Terroir Test 1

What's a cultivar?

A cultivated variety

Why do vineyards in stony soils often produce better wine?

Stony soils tend to retain heat from the sun better than fine-textured soils. The heat is radiated back into the air during the night, which helps to prevent frost damage and can accelerate fruit ripening in fall. Also, stony soils drain well.

What is a "supertaster"? Are they better wine critics?

Supertasters are people that experience an extreme bitterness when they taste PROP (a thyroid medication). About 1/4 of the population are super tasters or hypertasters. This group is very sensitive to other bitter compounds. Supertasters have a high density of taste papillae (structures on tongue that house taste buds) while non-tasters have relatively few. ST perceive all flavors as more intense. If someone is a ST, it does not mean they are a better wine taster necessarily. It is possible that ST actually enjoy wine less than the rest of us because they experience astringency, acidity, bitterness and alcoholic heat more intensely than the rest of us. Supertasters would also not necessarily make good wine tasters because there is too much learning involve in wine tasting. Wine experts must learn the odor complexities produced in wine. The normal person does not have a smell vocabulary, and so cannot describe and define odors

What continent has more grape species than any other?

North America does

Why are vigorous vines not good for wine quality?

"Plant food" (light captured by leaves through photosynthesis) is distributed to parts of the plant that are actively growing. Vines that are still growing vigorously will take the "plant food" away from the grapes, which then may not ripen. The viticulturist must constrain vine growth also because too much foliage will shade the grape. Too much water will produce berries that are too big and diluted. You want smaller berries with thick skins bc that is where the flavor is

What is terroir?

"somewhereness"... an wine that doesn't have terroir has "anywhereness" Viticultural terroir is a concept which refers to an area in which collective knowledge of the interactions between the identifiable physical and biological environment and applied viticultural practices develops, providing distinctive chracterisitcs for the products originiating from this area. Terroir includes specific soil, topography, climate, landscape characteristics and biodiversity features so..... -physical environment, biological environment, and cultural environment terroir is distinctive sensory components tied to a specific agricultural location

what determines soils composition?

% organic matter / what is currently growing in the soil climate bedrock and chemistry of the soil slope (a steep slope means thinner soil) aspect (what direction slope is facing) climate effects weathering--how deep the soil is

Describe the process of evaluating a wine. What are the important steps and what do they reveal about the wine?

(add to this w/ written notes) The eye: assesses clarity and color, monitors the presence of CO2 and alcohol The nose: (most important) temperature and agitation are important. Monitors whether wine smells fresh and clean, or whether there are any off odors. Also, intensity of the aroma (if aroma is pleasant, intensity is good). Taster must be able to describe the individual components that make up the aroma The mouth: Mouth often just confirms the observations of the nose. Measures the texture and dimensions of the wine (sweetness, acidity, bitterness, viscosity, and any other sensations of heat. The mouth can also analyze "mouthfeel" assessing the tannins. After swishing wine around in their mouths, professional tasters will spit out the wine and then register how long the flavor remains. After: A fine wine should continue to make favorable sensory impressions throughout the entire tasting process.

Phases of grape maturation

1. development of the grape structure; throughout this process, the grapes accumulate acids and experience rapid cell division 2. Veraison: red grapes turn from green to red, the skin of white grapes turns from being hard and green to being soft and translucent 3. Growth begins again but this time through cell enlargement not division and grapes accumulate sugar and phenolic compounds, acids decrease

What constitutes water deficit? How does the grapevine respond?

A plant experiences water deficit when it loses more water through transpiration than it takes up from the soil. One result of water deficit is stomata closure, which reduces water loss but also reduces CO2 uptake, which is necessary for photosynthesis Some people induce water deficit at certain stages to promote grape production. If this is done just before veraison, grapes will be riper and more flavorful. If temp goes past 95 and has little water, plant will shut down by closing stomata

What is the "finish"? What kind of finish characterizes a well-made wine (or one with great terroir)?

A wine with a good finish will linger in the mouth after it has been swallowed (as long as 10 min after). The lingering flavor should be complex, consisting of many different flavors, such as fruity blackberries, black currents, plums, pepper, clove, woody, tobacco, cedar, coffee, etc. The wine should be a complex combination of fruit flavors and aromatic overtones that result from the production process and influences from the terroir. A wine without a good finish will taste one dimensionally of the same simple flavors first identified. A good finish is difficult to achieve but very desirable.

When do most flavors arise in the winemaking process? How are they produced?

A wine's flavor character and aroma are locked in the grape and it's the yeast, through fermentation, that activates/unlocks these characteristics. A wine grape contains natural chemical compounds that are also found in other fruits and veggies. Fermentation, a simple chemical reaction, releases these compounds so that we smell and taste other fruit flavors in the finished wine. For example, the tangy apple flavor in chardonnay comes primarily from malic acid, the tart acid also present in apples. A yeasty, pastry-like flavor in white wines can be achieved by letting the wine sit on its yeast sediment

Do you need to be educated in wine to appreciate terroir?

According to Jacky Rigaux, terroir wines can only be appreciated by wine lovers, and those with an educated taste. Terroir wines are not "consumer projects" but "cultural creations" Prof says no

Which grapevines are used for wine- why not others?

All wine grapes are sub-species of the vitis vinifera satavia. The vitis vinifera is also known as the Eurasian grape vine because of its origin in the near east. Other grape varieties taste "foxy" so they are not used in wine

What is phylloxera? How did it get to Europe? How was it defeated?

American botanists sent a collection of native American grape vines vitus labrusca riparia and the roundifolia to their botanist friends in France. These American vines introduced phylloxera to the country. Because of this, all grape vines in Europe were almost wiped out in the 1860s. The American vines had developed immunity to the pest long ago. Phylloxera are microscopic, pale yellow sap sucking insects (root louse) that eat the roots and leaves of grapevines. They make cracks in the grape roots that allow other pathogens to enter. It leaves a poisonous juice on the wound. The only way to prevent phylloxera is to graft phylloxera-resistant American grapevine rootstock varieties to European vine shoots. They also have difficulty surviving in sandy soils. Do not like anything bigger than fine sand.

Why do some authors conclude that the concept of terroir is at odds with anglo-saxon culture?

Because terroir wine (a symbol of cultural diversity) is mysterious and hard to explain, it is disconcerting to Anglo-Saxon culture

How are grapevines propagated?

Before the 1800s, grapes were mostly propagated with seedlings. Once people understood Mendel's principles of genetics better, propagating by cuttings and layering became common practice. Layering is burying a living shoot until it develop roots and then cutting it loose and planting it. Even when using these techniques, it is very difficult to get an exact copy of the parent plant

Where would one find the temple of terroir?

Burgundy. No other wine-growing region has been cultivated for so long, and in such a precise way Burgundy's hierarchal system is based around the principle that different vineyard sites, often only a few meters apart, produce wines that vary substantially in quality Grapes used are pinot noir (red) and chardonnay (white) Within Burgundy, some vineyards make excellent wine, while others do not. The climate isn't changing much as we progress. It is the soils and geology that change (and make the difference in the wine quality)

What's the climate of Burgundy? What grapes are grown there?

Cloudy, foggy, East of Paris Pinot noir grape (red) Chardonnay grape (white) Both of these grapes like the climate cool and wet

What soil characteristics have been recognized as having a positive influence on wine quality?

Coarse, thin, warm soils, esp. on a southern facing slope. In some of the best vineyards, the soil is cobblestones overlaying clay. Water should be stored at a depth (vines will grow down and tap into water supply and become drought resistant. Good soils are often rocky/stony because they drain well and resist erosion on slopes. Stony soils also retain more heat and so help to prevent freezing during cold periods and speed up the ripening process during warm periods. Stony soils also preserve moisture and keep it from evaporating. Good soils gives a steady, moderate amount of water. Soil type is not as important if vines are irrigated

What's clone viticulture?

Cuttings from vines are used to produce new plants which are genetic clones (genetically identical to the parent plant). Attempting to grow vines from seeds results in too much genetic variation. Snip off a shoot in the spring, put it in the wet ground, and it'll grow--creates an exact genetic duplicate

How are vines and wines affected by bedrock type?

Depends. Residual soils are composed of the bedrock, so the soil texture and consistency are dependent on bedrock type aeolian soils are wind deposited, alluvial are river deposited, and glacial are from glaciers. These soils have little to do with the bedrock

What is the source of buttery flavors in wine?

Diacetyl, which can smell like butter and other dairy products is a particularly obvious sign of malolactic fermentation (process in wine-making where the tart tasting malic acid in grapes is converted to lactic acid, the acid in dairy) Wine makers add a strain of lactic bacteria to the wine, which converts the harsher malic acid to lactic acid, which makes the wine smell and taste like butter. So if wine makers want buttery characteristics like chardonnay they put some or all of the wine through malolactic fermentation

How do nutritive elements get from rocks to plants?

Elements are locked into a silica structure that plants don't have access to overtime, water (through weathering), breaks down the rock and transports elements The plant gets the individual elements as cations in the water

What is the homeland of the grapevine?

Evidence points to the Caucus Mountains. vine domestication first occurred around 7,000 years ago Georgia, Azer-bajan, Armenia, North of Iran, East of Turkey. Landscape is semi-arid, rocky Here, soils are composed from Jurassic and cretaceous limestones and basaltic lavas

Do concentrations of elements in soils correlate with the concentrations of the same elements in grape juice?

Generally no, except for iron. In most cases vine will only take what it needs, even if there is an excess of one element. Vines will take in extra iron though.

What is indicated by deep color in wine?

Generally, dark color indicates a hot climate and a ripe grape. It can also be a product of a particular wine making style. Different grape varieties make deeper or lighter colored wines. Cabernet Sauvignon, Syrah and Nebiolo make particularly deep red wines; Gewurztraminer and Pinot Gris make deep white wines because the grape skins are deep pink. A deep color can also indicate youth, long maturation, and thick skinned grapes in a red wine. Sometimes age, oxidation, barrel maturation, in white wines.

What is the relationship between grape variety and the expression of terroir?

Grape variety has little to do with the expression of terroir. The same variety can be grown only miles away, but if one vineyard gets more sun, or one gets more water, the taste of the wine will be completely different. However, certain grape varieties are much better at expressing terroir, particularly Pinot noir and Riesling. Sryah expresses terroir the most (tastes very different depending on place)

Is high clay content a good or a bad thing?

If you want to retain moisture, having some clay is good. Clay is critical in vineyards, influencing water and nutrient supply. Soils heavy in clays are porous, but root penetration is difficult and the soil is poorly aerated when wet. BC of this, roots must remain near the surface, exposing vines to severe water stress under drought conditions. Provided that clays are well enough structured and drained to allow successful root development and function, they serve well bc of their high water-holding capacity. Under dry conditions the stored water is released to the roots slowly and progressively.

How does the mouth sense excess alcohol in unbalanced wine?

In our mouth, we taste "heat" if there is excessive alcohol present in the wine. Monitoring the combination of sweetness, viscosity and any other sensation of heat gives a good indication of the likely alcohol content. Ethanol leaves a burning sensation in the mouth. Can taste bitter or astringent

What is the effect of cold vs. warm climates on the ripening of grapes? Can cooler be better?

In warmer climates, grapes only reach physiological maturity at sugar levels that are considerably higher than those in cooler regions. In cooler regions, grape harvest normally occurs when days are shortening and getting colder, making sugar accumulation more gradual. In these areas, grapes are mature when they have accumulated about twelve degrees of potential alcohol. If grapes in warmer climates are harvested with this much potential alcohol, the wine will taste unripe. Grapes that receive more sunlight are less acidic so having an open canopy without dense growth is ideal Cooler climates can be better: if temp is cooler, grapes can hang until the end of November, which produces a more complex flavor. If climate is too hot, sugar increases quickly and your wine will be too alcoholic. In CA they extract the alcohol afterwards so that they can get the complex flavors

What is "minerality"? What is is not?

It is not the actual taste of the rocks or minerals that the vines are grown in. Grape vines/roots can absorb cations in the water that they take up, but they do NOT take in whole rock chunks. Rocks themselves do not have taste or odor. While rock, clay, sand, etc do not end up in the grape, some elementary mineral compounds do. They are not present in large enough quantities to be tasted, but they do affect fermentation. Most of the mineral compounds in soil come from decaying organic matter, not rocks. Minerality is likely the complex mixture of compounds which we associate with the smells of soils and rocky areas. White wines that smell "minerally" to people probably have a sulfur compound (which is produced during fermentation by yeasts). Minerality could also simply be the way certain people perceive and describe acidity (especially in white wines with a low alcohol content) but it works better as a descriptor for salty wines

Why did Italy not develop a sense of appreciation for terroir in the way that France and Germany did?

Italy lacked Benedictine and Cistercian orders, which were represented to a far greater degree in France and Germany. The monks and nuns, whose wines and vineyards remained the standard for nearly a millennium, never wavered in their devotion to terroir. In France, terroir is fueled by a longstanding delight in differences and an acceptance of ambiguity

What are the principal phenological stages of the grapevine? What triggers them?

Jan: no leaves, last years canes only w/ buds (which will become leaves next yr) Feb: prune down the canes so each has about 2 buds (prune less if winter is cold) March: pruning complete April: "weeping" water oozes from the ends of the cuttings for abt a week mid-April: "bud break"--buds open. Most dangerous time of season Late-April: shoots out 6 in May: flowering tiny white flowers (self-polinating) Late-May: beginning of grapes Late May-Mid July: tendrils grow out 3-4 ft Early July: green berries-might pull off leaves Early August: "veraision" grapes change from green to purple Late Aug-Early Sept: grapes are purple, have to put up nets to keep out birds Late Sept: dark purple grapes- pick them! Oct: leaves turn red/yellow/orange Late oct-early november: first freeze December: vines harden (you want a gradual cooling)

Why might it be beneficial to have low nutrient levels in the shallow part of the soil profile?

Low nutrient levels in the upper levels of the soil cause the roots to grow deeper. This improves water supply to the vine and drought resistance. Roots can penetrate over three meters deep

Are the differences in wine flavors related purely to differences in the chemical compositions of wines?

Most flavor (that's not just personal perception) comes from chemical compounds in the wine. Flavor has a lot to do with the chemical composition of wine, but it is the fermentation process that brings out individual flavors. Grapes contain natural chemical compounds that are present in other fruits, vegetables, spices, etc. The spice taste of a California zinfandel comes from the same compound that gives black pepper its flavor. Different yeasts control the actual flavor of the finished product. One strain might produce more tropical flavors, while another strain might lend itself to a citrus flavor. The fermentation process is where winemakers can control what flavors come out, and will be present in the finished wine. If a wine is aged in an oak barrel, the barrel contributes a vanilla flavor to the wine. The barrel can also impart flavors of clove, nutmeg, cinnamon, caramel, chocolate and coffee

What parts of the flavor and aroma profile of a wine is most heavily influenced by its PHYSICAL terroir? Which parts least influenced?

Most impactful are climate and physical characteristics that create climate, esp. availability of water--too much water and berries are large and diluted, not enough and the entire plant is stunted Least influencing are: anything in the fermentation process (unless using the local/natural yeast), oak barrels

What are mycorrhizae?

Mycorrhizae are soil fungi that live in a mutually beneficial relationship with grape roots. They influence grapevine nutrient and growth. Have been shown to increase the uptake of phosphorous Mycorrhizae colonize the root system of the host plant providing increased nutrient and water absorption capabilities, while the fungi gets carbohydrates from the plant (formed from photosynthesis) Fungi hitches a ride on the plant roots, gaining energy from the plant, while the plant root gains an enhanced absorptive area and ability to extract mineral nutrients from the soil

Does it make sense to speak of the "terroir of Napa Valley"?

No. Only small places can have terroir, so talking about the terroir of Napa Valley does not make sense

Does every place or vineyard have terroir?

Not all sites have terroir. Not all wines, even if they are made in a certain place can possess terroir. A wine has terroir when it has a distinctive, reproducible characteristics associated with the place it is grown and made

What is the great Transatlantic Misunderstanding

Randall Grahm defines the Great Transatlantic Misunderstanding as the vast "chasm" that exists between the New World and the Old World when it comes to wine drinking & production In Europe, where you come from is incredible important, whereas in the New World, where you come from no longer matters. Terroir wine seeks to amplify the taste of a place, while New World wine is often technical (attempts to be homogeneously good)

What is sensitive crystallization? And how is it used?

Sensitive crystallization is the process of taking several milliliters of wine, mixing it with copper chloride solution, putting it into a petri dish, and letting it evaporate in a controlled environment. What is left is a distinctive pattern. Randall Grahm claims that the essence of the wine can be seen in these crystallizations. He attributes various patterns to qualities present in the wine, and environmental factors in the vineyards

What is closed wine?

Saying a wine is "closed" implies that there is something here that isn't here yet. Closed wines will become better over time, and will certainly benefit from aeration (as will almost all wines)

What factors influence the distribution of roots?

Soil characteristics, the presence of hardpans (impermeable layers) or other permeable layers, the rootstock variety, and cultural practices such as the type of irrigation system. Grapevines can be grown on their own root system, or on the phylloxera-resistant root stock of another variety (North American rootstocks are resistant) Also water availability. If water is deep, vines will go deep.

How are vines and wines affected by soil texture?

Soil texture is important because it determines how much water the soil retains and therefore how much water is available to the vine. Coarse, thin soils lead to better grapes, leads to better wine. Many of the famous vineyards are cobblestones over clay.

What soil characteristics have been universally recognized as having a negative influence on wine quality?

Soils heavy in clays are porous but root penetration is difficult and soil is poorly aerated when wet. Shallow hardpans reduce the usable soil depth, and enhance the tendency of soils to water-log during heavy rains. clay-rich, water-logged, cold = worst soils

What are tannins? How do they get in the wine? Which wines have them and which do not? How do they taste? Why are they there? (in the plant)

Tannins make the insides of the cheeks feel dry. The main difference between red and white wine is the presence of tannins (white wines have much lower tannin levels). Tannins comes from the seeds, stems, and skins of grapes, as well as from the wooden barrels sometimes used in the maturation process. The quality of tannins is the most important indicator as to whether the grapes were ripe when they were harvested. Unpleasantly bitter tannins point to a bad vintage, or defects in the production process. Mature tannins seem silky, transparent, and smooth. Mature tannins come from harvesting the grapes at the optimal ripeness and then maturing the wine gently. Tannins are thought to act as a defense mechanism for the plant, as the taste is off-putting to herbivores.

Is your experience in tasting wine derived solely from the interaction of chemical compounds in the wine with your nose and taste buds? Is tasting subjective? What factors besides the actual smell and taste of a wine can impact tasting experience?

Tasting is subjective. Each person experiences taste differently and many factors besides the actual smell and taste of a wine can impact the tasting experience. Environmental factors such as temperature, humidity, etc. can hinder tasting, as can an illness/sickness in the taster. Our knowledge and beliefs about the wine we are drinking help shape the sensory representation we have. If we care about flavor additions, and know they are present, we may perceive the wine to be of lesser quality Tasting is highly linked to smell, so anything that impacts smell will also impact taste

What is technical wine?

Technical wine is wine that does not have a terroir. "Commodity wine" Technical wines are manufactured wines. Location has little importance Technical wine is an attempt to create great wine by manipulating the wine, mixing grape varieties, stifling terroir

What part of the grape contains most of the color, aroma, and flavor constituents?

The grape skin and the thin tissue layer immediately below it contain most of the color, aroma, and flavor constituents as well as tannins. Because of this, small berries have more color, more tannins, and greater flavor because the skin constitutes a larger percentage of the total mass of small berries. Seeds contain tannins as well that contribute to wine astringency

What is veraision?

The stage when red grapes change color from green to red and the skins of the white grapes change from being hard and green to soft and translucent

why is mid slope the best grape-growing location?

The top of the hill is too cool, the bottom is too wet. The middle of the slope has ideal thin soils, which stress the grape and reduce water in the berry

What is thigmotropism?

Thigmotropism is the growing response to touch, which is exhibited by vine tendrils

Grapes are the sweetest berries on Earth, true or fasle?

True. They contain increasing levels of fructose and glucose as they mature. During fermentation nearly all of this sugar is turned into alcohol for the majority of wines. Other fruits don't have enough sugar to become alcoholic drinks

Why are young grapes hard, green, and high in acidity and tannins?

Unripe grapes are green because then they are harder for birds to see. They are also highly acidic, contain high levels of leafy-tasting pyrazines and have harsh tannins. This is all to discourage birds from eating them before the seeds are ready

When did the notion of terroir develop? Who developed it?

Until the 1900s, "terroir" referred to a rustic wine, often poorly made, and sometimes tasting of sour or rotten grapes. It wasn't until the 1930s and the beginning of France's AC system (which linked products to the location they were produced) that terroir began to have a more positive connotation. The term was first used in the 17th century to mean dirty wine. Dr. Merlot began using it as a good thing in 1831 when he discovered that, while all of the wine makers in Burgundy made wine the same way, the taste was not the same. He attributed the difference in taste to soil variations depending on location. He argued that wine attained its flavor from the rocks below it.

Why should viticulturists treat their vines somewhat harshly?

Viticulturists want to treat their vines harshly enough so that the vines will focus on fruit production, while giving them just enough of what they need so they don't suffer from water or mineral deficit, which would impede fruit production. Too much water and nutrients and the plant would focus on canopy production over fruit production.

How do we know if a wine has terroir?

When it has distinctive, recognizable, and reproducible characteristics that can only be associated with place

Is the notion of terroir at odds with science?

While many wine experts argue that the geological composition of soil directly influences the taste of wine, scientists know that this is not the case. Soil type and and climate play crucial roles in determining how much water the vines get, and so in this sense, tangible physical factors do determine wine taste, but not as directly as people think. Physical geographic conditions, such as the slope of the hillside, as well as climate, determine the taste and quality of wine. In "The Notion of Terroir" Matt Kramer writes, "But terroir holds yet another dimension: It sanctions what cannot be measured, yet still located and savored. Terroir prospects for differences. In this it is at odds with science, which demands proof by replication rather than in a shining uniqueness" certain terroir elements are easy to explain with science--Cabernet sauvignon will taste very different if one is grown in cold, one in hot. Underripe grapes contain pyrazine, which tastes "green" to us

Are people important in terroir?

Yes! Cultural practices certainly shape the wine. "No region on our planet is predestined to produce great wines, and that includes Burgundy (terroir temple). It is only the winegrower's perseverance, pushed to the limit of stubbornness, which led to the recognition of the Burgundian terroirs' particular aptitude during the course of the past centuries

Why don't phylloxera like coarse soils?

in the summer, soil with clay shrinks and creates a pathway around roots that phylloxera can travel in. If soil is coarse, it doesn't shrink and phylloxera can't travel

How was brand wine popularized?

mainly by means of Cabernet-Sauvignon, which was exploited by all winemakers in the entire world. A lot of color, tannins, and substance can be extracted from it

Why is Bordeaux not the temple of terroir

makes cabernet sauvignon, which is a blend of 4 different grape varieties, which mutes terroir

What is the principal source of vanilla flavors in wine?

new oak barrels that some wines are aged in

Does soil chemistry directly influence wine flavor?

nope! Vine will only absorb what it needs from the soil. Will not absorb an excess of what is there (unless it is iron)

How many varieties are cultivated in France?

over 120 varieties, but only under a dozen are recognized as classic

How do soil flora and fauna affect vines and wines?

pH and humidity contribute to more microbio in soils Soil structure is influenced by the burrowing action of soil fauna (animals), root growth, and frost action. Soils high in aggregate structure have a higher water holding capacity and so are considered to be agriculturally superior. A major benefit of soil fauna is the generation of the aggregate structure of soil. Bacteria are especially active in releasing polysaccharides that bind the cells to soil particles and soil particles to each other. Fungi help to hold soil particles together. If you have low organic content, then no Mycorrhizae exist to provide the plant with increased nutrients (in exchange mycorrhizae gets carbohydrates from the plants). Most of the nutrients on which soil biota survive come from green plants. These are derived from the leaves and the death of feeder roots. Initial decomposers are bacteria and fungi. These are grazed by the fauna (protozoa, nematodes, mites) or are consumed along with the soil during the feeding of earth worms. Feeding releases inorganic nutrients bound in the microbial fauna. This decomposition creates humus. Flora and fauna also participate in nitrogen fixation, releasing nitrates into the soil. Organic materials act as a store of nutrients which slowly become available to plants as they break down by oxidation. Also contributes to the ability to store water The take-up of nitrogen depends on microorganisms in the soil

Does the presence/amount of certain elements change the flavor of the wine?

probably not, but they do dictate whether or not the vine grows well or grows at all (vines don't like heavy metals, nickel, cadmium)

ways to classify soil types (based on how it got there)

residual soils: developed in place, come from bedrock aeolian soils: wind deposited alluvial soils: river deposited glacial soils: glacier deposited

What role does cation exchange play in root/vine and soil interaction?

roots are able to exchange hydrogen ions, which they pump out, for the cations attached to the negatively charged soil particles, such as clay and humus

How are vines and wines affected by soil color?

soil color is influenced by moisture content, mineral composition, and organic content. Soil high in calcium tends to be white, for example, while soil high in humus is dark brown to black. Color influences the rate of soil warming in the spring and the cooling in the fall. Dark soils absorb more heat than lighter soils do. Soils of higher moisture content, being darker, absorb more solar radiation, but warmer more slowly than drier soils. Warm soils may enhance microbial nitrification, enhance potassium uptake, and depress magnesium and iron absorption by the vine. Orange to red wavelengths likely help to ripen grapes.

What is the terroir in the mosel valley, Germany?

some of the steepest vineyards in the world, vines growing out of the devonian slate bedrock steeper south facing slopes are sought after because valley is at a high latitude (cold)