in this article.

The vineyard in Aloxe-Corton may contain a significantly steeper section than the vineyard in Vosne, with a 17% grade, but overall the Aloxe-Corton vineyard had the same average gradient as the plot in Vosne, at 10.5%. This indicates that part of that vineyard had to contain no more than a 5% grade. Additionally, this vineyard was the shortest plot at 53 meters, meaning as long as fast-moving runoff could not enter the plot freely from above, runoff should not be able to attain the same velocity as it might in Vosne. Because of this, we might anticipate erosion lower erosional levels. There is no specific information that might allow us to identify this vineyard. And while the author Jérôme Brenot included a photo and a brief reference to the grand cru vineyard of en Charlemagne (regarding rill erosion down to the limestone bedrock), the lieu-dits  of en Charlemagne is in neighboring PernandVergelesses, not Aloxe-Corton

Monthelie Clou du Chenes

The section of Monthélie studied is snug against the Volnay border. Here in 2012, some grass is now being allowed to grow between the vines. The vineyard above, La Pièce-Fitte, has one plot that is in pretty poor shape, with gaps between vines, and rills that because of the slight off camber row orientation cut right up against the vines, rather than directly between the rows. photo: googlemaps click to enlarge

The slope in the study with the steepest section, by far, was in Monthélie. The plot there reaches a maximum pitch of 24.5%, but the average gradient is only slightly greater at 10.7%, which again indicates much of the vineyard is gentile in its declivity. This vineyard, which would become a 1er cru shortly after the study was published, is the vineyard of Le Clou des Chênes,(2) and this parcel appears to share a border with Volnay’s ez Blanches vineyard. The study measured nearly twice the plot-wide erosion at 1.7 mm (± 0.5 mm year) as they did in either Vosne or Aloxe-Corton. However, in some locations within Le Clou des Chênes had far greater erosional levels: measuring as deep as 8.2 mm (± 0.5 mm) per year.

Notable is that the time under vine is much shorter, having been planted 32 years before the study. This makes the losses all the more alarming for these steeper slopes because the knowledge of how to resist erosion has improved so dramatically in the past twenty years.  

Data collection and methodology

This much erosion surely has had a tremendous influence on the character of the wines produced from these vines.

This much erosion surely has had a tremendous influence on the character of the wines produced from these vines.

Determining these numbers involved a massive data collection effort, imputing vine measurements on a meter by meter scale. With 10,000 plants planted per hectare, this translates into thousands of data points are required to arrive at the final calculations.

Soil loss was determined by measuring the exposed main framework roots from the current soil level to the point of the graft cut. The graft is typically made 1 cm above the soil level at the time of planting, and with this measurement original soil level at the time of planting can be established (NEBOIT, 1983; GALET, 1993). By dividing this measurement by the number of years since planting, a relatively accurate average rate of erosion can be established. This method of using plants to give a historical record is called dendrogeomorphology, which is a geologic adaptation of dendrochronology, the study of trees and plants to determine the historical climatic record.

An unequal field of study

Photo: Jérôme Brenot et al

Photo: Jérôme Brenot et al

In the end, there was a single factor that differentiated these study vineyards: the road and the stone wall below the Les Damaudes vineyard in Vosne. Because of this road and wall, it also was the only vineyard that had an area at the base of the slope that was able to retain alluvial sediment. This proved to be an important last gasp defense regarding soil loss and allowed that sediment to be returned to the slope. With this material, workers could fill the rills in Vosne, that would grow into gullies down to the base rock in Aloxe-Corton and Monthélie.

The return of the sediment to fill the rills was preformed bi-annually in the Les Damaudes parcel. However, the owners of this vineyard were lucky rather than preventative. The wall was built as the headwall of the small clos that surrounds the vineyard below, and the access road that runs between the vineyards proved to provide the necessary flat collection area for the alluvium.

Inexplicably, the author chose to simply say that in Monthélie, the practice of returning  soil to the hillside had never been done, whereas in Vosne it had been practiced every two years. Strictly speaking this was true.  However when looking at satellite images of the vineyard, this statement appears somewhat disingenuous. In reality, the decision to plant the entire area Le Clou des Chênes in long rows without any roadways or other vineyard breaks, when coupled with the  parcel’s physical position on the hill, created a highly erodible vineyard in which no level “toe of the slope upon which might sediment gather. Returning sediment, that doesn’t exist, to the hillside is simply not possible. That does not excuse the vineyard owner from not removing vines to build a walls or taking other erosion prevention measures, but it also gives and indirectly assigns blame for this lack vineyard maintenance. The Aloxe-Corton parcel (where ever it was) is not mentioned as the owners never having returned alluvial sediment to the hillside, although this was apparently the case.

In 2006, the researchers took the adjacent photograph of Le Clou des Chênes, showing that rills had developed into gullies due to the lack of effective intervention by the grower. They also included photo looking up towards the Bois de Corton (which I have not included), with a rill/gully that extends down to the raw limestone base rock below.  In each photo, the vines roots can be clearly seen, having been exposed by the continuing erosion of these gullies. 

Study design: did the study reveal unexpected results?

In some ways, the wall below the parcel in Vosne was problematic to the study. The stone wall, and ability the return of the sediment by the grower directly impacted the amount of erosion recorded. The study’s author reports this in the write-up as: “by a factor of two”.  It not clear that the researchers anticipated this would be such a weighty factor when they formulated the study, since the focus of the study did not seem to take into account the effectiveness of wall in diminishing erosional forces. However the effect of the wall and the “anthropogenic factors” (meaning in these studies: the actions by man of returning the sediment to the hillside) certainly did have a dramatic effect on reducing the total soil lost, and the authors rightly took the opportunity to underscore the roll and value of murgers and clos as a primitive, but effective form of erosion control. (4)

But because of the wall (and the author’s eventual focus on it), other opportunities were lost. Since Les Damaudes in Vosne possessed the longest slope which also had the most consistent gradient, knowing how those factors affected erosion would have been instructional.  Had the erosion measurements been made before the anthropogenic resupply of the sediment to the slope, this information might have been gained. But since the measurements were taken after the rills were filled, ascertaining the impact of degree of slope and the length of the run can not be readily determined if the Vosne parcel is included in the analysis.

Further analysis of  meter by meter grid data, might answer some of these questions surrounding how much erosion is affected by increasing slope gradient and increasing slope length. Here the shorter Aloxe vineyard could have been compared to the top 53 meters of the steeper Monthélie vineyard. What were the erosional differences within these sections? What was the difference between erosion between the upper slopes and the lower slopes of the vineyards. Could these differences have been attributed to gradient or soil type? What were the soils left behind in the inter rows? Were they significantly different to the soils directly under the vines where the soil is more protected from rain strike and rill erosion? Then, if the full length of the Aloxe vineyard could be included, would there be greater erosion on the steeper sections where gravity has more effect? What about on the lower sections of the plot where increase water volume, speed and velocity might be expected to increase? It does not appear that these questions were asked by the study’s researchers in 2006.

It would be interesting if the data still exists and can be analyzed to examine those questions as well. It certainly would shed a more quantitative light on erosional forces on Burgundian hillside vineyards.

Study’s Opinion

In the opinion of the study, while in the short-term, erosion didn’t affect the vines production as long as the root system was not exposed, over time, the overall surface soil level declined despite the best efforts in Vosne to return the alluvial sediment to the hillside. At the time of the study, the most alarmed of growers had begun been attempting to restrict erosion by allowing grasses to grow between rows, shortening the length of rows and rebuilding walls. The authors suggest these processes be applied to all hillside vineyards.

The study of a single rain event in Vosne-Romanée

The second study released by this team in 2007 is far more detailed, focusing solely on the Damaudes vineyard. Entitled,Soil degradation caused by a high-intensity rainfall event (3) the paper details soil loss related to a single storm on June 11, 2004. This study is much more focused and is far more precise and instructional in its findings.

Vosne Damaudes erosion study

Click to enlarge.

The study’s centers on the erosional path, volume, and sediment type, as well as the net erosion levels measured in the vineyard after workers had returned sediment to the hillside, post-storm.

Soil analysis of the plot

The soils native to the vineyard are within this description from the text of the study. The prose is tight and dense so I will quote the author, Emmanuel Chevigny, here.

“The texture is rather homogeneous over the whole plot and is composed of 40% of clays and silts, 50% of gravels (2 mm to 10 mm) and a low sand and boulder content. The topsoils are ploughed (Mériaux et al., 1981). The argillaceous aggregates with polyhedral blunted to grained form are slightly structured. No pedogenetic segregation has been observed.”

The soil, as described, is a marl, with what I would think has a surprisingly high clay content for being this high on the slope. A better breakdown of clay and silt would be informative, because (as detailed in Part 2.1  and 2.2 regarding soil formation), clay is metamorphosed from limestone and other materials, and very fine in size, while silt is larger (between 0.0039 to 0.0625 mm), and not metamorphosed. Silts are often parented from quartz, which unlike limestone is not prone to chemical alteration, and thus will not produce clay minerals. The origin of this silt must have been transported from farther up-slope, having arrived in Les Damaudes through erosion.

The vineyard’s soil has a low sand content.

The author then writes about argillaceous aggregates, which are clay aggregates. In this sentence, they are writing about the type of soil structure found in the vineyard. Clays tend to form into blocky structures, where each clay units sides is the same shape or a cast of the aggregate next to it. In other words, when the blocky structures form, they are literally cast so that they fit together like a puzzle. Here he is saying that the edges of these casts of the aggregates have been blunted making them more grain like.  There is a soil type, classified as granular (grain-like), that is common to soils in grasslands with a high organic content, and Chevigny is clearly saying these are not granular soils.

Lastly, Chevigny notes that the researchers observed no pedogenetic segregation, meaning they could observe no identifiable soil creation nor the beginnings of soil horizons (sedimentary layering). This would lack of soil generation could be caused, in part, by plowing which disrupts soil horizons and encourages the erosion of weak young soils that have not developed into stronger aggregates. More on the concept of what soil is and pedogenesis later.

The gravel, or scree, which constitutes 45 percent of the vineyard’s soil makeup, (by definition) has slid into the vineyard by gravitational erosion, from higher on the hill. With the clearing of land and subsequent planting of the vines, this gravel has long ago been plowed into the clay-silt mixture. It is never mentioned by the study author, whether the scree is primarily limestone or not. Limestone is not a factor for these researchers, the particle size is squarely considered to be the issue.

By the numbers

While study revolves around the analysis of a tremendous amount of numerical data, to examine each piece of analysis is beyond the scope of this article, but their findings are none-the-less important and tells the story of erosion within a Burgundian vineyard very well. Below I’ve listed what I see as the most important changes to the hillside following this particularly heavy storm system:

  • Both rill and sheet erosion occurred, but rill erosion accounted for approximately 70% of all soil lost from the hillside.
  • A total of 13 rill erosion were noted, some forming a mere 30 meters from the upper plot boundary, that ran in straight lines down the slope, each time in the inter-rows.
  • Rills occurred across 59% of the inter-row area
  • The rills were U-shaped with strong vertical walls.
  • Estimated soil loss from the rills alone was 4.77 meters
  • A rill erosion for this rain event is estimated at 7.8 cubic meters (.275.5 cubic feet) and weighing roughly 6 metric tons (13,227 lbs)
  • An estimated 1.6 meters erosional material was deposited into 7 alluvial fans at the base of the plot.
  • The sedimentary fans consisted primarily of very fine sand to coarse sand that was between 63 μm (roughly the thickness of paper) to >2 mm. Only 10% of the fan sediment was silt clay fractions of less than 63 μm
  • Fan #4 had a total sediment area one-half of a meter cubed (.5m3).
  • The two rills that fed fan #4 had a total eroded area of .93m3  *
  • If 10% of the rill volume is sand, then 70 percent of the fan debris came from the rills while a remaining 30% must have come from surface erosion which fed into the rills and were deposited into the fans.
  • Topographic soil loss in inter-rows with rills was 3.9 mm, or 48 metric tons per hectare (105,800 lbs)  even after anthropogenic resupply of fan sediment to the hillside.
  • Mean (average) soil in non-rill effected vineyard area, was 1.4 mm, or 24 metric tons per hectare (52,900 lbs)

*1 cubic meter is equal to 1000 liters, or 6.29 oil barrels or 264 U.S. fluid gallons.

Storm size and frequency

Annual rainfall in the  Côte de Nuits is between 700 and 900 mm (27 inches to 34.4 inches) per year writes Chevigny, citing the Météo France weather service’s Atlas climatique de la Côte dOr 1994.*  The study also cites that storms with rainfall of more than 30 mm per day, occurred 10 times between 1991 and 2002. Nine of these rain event dropped between 30 and 50 mm, (1.1 inches to 2 inches) and a single storm dropped 63 mm (2.5 inches) of rain water per event/day. Based on this, we might expect that there have been 50 such events between planting and the 2006 study.

The storm event of June 11, 2004, was uniquely powerful because 40 mm fell in a two-hour period, which caused causing 3 times the annual erosion rate established by the 2006 study of 1 mm per year. Perhaps most importantly, the erosion of this single event is averaged into that 54 year period. This indicates that some years little erosion occurred. Because the study only includes storm records from 1991-2002, we can’t estimate the distribution of erosion over the span of these 54 years.

With global warming, storm intensity seems to be on the upswing in Burgundy, just as scientists have noted in other parts of the world. The severe hail events of 2012, 2013 and 2014, which centered over the hapless villages Pommard and Volnay, resulted in total crop loss for some growers.  In the Côte de Beaune, where precipitation and hail has recently been at its most extreme, has also been remarkably varied in its distribution. According to Jancis Robinson, in July of 2013, Volnay saw 57mm of rain (2.25 inches), while neighboring Monthelie only got 9.4mm. Needless to say, with this high degree of weather localization, these data figures are representative of the rainfall collection points only. There were likely areas of Monthelie that got much more rain, and areas Volnay that got much less rain than the data collection sites.  The massive storms of late November 2014 that saw 200-300 mm of rainfall along the Mediterranean coastline and into Austria, the Dijon saw 95 mm of rainfall over a 24 hour period. So, in terms of storms, it would appear that while the Côte d’Or gets regular, low volume rain events, it is by and large, relatively protected from major storm fronts.

*Current monthly statistics are can be found here, and the average rainfall in Dijon as of 2015 is 775 mm (30 inches) per year.

The sediment at the “toe of the slope” 

When examining sediment in the alluvial fans, researchers discovered that it was made up of 90% sand and 10% fine sediment. Fan number four, on which researchers focused their examination, contained nearly one meter of alluvial material. The fact that it contained little silt or clay, indicates that when the water became backed up at the stone wall, its movement did not slow enough for particles smaller than 63 μm (which includes all clays and silts) to fall out of suspension. This suggests there was a significant depth of water Then as the runoff began to gather enough volume to circumvent the murger, and continue downslope, it gained sufficient speed and velocity to quickly form rills in its path around the wall. The runoff carried virtually all particles smaller than fine sand out of the vineyard.

Study inconsistencies, and outdated or generic source material

Between the two articles, the explanation of soil and bedrock type differs. It is not clear why the authors of both studies would quote articles that are 35 to 45 years old, and that generic to the region rather than performing a shallow excavation themselves, in order to obtain information specific to that vineyard.

“The slopes are composed of Middle to Upper Jurassic limestones and marls (Mériaux et al, 1981) …“For example, the sandy-clayey screes (grèze litée) reach 3 meters on Comblanchien limestones in Vosne-Romanée.

In the second study they write:

“The hillslopes develop on Middle to Upper Jurassic limestones and marls, and are covered by colluvium soils of argillaceous-gravelly nature and formed by Weichselian cryoclastic deposits (grèze litées) reaching up to 3 m thick (Journaux, 1976).”

Writing of Comblanchien as a class of limestones is a red flag, as it is distinctly a singular type of limestone. Adding to the confusion is the soil percentages that at first appear to be attributed to the vineyard, are actually from the 1981 Mériaux et al study and generic to the  Côte d’Or. Later in the study, the percentage of sand is increased to >20% (from 10% sand and larger stones). 50% gravel content in the vineyard, which is cited in early in the text, is reduced to 45% later in the study write-up.

 

Computer modeling projects grain-size transition 

Computer projections of grain size changes after each major storm event.

Computer projections of grain size change after each major storm event. Click to enlarge

Because the researchers must begin their work with the soil percentages they observe, this 45% gravel, 40% clay/silt and 15% sand, was their starting point. It was quickly recognized that outgo of clay minerals, coupled with the simultaneous retention of sand would eventually change the vineyard make-up, so they developed a computer program to predict future changes in grain size distribution of the soil composition. Computer models showed after only 4-5 rain events of similar magnitude as the one in 2004, there would be significant changes to the soil makeup. The results of those projections are to the right.

Chevigny encapsulates their findings with this statement.

“…the results of our simulation clearly show that repeated rainfall events modify significantly and very rapidly surface soil grain-size distribution: after only a few events, the top soil has lost more than 30% of its fine material.”

The ultimate effect of this would be the loss of organic materials, nutrients and ultimately soil sustainability.

Study conclusion: vineyard practices enhance rill development and erosion

While the wall slows the net output of soil volume from exiting the plot, the most soils most viable for farming are being lost, while simultaneously, the soil texture and particle size are being irrevocably changed as the sand sediment is returned to the hillside, and disked back into the soil.

It is forwarded by the author, that this action, is part of the problem since rills continue to re-emerge in the same locations, year after year. They submit that ill propagation in the inter-rows is heightened by tilling and repeated passes tractors and foot traffic, and the regularity of rill spacing are evidence of this.  These practices, he writes causes decreased soil porosity (compaction) and restricts rainwater infiltration. Such wheeled ‘passage’ creates flow zones which increase the volume and velocity of runoff in a concentrated area, multiplying the quantity and size of material the runoff can carry. The evidence of these anthropologically created flow zones is the re-emergence of rills that return, repeatedly, in the same inter-rows, despite workers attempts to eliminate them by filling the rills and disking those areas.

It is clear the effort must be made to properly identify the flow zones and attempt to eliminate them but to do so is to understand their formation to begin with, and limit or eliminate that activity altogether.

For me, the results of the computer modeling and projections are not surprising. While this research team and Burgundian winemakers can only look forward to what is next, we have the opportunity to use this information to hypothesize what came before.  This will allow us to see the true arc of geomorphological progression in the vineyards, and thus how winemaking styles have and will continue to change in Burgundy.

Next UP:  Turning our understanding of the limestone Côte on its head

 

 


 

(1)  Vineyards typically are areas with no breaks or obstacles to slow or impede storm runoff, so longer vineyards tend to suffer more greatly from erosion. However, this was not identified as an erosional factor in the study write-up. The length of this Vosne vineyard was listed in the first study at 130 meters, while in the second study it was written as 126 meters.

(2)  Le Clou des Chênes’ increased prestige and vineyard value can be a tremendous incentive to better maintain a vineyard. The vines and vineyard appeared to be in good health in 2012, the last time googlemaps car drove up this stretch of road. Still, no murgers had been built as of that time.

(3) published by Emmanuel Chevigny of the Université de Bourgogne in 2007

Understanding the Terroir of Burgundy: Part 4.2 Erosion: fundamentally changing terroir

Erosion banner

 

 

Erosion is constantly changing the terroir of Burgundy, and in turn, it is altering the weight and character of the wines from virtually every vineyard on the Côte. How significant is erosion in Burgundy today? As mentioned in Part 4.1, a study during the late 1990’s measured the soil loss in unspecified vineyards of Vosne-Romanée to be 1 mm per year, and the same erosional levels were measured off of the vineyards of Aloxe-Corton.  Ath that alarming rate, losses over the next century would have averaged 10 centimeters or almost 4 inches of topsoil if corrections were not taken. On the even steeper slopes of Monthelie, a study measured almost twice the erosion at 1.7 mm (± 0.5 mm year), with sections of the vineyard which measured a shocking eroded up to 8.2 mm (± 0.5 mm) erosional rate. Luckily, many growers have improved their farming practices, particularly since 2010, and these figures should be lower today. Only future studies can tell us what improvement has been made.

The grape harvest Annonymous 16th century, Southern Holland

“The grape harvest” Anonymous 16th century, Southern Holland

For centuries the solution for this problem was to bring in soil from outside areas to replace what was lost on the slopes of the Côte d’Or. However, in the name of terroir, this is no longer allowed. Current law allows growers to redistribute only the alluvium that comes to rest within appellation boundaries. One can imagine that the laborious process of shoveling out the alluvium from the toe of the plot and redistributing higher in the vineyard is a yearly chore. What earth escapes the appellation lines however, is gone to that appellation forever.

The intention of preserving the purity Burgundy’s unique terroir by forbidding introduction of exogenous soils is somewhat paradoxical, since it is only attempting to preserve the terroir à la minute. While in reality it is ultimately is failing at that – due to erosion. 

A positive, unintended consequence of this inability to replace soil is that growers have finally realized that soil conservation is now more critical than any time in Burgundies’ 1500+ year-old viticultural history. They now know that they must fully understand the factors of soil structure and erosion, while at a municipal level, their villages must invest in effective storm water management; both of which are in various states of development or improvement. 

The long uninterrupted run of vertically oriented rows presents unrelenting erosional pressures on this section of Les Folatieres.

The long uninterrupted run of vertically oriented rows presents unrelenting erosional pressures on this section of Les Folatières. photo googlemaps

While the best modern practices are stemming the tide of erosion, vineyards still can be threatened. Even great vineyards on the mid-slope, like Les Folatières in Puligny-Montrachet, which have long, open stretches of vines without significant breaks in planting, are prone to extensive erosion. While soils are depleted not only in terms of depth, they are changing in terms of particle size and makeup. Erosion most easily targets fine earth fractions, detaching them from their aggregate groupings, and sending them into vineyards farther down slope. Light to medium runoff acts like a sieve, carrying away only the smallest particles, leaving behind material with of larger particles sizes. This in a very real way changes the vineyard’s terroir, and in turn, the wines that are grown there. Wines from vineyards that retain only course soils of large particle size (1) tend to produce wines with less fruit the and less weight, and by consequence revealing a more structured, minerally character.

Even more critical is that soil loss can threaten the vitality and health of the vines, as the soil is literally carried away from beneath them. A vine’s main framework roots is said to require a minimum 11-13 inches to anchor itself to the earth and survive. The problem arises when a section of vineyard does not have extensive fracturing, and the soil level begins to drop below that one foot level. To address this, various growers have responded by “reconditioning” their land. By using a back hoe to break up the limestone below, this can give new vines planted there the living space so the vineyard can continue. Does this change the terroir and the future wine more than inputs of exogenous soil? I should think the answer is yes, significantly. 

 

Rainfall and rain strike: the first stage of erosion

rainstrike. photo: agronomy.lsu.edu/

rainstrike. photo: agronomy.lsu.edu/

Rainfall is measured by its size and velocity. A raindrop from a drizzle is typically .5 mm in size, and has a terminal velocity (the maximum speed the drop can reach) of 2 meters per second, or 4.5 miles per hour, in still air. The speed it falls, with no assistance from the wind is determined by its ratio of mass to drag. Large raindrops of 5 mm, have more mass in relationship to its drag and accelerate to 9 meters per second, or 20 mph.

Rainfall, meaning the actual physical strike of each drop, can break down soil aggregates (fine sand,  silt clay, and organic materials) and disperse them. Splash erosion has been recorded to drive particles of earth up to 60 cm into the air, and 1.5 m from its point of origin.

Once their limited bonds are broken, the ensuing runoff can carry these materials downslope. Runoff, the most obvious form of erosion, occurs when rainwater cannot infiltrate the soil quickly enough, and exacerbated by the lack of cover crop, lack of organic material, lack of soil structure and negative effects of soil compaction. Of course, this process is most noticeable during high-intensity rainstorms, the amount of soil lost during longer but low-intensity rainfall can be significant. This slower erosion can go largely unnoticed until most of the productive topsoil has been removed by what is referred to as sheet erosion.

Seasonal protection from rainstrike

Compared to most growing regions, the Côte d’Or has a very wet growing season. Storms during this period can bring irregular and unpredictable rain events that can be heavy and long in duration. The winds during harvest tend to be westerly, with warm humid winds bringing rain first over the Hautes Côtes, then to the Côte d’Or, then out across the Saône Valley. The wet warm humid conditions often encourage powdery mildew in the wake of the storms, so there is a tendency to want to prune to open up the canopy for ventilation to prevent mildew. However, the vine canopy can provide significant protection against rainfall strike, depending of course, on the orientation the rows and the of the wind direction. So good canopy coverage for the period that half of the precipitation occurs (April – September)(2) is beneficial in terms of protection from erosion.

As winter arrives, the vines will have lost their foliage, exposing the soil directly for the entire winter and spring to whatever nature has in store.

Rain Rate

storm.1

Summer storms. Bottom right Photograph: Louise Flanagan theGuardian.com, Bottom left photo Caroline Parent-Gros of A.F. Gros, Top photo Decanter.com

Rainfall is typically measured in millimeters per hour, with a light rainfall slightly tipping the scales at up to 2.5 mm per hour or less than a tenth of an inch per hour. Moderate rainfall is considered to be from 2.5 mm per hour to 10 mm per hour. A heavy rainfall falls between the range of 10 to 50 mm, and a violent rainfall is above 50 mm per hour.

 

Light rain – drizzle 2.5 mm per hour with a terminal velocity of 2 meters per second

Moderate rain 2.5 mm per hour to 10 mm per hour

Heavy Rain  10 mm per hour to 50 mm per hour

Violent rain, above 50 mm per hour

 

Good soil structure resists damage from rainstrike and runoff

Good soil structure is the result of the binding of soil into clumps of both small and larger aggregates, meaning sections of soil will bind more strongly together, than those next to them. This allows the soil to maintain the necessary small and large pore spacing, which allows water, air and nutrient infiltration and movement through the soil. Larger amounts of older, more stable organic matter tend to strengthen soil aggregates so any farming practice that increases organic matter, and the subsequent microbiological activity will result in healthier soils.  Stable soil aggregates allow the soil to resist disintegration due rain strike and thusly helps deter erosion.  It also encourages root penetration by creating weak spots between aggregate masses.

Conversely, unstable soil aggregates are more easily dispersed by rainstrike, and the ensuing erosion clogs larger pore spaces of the surface soil. This clogging forming hard crusts on the surface which both restricts both air and water absorption and increases runoff.

The fix apparently is simple. According to soilquality.org, soil forms aggregates readily with the addition of organic manure, as well as allowing cover crops to grow, which has the additional benefit of protecting the soil from rain strike and the ensuing erosion.

Infiltration rate

Erosion Runoff Ardeche

Rill Runoff running fast in Ardeche. Photo http://www.geo.uu.nl/

The speed at which rain can be absorbed into the soil is referred to as infiltration rate. An infiltration rate of 50 mm per hour is considered ideal for farming, because even in heavy rainfall, a well-structured loam will not allow puddling. While the farmers of Burgundy do have some loam in their soils, the geological and topographical factors they face are far more and varied and thus more complex than that of the typical farming situation. I could find no studies done specific to infiltration rates of Burgundian soils, but below are the general rain infiltration rates of general soil types, starting with clay.

The infiltration rate of clay soils, with good to average soil structure, unsurprisingly, do not drain all particularly well, due to their very small-sized particles. Clays typically have an IR of 10mm-20mm per hour. And as we know, transported clay, with its aligned particles, and plasticy quality greatly restricts water flow, and while it will absorb water, it will not allow water to pass through until the entire structure is saturated, greatly slowing drainage. Worse, due to poor farming practices, clay soils can have a decayed structure, which can slow absorption to less than 10 mm per hour. Water tends to puddle on clays with poor structure, causing them deteriorate to the point of deflocculation.

The study of water and how it drains is researched acutely in areas where water is scare, whereas little study of drainage is done in France where rain and water are plentiful. Hence, my investigation of water infiltration in calcium-rich soils lead me to agricultural water policy studies conducted in Palestine and Spain. One such study found that Clayey Marl, with a plasticy character, had an infiltration rate of only 4-8 mm per hour. This low rate of infiltration suggests the soil structure had already been degraded through poor farming practices. Often the villain of low infiltration rates is a combination of frequent deep tillage, herbicide and pesticide use and compaction by walking on or working wet soils, which collapses weaken soil aggregates.  In deeper soils, like at the base of the slope, collapsed soil aggregates can result in hardpan development below ground, while on sloped vineyards, disrupted soil aggregates are very susceptible to erosion.

Clay-loam and clayey-marls, like those found on many lower-slope vineyards, that retain good soil structure, have IR rates beginning at 20 mm per hour. As the percentage of loam increases (equal parts sand, silt, and clay) the IR rate increases up to 50 mm per hour as long as it retains good aggregate stability and there is no compaction.

Loam to sandy soils, which some Bourgogne-level and Village-level vineyards possess, can have very good infiltration rates, again as long as soil structures are good.  Ideally, they can absorb 50 mm of rain per hour, which is the amount that a heavy rainstorm will produce. These vineyards, however, receive all the runoff from the slopes above, and their “well-drained” soils can be overwhelmed.

Sandy soils and Calcareous (limestone) soils can have infiltration rates well in excess 150mm per hour to 200+mm per hour. The problem is these soils drain excessively well, and tend to not retain water well, and are prone to high evaporation rates.  Off point, but quite interesting, are two studies in south-eastern Australia Bennetts et al. (2006) and Edwards & Webb (2006) found that rainwater remained relatively unchanged as it moved though these porous soils that lacked significant amounts of fine earth fractions and organic material. However, water changed its chemical signature quite significantly as it passed much more slowly through clay-rich soils. This finding certainly challenges the long-held assumption that it is the limestone lends many Burgundies their mineral character.

Infiltration Rate, Slope, and Runoff.

Vogue's parcel of Musigny. Source Googlemaps

Vogue’s parcel of Musigny. Grass growth does not seem to be encouraged here. Given Cerdà’s study regarding the erosion of bare soils, one can only wonder how much greater this vineyard could be? The mitigating factor is the vineyard runs horizontally along the top of the hill, and is not deep or highly sloped. Runoff has little opportunity to gain significant suspension velocity. Photo Source googlemaps.com

A study in Spain by A. Cerdà (Univ. de València) examined infiltration rates, runoff, and erosion, on clay, marl, limestone and sandstone. Additionally, he ran these trials with three levels of vegetation covering the soil material: bare, intermediate and vegetated.  The amount of water delivered was 55 mm per hour (which some soils easily absorbed). The study showed slower rates of infiltration on the bare soils, while more highly vegetated soils reduced and almost eliminated runoff and erosion.  Interestingly, marl soils fare the worst for both runoff and erosion rates on bare soils. Yet on vegetated soils, runoff and erosion of the marl were minimal.

They observed, of bare soils, an infiltration rate of  3 to 55 mm per hour, the runoff from 0 to 83%, and the erosion rates from 0 to 3720 grams per hour.

The easily erodible marl soils had up to 83% runoff and a maximum erosion of 3720 grams per hour. So it turns out that marl soils are particularly vulnerable to erosion which sets up an interesting dichotomy: Burgundian’s penchant for discouraging ground cover between the vines, actually encourages erosion – something they seek to, and direly need to avoid.

Clay (soil) and limestone (soil) both had what Cerdà considered to be intermediate levels of runoff and erosion; with a maximum of 46% runoff, and a maximum of 131 grams of soil material eroded per hour.

When we talk about erosion, we are implying there is a slope.

Nearly level: Level, 0% Nearly level <3%
Gently sloping: Very gently sloping >1%, Gently sloping <8%
Strongly sloping: Sloping >4%, Moderately sloping <8%, Strongly Sloping <16%

Source: nrcs.usda.gov

On the rockier terrain of upper slopes, the uneven the soil surface can slow the momentum of water coming down the hillside, despite the steeper grade. However, as the runoff moves downslope, and the soil becomes smoother, the water grows in volume as in joins other rainfall which has not yet infiltrated the topsoil. This increase in volume causes the runoff to increase in its speed and its velocity. Speed and velocity increases are exponential, as its mass allows it overcomes the friction of moving over the soil below. 

Despite the fact that these moderate slopes can attain fairly significant soil depth with normal, moderate rainfall, they are also prone to erosion when exposed to heavier storm-induced runoff. Any long, uninterrupted stretch across these moderate slopes encourages a fast, and often damaging, runoff. As the speed of the water increases, it achieves a volume sufficient to carry larger and larger particles. Cerdà’s study suggests that the marl that has developed on these slopes are particularly vulnerable to heavy runoff if no vegetative cover is allowed to grow among the rows. 

Suspension velocity

water suspension velocity

water suspension velocity source: water.me.vccs.edu/

The ratio of surface area to weight determines a soil particle or rock’s suspension velocity. This is the amount of water velocity needed to carry the object in its flow. As the flow decreases, rocks with higher suspension velocity, meaning they require fast-moving water to carry them, settle out quickly, and are said to have a low settling velocity. As the water slows, it is these, the densest objects, that fall out of suspension first.

Silt and Clay particles have a very low suspension velocity due to their extremely small size, regardless of their density. These particles are easily picked up and washed away by water movement. Unless the clay particles in suspension are adsorbed as it slowly passes a homogeneous clay body (ie. a kaolinite clay body attracts kaolinite clay particles and illite particles will flocculate with an illite body), clay particles will not settle out of solution until the water becomes still and ponds. The same is true with silt, with its slightly larger particle size.

Sand and gravel are larger, with enough density to resist slow-moving water. They are considered to have a higher suspension velocity than silt or clay. But neither sand, gravel, nor even rocks the size of the palm of your hand, are immune from alluvial transport.

Up next: Erosion 4.3 In the water’s path: Studies of Erosion in Vosne

 


(1) It could be argued that because of Burgundy’s monoculture and high erosion rates will only allow calcisol, and because of that soil development (pedogenesis) is not possible due to the filtering out of fine particles, both mineral, and organic, by erosional processes. Conservation tilling or zero till could greatly change that dynamic, and it is possible with these and other techniques, that growers could expose the truer terroir of Burgundy.

(2) The Wines of Champagne, Burgundy, Eastern and Southern France,  by John J. Baxevanis Rowman & Littlefield Publishers (October 28, 1987)

(3) Could this chemical signature change the flavor of wine? This certainly raises a whole host of questions regarding the impact of fast draining limestone on the flavor or minerality of in wine. This study would suggest the long-held belief by many that limestone gives wines a minerally characteristic is false.

 

 

Understanding the Terroir of Burgundy: Part 4.1 the history of erosion, defense, and restoration

Erosion and man

 

Historical vineyard defense and restoration

 

During the late 1990’s and early 2000’s, soil measurements in both Vosne-Romanée and Corton determined that the erosion rate for both areas were approximately 1 mm per year. Considering that the entire Vosne hillside, as well as all of the hill of Corton are either premier or grand cru sites of enormous value, one would have assumed that every effort had been made to limit erosion. But that assumption would not have been completely true.

 

Even now, 15 years later, with ever-improving an information, and a growing acceptance that erosion is significant problem that needs to be further addressed, not every farmer is making the necessary changes. While soil management may not be ideal in every plot, vast improvements have been made from the time of the Middle Ages, when erosion ravaged vineyards of the Côte d’Or.

One of Vogue's parcels of Musigny denuded of all grass. While there is no denying the quality of the wine today, what of the vineyard in the future? photo: googlemaps

One of Vogue’s parcels in Les Musigny, denuded of all grass. While there is no denying the quality of the wine today, what of the vineyard in the future? photo: googlemaps

Man has waged an epic war against erosion for centuries; which, until recently, has been largely futile. The early Burgundians were understandably ignorant of soil structure and proper tillage techniques, both factors that greatly mitigate erosion. They had no way to know that it was the way they farmed that actually caused the huge erosional problems they fought so unsuccessfully to reign in.

Change, in an old, tradition-bound culture is resisted; and that is nearly as true in Burgundy today as it was in the middle ages. New techniques such as conservation tillage can be very slow to be adopted, much less having a discussions with older generation about whether a vineyard should be tilled at all. That this ancient practice of zero tillage has been implemented with success in other areas as long ago as 1971, is of no consequence.

Many farmers still restrict the growth of ground cover by use of either pesticides and or routine tilling, both of which diminish soil structure and increase exposure to erosional factors. This can be seen even in Comte de Vogue’s perfectly neat parcels of Les Musigny, where only a few tufts of grass evade the plow blade or the hoe. While it is difficult to argue with Vogue’s results in the bottle, the unseen menace of sheet erosion exists robbing the soil of fine earth fractions, ever so slowly.(1)

Before global warming, the vines were planted in Burgundy in east-west rows, straight down the slope. This directional planting was done in belief that it opens the vines to the early morning sun, allowing better ripening. Unfortunately, any truth to this is offset by increased erosion. While the weather was often predictably cold, and complete ripening could be hit or miss, the soil is a not a renewable resource. As we examined in Part 4, soil lost over 6,000 years ago from the hillsides of central France at the hand of Neolithic men, still has not, and in all likelihood, will never really repair itself.

Burgundy’s historical defense of the vineyard

flooding gate

photo: Caroline Parent-Gros

Murgers, or stone walls, have historically been the farmers first, and perhaps only, line of defense since antiquity.  Murgers (or Clos if the wall completely surrounds a vineyard) as part of the idealized visage of Burgundy, shows itself as part of many vineyard’s name, ie. Volnay Clos des Chênes or Nuits St-Georges’ Les Murgers.

Most murgers were no more than stacked stones constructed from rock that had been removed  from between the rows of vines because they were plowing obstacles. Stacking them into walls to protect the vineyard from erosion naturally evolved in the fields. In the 18th and 19th century, some of the more wealthy landowners began to have murgers constructed from brick and mortar, then covered with a fine glaze of lime plaster.  Grandiose entrances to these murgers were hung with intricate iron gates, meant to indicate both the importance of vineyard, and the owner.  In either the case of a stacked stone wall, or a much more extravagant Clos, walls have been the leading defense the vineyards for centuries. They not only serve to direct runoff around the vines, also have the equally important function of keeping the soil that is in the vineyard from being carried out.

Folatieres wall

 

Vineyard reconstruction in the middle ages

It is now widely understood that the simple act of farming causes erosion, and poor farming techniques can cause tremendous erosion, particularly on slopes. The earliest record of man’s attempts to fix the vineyards eroded to the point where they could no longer support vines, comes from documents kept in the later Middle Ages.

Jean-Pierre Garcia, a noted scholar at the Université de Bourgogne, quotes manuscripts in which detail the fight against erosion 600 years ago, in his paper “The Construction of Climates (Vineyards) in Burgundy during the Middle Ages(from French). Translating these ancient texts from the French of the Middle Ages into modern English is challenging, but the message these manuscripts contains is clear: fighting erosion was back-breaking and exceptionally expensive, despite the luxury of cheap labor. This work was likely paid for the Dukes of Burgundy or the Church, or on possibly a smaller scale, by the Duke’s seigneurs, noblemen whose the manors covered Burgundy.

Murgers in Vosne

click to enlarge. photo: google maps

The accounts are as such: In Corton in 1375 and 1376 AD, 38 days of work were required to remove a drystone wall that had collapsed “in the vine” and rebuild it “four feet high along the vine Clement Baubat to defend of acute coming from the mountain.”  In Volnay, it was written in 1468-1469, that men had to excavate the earth below the Clos which had eroded down to rock, and “lifted from earth” returning the topsoil to the vineyard. In 1428 there is a reference of constructing a “head” “above the Clos Ducs Chenove for the defense eaues to descend along said cloux.”

By the end of the middle ages, there are the first references to “exogenous inputs of land”, meaning that earth is brought in from an outside area to replace the topsoil lost to erosion. Land was taken in 1383 from Chaumes des Marsannay and from below the “grand chemin” (highway). This was a huge undertaking that was completed over the scope of “691 workers demanding days”.

Horses and wagons were very expensive in the middle ages. Having 800 wagon loads plus the labor was a major undertaking.

Horses and wagons were very expensive in the middle ages. Having 800 wagon loads plus the labor was a major undertaking. This, a woodcutting from 1506 depicts the power associated with the horse-drawn cart, is called “The Triumph of Theology”.

Then again in 1407 through the spring of 1408, it took 128 days of work were “to flush the royes and carry the earth in the clos,” and 158 working days “to bring the earth into the Clos.” It is immediately obvious that medieval French measure was unique to the time, and is very difficult translate. In one instance, it was recorded that for 28 days carts carried earth into a vineyard in Beaune, and “28 days labor and 48 days working.” In 1431 there was this reference that “six days a horse hauler, dumped 30 days to 2 horses (are needed to dig from) the Chaumes de Marsannay and the road beneath the Clos where piles of earth were raised.” While the exact labor is impossible to gauge, it is very apparent that immense effort was made, by whatever means necessary to return the vineyards of Burgundy to agricultural viability.

Here rill erosion has stripped the soil down to the limestone base in Corton-Charlemagne. photo from an excellent study by  J Brenot et al of the Segreteria Geological Society in Rome.

Here rill erosion has stripped the soil down to the limestone base in Corton-Charlemagne. photo from an excellent study by J Brenot et al of the Segreteria Geological Society in Rome.

The practice of bringing in soils from outlying areas continued through at least through the 18th century. When the RomanéeConti vineyard (a national property) was sold in 1790, the sale documents reveal that in 1749 the “Clos received 150 carts in grass taken off the mountain” of Marsannay.

1785-1786 “dug near the bottom of the vineyard and removed 800 wagons of earth, and this was spread in areas devoid of ground and low parts.”  This practice appears to have ceased, or as Garcia writes “at least on paper” after 1919 when the Appellations of Origin was established. The INAO has certainly forbidden exogenous soil additions since it was formed in 1935.

Interestingly, while on the subject of Romanée-Conti: some of its soils are clearly foreign to the Vosne-Romanée, according to geologist Francois Vannier-Petit,  a void appears in the substrata of the south-western corner of RomanéeConti  which suggests the hillside had been quarried at some point, and filled in with “exogenous” landfill. James E. Wilson noted this void as well in his book Terrior (p 137), where he notes that seismic data suggest this void was created by a fault, but electrical resistivity data suggest an erosional scarp (meaning ancient erosion created a cut out in the hillside) into what Wilson identifies as Ostrea acuminata marl below. Wilson, in either case, assumed that subsequent gravitation induced rock slides and erosion from above filled the void with colluvium. Any of the three possibilities are viable explanations, but the manuscript from the  1785-1786 do clearly state 800 wagons of earth” were “spread in areas devoid of ground and low parts.”

The issue of a quarry in Romanée-Conti is far from clear cut. click to enlarge. photo googlemaps

The issue of a quarry in Romanée-Conti is far from clear-cut. click to enlarge. photo googlemaps

At this point, no record has been found regarding a quarry having been excavated at the site of RomanéeConti, but many governmental and clergy records were destroyed during the revolution. With this, the argument that these vineyards have “special dirt” has been laid open as fallacy. The topsoils of the Côte have been reshuffled for centuries, integrating alluvial loams and clays from the base of the slope (or from elsewhere) back into the fold of the upper slopes of the Côte d’Or. The vignerons of Marsannay who are lobbying for 1er cru classification for their vineyards would certainly point to the fact that their dirt is very similar to the dirt in Gevrey. Better yet, it is clear that a fair amount of Marsannay dirt contributes to create RomanéeConti, the greatest wine all of the Côte d’Or, and that dirt has been there for centuries.

As if by divinity, the some potential erosional problems were avoided by the fact that Burgundy’s vineyards tended to be quite small. Murgers at vineyard boundaries could then slow the velocity of the runoff as it moved down the hillside, not allowing it to gain so much momentum that a high suspension velocity can be reached. These vineyard breaks have been crucial in even wider erosional damage in many areas.

The creation of small vineyards was often caused by two factors. The first being economically large vineyards did not make sense. There wasn’t sufficient demand for wine to produce significantly more than the greater Burgundy area could consume. The poor roads and the lack of safety between villages and cities made medieval trading slow and perilous. Additionally the division and subdivisions of France and the rest of Europe meant that lords had the right to restrict passage and to impose fines and tariffs upon merchants.  These factors diminished the volume and frequency of trade within the continent, and in turn limited the amount of wine needed to be produced. Large tracts of vineyards were not necessary. The second, and perhaps the greatest limiting factor of vineyard size would be size of a plot that a single man could work in a day.

Les Glaneuses (1857) by Jean Francois Millet

Les Glaneuses (1857) by Jean Francois Millet

While ouvrées simply means worked in modern French, it was used in the past as a measurement of land based on how much land a single farmer could work himself.  Thus, one ouvrées (4.285 ares (2) or a tenth of an acre) is the amount one man can work in one day without a horse.  Madame Roty re-counts her family’s history in explaining that in the late 1800’s an earlier generation did not bother to plant their vines in rows since they could not afford a animal.

This suggests an interesting fact set of circumstances. Before the Revolution, (the Roty’s farmed Gevrey since 1710) farmers who specialized in grape cultivation, worked a handful of parcels on the local Seigneur’s manor, in the open field system described in Part 4. In this feudal society, they had the use of a shared horse and plow which belonged to the estate. However, after the ownership of land was released to the serfs following the Revolution in 1793, they may have now owned their parcels, but they so poor they could not afford the animals to farm them. This forced most of the peasants of Burgundy use to no-till farming methods. Later as economics of the region improved, a horse could be bought (perhaps in co-op one with one or more families), the Roty’s were forced to remove some of the vines so the animal and plow could pass through.

Farmers who could afford a horse, found the animal multiplied their efforts eight-fold, allowing them to plow 8 ouvrées in a day.  A family with a horse could now manage seven hectares of land, which were, of course, divided into the same feudal era parcels families of the area had always farmed, just as they do today.

The emergence of tractors opened up the capabilities substantially more, allowing growers to farm much larger areas of land. Additionally that extra time has allowed growers to farm in farther flung vineyards, in villages outside of their own.

 

Next Up: Part 4.2 Erosion fundamentals: infiltration rates, runoff and damage, and how it has changed the wines of Burgundy.

 

 


(1) Musigny has three factors in its favor. It has a shallow slope which aids in its soil retention.  It is a shallow vineyard, in that its rows are not long, and runoff can not achieve a high suspension velocity. And third, it is enclosed by walls that help protect it from some erosional forces.

(2) Ares is 100 square meters, and a hectare is 100 ares.

 

 

Understanding the Terroir of Burgundy: Part 3.4 The Grand Crus

 By Dean Alexander

While working my first wine shop job twenty years ago, I asked the store manager – who was a Burgundy guy of significant reputation: “Why is Rousseau’s Ruchottes-Chambertin not as good as as his Clos de Bèze and Chambertin?”  The answer I got was honest: “I don’t know. I’ll have to ask next time I’m there.”

It years later that realized that I had asked the wrong question. The question I should have asked was: What causes these neighboring vineyards to produce wines of such different character? 

Today, twenty years later, I can answer that question. If you have read my previous 12 articles in this series on Understanding the Terroir of Burgundy, it is likely you can answer it too. More importantly, some of the lessons here can be used to understand other appellations where less concrete information is known.

Clos des Ruchottes to the right, and Ruchottes du bas, on the left. photo: googlemaps

Clos des Ruchottes to the right, and Ruchottes du bas, on the left. photo: googlemaps

The short answer

Chambertin, Chambertin-Clos de Bèze, and Ruchottes-Chambertin

These three grand cru vineyards sit in a row, shoulder to shoulder on the same hillside. All have their upper-most vines smack up against the forested hillside, and all have virtually the same exposition. The legendary domaine of Armand Rousseau farms and makes wine from all three of these vineyards; yet one, the cru of Ruchottes-Chambertin, does not seem to be cut from the same cloth. The wine made from Ruchottes is not as rich or opulent. It tends to be lighter, more fine-boned, and more angular in its structure. The primary reason for this difference in wine character is that right at the border of Clos de Bèze and Ruchottes, the limestone beneath changes significantly. Unlike the other two vineyards, Ruchottes-Chambertin sits over very hard and pure limestone that is composed of almost completely of calcium carbonates and very little in the way of impurities, such as mud or clay.

The impurities within the stone, (bonded by the calcite) is what determines how much clay and other materials will be left behind as bedding materials when the stone has weathered. The more impurities in the limestone, the more nutrients will be available for the vines when the stone weathers chemically.  Further, it will reflect not just how fractured the stone has become due to extensional stress, but it will have often been the determining factor of whether the bedding has become friable as well. The wines of Chambertin and Clos de Bèze have this sort of impure limestone as a bedding under three-quarters of its surface area. It is a significant factor in giving the wines of Chambertin and Clos de Bèze a heavier weight and richer character than the wines from Ruchottes.

Another major factor in this differential in wine weight is that Ruchottes is a much smaller appellation, which confines it solely to the upper-slope. Its location makes it subject to all of the factors that challenge upper slope vineyards, details that are examined in Part 3.3.  Conversely, both Chambertin or Clos de Beze extend almost three times farther down the hill, all the way to the curb of the slope. Additionally, while the degree of slope may kick up in the upper final meters of the Clos de Bèze and Chambertin, the area under vine upon upper slope (that will produce a lighter wine) is relatively small compared to the entire surface area of those vineyards.  

Unlike Ruchottes, the long slopes of Chambertin and Clos de Bèze will reach down to almost to where the slope completely leveled off. There at the base of the slope, rock and soil colluvium will have been transported by gravitational erosion, adding generously to the depth the soil. This depth allows more water to be absorbed and retained for use by the vines. It is rich in limestone rubble, gravel, and catches and holds more fine earth fractions including transported clay that has flocculated there. Above ground scree litters the vineyards

The fact that most ownership parcels run in vertical rows, from the top of the vineyard, to the bottom, assures that any lighter, more finessed wines will contribute, but not dominate the overall blend. In other words, blending of heavier wines lower on the slope masks the lighter wines from the top of the slope. 

It is abundantly clear that the vines benefit from the higher levels of nutrients in these deeper soils. They develop grapes that carry more color (anthocyanins) and brings many times more dry extract to the wine. This translates as the wines of these vineyards having a richer, more velvety texture, increased depth, all of which covers the structure. On the opposite end of the spectrum, the upper-slope position of Ruchottes-Chambertin dictates that the soils there are very shallow, and while there is a high percentage of colluvium, it is not as rich in sand, silt or clay sized particles.  In fact, there are places the topsoil has completely eroded away, leaving fractured stone and primary clay and marly-limestone between the voids and breaks in the rock.

New research allows new understanding

Today we can examine this variation of limestone within a vineyard with a precision that was not possible a decade ago. This is due to the groundbreaking work of geologist Françoise VannierPetit and her mapping of the dominant limestone beddings of Gevrey. Through her work, we know that Ruchottes is a very homogeneous terroir, one with a very pure and hard limestone bedding dominating the vineyard. While the stone does not provide much in the way of nutrients to nurture the vines, we know it is well-fractured by two large faults that run through the vineyard.  Because of the vigorous faulting and fracturing throughout the vineyard, Ruchottes does produce a grand cru class wine, but it is a grand cru of a different character.

The geological factors in Ruchottes do not typically produce a wine with the substantial fruit or thickness of a Chambertin, and this ‘reduced’ level fruit often does not completely ‘blanket’ of structure in the wines from Ruchottes. This obvious structure is often mentioned in wine reviews, noting heightened acids and tannins, lending the wines a more angular construction than in other grand crus. By the same token, the wine from Ruchottes is often quite aromatic, with finer bones, for this wine, it means exhibiting more finesse, as well as giving the taster a heightened awareness of the wine’s precise rendering of detail. In another vineyard, this might be attributed to the grapes achieving less phenolic maturity, but the wines of Ruchottes are ripe, they just aren’t typically as large scaled or heavy. Moreover, they can be remarkably beautiful wines that can age effortlessly, for decades; often gaining poise, polish, and balance while doing so.

The gentle slopes of Chambertin. Photo: googlemaps

The gentle slopes of Chambertin. Photo: googlemaps

The substrata of Chambertin and Clos de Bèze is much more varied. With Vannier-Petit’s mapping information, we know that 35 million years ago the vineyards of Chambertin and Clos de Bèze were opened up by a large fault. This exposing the older (2 million years +/-) of softer bedding planes below.  They are both divided by four bedding planes, three of them being of soft, friable, impure materials, giving excellent nutrients.  This softer, highly fractured bedding allows the vines to thrive, and produce wines with much higher levels of fruit. This is the heart of Chambertin and Clos de Bèze.

Additionally, the twin vineyards are perfectly situated, mostly upon a gentle gradient which will resist erosion, or better yet, at the curb of the slope, where the soil is deeper,  The vineyards are well protected from wind, being squarely behind the hillside of Montagne de Combe Grisard. These two vineyards sit in the sweet spot of the heat trap formed by the hyperbolic concave of the slope. This positioning allows ripening occur even in most cold, wet years. Ruchottes, while fairly well protected, it is nearer the Combe de Lavaux through which cooling winds flow down the vast gorge.

All of these factors make the wines made from Chambertin and Clos de Bèze much easier wines to understand because they have so much to give. They can be very seductive and complex, and can be drunk either young or old.  Are they typically better wines than can be made in Ruchottes?  The knee-jerk reaction is yes, as Ruchottes can be equated to the man fighting with one hand tied behind his back. But when a well-made wine from Ruchottes is opened at the right time, and served with the right meal, it can be perfection.

Armand Roussaux parcel map

Chambertin clos de Beze

 

Digging deeper 

Gevrey-Chambertin topography

Generally speaking, when compared to vineyards in some of other villages, the grand vineyards of Gevrey are fairly mild in their gradient. The uppermost vineyard sites of the Chambertin-named vineyards butt up against the Montagne de Combe Grisard’s “chaumes”, (or ‘scruff ‘ in English). But unlike the steep upper hillsides of Vosne or Volnay that were able to be planted to vine, there is an unarable, rocky, forested landscape. Here in the chaumes, where no vines are planted, the hillside above Gevrey becomes steep.

The premier cru of Bel-Air is the one real exception. Carved out of a void in the rocky forest, and perched directly above Chambertin Clos de Bèze, Bel Air is a steep vineyard. It is a superb example of the struggles upper-slope vineyards face. See Part 3.3.1 for more on this. According to Vannier-Petit, a white Oolite formation underlies the uppermost section of Bel Air, and Premeaux Limestone underlies the lower part. Several writers have describe Clos de Bèze as having Oolite formations below the soils, but Vannier-Petit does not note this. Instead, it is likely that Oolite has slid, as scree, or even in large chunks as a rock slide, into Clos de Bèze, from Bel Air above.

A prominent feature of the area, as outlined by the late James E. Wilson, a geologist, and author of Terroir (1998), is a rocky outcropping he referred to as a “Comblanchien cap“. While this was not part of the vineyard landscape, he described it as a major feature of the “Nuits Strata Package.” This term,“Nuits Strata Package,” as coined by Wilson, is an overarching reference to the bands of limestone bedding that stretch from Marsannay to Nuits-St-George, a layering of limestones unique to the Côte de Nuits. An upper-band of Comblanchien stone, he wrote, formed a structural bulwark or ‘cap’ which has allowed the upper-hillside to resist erosion, while the softer center eroded more quickly. This has caused the Côte de Nuits to develop its hyperbolic concave slope-shape. This concave slope relief, as I wrote earlier, allows the heat of the sun is trapped, allowing fruit to ripen fully. This is particuularly true for vineyards such as this that sit in a wind shadow which is created by the trees and hillside above.

Interestingly, a much more recent map of Gevrey by Vannier-Petit, does not deem it necessary to include hillside construction above the vineyards.  So while she shows no Comblanchien cap rock at the edge of the Gevrey’s vineyards, as it seems Wilson described them, she does shows that the Premeaux stone extends one hundred or so meters up-slope. This extends well beyond the farthest, uppermost edges of the vineyard land.  While she may have felt the composition was outside the scope of the project, certainly anything that will wash, slide, or roll into a vineyard, is of great importance to our understanding of the physical vineyard makeup.

Ruchottes-Chambertin: a largely homogeneous appellation 

Here, a photo by Armand Rousseau illustrating the lack of topsoil, and the width of the fractures in the Premeaux limestone. No doubt this is a more extreme section, but it gives us the understanding of the relationship between the hard stone, fracturing and the difficulty of dealing with erosion in these vineyards.

Here, a photo from Armand Rousseau illustrates the lack of topsoil, and the width of the fractures in the Premeaux limestone. No doubt this is a more extreme section, but it gives us the understanding of the relationship between the hard stone, fracturing and the difficulty of dealing with erosion in these vineyards.

Ruchottes-Chambertin, and it’s ying-yang partner. Mazy-Chambertin (also spelled Mazis-Chambertin), sit at the tail end of the string of grand cru vineyards. The primary limestone beneath both vineyards is the significantly calcium-pure, Premeaux. Premeaux limestone, which is marketed as marble, is highly desirable for construction and prized for its pink color. It is very similar to Comblanchien (which is a creamy white), but slightly less pure, (hence the color), and slightly less resistant to geological strain. See Part 1.1 for detailed compressional strengths of various commercial limestones.

Technically, the Ruchottes appellation is made up of three small, roughly equally-sized vineyards:  Ruchottes Bas, (meaning the below) Ruchottes Hauts, (meaning above), and next to that, against the forested outcroppings at the top of the hill, Clos des Ruchottes. The Clos, is a monopole owned by the firm of Armand Rousseau.

While the lower half of the Clos des Ruchottes shares the rest of Ruchottes’ Premeaux limestone, the uppermost section, is covered in a layer of white Oolitic stone. Oolitic stone is made up of millions of small, oval, carbonate Oolite (egg stone) pellets that are fused by mineral cement. This composite construction makes the stone more susceptible to fracture, and the vines find it far easier to penetrate the many weak spots in this more porous stone. If anything, this is a benefit that the Clos des Ruchottes has over the rest of the Ruchottes appellation, especially since it is so high upon the hill. However we don’t know if the Oolite is of significant depth, and it is likely that Premeaux lies directly beneath it anyway. In either case, as vineyards go, the entire appellation of Ruchottes-Chambertin, is remarkably homogeneous in character.

The excellent Armand Rousseau website discusses Ruchottes Oolitic limestone, as well as shows the firm’s holdings in the vineyard, and is fairly detailed, and seemingly competent in their geological explanations, a surprising rarity in Burgundian marketing. Below is an excerpt.

The soil is composed of a shallow layer of red marl up to the top of the area. It is very pebbly, shallow and not fertile. The vines are based on oolithic limestone dating from Bathonien which disintegrates if frozen producing scree. This soil type forces the roots to go deeper into the rock. This results in a more fragrant, mineral style of wine that is lighter in colour but with a fine and elegant body. domaine-rousseau.com/en

Examining Ruchottes faulting and fracturing

We know through of the study of fracturing along the Arugot fault in the Dead Sea Basin, that as the distance from the fault increases, fracturing diminishes in frequency. This means that fracturing still occurs in its clusters, but the spacing between clusters is farther apart, leaving stretches of relatively undisturbed stone between areas of fracturing. As Ruchottes is located at the farthest possible distance in Gevrey from the main Saône fault, we rightly might expect this hard stone to be only intermittently fractured. Certainly there have been numerous accounts over the past century of vignerons having to dynamite sections of these vineyards to break up the stone enough to plant their vines.

Mazy and Ruchottes Chambertin with dip and strike oriented faults. Significant outcropping has emerged from this hard Premeaux stone at the convergence of these faults. Interestingly its both parallel and perpendicular to the extensional, horizontal faulting

Mazy and Ruchottes Chambertin with dip and strike oriented faults. Significant outcropping has emerged from this hard Premeaux stone at the convergence of these faults. Interestingly its both parallel and perpendicular to the extensional, horizontal faulting

Unknown before Vannier-Petit’s work were the locations of sub-faulting that occurred at the same time that the Saône Fault developed.(1) Two sub-faults bi-sect Ruchottes and Mazy, right at the border with Clos de Bèze. The vertical fault-line follows the boundary between the Premeaux stone and the various beddings that make up Clos de Bèze.

Ruchottes origin during of the Côte’s creation 

The once level Premeaux limestone bedding of Ruchottes came under great strain as the land that now forms the Saône Valley Basin pulled away and began its slide down. As the limestone slab was pulled extensionally, the once solid piece of limestone bedding first began to microfracture, then to fracture throughout the body of the stone. As understood by the study of fluid mechanics, stress intensifies exponentially upon weakest areas of the stone, from which fracturing propagates, until the main horizontal break, or fault occurs.

As this faulting occurred, the neighboring blocks of limestone were pulled downward by the void made by the dropping/falling off the fledgling Saône Valley. As this happened, bedding of Ruchottes began to tilt and slide downwards, both pulled and sliding with the adjacent formations. It is not clear if this was a rapid, cataclysmic event, or that it happened over the span of hundreds of thousands, or even millions of years. Either way, the stress upon the Premeaux bedding of Ruchottes was extraordinary, and what fracturing that was not caused the faulting, certainly occurred as it tilted and moved its position downward.

Often times, faulting can cause one plate to sit significantly higher than the next, forming a drop off which may or may not fill with soil.  In some locations, such as the fault between Chevalier-Montrachet and Le Montrachet, this has occurred What soil was lost by Chevalier to erosion, found a fine resting place in Le Montrachet, allowing the soils of Le Montrachet to become much deeper (and richer).  In other instances, erosion may once again level any difference in bedding height created by faulting. Alternately, the bedding may remain at the same height following the fault creation.  To the best of my knowledge, any height differential between Ruchottes du bas and Mazy Hauts is not documented.

Looking at the satellite image, there are certainly several visual clues that this faulting exists. Most obvious are the signs of significant stress are the limestone ridges, where the bedding has folded upon itself, that pushed above the topsoil. These are dominate features directly above the southern end of Mazy Haut, and just like the walls of Clos, these limestone ridges greatly reduce erosion in these areas, which results in deeper richer soils and thus weightier wines, not only in Mazy, but in that area of Ruchottes du Dessus.

Clos de Beze & Chambertin: four distinct bedding planes

Here the soft friable makeup explains the ease that the vines have in extracting nutrients and water from the base rock

Here the soft friable makeup explains the ease that the vines have in extracting nutrients and water from the base rock

While Chambertin and Chambertin Clos de Bèze are very similar to each other, they are unique to all other vineyards in Gevrey. Both vineyards share the same four bands of bedding planes, in roughly the same proportions. The one largest difference between them is that there is a higher percentage of Crinoidal stone in Clos de Bèze than exists in the northern end of Chambertin.  However, what is farmed depends completely on the parcels owned, not what exists in the vineyard itself.  It is increasingly clear is that a parcel is a vineyard in itself, and sections within parcels can hold wide variation in the character of wine it will produce.

Upper-slope Bathonian beddings:

Premeaux limestone and Argillaceous limestone/Shaley limestone

The uppermost sections of both Clos de Bèze and Chambertin sit over the very pure, and hard, Premeaux limestone, formed during the Bathonian which is a 2 million year period of the upper middle Jurassic. As in Ruchottes, we can expect this Premeaux limestone to be fairly well-fragmented. If this were the only stone found below the surface of these vineyards, the wines would taste much more like Ruchottes, but that is not the case.

The middle-upper section of these sibling vineyards is argillaceous limestone. This is a calcium-rich clay matrix may be indurated into stone, or it also may be soft and more marly. The clay, or argile as it is called in French, normally composes up to 50% the matrix, with roughly the balance being calcium carbonate and impurities. To this Vannier-Petit adds the word hydraulique, (in parenthesis), which refers to the fact that this particular limestone contains silica and alumina, that will yield a lime that will harden under water.  The assumption is that this Calcaire Argilleux formed underwater in the Jurassic lagoon or seashore, by secreting quicklime which bound with the clay, 168 million years ago.

Decanter Magazine alternately, and perhaps inaccurately, translates from the French Calcaire Argilleux, into Shaley Limestone, (as seen in the map box). That said, Françoise VannierPetit describes in an interview, that the relationship of clay and shale, is almost as one material that continually is in a transition from clay to shale – and back again, depending on how hardened (indurated) it becomes, or degraded. That stated, shale is generally regarded as lithified clay mixed with silt, the blend of which causes the notable horizontal striations, while a body of transported clay (of a single type, ie. Kaolin) that has been indurated (hardened) is termed claystone. Geologist are notorious for their loose use of terms, which makes it challenging for the rest of us to catch up, and I suspect Vannier-Petit is often guilty of this. AC Shelly is credited with writing in 1988 that “The term shale, however, could perhaps be usefully abandoned by geologists, except when communicating to engineers or management‟

Nothing is as simple as a name. Shale can be found in many forms. The relationship between clay and shale is very tight, just like water and ice.

Nothing is as simple as a name. Shale can be found in many forms. The relationship between clay and shale is very tight, just like water and ice.

Middle to lower slope Bajonien beddings: 

Marnes à Ostrea acuminata & Crinoidal Limestone

The oyster, and other fossils that sedimentologists are constantly mentioning as being present the bedding is really only relevant because it allows the scientist to easily reference age of the material. The fact certain creatures lived only during distinct periods of time, and only in certain environments. So not only does it give scientists the age of the strata, but it tells them a lot about the particular conditions that existed in that location, quickly allows the scientist to assign the formation of the bedding material to a particular period of time. As the fossils display different signs of evolution, (in the case some oysters, their valve position changed over long periods of time) the sedimentologist can establish the age bedding, and allow them to recognize a change of bedding (at on the surface) simply by the fossils in each location.

Using this methodology, the scientist gleans information about how the bedding has shifted position, or even its location. These shifts have been very significant in the Côte. By categorizing strata by type, and fossil type. and date, they can match one strata in one location with its mate in another.  This methodology allows sedimentologists to correlate strata worldwide.

Oyster bedIn the vineyard of Chambertin, the marl (Marnes à Ostrea acuminata) lies in a layer just beneath the argillaceous material that once was an ancient oyster bed. It is loaded with fossilized oyster shells (Ostrea)  from the upperBajocien period. This soil, into which the fossils are bedded, contains a large amount of the clay, montmorillonite, which has a very high cation exchange rate, and such soils, with their negative charge, attract and hold positively charged ions called cations (minerals like calcium (Ca++), magnesium (Mg++), potassium (K+), ammonium (NH4+), hydrogen (H+) and sodium (Na+) that are crucial for plant growth. This makes this particular marl which lies in the heart of Chambertin, a particularly sweet spot for vines. And because this is a bedding plane that underlies the Argillaceous material above it, those vines whose roots can reach that deeply, may benefit from the Marnes à Ostrea acuminata too. That said, the deeper roots, it is reported, do not typically supply vines significantly with nutrients, that vines rely on their shallower root systems for this function.

gevrey pre slideThe age of the Marnes à Ostrea acuminata dates back to the very late Bajocian, parkinsoni zone 168.3 +/-, well before the Premeaux which lies above it was formed on top of it. This important because this decisively shows that the Comblanchien bedding, which lies at the base of the hillside (and was formed later in the Bathonian), slid down slope, and was pulled eastward with the falling valley. This slide of the Comblanchien, which at one time overlaid the argillaceous and oyster marl material and lay next to the Premeaux, moved downward almost 100 meters and eastward by roughly 200 meters. exposing this older marl and crinoidal bedding to the air, after having been buried underground for the previous 133 million years. The next bedding plane is the also Bajocien in origin, again being older than the Premeaux higher on the hill, and older than the Comblanchien which sits below both Chambertin and Clos de Beze.

The lowest section of Chambertin, and the largest percentage of Clos de Beze’s acreage consists of the well-fractured Crinoidal Limestone. This is the most common base rock upon which, the classified crus of Gevrey are planted.

Crinoids were extremely prevalent the lagoons and Jurassic seas worldwide, until the Permo-Triassic extinction when they were virtually wiped off of the geologic record. Their fossilized remains create weakness in the stone that encases them. This weakness in the stone, coupled with the geological fracturing of the area, has made it relatively easy for the vine’s roots to penetrate deep into this rock strata. Impurities in the stone’s construction, allows for chemical weathering, brought about by rainwater infiltration, to create rich primary clay bedding for the vines, within the breaks and gaps in the rock. These factors have proved that Crinoidal limestone provides a very effective and fertile bedding for Pinot Noir to grow.

Wilson described the Crinoidal limestone as being “cracked by numerous small faults which ‘shuffle the cards’ of strata, but generally are not large enough to ‘cut the deck’ to introduce markedly new strata.” Terroir (1998) p.131.  This is typical of his breezy style, and while it is visual (in terms of cards), it really doesn’t have much concrete meaning, other than being a colorful way to say the crinoidal stone is well-fractured. He does go on to say that this extensive fracturing allows the stone to be a good aquifer for the vines.

crinoids

Colluvium: atop the bedding planes

Almost every grand cru vineyard in the Côte de Nuits has significant amounts of colluvium mixed in their soils. While Ruchottes-Chambertin does have colluvium is one of the most glaring exceptions it is not significant in quantity.  Typically, this colluvium is accompanied by a fair amount of transported clay, which when together often forms marl.(2)  Rarely does one exist without the other in vineyards that have been classified as grand cru.

In the Côte de Nuits, there tends to be more colluvium in the colluvium to clay matrix, while in the Côte de Beaune, there tends to be more clay.  This tends to the case because there are many more marl bedding planes in the Côte de Beaune than there are in the Côte de Nuits, where marl bedding is rarer. There may be more shale in the Côte de Beaune as well.

 

The tête de cru, –  the very finest of the grand cru vineyards, have relatively equal proportions of marl and colluvium and sit only upon the slightest of slopes. This applies to the vast majority of Chambertin and Clos de Bèze vineyard area. These crus possess a perfect planting bed for vines: they have colluvium/marl based topsoil that is at least 50 cm (19 inches) deep where the absorbing roots are active.(3)  Because of this construction, the soil has good porosity for root and water infiltration but is not so porous a material that the water does not drain right through it, or cause it evaporates quickly from it. Additionally, because of its rocky nature, the grand cru soils tend to resists compaction.

While there is a band of harder, less fertile Premeaux stone on the uppermost slopes of Chambertin and Clos de Bèze, this represents a minority proportion of these vineyards. Parcels that have vines on these upper slopes, often lend a measure of finesse to the finished wine, without impacting the palate impression of the finished blend. For these reasons, Chambertin and Chambertin Clos de Bèze are among the finest vineyards in the Côte de Nuits.

Clos des Ruchottes, (and Ruchottes in general) is a far different vineyard than its two neighbors. With the near-pure calcium stone beneath its shallow soils, the low levels of impurities mean that when it weathers,  very little clay is produced. Because of the scant soil, the vineyard their neither contains nor can it attract, as much in the way of nutrients for the vines as can Clos de Bèze with which it shares a border. The resulting wines typically have less fruit, less color, seem more structured or tannic, and have a finer, though thinner texture. On the upside, the vineyard produces a very classy wine that can have excellent aromatics, remarkable finesse, and has excellent age ability.

Agree? Disagree? Comments are welcome and encouraged! Please feel free to like or share this, or any other article in this series!


Note: Many authors note that Clos de Bèze has Oolitic limestone. Vannier-Petit does not note this on her map. Instead, she places the Oolitic stone in the premier cru of Bel Air, which sits directly above it. A likely explanation of Oolite being cited as existing in Chambertin is scree/colluvium from Bel Air has slid down, to litter Clos de Bèze from above.

(1) The problem with always talking about the Saône Fault, is it ignores the fact that the fault is really the most minor part of the geological event that happened. It was a continent being pulled apart, that caused a void into which the land adjacent to the Cote d’Or fell into a trough which would become the Saône Valley. The Saône Fault is nothing more than as scar marking that event. And in fact, the Saône Fault lies buried quite deeply underground – its general location is only estimated.

(2) Marl would require a smaller particle size than just rock and gravel sized limestone pieces to produce the non-clayey consistency that marl displays.

(3) Despite the conventional wisdom to the contrary, it is this shallow absorbing root system that gathers the majority of nutrients that vines require.

 

Understanding the Terroir of Burgundy: Part 3.3.1 Fracturing variations within upper vineyards

Vineyard and plot variation confuses our understanding of Burgundy

High on the upper slopes, the farthest away from the Saône Valley Fault, the magnitude of fracturing within the same vineyard can vary significantly, even within the span of a few meters. Not only that, but there is evidence that the farther one moves from the main fault, the occurrence of fracturing patterns widens in its spacing, being further and further apart, and more irregular in its distribution. This means that if the fracturing is unequal within a vineyard, so can it to be unequal within a parcel. Following this uneven fracturing distribution, it becomes quite clear that a wine produced from different vineyard sections may produce wines of differents weights, and possibly character. We can only assume that this kind of intermittent fracturing, hidden beneath the topsoil, has unequally affected not only the wine made by these plots but the reputation of the vignerons who farm these plots as well.

Fractured limestone of Les Perrieres

The patterns of fracture propagation

Looking back at Part 1.2 about the deformation and fracturing of limestone, the stress that causes the main fault, and many of the parallel faults also weakens the entire stone structure through deformation. Micro-fractures appear throughout the stone, independently of one another, usually in clusters. As the cracks propagate, they do so often in a tree-like pattern, forking and spreading upward from the origin fracture, deeper within the stone. Depending on the brittleness of the limestone and the direction of the strain, these microcracks will form tensile fractures (extensional strain) or shear planes (compressional strain). Additional strain will be concentrated on the most fractured, weakest part of the stone, and this becomes the path of the fracture. Because these areas have been forced to bend and ultimately fail, this movement causes the strain to localize, increased by the stone’s own failure, causing even greater fracturing.  Alternately in the areas between the crack arrays, the stone will be only lightly fractured, and in some places, maybe not at all. It is this that makes plots within the same vineyard unequal, as much as the skill and style vignerons are unequal.

 

I have laid a vertical tree in a horizontal fashion to more dramatically illustrate fracturing within parcels. Fracturing actually happens from deeper in the stone and moves upwards to the surface, often widening and splintering as it goes. Fracturing does not always reach the surface, and this shows the disparity in fracturing one area vs. another. Mechanical weathering will accentuate fracturing where it does extend to the surface, breaking up the stone, while chemical weathering will reduce the stone to Co3 and primary clay, creating marly limestone.

I have laid a vertical tree in a horizontal fashion to more dramatically illustrate fracturing within parcels. Fracturing actually happens from deeper in the stone and moves upwards to the surface, often widening and splintering as it goes. Fracturing does not always reach the surface, and this shows the disparity in fracturing one area vs. another. Mechanical weathering will accentuate fracturing where it does extend to the surface, breaking up the stone, while chemical weathering will reduce the stone to Co3 and primary clay, creating marly limestone.

 

Clues to the Côte by examining another fault/escarpment

 

The Arugot Fault near Jerusalem is unique because the fractures to its dolomite slabs (limestone containing magnesium) lie above ground, not covered by sand or soil. Geologists are reasonably certain that the Arugot fault was an extensional occurrence (like the Saône Fault), not caused by slip-shear or other earthquake-related stresses. The Arugot fault, like the Saône Fault, was created an escarpment as the Dead Sea Basin pulled away, in a horst/graben relationship.  The area is prone to flash flooding, particularly through the deep canyons that bisect the escarpment (not unlike the combes of the Cote), and it was the erosion that rapid water movement causes have left the vertically fractured dolomite uncovered and available to be studied. The general geographical similarities of the Saône and Arugot are marred by the fact that the Dead Sea escarpment is twice as tall (600 meters), and many times more steep, with very steep angles of 75% to 80% that drop into the Dead Sea depression.

The fault itself is believed to extend several hundred meters into the earth. Parallel to the fault, a series many extensional fractures were formed, marching up the escarpment away from the main fault.  There is ample evidence that these fractures propagated from below, as the fractures are tree-like, branching vertically, splitting the rock into smaller and smaller divisions as they move toward the surface. They often, but not always, fracture through the top of the stone. Nearest to the Arugot fault itself, the fractures are very close together, and the farther away from the fault the wider the spacing between fractures until they discontinue hundreds of meters away from the main fault. The relevance of this increased space between fractures is that explains the variation between well-fractured sections of limestone, and poorly fractured sections, all within the space of a few meters. This variation extends to, and explains not only to the difference between two vineyards, but the difference between plots, or even within sections of the same plot.

fracture propagation from the Arugot fault near Jerusalem. The fractures are tree-like, and as you move away from the fault, the fractures are spaced wider and wider apart. source: earthquakes.ou.edu

Fracture propagation from the Arugot fault near Jerusalem. The fractures are tree-like, and as you move away from the fault, the fractures are spaced wider and wider apart. source: earthquakes.ou.edu

Understanding the Terroir of Burgundy: Part 3.3 The Upper Slopes

Shallow topsoil over hard limestone: a site of struggle

As I touched on in the introduction of slope position in Part 3.2, there are significant variables effecting which vineyards can produce weightier wines further up the slope. However, as a general rule, the steep upper-slopes are far less capable of producing dense, weighty and fruit filled Burgundies that are routinely produced on the mid and lower slopes.

The lack of water, nutrients and root space

The scree filled Les Narvaux in Meursault. photo: googlemaps

The scree filled Les Narvaux in Meursault. photo: googlemaps

In many of these upper vineyards, the crushed, sandy, and in some places powdery, or typically firmer and more compact, the marly limestone topsoil overlies a very pure limestone, such as Comblanchien, Premeaux and Pierre de Chassagne. Here, the extent of that the stone is fractured determines the vines ability to put down a healthy volume of roots to support both growth and fruit bearing activity. Any gardener can tell you that insufficient root space, whether grown above a shallow hardpan or in a pot, will cause a plant to be root bound and less healthy.

Because these steeper vineyards can neither develop, nor hold much topsoil to its slopes. The topsoil, which can be measured in inches rather than feet, tends to be very homogeneous in its makeup; a single horizon of compact, marly limestone, with a scant clay content of roughly 10-15%. The infiltration of rainwater and the drainage are one and the same. Retention of the water is performed almost solely by this clay content, and evaporation in this confined root zone can be a significant hazard to the vine. Fortunately rain in Burgundy during the growing season is common, although rainfall from April to October, and particularly in July, the loss of water in the soil is swifter than it’s replacement from the sky (Wilson, “Terroir” p120).

Infiltration Rates of Calcareous Soils

A study by A. Ruellan, of the Ecole National Supérieure Agronomique, examined the calcareous (limestone) soils of Mediterranean and desert regions, where available water and farming can be at critical odds.  He studied two major limestone soil types. The first was a light to medium textured, loamy, calcareous soil (60 – 80% CaCO3), and the second was a powdery and dry limestone soil with no cohesion. This second soil had a calcium carbonate content that exceeded 70%, and had 5% organic matter and a low clay content. The water holding capacity of this soil was a mere 14%. The depth of this soil was over 2 meters deep, which likely does not allow weathered clay accumulate near the surface, as it does in Burgundy.

Both limestone soils had very high permeability, with an infiltrate at a rate at a lightning fast 10 to 20 meters per day (or between 416 mm per hour and 832 mm per hour).  Even if rainwater infiltrated at half that rate through Burgundy’s compact limestone soils, it would virtually disappear from the topsoil. This is the area where the majority of the vines root system exists, and part of the root system responsible for nutrient uptake is within this topsoil region.  In this case of these soils, the vines must send down roots to gain water in the aquifer. Wittendal, who I wrote of in Part 3, suggests in that the vines literally wrap their roots around the stone, and suck the water from them.  I have seen little evidence that limestone actually absorbs water due to many limestone’s high calcium content and lack of porosity. This would be particularly true on the upper slopes under consideration now. It would be up to the roots to attempt to penetrate the stone in search of the needed water.

The root zone

Root development through soil

This slide represents the root development in shallow topsoil over a lightly fractured limestone base vs a deeper soil situation with four or five separate bedding horizons, such as exists lower on the slopes of burgundy.The effect infiltration rates have depends significantly on the distribution of vine roots. In most planting situations, 60 percent of vine roots are within the first two feet of topsoil, and have been known to attain a horizontal spread of 30 feet, although the majority of the root mass remains near the trunk.

By design, vines rely on the roots established within the surface soil – which is where nutrients (ie nitrogen, phosphorus, potassium) are found – to gain the majority of their sustenance. They send down deeper roots to gain water when it is not available nearer the surface. However in Burgundy, many of the steeper slopes present planting situations where not only is the soil very shallow, but the nutrients are poor. The limestone in these vineyards often is hard and clear of impurities, and within the same vineyard may vary significantly in how fractured the stone is. Because of this, in some locations vines have difficulty establishing vigorous root penetration of the limestone base, and this can dramatically limit the vine’s root zone.

Additionally, because of the soil’s shallow depth, , and because of the soils high porosity and low levels of clay and other fine earth fractions, only a limited volume of water can be retained

Water is critical for both clay’s formation and its chemical structure, and the clay will not give up the last of what it needs for it own composition. The evaporation rate of what little water there might remain, can be critically swift.

Rainwater’s infiltration of the limestone base, and its retention of water can also be limited where significant fracturing has not occurred. Any water that cannot easily infiltrate either the soil or the limestone base, will start downward movement across the topsoil as runoff. That means any vine that has been established in shallow topsoil, or the topsoil has suffered significant losses due to erosion, will be forced to send roots down to attempt to supply water and nutrients.

Vine roots and a restricted root zone

In non-cultivated, non-clonal vines, powerful tap roots are sent down for the purpose of retrieving water when it is not available in from the surface soils. However our clonal varieties are more “highly divided” according to the “Biology of the Grapevine” by Michael G. Mullins, Alain Bouquet, Larry E. Williams, Cambridge University Press, 1992. The largest, thickest, roots develop fully in their number of separate roots, by the vine’s third year, and are called the main framework roots. Old established vines in good health may have main framework roots as thick as 100cm (40 inches) thick. This main framework root system, in normal soils, typically sinks between 30 cm (11 inches) and 35 cm (13 inches) below the surface.  In shallow soils, they may hit hard limestone before full growth, and may have to turn away, or stop growing. Anne-Marie Morey, of Domaine Pierre Morey, echoes this in talking with Master of Wine, Benjamin Lewin, of their plot in Meursault Tessons. “This is a mineral terroir: the rock is about 30 cms down and the roots tend to run along the surface.”

From the main framework, grows the permanent root system. These roots are much smaller, between 2 and 6 cm, and may either grow horizontally (called spreaders) or they may grow downward (known as sinkers).  From these permanent roots grow the fibrous or absorbing roots. These absorbing roots are continually growing and dividing, and unlike the permanent roots, are short-lived. When older sections absorbing roots die, new lateral absorbing roots to replace them.

This cutaway of the topsoil of Gevrey Bel Air shows just how limited the root zone is in this premier cru vineyard. The Comblanchien below is being 'reconditioned' in this plot. More on this in a near future article. click to enlarge.

This cutaway of the topsoil of Gevrey Bel Air shows just how limited the root zone is in this premier cru vineyard. The limestone below is being ‘reconditioned’ in this plot. click to enlarge.

Although the permanent sinker roots may dive down significant depths, the absorbing roots (which account for major portion of a vine’s root system account for the highest percentage of root mass, typically only inhabit the first 20cm to 50cm, or between 8 inch and 19 inches of a soils depth (Champagnol,  Elements de Physiologie de la Vigne et de Viticulture Générale 1984). Clearly this is an issue if the topsoil is only 30 cm (12 inches) to begin with.  If the absorbing roots are not growing sufficiently on the sinkers, the vine must rely on the exceptionally poor topsoil of the marly limestone.

South African soil scientist Dr. Philip Myburgh found (1996) that restricted root growth correlated with diminished yields. He also found that the “critical limit’ of penetration by vine root was 2 MPa through a “growing medium”. Weakness in the bedrock, and the spacing of these weaknesses, contributed to a vines viability.

The vines on these slopes, on which there is limited fracturing of the harder, non-friable limestone, have difficulty surviving. These locations often shorten the lifespan of the vines planted there, compared to other, more fertile locations in Burgundy, where vines can grow in excess of 100 years. It is these vines, with barely sufficient nutrients that make wines that don’t have the fruit weight that I wrote of before, simply because they cannot gain the water and nutrients necessary to develop those characteristics. The amount of struggle the vine endures directly determines the wine’s weight, or lack of it.

It is ironic, that when we research the issues the catchphrases of wine describe, ie, the “vines must struggle”, or that a vineyard is “well-drained”, or the vineyards are “too wet to produce quality wine”, we see the simplicities, inaccuracies, or the shortcuts that those words cover up. Yet these catchphrases are so ingrained in wine writing, that we don’t even know to question them, or realize that they require significantly more nuance, or at minimum, point of reference. Yes, the vines on the upper-slopes are particularly well-drained. They do indeed struggle, sometimes to the point of producing vines are not healthy, and cannot the quality or the weight of wine that the producer (dictated by their customers) feels worthy of the price.

Extreme vineyard management

Blagny sous la dos d'Ane's shallow red soils produce a Pinot that is too light for the market to bear at the price it must be sold. photo: googlemaps

Blagny sous la dos d’Ane’s shallow red soils produce a Pinot that is too light for the market to accept – at the price it must be sold. photo: googlemaps

In Blagny, the Sous le dos d’Ane vineyard, which lies directly above the small cru of  Aux Perrières, has seen at least one frustrated producer graft their vines from Pinot Noir to Chardonnay. The Pinot, from the red, shallow, marly limestone soils, was felt to be unsatisfactorily light in weight. Not only would a lighter-styled, and minerally Chardonnay be well received, the producer will be able to sell it much more easily – and for more money because he could then label it as MeursaultSous le dos d’Ane, a much more marketable name.

Bel Air. More photos on this excellent website, and a terrific discussion in the comment section, albeit in French. Worth running through a translator. source: http://www.verre2terre.fr/

Bel Air. More photos on this excellent website, and a terrific discussion in the comment section. source: http://www.verre2terre.fr/

Producers in the Côte de Nuits rarely have the option to switch varietals. They typically must produce Pinot Noir to label as their recognized appellation. In the premier cru of Gevrey-Chambertin “Bel Air”, and Nuits St-Georges “Aux Torey”, growers have gone to the extreme lengths and expense of ‘reconditioning’ their plots. To do this, they must rip out their vines, strip back the topsoil and breaking up the limestone below. In the adjacent photo, a field of broken Premeaux limestone and White Oolite has been tenderized, if you will. The soil is replaced and the vineyard replanted. The entire process requires a decade before useful grapes can be harvested once again from the site, costing an untold number of Euros spent, not to mention the money not realize had the old vines been allowed to limp on. The same has been done in Puligny Folatières in 2007 by Vincent Girardin, and there again in 2011 by another unknown producer. Ditto with Clos de Vergers, a 1er cru in Pommard in 2009.

 

http://www.wineterroirs.com/2009/11/landscaping.html

click here: for the previous article, Understanding the Terroir of Burgundy: Part 3.2 The lower slopes

Understanding the Terroir of Burgundy: Part 3.2 The lower slopes

by Dean Alexander

° of Slope =  Soil Type + Soil Depth  → Wine Weight

In Part 3.1, I covered how the position and degree of slope determined the type of topsoil that lies there. In the next two sections, I will talk about how the position on the slope not only greatly influences topsoil composition but independent of winemaking decisions, is a significant determiner of the weight of the wine. In this section I will discuss this concept, focusing primarily on the vineyards below the slope, the flatlands vineyards most burgundy aficionados have traditionally ignored. This disdain for these lower-lying vineyards is changing because massive improvements in wine quality have made them relevant, and equally massive increases in wine prices have left them as the only wines tenable to those without the deepest of pockets. Additionally, sommeliers looking for high-quality wines of relative value, have begun to much more closely examine the wide-reaching Bourgogne appellations and the village level wines of the Côte d’Or. These are wines that fit price points and quality standards premier cru vineyards used to fill and often fill that void admirably.  


 The relationship of slope to wine weight

Soil depth and type can greatly determine wine weight and character

Soil depth and type can greatly determine wine weight and character

It has become increasingly apparent over the past decade, that there is a direct connection between the depth and richness of soil, to the weight of the wines produced from those vines. Vineyards that have a modicum of depth, and at least a fair amount of clay or other fine earth elements, coupled with a fractured limestone base, produce weightier wines. These vineyards typically exist from quite low on the slope to roughly mid-slope. The higher up the slope one goes, the more crucial it is that the stone below is well-fractured to be easily penetrated by vine roots. Softer limestone bases, like the friable, the fossil-infused crinoidal limestone, which is weakened by the ancient sea lilies trapped within it, or like clay-ladened argillaceous limestone, makes it possible to produce great wine from the steeper, upper-slopes. Examples of these vineyards include the uppermost section of Romanee-Conti and all of La Romanee, which sits above it. These appear to be rare exceptions, however.

Most wines produced from the steeper, upper slope vineyards, with shallower, marly-limestone (powdery, crushed-stone with low clay content) soils, lie over harder, purer limestone types like Comblanchien, Premeaux, and Pierre de Chassagne. These limestone types must have at least moderate fracturing and a high enough degree of ductile strain to plant above them. Wines from these types of vineyards are, without question, finer in focus and have greater delineation of flavor. It is not unusual for these wines to be described as spicier, more mineral laden, and have greater tannic structure. The short explanation is the upper-slope wines have less fruit to cover up their structure, while the wines from more gently sloped vineyards have more weighty fruit.  This fruit provides the gras, or fat, that obscures the structure of these weightier, more rounded wines. The upper slope vineyards will be covered in greater depth in the upcoming Part 3.3.

Because of the weathering of limestone on the upper slopes, and subsequent erosion, the soils, and colluvium collect on lower on the slope, making the topsoil there both deep and heavy. They are full of a wider array of fine earth fractions, and more readily retain water and nutrients necessary for the vines health and propagation of full, flavorful, berries.  On the curb of the slope they do this splendidly, with an excellent mix of clay and colluvium, giving the proper drainage for the typical amount of rainfall, yet retaining the right amount of water most times of year when rain does not fall.

The last vineyard before the pastures begin. The village of Puligny Montrachet is in the distance

The last vineyard before the pastures begin. The village of Puligny-Montrachet is in the distance. source: googlemaps.com

The “highway” and the low-lying vineyards below

For decades we have been told that the low-lying vineyards of Burgundy, were too wet to grow high-quality grapes, and we could expect neither concentration nor quality, from these village and Bourgogne level vineyards. The reason, we were told, was grapes grown from these flat, low-lying vineyards became bloated with water, and the result was acidic, thin, and “diluted” village and Bourgogne level wines. Alternately we were told the wines from lower vineyards were too “flabby”, as James E. Wilson ascribes on in his groundbreaking book Terroir published in 1988 (p.128). Thusly, an entire swath of vineyards, from below the villages of Gevrey and Vosne, all along the Côte, all the way to down to Chassagne, were dismissed as thin and shrill, lacking both character and concentration. These wines were generally considered by connoisseurs to be unworthy of drinking, much less purchasing.  At that time, given the poor quality being produced, that seemed perfectly reasonable.

This set in motion a series of generalizations and biases, many of which remain to this day. “The highway”, as Route Nationale 74 is often referred, became the demarcation between the possibility of good wine and bad. The notion that this roadway, something that is built for the sole purpose of moving from one village to the next, had become an indicator of wine quality, is so pervasive, that the grand crus with N74 at their feet, such as MazoyèresChambertin and Clos Vougeot, have been cast in a bad light simply due to their proximity to it. It has colored perceptions so much, that many people, to this day, equate being higher on the slope with being “better situated”. The fact that there are grand crus and premier crus on the upper slope, but none on the lower slopes only buttressed this idea.  However…

We now know this is not true.

Puligny Folatieres after a rain

The road below Paul Pernot’s Clos des Folatières, filled with water. However, this water is not allowed to enter the 1er Cru of Clavoillon below. This is an example of containing and redirecting excess water coming down the hillside, into noncrucial areas. click to enlarge photo source: googlemaps.com

There are many Bourgogne level vineyards that are more than capable of producing wines with good concentration, so long as the vigneron sought to produce quality over quantity, and the plot is not in an excessively poor location. So why were these myths that Bourgogne level vineyards could only produce light, thin, acidic wines, propagated by winemakers, wine writers, and importers?

The optimist would point to a lack of technical knowledge in the field and cellar made this true. The optimist would also say that the long tradition of creating simple, inexpensive, quaffing wine made it acceptable.

But there were other factors. Cold weather patterns from the mini ice-age, which ended in the 1850s, certainly set up long-standing expectations of wine the wine quality that was capable from various vineyards. These expectations were absolutely cemented in after the widely influential book by Jules Lavalle, Histoire et Statistique de la Vigne de Grands Vins de la Côte-d’Or was published in 1855. In this revered reference, Lavalle classified the vineyards of Burgundy the same year the French Government classified the chateaux of Bordeaux. No doubt the timing of this gave Lavalle’s unsanctioned work credence. After the first half degree average temperature increase which occurred around 1860, the climate in central Europe only gradually grew warmer over the next 135 years until 1990 when global warming really began in earnest. Before that, the weather would not allow the consistent ripening patterns that routinely we see today.

Another major factor was that there was not a complete understanding of how to control and divert runoff. Nor, prior to 1990, was it likely the villages along the Côte wealthy enough to make the large-scale improvements that were necessary to control rainwater runoff. Until the prices of Burgundy began to rise, overall the region was experiencing some economic depressed. This economic struggle, coupled with the inevitable political obstacles required to spend sparse civic funds, could delay improvements a decade.

On the other hand, the skeptic would point to the problems of greed, and it’s accomplice, over cropping. Vignerons could achieve 3 to 5 times higher production levels from the same vines, which was profitable, and required far less knowledge, less diligence in the field, and other than taking up more labor in bottling and space in the cellars, far less work in the cellars. It was not only the Bourgognes that fell into this net of profit over quality, but the village level wines were often fairly low in concentration, with under-ripe fruit, and low in quality. Even now, a producer that has reduced yields by a division of 3 in order to make a quality village or Bourgogne, is making less money per hectare than they would if they still over-cropped – and working harder in the field to do it.

Overcoming wet soil issues

Water features below Puligny Les Pucelles. Controlling and redirecting water away from lower vineyards is a major key to improving quality there. photo: googlemaps

Water features below Puligny Les Pucelles. Controlling and redirecting water away from lower vineyards is a major key to improving quality there.  click to enlarge  photo: googlemaps.com

Excess water in lower vineyards is a serious issue, and each vineyard is not equal in its ability to contend with heavy rainfall. Although flat is the quickest descriptor, the topography of each vineyard varies, as does the bedding (layers of soil) of each vineyard. These variances can dramatically determine the challenges presented to each grower in each day, season, and year, be it rain storm or drought.

In farming, an infiltration rate of roughly 50mm of rainfall per hour is considered ideal. That is precisely what a well-structured loam can typically absorb at normal rainfall rates, without significant puddling and runoff. Clays, however, drain much more slowly, with an infiltration 10-20mm per hour.  These optimal figures can all be thrown out the window, however, if the soil structure has been degraded through compaction or farming practices that commonly degrade the soil. Poorly structured clay soils can drain as slowly as 5-8-10mm per hour.

Alluvial soils, with their graded bedding, created by heavier gravel and sand falling out of water suspension before silt and clays, typically have good infiltration rates. Loam soils that have moved in from the Saône Valley pasture lands, and have weaved themselves into the fabric of the lower vineyards, have ideal infiltration rates. Sandy sections are likely to exist in some vineyards, will have very rapid infiltration and drainage, 150mm to 200+ mm per hour. Where solid layers of transported clay, in thick slabs have formed, drainage can be severely affected.  These plastic-y clays may repel water as much as they slowly absorb it. I wrote a much more complete examination of soils in Part 2.2.

What is important to consider, is that in all but the upper-most vineyards, soils are layered in horizons of soil types. It is normal, around the world, that there are typically 5 horizons of soil and subsoil layers in any given place, although there may be more, or as on slopes, fewer. Each horizon will affect the drainage of the plot, depending on its soil makeup. Geologist Francois Vannier-Petit presided over an excavation of Alex Gamble’s village-level Les Grands Champs vineyard in Puligny-Montrachet. In this vineyard, she records two horizons within the 80 cms that they dug, and she noted most of the vines roots existed in this zone. At the time of the excavation, she noted the soil was damp, but not wet, with good drainage.

The calcium, which is freed from the limestone rubble with weathering on the upper slopes, is not as prevalent and effective in the farther-flung Bourgogne vineyards. The calcium which helps disrupt the alignment the clay platelets, and aiding is drainage, may not be carried far enough by runoff to sufficiently strengthen the soils of these more distant vineyards.  Certainly, most of these vineyards are located beyond the Saône Valley fault, and the continuation of limestone that virtually sits on the surface of the Côte lays buried by at least a hundred feet of tertiary valley fill and has no effect on wine quality there, other than by its remoteness.

flooding

Turbid flood waters carry away gravel, sand, and fine earth fractions. These will be redeposited as alluvial soils, created graded bedding and clay minerals will flocculate onto, or into, other transported clay bodies. photo: decanter.com

The most severe problems revolve around the maximum amount of water the soil or clay can hold and fail to drain quickly enough through to the unsaturated/vadose zone, through capillary action to the water table below. With clay, this is called the plastic limit, or the point just before the clay loses its structure and becomes liquid. Flooding would ensue, and large volumes of soil would become suspended in turbid flowing waters, causing massive erosion, particularly from vineyards up-slope. This would truly be the worst case event, and I won’t say it doesn’t happen.

Another, significant problem, at least for vintners, although less apparent to the wine drinking public, is less wet soil is that it causes the vines to have difficulty acclimating to colder weather, and affects their hardiness if severe weather sets in.

However, in many vineyards, the wet soil has now been addressed by investments in drainage. Large yields are eliminated and concentration is gained by pruning for quality, coupled with bud thinning or green harvest. Vigilance against rot is key in these lower vineyards, as well as odium, and other mildews, which thrive in humid wet vineyards. This is a key element in quality since rainfall during the growing season is very common in Burgundy. With all of these precautions, there are now many producers who now make excellent Bourgogne level wines. And despite the tripling and quadrupling of the prices of Bourgogne, they are now well-worth drinking – often equalling  the premier cru wines of yesteryear in terms of quality.

It is often cited that Puligny-Montrachet has no underground cellars because of the high water table there. Yet Puligny is arguably the finest region for growing Chardonnay in the world. I submit that much of the success Puligny has enjoyed, is in part because the water table is high, coupled with the fact that the village and its vignerons have invested heavily in water control features to channel and redirect excess runoff.

Reshuffling the wine weight matrix

The revelation that well-concentrated wines can be produced from these “wet” vineyards, has thrown slope position into a far clearer focus. No longer did we have lighter-to-medium weight wines on the upper slopes, the heaviest wine on the curb of the slope, and the very lightest wines coming from the lowest and flattest areas of Burgundy. Now it was clear: the areas with deeper, richer soils, particularly those with clay to marl soils, can universally produce richer fuller-bodied wines. This increasing quality of Bourgogne and the lower-situated village wines has dramatically raised the bar of expectations of wines across the Côte d’Or. With Bourgogne’s challenging the more highly regarded village-level vineyard in terms of quality, and village wines posing a challenge in regards to quality to many of the premier crus, lackluster producers were now put on notice to raise their game in terms of coaxing harmony and complexity out of their wines. Now that wine weight can be achieved in vineyards all across the Côte, despite a low slope position below the highway, expectation that Bourgognes are the simple, light and often shrill wines of yesteryear has been largely shattered.

Additionally, there is adequate evidence that deeper soils, particularly those with moderate-to-high levels of clay (or other fine earth fractions), can be a positive factor, for their ability to retain water and nutrients for the vines. This allows them to develop anthocyanins and other flavor components within the grapes. The challenge in these low-lying vineyards is controlling, and dealing with excess water.  In wet years, vignerons have demonstrated that adequate investment to direct and control runoff, even most lower vineyards will not be too wet to grow good to high-quality fruit. Examples abound of village crus, from top vignerons, costing more than many grand crus; and these producers Bourgognes are not far behind in price. It’s not magic; it’s investment and hard work, in a decent vineyard, that makes this kind of quality possible.

Author’s Note: To avoid misunderstanding, this is a discussion of wine weight and concentration, not wine quality or wine complexity. Too often these things are confused, along with the notion that increased enjoyment equals increased complexity or quality. The goal is to understand and appreciate the differences and nuances that each vineyard provides by its unique situation, not to make it easier to find the most hedonistic wine possible.

Understanding the Terroir of Burgundy, Part 3.1: The confluence of stone, slope and soil

Analysis: Combining what we know about limestone and soil, and applying that to a slope allows us to be predictive of topsoil makeup.

by Dean Alexander

slope comparison

Rise ÷ Run = Slope

It has always been my contention that the slope determines a vineyard’s soil type, and it is the soil type that is a major factor in wine character. Because many vineyards carry through the various degree of slope through the profile a hillside, the soils vary greatly from top to bottom. Water and slope work together to cause this. Rainwater both causes the development of clay on the hillside, and is the reason clay and other fine earth fractions will not readily remain on a slope. But lets start with a hillside typical of one found Burgundy, and the fractured stone and scree and colluvium that resides there.

Slope diagram

The 315 meter elevation represents a grand cru vineyard profile. The 350 meter profile represents a steeper rise which would be typical of a premier cru, which sits above a grand cru located on the curb of the slope. This added elevation and degree of slope, greatly changes the soil type at the top of the hill and decreases the soil depth, and at the same time increases richens and thickens the soil type, and deepens the soil in the lower grand cru section.

The typical Cote de Nuits hillside vineyard rises about 100 meters (328 feet). The base of many appellations sit at roughly 200 to 250 meters elevation, and here the vineyards are quite flat. As you move toward the hillside (facing uphill) it is common for there to be roughly a half a degree rise on the lower slopes. After 300 to 400 meters, the slope gently increases over the next 150 to 200 meters to roughly a 2 to 3 percent slope, where the grand crus generally reside. The upper slopes can rise dramatically in places, depending on the how wide the sections of bedding plates between faults, and pulled out and down with the falling Sôane Valley, and how much the edges of those bedding plates have fractured and eroded, also sliding down the hill. Areas like Chambertin, this slope remains moderate and the vineyard land remains grand cru to the top of the slope. However, above Romanee-Conti, the slope becomes much more aggressive, and the classification switches to premier cru at the border of Les Petits Monts. This uptick in slope, and the change in classification is common, but not universal in its application. As most things in Burgundy, there are a lot of exceptions to classification boundaries, notably for historical /ownership reasons.  

fractured limestone base exposed

If we were to strip away the fine earth fractions what we would expose is a fractured limestone base. Here the exceptionally shallow soil of Meursault Perrieres is peeled away and the limestone below is laid bare. The very shallow depth of soil, despite the relatively shallow slope suggests significant erosional problems.

Limestone derived topsoil types

If you could magically strip away all the dirt from the fractured limestone base of the Côte d’Or, leaving only a coarse, gravelly, sandy, limestone topsoil, and watch the soil development, this is what would happen: Over time, with rainfall, carbonization (the act of making the calcium carbonate solvent by carbonic acid in rainwater) would produce clay within the fractures of the stone. This new clay, is called primary clay (see Part 2.1) and gravity would have it settle to the lowest point in the crevices between the stones, below actual ground level. This primary clay will be rendered from weathering limestone everywhere on the Côte, from the top of the slope to the bottom of the slope, and tends to develop into a 9:1 to a 8:2 ratio of limestone to clay. This is the origin of limestone soils, and it is called… marly limestone.

Limestone to Clay diagram

 

limestone-clay diagram 2

I developed this diagram to express the different combinations and geological names of limestone mixed with clay and their agree upon percentages by the geological community. Marl dominates a full third of this diagram from 65 percent limestone/35 % clay to 65% clay / 35% limestone.

 

Marly Limestone – upper slopes: 90% to 80% limestone to clay

There are two common (and well-defined) terms that describe essentially the same soil type, applying different names and using differing parameters. This represents the purest, least mixed soil type on the Côte, and it is found on steeper (typically upper) slopes.

Clayey Limestone: the proportion of limestone in the mix is between 80% to 90% – source Frank Wittendal, Phd. Great Burgundy Wines A Principal Components Analysis of “La Côte” vineyards 2004) 

Marly Limestonecontaining 5-15% clay and 85-95% carbonate. source: The Glossary of Geology, fifth edition. (julia a. jackson, james p. mehl, klaus k. e. neuendorf 2011).

This is new, primary clay is not sorted by size, causing it to be rough in texture. Also of note, it is not plasticky like potters clay (kaolin clay) because of the irregularity of the particle size, which doesn’t allow its phyllosilicate sheets to stack, like it will once it is transported by water and reforms lower on the slope.

 

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The Limestone to Clay diagram can virtually be tilted on upward and applied to the Côte to represent its topsoil makeup. The only part of it is missing is pure limestone because wherever there is limestone, clay has weathered from it.

It is no accident that you can turn this progression of limestone to clay into a general slope-soil diagram. The reason, as always, is water.

It is no accident that you can turn this progression of limestone to clay into a general slope-soil diagram. The reason, as always, is water.

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The fact that limestone and clay continues to exist in this 9:1 to 8:2 ratio (the stone does not continue to accumulate clay although it continues to develop it) allows us to deduce two things: First, the clay gains sufficient mass (depending on how close to the surface it is developing) where it can be eroded down the hill by rainwater runoff when it reaches roughly a 5% to 20% proportion of the limestone soil matrix. This static ratio also suggests that it exists only where erosion is a constant condition, meaning marly limestone can exist only on limestone slopes. It is erosion that maintains this general ratio of clay to limestone; limestone which will always produce primary clay as long as there is rainwater present. Of course, there may be other materials as well present in this mix, perhaps fossils, quartz sand, or feldspar.

I asked Pierre-Yves Morey, a noted winemaker in Chassagne, what was the texture, or the feel, of this marly limestone soil, is, and he described it simply as compact. “You would have to come to Burgundy and come see it.” I was looking for a little more richness to his description, but that is what I got. So… the definition of compact. The Glossary of Geology, 5th ed., defines compact (among other meanings) as “any rock or soil that has a firm, solid, or dense texture, with particles closely packed.” So there you have it. Clayey Limestone/Marly Limestone.

Argillaceous Limestone – mid-slope: 80% to 65% limestone to clay

The next incremental level of limestone to clay (75% to 25%) is not commonly cited, but sometimes referred to as Argillaceous Limestone or Hard Argillaceous Limestone. As a pure descriptor, this name isn’t especially helpful, since Argillaceous means clay. I also found another reference that called this ratio of limestone to “Mergelkalk” which is the German  for “marl chalk”, and this name indicates at least a progressive amount of clay over clayey limestone. This ratio of limestone to clay is not widely used, because, I suspect, it exists in the fairly narrow area of transition areas between marly limestone and Marl.

We might presume this ratio of limestone to clay appears not on the steeper slopes (generally above), but rather as the slopes grow more gentle, where to transported clay (from the steeper grades) may begin to flocculate as the rainwater runoff slows, adding to the primary clay growing in situ.

Because primary clay is more prone to erosion because of its mixed sized particles make its construction less cohesive, it is likely some of the primary clay developed in this lower location will be eroding further downslope, even as finer clay particles traveling in the rainwater runoff are starting to flocculate into transported clay in the same location.

With this high ratio of limestone to clay, it would be likely the be a compact soil, but because of the increased amounts of clay, not to mention some of it being transported clay, it will both have more richness and better retain water and prevent rapid evaporation.  Incidentally, his ratio of 75% limestone and 25% clay incidentally, is the recipe for industrially made Portland Cement.

Grand crus on compact marly limestone or argillaceous limestone: None

 

Marl – mid to lower slope: 65% to 35% limestone to clay

The beauty of, and the problem with, the word marl is its breadth of meaning. Marl as a term covers a wide variation of soils that contain at least some clay and some limestone, with many other possible components that may have been introduced from impurities on the limestone or from other sources within or outside the Côte.(1) But since we have magically stripped away the hillside, let’s imagine marl of its most simple combination: limestone and clay. Once the proportion of clay has risen to 1/3 of the construction with limestone, it is considered marl. It will continue to be considered Marl until clay exceeds 2/3 of the matrix. This is the definition established by the American geologist Francis Pettijohn 1957 in his book, Sedimentary rocks (p410).

Marl is an old, colloquial term that geologists may not have completely adopted until fairly recently. Perhaps it is because of this, that the definition of marl has an uncharacteristically wide variance in meaning, can be applied to a fairly hard, compact limestone soil, to a loose, earthy construction to a generally fine, friable, clay soil.  I imagine that on the clay end of the marl spectrum, the soil begins to become increasingly plasticky, due to the increasing alignment of the clay platelets by the decreased lime in the soil. This is purely subjective on my part.

Marl is most often noted in the same positions on a slope as colluvium, at a resting place of not much more than a 4 or 5% grade.  To attain a concentration of clay of at least 1/3 (the minimum amount of clay to be marl) rainwater runoff must slow enough for the clay’s adsorptive characteristics to grab hold of passing by like-type phyllosilicate minerals and pull them out of the water passing over it. As you can imagine, in a heavy deluge, with high levels of water flow, this will only happen lower on the slope, but in light rain, with a much less vigorous runoff, this will occur higher on the slope. How far these clay mineral travel down the slope before flocculation all depends on the volume of water moving downhill, and its velocity, which tends to be greatest mid-slope.

We can safely deduce that the first marl construction on our magically stripped slope consists of 15% primary clay (maximum) because that is what we started with, 20% transported clay which has been adsorbed to the site, and 65% limestone rubble (rock, gravel, sand and silt). Here, the ratio of stone in the topsoil is lower than in the slope above, because the topsoil is deeper, and the stone represents a small proportion of the ratio. Additionally, it is very possible that some of the primary clay, which is more readily eroded, may have been washed further downslope, in which case the percentage of transported clay would actually be higher.

It also stands to reason that the soil level is significantly deeper where marl resides by a minimum of 15%, due, if only because of it’s increased volume of clay to those soil types above if the limestone concentration in the soil remains constant from top to bottom.  Of course, we know that fracturing of the limestone, erosion and gravity have moved limestone scree downslope.  If you could know that volume of additional limestone that had accrued on the slope, and then factor in the percentage of clay, you could effectively estimate the soil depth. Farther down the slope, marl with 65% clay to 35% limestone, we can assume to have a minimum of 30% deeper soil levels, but again, that depends on the limestone scree that has moved downslope as well. Notes of excavations by Thierry Matrot in 1990 in his parcels of MeursaultPerrières show one foot or less topsoil before hitting the fractured limestone base, whereas his plot of Meursault-Charmes just below it, was excavated to 6 feet before hitting limestone.(3) This indicates, a significant amount of limestone colluvium had developed in Charmes (some of which may have been the overburden removed from the quarry at Clos des Perrières?) that has mixed with transported clay to attain this six-foot depth of marl dominated soil.

Wittendal’s work analyzing the vineyards of Burgundy (2004) revolved around statistical methods tracking values of slope and soil type, among other 25 other factors. From that, he plotted the vineyards as data points to try to develop trends and correlations. I was not surprised by his results, as it confirmed many of my assumptions about slope causing the types of soils that develop there. Of note, though, to some degree, his work dispels some of the assertion that marl/clayey soils reside more in Beaune and limestone/colluvium soils reside primarily in the Nuits.

Wittendal plots a perfect 50-50 marl to colluvium, as point zero in the center of a four quadrant graph (Figure 8 – The Grands Crus picture components 1 & 2). On the left side of the graph would be the purest expression of marl. This represented as negative four points of standard deviation ( σ ) from zero (the mean). On the right, the purest representation of colluvium is four points positive of standard deviation ( σ)  from zero (the mean).

Grand Crus on marl soils: more than one standard deviation (neg)Corton Charlemagne (one section with a standard deviation of -3.5, and another section at -1.5 )  Chevalier-Montrachet -1.75.

Grand Crus Primarily on marl soils with some colluvium: near one standard deviation (neg). Only one lower section of the Pinot producing Corton has a surprising amount of marl – the vineyard is not named (-1.25 ) and Le Montrachet with a surprising amount of colluvium (-.8 )

Grand Crus on slightly more marl than colluvium: Romanee-Conti sits on slightly more marl than the mean  (-.3), La Tache sits right near zero.

Grand Crus on slightly more colluvium than marl: less than one-half the standard deviation. Musigny, Bonnes Mares and Ruchottes-Chambertin. (.333)

 

Ruchottes inclusion here is at first surprising. But since there appears to be little chance of colluvium to develop on this upper slope, coupled with its shallow soils, it is this soil construct makes sense. In fact, this highlights that Wittendal’s work represents the ratio of marl to colluvium, rather than the depth of marl and colluvium present.  It is my contention that the most highly touted vineyards have significant soil depth and typically have richer soils. Ruchottes, which many have suggested should not be grand cru, has little soil depth (which is a rock strewn, quite compact marl), and the vines there can struggle in the little yielding Premeaux limestone below. A vine that struggles, despite all of the marketing-speak of the last two decades, does not produce the best grapes.

 

Clay Marl – lower slope: (a subset of marl)

Clay marl seems to be within the defined boundaries of Marl. One would suspect this to be in the 35-45 limestone with the remainder being clay. It is described by the Glossary as “a white, smooth, chalky clay; a marl in which clay predominates.” No specific ratios are given.

Marly Clay – lower slope 15% carbonate 

Marly Clay, and also referred to as marly soils are 15% carbonate and no more than 75% clay. At this point, it seems the use of the word limestone has been discontinued. Perhaps at this level we are dealing with limestone sand sized particles and smaller, perhaps with pebbles. There must be silt and clay sized limestone particles before complete solvency, but I have never seen mention of this. It is likely the carbonate is solvent, influencing, and strengthening the soil structure, and affecting to some degree, clay’s platelet organization? As much as I have researched these things, I have never seen this written. The soil just is the soil at this point.

Deceptive here is the need to discern limestone sand from quartz or other sands. Limestone sand will be “active” meaning it would be releasing significant calcium carbonate into the soil (disrupting the clay’s platelet alignment) and would be actually be considered marl. I imagine the degree of plasticity to the soil would be the shorthand method to determine this, although I understand if you pour a strong acid on a limestone soil, it will visually start carbonization (fizzing).

Could it be, that in marketing of limestone as the key factor in developing the legend of Burgundy, the Burgundians may have swept the subjects of claystone and shale under the rug?

 

Clayey soils – Sôane Valley fill 

Worldwide, most clayey soils develop from shale deposits. Geologist Francoise Vannier-Petit uses the word shale to explain clay to importer Ted Vance in his writing about his day with her. In fact, she virtually used the term clay and shale interchangeably. However, other than that writing, I have never seen the word shale used in Burgundy literature. This might lead one think that shale is not existent on the Côte. Clayey soils are a large component of the great white villages of the Côte de Beaune however, and ignoring shale as a major source of this clay may be a mistake. Vannier does mention alternating layers of limestone and claystone in Marsannay in the marketing material the Marsannay producer’s syndicate produced which I discussed at length in Part 1.3.  Could it be, that in marketing of limestone as the key factor in developing the legend of Burgundy, the Burgundians may have swept the subjects of claystone and shale under the rug?

 

Clayey sand and loam (no carbonate)

We've seen this before, under the guise of the USDA soil diagram. Here is the original by Francis P. Shepard

We’ve seen this before, under the guise of the USDA soil diagram. Here is the original by Francis P. Shepard

Wittendal uses “Clay with silicate sand” as one defining soil type in his statistical analysis of Burgundy vineyards. He does not give a percentage breakdown he is using for this soil type. However, reaching again to the Glossary of Geology, the most straightforward of definition is attributed to Geologist Francis Shepard: An unconsolidated sand containing 40-75% sand 12.5-50% clay and 0-20% silt.’ (Shepard 1954)“. Unconsolidated means that it is not hardened or cemented into rock. Of note: the definition attributed to Shepard is slightly at odds with the diagram to the right which Shepard is most known for, which has clayey-sand contains no more than 50% clay. The definitions of clayey-sand and loam clearly overlap. At one extreme, Clayey-sand can also be defined as a loam.

Clay-loam – clay sand

Clay-loam is a soil that contains clay (27-40%),  sand (20-45%), with the balance being silt, all of which have very different particle sizes. If you apply the lowest percentage of clay 27%, and a high percentage of sand 45%, and the remainder, silt at 28%; this combination doesn’t somehow doesn’t seem to fit the description well. Clay-sand is overlapping with clay-loam but generally consists of 60% sand, 20% silt and 20% clay.

Clayey-silt

Clayey-silt In 1922 geologist Chester Wentworth defined grain size. Clayey-silt thusly is 80% silt-sized particles, no more than 10% clay (which particles are substantially smaller), and no more than 10% coarser particles of any size, though this would be primarily of sand-sized and above.  Conversely, Francis Shepard’s definition of clayey silt in his 1954 book, is 40-75% silt, 12.5-50% clay and 0-20% sand. 

*Grand Crus on clayey soils: None

Colluvium, Breccia – mid to lower slope (and Scree – everywhere)

The scree filled Les Narvaux in Meursault. photo: googlemaps

The scree filled Les Narvaux in Meursault. photo: googlemaps

Colluvium and breccia are very similar. They are both rubble that has amassed on a resting place on a slope.

Breccia has a more specific definition, being at least 80% rubble and 10% clay, and can be loose or like any soil type, become cemented into rock. Incidentally, that 10% clay ratio has come up again, because just as the marly limestone I spoke of before, the stone will weather primary clay, but rainwater erosion consequently will remove it as the clay gains mass. The stones that form these piles are what geologists refer to as angular because they are fractured from larger rock, they have angular or sharp edges. This remains true until the stone has become significantly weathered by the carbonic acid in rainwater.

Colluvium, on the hand, is a construction of all matter of loose, heterogeneous stone and alluvial material that has collected at a resting place on a slope, or the base of a slope.  These materials tend to fall, roll, slide or be carried to the curb of the slope as scree (those loose stone that lies upon the surface) or washed there by runoff. In Burgundy, the rocks of colluvium and breccia are likely mostly limestone.

Rocky soils, such as colluvium and particularly breccia, are less prone to compaction because of the airspace is inherently formed between the rocks as they lay upon one another. This protection against compaction should not be overlooked as a major indicator of vine health and grape quality these colluvium sites provide. Drainage through a rocky colluvium surface material can be, let’s say, efficient, and this too is a natural defense against soil compaction, because a farmer must be cautious about trodding on wet soils because they compact so easily. Chemical weathering will develop primary clay deposits amongst the stone, and the stones themselves will slow water as it erodes down the hill, likely giving this primary clay significant protection from erosion.

Grand Crus on colluvium soils more than one standard deviation. With the most colluvium are the vineyards of Clos Vougeot with a range of σ ( 2 to 2.7) and Romanee St Vivant (1.8). followed by Most of the red vineyards of Corton sit largely on colluvium (1.25 to 1.75) Echezeaux (1.1).

Grand Crus on colluvium but with more marl: within 1 standard deviation. Charmes, Latricieres, and Richebourg form a cluster of vineyards with a σ of  (.5 to .75) with just a little more colluvium than the Musigny, Bonnes Mares and Ruchottes all at roughly a σ of .4.   source Wittendal 2004 (figure 8)

Here we find some interesting groupings. First, the grand crus with the most colluvium are generally considered in the second qualitative tier. The outlier there would be Romanee St-Vivant, which while great, is not considered to be in the same league as Vosne-Romanee’s other great wines, Romanee-Conti, La Tache, and depending on the producer, Richebourg. Are high levels of colluvium cause the vines more difficulty than those planted to vineyards with a heavier marl component?

Colluvium Creep and landslide, in this case at Les Rugiens in Pommard. The steep slope being Rugiens Haut, and in the foreground, its benefactor, Rugiens Bas. Here is an example of two vineyards that should be separated in the appellation, but both are labeled as Rugiens.

But this question rolls back to ratios of how much colluvium there is in relation to how much marl is in that location, what is the ratio to clay to limestone in the marl at each site (which would change the placement of zero (which would change the mean), and lastly, at what point is it no longer colluvium but marl or vice-versa?

Colluvium Creep

Colluvium is known to creep, meaning it continues to move very slowly downslope since it is not anchored to the hillside bedrock, rather it rests there. It is not uncommon to see the effects of this creep in tilted telephone poles and other structures on hillsides. Creep is essentially a imperceivably slow landslide. The most obvious creep/slide in Burgundy is the slope of Rugiens-Haut onto Rugiens-Bas, in Pommard.  Gravity, being what it is, nothing on a slope is static, and colluvium will, so very slowly, creep.

 

 


 

Authors note:

What I write here, is a distillation of the information laid out in the previous articles, and my weaving together all the information to build a picture of the various soil types and the slopes that generate them. Much of this is my own analysis, cogitation, and at perhaps at times conjecture, based on best information. 

As I mentioned my preface, I had come to some of these conclusions when researching vineyards for marketing information and noticed a correlation between slope and soil type.  The research that formed the basis of the previous series of articles, was done to see if the science of geology supported my theory that a vineyards position dictates the soil type there. I think it does.  Ultimately the goal of these articles is to lay down a basis for explaining and predicting wine weight and character, independent of producer input, based on a vineyards slope and position.

Where science generally begins and ends are with the single aspect of  their research.  That is the extent of their job. Scientists rarely will connect the dots of multiple facts for various reasons. It can move them outside their area of examination, or it may not have a direct evidence to support the correlation, or the connection of facts may have exceptions. The study of the cote is clearly would b a multi-discipline enterprise. There is no cancer to be cured, no wrong to be righted, and no money to be made off of understanding it’s terroir. So it has been largely left to the wine professional to ponder.  These are my conclusions. I encourage you to share yours.


 

(1 & 2) Vannier-Petit discusses alternating layers of Claystone and Limestone in Marsannay. While I have never read this of the rest of the Côte d’Or, the Côte has never been examined as closely as Vannier-Petit is beginning to examine it now. Layers of claystone may well exist, and given the amount of clay in the great white regions, this may well be the case.

(3) Per-Henrik Nansson “Exploring the Secrets of Great Wine” The Wine Spectator, Oct. 25, 1990

 

Understanding the Terroir of Burgundy, Part 2.2: Soil formation

We all know what soil is, or at least we think we do. If I were to ask you what was in soil, what would you say?

by Dean Alexander

In healthy soils, minerals typically only represent slightly less than half of the volume of soil, while air and water incredibly represent much of the rest. Here is the soil of La Tache in Vosne Romanee.  photo: leonfemfert.wordpress.com

Soil: 45, 25, and 25%

Despite all the talk about limestone, to really understand the terroir of Burgundy, we really have to understand what soil is and the material from which it is eroded. The mineral component, or the part we think routinely of as soil, are typically only 45% of the soil matrix. The balance is actually 25% air, and a further 25% of water, with the last 5% being split between humus (4%), roots (.05% ), and organisms (.05). It would make sense that this percentage changes seasonally, depending on how much water is in the soil from rainfall (or the lack of it) which changes the ratio of minerals, water, and air. Further, these ratios can change based on soil compaction, which decreases the air in the soil, which in turn increases the percentage of the mineral and organic component.  Why is this important? Because this is the environment that the vines live and they require a certain ratio of each of these components to produce high-quality grapes.

Cote soil influencers

I developed this graphic to illustrate the assorted soil formation processes that affect the Côte, and are described in depth in Limestone Fracturing in Part 1.2, and from Limestone to Clay in part 2.1, in earlier articles in this series. This article, Part 2.2 Soil Formation, builds upon those earlier concepts.

 The 45%: Burgundy’s mineral makeup

The French refer to the loamy Saône Valley fill as Marne des Bresse. The earth there is very deep, and typically is too wet for high-quality grape production. Historically this been used for pasture land for sheep and cattle. With every storm, this rich loam from the valley intermixes a little bit more with the soils of the boundary vineyards, and even encroaches on the loose, stony soils of the Côtes lower slopes.  ‘Interfingering’, was how geologist James E. Wilson described this mixing of soils in his 1990 book, Terroir: The Role of Geology, Climate, and Culture in the Making of French Wines.

Bore samples, according to Wilson, had indicated that this interfingering has reached westward, up the hill, to influence the soil construction of the lower sections of the grand cru Batard-Montrachet. With this information, he inferred that the Saône fault must be near.  It is notable that in 1990 precise location Saône fault was not known, and around Puligny, it still may not be. I suppose the wealthy Puligny vintners have no need to explain why Puligny-Montrachet is great. Vannier-Petit however, does tacitly show the Saône fault in her map of Gevrey, which is represented by the abrupt end of the limestone bedding east of RN74.

The ravine Combe de Lavaux defines character of most of the premier crus of Gevrey-Chambertin, but more importantly, its alluvial wash greatly expanded the growing area of vineyards below the village. Click to enlarge

The ravine Combe de Lavaux defines the character of most of the premier crus of Gevrey-Chambertin, but more importantly, its alluvial wash greatly expanded the growing area of vineyards below the village. Click to enlarge

Because the Côte is an exposure of previously buried, older limestone, younger soils line the divide on either side of the escarpment. The Saône Valley’s Marnes de Bresse brackets the Côte on the eastern, lower side of the slope, while younger rock and soil material that cover the tops of the hills, to the west, and beyond.

From the hilltops above, those younger soils have eroded down, bringing feldspar and quartz sand, silt, as well as phyllosilicate clay minerals, to help fill in and strengthen the rocky limestone soils of the Côte. In many places, geological faulting, coupled with runoff or streams, have created combes or ravines which have allowed substantial alluvial washes to extend the planting area of the Côte. A prime example of this is the Combe de Lavaux which is a dominate feature of the appellation of Gevrey-Chambertin.  It has sent a large amount of alluvial material around and below the village of Gevrey, creating good planting beds for village-level vineyards. Alluvial soils are nothing more than a loose assortment of uncemented of soil materials that have been transported by rain or river water. These materials are typically sand, silt, and clay, and depending on the water flow, various sizes of gravel particles. It is this sand and gravel that has traveled with the water flow from the Combe, that provides these vineyards that protrude past the limestone of the escarpment the drainage the vines require.  These are not, however, the soils that will produce the great premier cru, or grand cru, wines for which Burgundy is famed.

a graded sediment bedSoil suspension and graded bedding

Soil moves downslope by water erosion, the force of gravity, and even is transported by the force of significant wind. With movement, the particles within the topsoil are in a state of suspension. Geologists refer to this movement and suspension as turbidity. Because of their weight, gravel travels downward in the moving soil, creating a progressively sorted soil, with coarser pieces on the bottom, while the finer particles find their way to the top.  The result of this is called a graded sediment bed. (1)

While it is easier to see how a graded bed might be created in a stream bed below a ravine like the Combe de Lavaux, I was somewhat perplexed how this might occur in Alex Gamble’s Les Grands Champs vineyard in Puligny-Montrachet, see Clay part 2.1.  Here gravel bedding lay at 80cm, a little more than two and a half feet below the surface. Above the gravel, sat a foot and a half of heavy, yellow, clay-dominated soil. This was, in turn, topped by nearly a foot of loamy-clay soils. Vannier-Petit estimated these soil horizons, as geologists refer to them, were created between two and five million years ago by water runoff. What kind of run off?  I realized that the kind of runoff that creates graded bedding happens often, like in this photo (below), taken in Pommard during the winter/spring of 2014, by winemaker Caroline Gros Parent.

This is how graded bedding develops.

This is how graded bedding develops. Here the road to Pommard has flooded in the winter storms of 2014. Photo: Caroline Parent via twitter

Parent material

Geologists talk about a soil’s parent material because every element of soil came from a different material, which was then weathered, both mechanically and chemically, into various sizes. These minerals will then accumulate, either poorly sorted into an aggregate material, or they can be well sorted by the wind, water, or gravity into size categories. Sand and silt are generally said to have been created by mechanical weathering, although chemical weathering is always a present force, as long as there will be rain. Sand can be made of any parent rock material, but in Burgundy, there are sands made of granite, in addition to plentiful limestone sand. (2) We know this because there is loam present (as well as graded bedding), in the Grands Champs vineyard from the Saône valley fill below. The water that carried this non-limestone, Côte-foreign material, would have carried quartz sand with it as well when it created the graded bedding there. This gives us a very important insight into the construction of the soils of Burgundy.

Fine earth fractions

Fine Earth Fractions are the trinity of sand, silt, and clay. Gravel and sand can be made of limestone or other rock that has been weathered into smaller and smaller pieces, but silt is typically feldspar or quartz. Clay is much, much smaller in size, and is created by chemical weathering of rock. Its parental material can be limestone, granite or other stone.

Geologists grade soil minerals by size; the basis of which are particles that are 2 mm and smaller. These are called fine earth fractions and consist of sand, silt, and clay. In equal thirds of each of the three soil fractions is considered perfect for farming crops, and is termed loam. The various sizes of minerals in the soil makeup gives the soil its texture.

Clay, we have talked about in length in part 2.1, and differs from silt and sand because it is a construction from stone that has been chemically weathered, whereas silt and sand are derived from mechanically weathered rock. Additionally, clay is a construction of clay minerals that are bound with aluminum and oxygen by water and carries minerals within its phyllosilicate sheets. It is also important to mention that clay’s particles are considerably smaller in diameter, being less than 2 microns in size.  Soils with more clay hold more water,  so they require less frequent application. An overabundance of water in clay soils causes oxygen depletion in the root zone.  This can limit root development.  The abundant solvent calcium in the limestone soils Burgundy misaligned the clay platelets, loosening the soil, and allowing better drainage.

Diatoms (top) and Radiolarians bottom, fill the ocean floors with sediment.

Diatoms (top) and bottom, fill the ocean floors with sediment.

Silt is specifically formed from quartz and feldspar, and is larger than clay, being 0.05 mm-0.002 mm. We know that any feldspar in the soil, could not have come from weathered stone; neither limestone or granite, which was the dominant stone in the area when the limestone beds were forming, because it would have metamorphosed into a phyllosilicate clay mineral if it had. This means the feldspar has traveled onto the Côte, either from above or below the limestone strata.

While it might seem logical to assume the quartz in silt originated in the earth’s crust, and perhaps degraded from granite that was prevalent in the area, this may not be the case. The first problem is quartz is resistant to chemical weathering. And physical weathering like frost wedging of sand particles may continue to yield results beyond a certain size.

Researchers from the University of Texas at Arlington used (and I cut and pasted this) a “backscattered electron and cathodoluminescence imaging and measure oxygen isotopes with an ion probe.” They found that the 100% of silt quartz found in 370 million-year-old shales of Kentucky were made from the “opaline skeletons” of plankton, radiolarians,  and diatoms. This, they reasoned, might explain the lack of these kinds of fossils during the same period. These tiny animals had all been incorporated into the then forming shale. This may also be the case for the silt quartz of Burgundy, itself too having once been a Jurassic, seaside resort. This, in fact, this information also suggests this quartz silt may come from weathered shale that is much older than the limestone of the Côte.

A sandy soil horizon

A sandy soil horizon

Sand is larger than silt. being less than 2 mm, and typically is constructed of quartz or limestone particles. The limestone sand will weather to solvent calcium carbonate, but the quartz will not weather and will remain as sand. It is likely that significant quartz sand has been washed down from the hillsides, and certainly is a major contributor to alluvial soils below the combes. Sand drains so quickly that vines grown in sandy soil have more frequent water requirements, but require a lesser amount of water.  Adequate water maintains plant growth while minimizing the loss in the root zone.

 Plant and animal soil contributors

Grasses, with their dense root systems, are positively impactful to the topsoil. In their decomposition, darker soils are created to deeper depths, and the resulting soils also tend to be more stable.  In a monoculture of grapevines, many growers are finding this to be a significant advantage. In Australia, some grape growers are using grasses to help lower soil temperature in efforts to slow down ripening in an ever-warming climate.

Much is made by those practicing sustainable and organic cover crop encourage populations beneficial predator insects and birds, but grasses and cover crops also encourage subsoil organisms and microorganisms growth as well. Most common are bacteria and actinomycetes (rod-shaped microorganisms), which by weight have been found to be four times more present by weight than earthworms in healthy soils. While these are important to the quality of the wine, they are only an intricate part of terroir if it is practiced by the farmer.

The 25%: Air (and soil compaction)

Soil compaction relates to poor water infiltration and low oxygen levels. drawing: landscaperesource.com

Soil compaction relates to poor water infiltration and low oxygen levels. drawing: landscaperesource.com

The proper amount of airspace between mineral fragments is very important for vine growth and allow for water to penetrate and be retained by the soil. Soils with diminished airspace are said to have soil compaction, and compaction is difficult to correct once it has occurred. The Overly tight spacing between the mineral component of a soil restricts oxygen levels and contributes to a poor water holding capability.  Rainfall itself can cause some soil compaction, but most commonly walking or operating farming equipment on moist soils does the most damage. In drought years, soil compaction can lead to stunted vine growth and decreased root development. In wet years, soil compaction decreases aeration of the soil and can cause both a nitrogen and potassium deficiency. Additionally, without adequate porosity to the soil, water cannot easily penetrate the soil during a rainstorm. Water that cannot infiltrate soils of flat terrain can stagnate, which further compacts the soil,  or on sloped terrain will runoff, which can create erosion problems.

Positive effects of moderate compaction

As moisture of the soil increases, so does the depth of compaction.

As moisture of the soil increases, so does the depth of compaction.

Moderate compaction can have some desirable effects. Moderate compaction forces the plant to increase root branching and encourages secondary root formation. This additional root growth is the plant’s response to not finding enough nutrients with its existing root system. Plants with more extensive root systems are more likely to find nutrients that are not carried by water, like phosphorus.  Obviously, more compaction is not better, because it impedes root growth, lessens the oxygen in the soil, and repels water from penetrating the soil.

While deep tillage 10-16 inches can shatter the hard packed soil, studies have shown that crop yields will not return to normal following the effort. While there are factors that might cause the soil to return to compaction, like a farmer, unintentionally re-compacting their soils, more than likely tilling does not return the airspace that was lost in the soil itself. Further continuous plowing and tilling at the same depth can cause serious compaction problems on the soil below the tilling depth.

The 25%: Water (the key to everything that Burgundy is)

It should be impossible to talk about soil without talking about water, given it is optimally 25% of soil’s makeup. It is certainly tempting to pass over the subject of groundwater and lump it into erosion, but that would really shortchange our understanding of the Cote. Part of Burgundy’s success can surely be attributed to relatively steady rainfall year round, coupled with the fractured limestone’s ability to hold water until its reserves of water which is held within the stone can be recharged by future storms.

Good drainage, well-drained? Let’s reset the dialogue.

The infiltration of rainfall by the soil is the first and perhaps most important factor in recharging groundwater levels. Like I wrote of compaction, the soil has to be porous enough to penetrate the topsoil and subsoils successfully. The buzz word in the wine world is drainage, with terms like well-drained, and good drainage appearing often. I suppose we picture the roots drowning in mud if there isn’t good drainage. But the idea of good drainage really simplifies the issue. Drainage can have to do as much to do with compaction as soil materials or slope. Soil drainage is important in fighting erosion as well not causing additional soil compaction. Good drainage, which is what happens with a well-aerated soil, allows the vines roots sufficient oxygen and nitrogen and allows the roots to take in nutrients like phosphorous and potassium. But none of this can happen if the soil releases rainwater too quickly, and the vine can perform none of these vital tasks. The reality is, it is not the fact that a soil well-drained, but rather it drains at the adequate rate for a given rainfall. Obviously, this will not always be a perfect equation since rainfall varies greatly depending on the year and the time of year.

The speed of drainage

water movement through various soil types. source: usda-nrcs

Water movement through various soil types. source: USDA-nrcs

The kinds of materials that make up the soils contribute greatly to the rate of water ability percolate through the material. The speed of the mater’s movement depends on the path the water is channeled in. The most direct path that is in line with gravitational pull will give the fastest drainage.

Water movement comparison through sand and clay. Soure Coloradostate-edu.

Water movement comparison through sand and clay. Source Coloradostate-edu.

Sandy soils, as one might expect, drains quickly because it consists of only slightly absorptive, small pieces of stone, that allow the water to essentially slide right past.

Clay, on the other hand, is very dense and plasticity. These characteristics, as you might expect, would be resistant to allowing water to pass through, and large bodies of transported clay can redirect horizontally, the flow of water percolating through from above due to it’s slower absorption rate. But what isn’t obvious is that clay’s construction encourages capillary action. The clay body will distribute water throughout its mass, counter to gravitational pull, becoming completely saturated, before releasing excess water through to the material below.

Argillaceous Limestone

Argillaceous Limestone with its horizontal fracturing slows water percolation. click to enlarge

Highly fractured limestone that is still in place, is often is fragmented in a prismatic pattern. However some limestones, like this soft argillaceous limestone to the right, with its high clay content, may fracture horizontally. The type of fragmentation would depend on the stresses upon the stone, the freeze-thaw effects of water and temperature, as well as the material of the stone’s construction. Clay based stones will tend to fragment horizontally and when they do, they are considered platy, and water will percolate more slowly than stones that fracture in a prismatic fashion.

Water movement through soil

The hillside of the Côte is a recharge area for water collection, while the valley below is a discharge area, where excess water is expelled. The water table is at the capillary fringe. Water uses faults and fissures to move quickly into and out of the saturated zone. It is likely there are aquifers, meaning caves which have been cut out of the limestone by carbonization below the Côte, where the water is stored.

 

a small karst aquifer Photo:planhillsborough.org/

A small karst aquifer in Florida. Photo:planhillsborough.org/

Groundwater, the water table, and karst aquifers

In writings regarding Burgundy, very little is said about ground water, other than there are no cellars built underground in Puligny because the water table is too high there. A plentiful water supply may be one of the features that propel the vineyards of Puligny into the ranks of the worlds best. As my diagram above shows, water percolates through the soil and stone. This upper section is called the vadose zone, or unsaturated zone. Slabs of limestone, fissures, faults, and clay bodies all can change the course of the water flow. Each horizon of soil and each layer of stone have their own rate of percolation. With this much limestone, it is very likely there are karst aquifers or large caves caused by the carbonization of calcium carbonate beneath the Côte, but I could find no specific mention of aquifers in close proximity to the Côte. There is a mention in a European Academies Science Advisory Council‘s country report for France, that in Burgundy there are “karsified Jurassic limestone layers” somewhere in the region, but nothing more is elaborated upon.

There is a very famous and massive karst aquifer with seven very deep layers that spans from north of Burgundy across the Paris basin to the English channel. The deepest level of water is brackish. The uppermost section is called the Albian sands sits at than 600 meters, and was first was drilled into in 1840 taking well more than 3 years to achieve. The water there is 20,000 years old, and there has been discussion whether the water should be considered fossil, meaning there is a question whether there recharge from the water above, or not.

 

Next up: Understanding the Terroir of Burgundy, Part 3: Confluence of stone, soil, and slope

 


 

(1) Interestingly, larger stones, especially the flatter, rounded shaped stones that the French refer to as galets, tend move to the surface, probably because of their larger displacement values.

(2) Sand from other parent rock material is likely to be available as well.