Cultivar, Rootstocks, and Trellis Blocks of the W-MEA Viticultural Model

I began the "fleshing out" of the Wine -- Mise en abyme (W-MES) Viticultural Model with an elaboration of the Site Complex and a comparison of the best practices elements to the Masseto site conditions. In this post I continue this "fleshing out" by detailing the elements of the Vineyard Establishment Complex (identified below within the red oval). As before, I will attempt to identify best practices and compare them against the Masseto conditions where data are available.

Variety
A number of factors are considered in selecting the variety (or varieties) to be planted: (i) experience of other vineyards in the area; (ii) the quality of the variety; (iii) the speed at which it completes its annual reproductive and vegetative cycles and how do those cycles match to the climate of the region; (iv) the yield potential; (v) adaptation to climate; (vi) adaptation to soil conditions; (vii) its resistance to disease; and (viii) the varieties that are allowed by existing legislation (in an area where that is a concern).

The climate of a grape-growing region will determine, to a large extent -- and all things being equal -- both the grape varieties that can be grown and the styles of wine that can be produced. The climatic requirements for successful viticulture include: a growing season long enough to mature both the fruit and vegetative aspects of the plant; production of sufficient carbohydrates to ripen the fruit as well as to maintain future productive potential; and an adequate supply of water.

The common wisdom holds that varieties produce at their best when grown at the coolest margins of viable ripening. Grapevines are selected either through mass or clonal selection and cuttings are grafted onto rootstocks based on the attributes required.

Rootstock
Most of the world's quality wines are based on vitis vinifera, a species which, when grown on its own roots, will succumb to attacks from phylloxera and parasitic nematodes. This problem has been solved by grafting the vitis scion onto phylloxera- and nematode-resistant rootstock.

Vine vigor and soil capacity are additional important inputs into the rootstock-choice decision. Varieties with large canopies (high-vigor varieties) can become less fruitful over time (thus reducing the capacity of the vine) due to reduced cluster number and size. Dr. Andy Walker of UC Davis defines vine capacity as "the ability to grow and produce foliage, roots, and fruit and to establish a trunk." According to Dokoozlian and Kliewer (AJEV 46, 1995, pp. 209-218), vigor is used to describe the growth capacity of grapevines, with those having "large dense canopies and low sunlight exposure ..." being referred to as high-vigor vines. Dense canopies can be detrimental to vine yield in that (i) the plant is deploying its resources in "unproductive" areas and (ii) they reduce the amount of light getting to internal leaves. And human activity (with the related costs) is required to reduce this physical manifestation of vine vigor and re-direct the vine's resources to more productive use.

Soil capacity is a function of the water-holding capacity and mineral wealth of the soil. Vine capacity, on the other hand, is the soil capacity plus the levels of carbohydrates stored in the vine trunk and cordons. Growers seek to blunt the upside of vine capacity by employing low-vigor rootstocks but, in most cases, capacity will trump vigor.

Rootstock(s) utilized in the vineyard environment should be (http://iv.ucdavis.edu/files/24347.pdf):

• Resistant to present and potential soil pests
• Suitable for the soil’s texture, depth, and fertility
• Compatible with soil chemistry (pH, salinity, lime content)
• Favored for the anticipated soil water availability, drainage, and irrigation practice
• Appropriate for the vineyard design
• Appropriate for the fruiting variety’s growth and fruiting characteristics.

Trellis
The rationale behind vine training systems is (i) an understanding that increasing the exposed leaf area improves fruit quality, (ii) that exposure of leaf area can be manipulated by training, and (iii) training alters the microclimate of the canopy. The amount of leaf area that can be exposed to the sun is a major consideration in the choice of a training system. It is affected by (Reynolds, Andrew G., and Justine E. Vanden Heuvel, Influence of Grapevine Training Systems on Vine Growth and Fruit Composition: A Review, Am. J. Enol. Vitic. 60(3), 2009, p251):

• The disposition of the bearing units
• the Trellis height
• The associated type of training.

Growth, yield, and quality are directly proportional to the ratio of exposed leaf area to fruit weight with a range of 7 - 14 cm² total leaf area/gram of fruit required to achieve full fruit maturity. The higher end of the range should be pursued in colder climates in order to ensure that the vine can complete its important physiological functions (Reynolds and Vanden Heuvel).

The trellis serves as the framework within which the vines are trained and supported and must (Paul Domoto, Constructing a Vineyard Trellis, Presentation, Iowa Grape Growers Conference, 2002):

• Be strong enough to support large crops and withstand high winds
• Last for 20 or more years with routine maintenance.

One of the most important considerations in trellis selection is the size of the canopy that it will be supporting. The vines growth potential has to be taken into consideration in order to ensure that it will bear the weight of the vine at maximum vegetative growth. The factors which drive vine growth potential are as follows (http://www.ucanr.org/sites/intvit/files/24348.pdf):

• Temperature
• Annual rainfall
• Sunlight exposure
• Winds
• Soil texture
• Vine rooting depth
• Pre-Plant soil preparation
• Cultivar
• Rootstock
• Cultural practices

Other elements that factor into the trellis decision are (Reynolds and Vanden Heuven):

• Plant and row spacing
• Row orientation
• Establishment costs
• Equipment requirements
• Desire for mechanization.

The details of the model elements for the W-MEA Model Vineyard Complex are provided in the table below. Red-colored text indicates a best-estimate.

      Masseto Vineyard Versus the W-MEA Viticultural Model -- Vineyard Complex

Block	Component	Element	Optimal Value	Masseto Position
Variety	Nomenclature		Depends	Merlot
	Climate Adaptation		High	High
	Soil Adaptation		High	High
	Local Custom		N/A	Compliant
	Variety Quality		High	High
	Yield Potential		Balanced	High
	Disease Resistance		High
	Allowed by Regulation		Compliance	Compliant
Rootstock	Nomenclature		Depends	N/A
	Soil Pest Resistance	Phylloxera	Med-High	Med-High
		Nematodes	Med-High	Med-High
	Soil Qualities Suitability	Texture	Loam, sandy loam	Clays
		Depth	Ø  3 feet	N/A
		Fertility	Low-Med	High
	Soil Chemistry Compatibility	pH	6.0-6.8	N/A; assumed high
		Salinity	Threshold 1500 μmho/cm	N/A
		Lime Content		N/A
	Water Availability	Drought Conditions	Adaptable	N/A
		Wet Soils	Adaptable	Inhibits performance
Trellis		System	Depends	Spurred Cordon
		Strength	Wind resistant; supportive of vine growth potential	Compliant
		Longevity	Ø  20 years	N/A
		Plant and Row Spacing	2.5 m between vines in Bolgheri	3 m x 0.85 m
		Row Orientation	Depends	Perpendicular to the fall line of the slope
		Set-Up Costs		N/A
		Equipment Requirements		N/A
		Mechanization Plans		N/A

©Wine -- Mise en abyme

Wine and Climate Change: A review

Orley Ashenfelter (Joseph Douglas Green Professor of Economics, Princeton University and President of the American Association of Wine Economists (AAWE)) and Karl Storchman (Clinical Professor of Economics, New York University and Managing Editor, Journal of Wine Economics), having both written extensively on the economics of grape growing and wine production and distribution, recently collaborated on a study of wine and climate change. That study, succinctly titled Wine and Climate Change (AAWE Working Paper No. 152, March 2014), utilizes comprehensive literature surveys to: (i) identify the projected physical impacts of climate change on viticulture; (ii) illustrate the associated economic impacts; (iii) proffer adaptation strategies; and (iv) identify potential winners and losers. I will use the findings of this study to determine what changes, if any, will be imposed upon the baseline viticulture architecture (shared in my previous post) as a result of the identified impacts and effects of climate change. Given the makeup of the viticulture architecture, the scope of this effort will be limited to the physical effects of climate change, adaptation strategies, and winners/losers. The economic impacts, while intriguing, do not lend themselves to inclusion/comparison against the viticulture model.

Ashenfelter and Storchman assessed the physical impact of climate and weather along four planes: Temperature, Carbon Dioxide, Pests, and Water. Before reporting on the findings in each of these categories, however, I would like to revisit my architectural framework in light of some of the ideas advanced in the paper.

In my post on viticulture architecture, the Adequate Sunlight and Heat component (see below) would appear to encompass the first of the four analysis planes mentioned above.



While my focus in the architectural baseline was on the temperatures required to promote the vegetative and reproductive aspects of the grapevine, the authors additionally stress the importance of the dormancy period which occurs when temperatures fall below 10 degreesC (50 degreesF). According to the authors, winter dormancy: (i) helps to sybnchronize the growth stages of the vines and (ii) increases the productive lifetime of the vine. The authors illustrate the importance of this dormancy period by comparing grapegrowing in the tropics to grapegrowing in traditional quality-wine zones. In the tropics, a lack of dormancy can sometimes allow two or more crops annually, according to the authors, but, in addition to the grapes not being suitable for wine making, is also accompanied by a host of issues that are not common in the traditional regions. The key finding here is that my viticulture architecture will need to be expanded to accomodate a dormancy period.

Physical Impacts

The key climate and temperature impacts reported by the authors are as follows:

Temperature:

• All varieties exhibit lower fruit-set, ovule fertility, and berry size as temperatures exceed 25 degreesC (77 degreesF)
• This suggests that warming above cultivar-specific optimums reduces crop yields
• High temperatures increase grape sugar accumulation and reduces grape acidity
• Enzymes that initiate the physical softening of berries and contribute to the accumulation of flavors, aromas, and pigments can be inactivated or destroyed by very high temperatures
• Increased warming may increase the number of good vintages in cold-climate wine growing regions while simultaneously decreasing the number of good vintages in hot-climate growing areas
• Extreme temperatures, at both ends of the spectrum, will be detrimental to the vine plant or grape.
• Substitution capability diminishes with increasing heat.

Carbon Dioxide:

• No demonstrable impact to grape vines or berries as a result of increased levels of carbon dioxide (Editor's Note: other than everything that we are talking about, that is).

Pests:

• Warming temperatures are likely to increase disease and pest pressure on grapevines
• The incidence of fungal diseases (black rot, downy mildew, etc.) will increase with warmer weather

Water:

• IPCC expects increasing water deficiencies in most grape growing areas.

In the foregoing list, carbon dioxide has no clear effect on the grapes while the threats presented by water and pests appear to be things that could be fought with the tools we have in hand today. The issue of most concern then, as it relates to the physical impact of climate change, is increasing temperature.

Selected Economic Effects

While the bulk of the economic analysis is beyond the scope of this paper, I would like to point out a few of the economic effects noted by the authors because they are straightlined from the physical impacts and then feed into the further discussions of price and profits. One of these areas is the availability of suitable vineyard areas in the the face of the physical impacts of climate change. One of the studies cited by the authors (White et al., 2006) posit a reduction of suitable vineyard area in the US from 4.1 million square kilometers to 3.5 million square kilometers by the end of the 21st century. For the highest quality growing regions, White et al., see a reduction of 81% in suitable growing areas in the US. Further, as suitable areas migrate to more humid and higher-precipation areas, higher levels of funding will be required to keep fungal diseases under control. It goes without saying that with less vineyard space, and increased costs of keeping pests and diseases from the remaining space, the implications for costs are immense.

Another proposed temperature effect revolves around yields. The standard for high quality grapes is to manage yield down but, according to one of the studies cited by the authors, a 3 degreeC rise in temperature could result in a 90% increase in yields in the coastal California area wine growing regions.

Finally, the authors discuss quality implications for various wine regions as a result of temperature increases. They foresee quality improvement in the wines of currently cool climes like northern France and Germany while they see a simultaneous decline in quality in the Rioja region of Spain, California, and South Australia.

Potential Adaptation Initiatives

The authors' proposals for adaptations to combat climate change can be classed as tactical and strategic (or, more colloquially, "shelter in place" and "get the hell out of Dodge") and are presented in the table below.

                     Potential Adaptation Initiatives

Tactical	Strategic
Harvest date shifts	Movement towards the poles
New cultivars and rootstocks	Movement to higher elevations
Use of canopies to mitigate the sun’s effect
Row re-orientation
Cover crops between rows to reduce reflected heat

Source: Derived from Ashenfelter and Storchman AAWE Working Paper

While harvest-date shifts, increased canopy size, and cover crops have relatively low cost implications, the same cannot be said for the other tactical adaptations. First, at the warmest extremes of today's viticultural environment, cultivar substitution is not a realistic option. Secondly, cultivar substitution and row re-orientation have both direct and opportunity costs associated with replanting and then waiting for the new vines to become contributing members of the vine society.

In the case of the strategic solutions, the authors point out a number of issues and gating factors which will have to be addressed along the way. In the case of the US, the authors see the Rocky Mountains and the border area between Washington and British Columbia as becoming viticultural desirable as traditional wine-growing areas become warmer. Movement to these areas, however, will place the viticulturist into conflict with native flora and fauna. In the case of Europe, the issues that would have to be addressed include:

• The tying of cultivars to specific appellations
• Irrigation prohibition in many appellations
• The need for planting rights in order to plant vines anywhere in Europe
• The EUs historical reluctance to award new planting rights

Conclusions

The American public and its representatives continue to take a "see no evil, hear no evil" approach to climate change and while viticulturists cannot on their own change the course of history, they would be guilty of negligence if they were not planning for the future that will be. The Ashenfelter and Storchman Working Paper, in the IPCC style, uses a broad range of research to provide an updated picture of the implications of climate change for the wine industry and potential paths forward. While not fine-grained enough to surface potential changes to the needs-driven viticulture architecture, it provides a strong sense as to where the strategic viticulture focus should be: on the site selection and vineyard establishments aspects of viticultural science.

©Wine -- Mise en abyme

Modern viticultural science made me do it (turn to Biodynamic viticulture that is)

Winemakers who are turning to biodynamic viticulture are not doing so just to be contrarians. Rather, they are being driven there by inexorable, wrong-track trends in traditional viticulture.  At least that is the perspective of Jason Tippetts as presented in the Spring 2012 issue of Gastronomica: The Journal of Food and Culture (The Science of Biodynamic Viticulture). This post examines Mr. Tippets' arguments.

As I have noted previously, quality grapes are a precursor of quality wine, and the science of viticulture has developed and evolved with a single goal in mind: the delivery of high-quality wine grapes to the cellar door.  The quality of wine grapes produced in a specific harvest is not only a function of that year's harvest conditions; it is also dependent on a combination of factors which, together, represent the full scope of viticultural science.

Mr. Tippetts takes issue  (based on his arguments) with my characterization of viticultural science as being quality-focused.  Rather, he sees the discipline as the problem.  In his view, there are two trends shaping the future of conventional viticulture: (i) a focus on the marketability of wine (which, over the long haul, will lead to mediocrity) and (ii) what I term the vineyard-imbalance cycle.  Let us examine these trends in turn.

The road to banality begins, according to Mr. Tippetts, while the viticulturist-in-training is still in school.  Deep dives into a broad array of science courses causes the budding viticulturist to "lose sight of what she loved about wine" and "why she thought it was important to be a winemaker in the first place."  The ideals and perspective of the fledgling has been hijacked and dulled by the weight and rigor of science.

The graduating student is a full-fledged agriculturist with no "insight into how winemaking might have significance beyond being a means of employment."  The graduate will be in possession of minimal amounts of inventiveness and innovation.  The scientific knowledge absorbed in the classroom will be unleashed against the problems (real or imagined) encountered in the vineyard.

The application of science-based, recipe-type solutions to vineyard problems has led to a "narrowing" of the focus of modern winemaking, according to Mr. Tippetts.  Rather than pursuing greatness in the bottle, winemakers are instead pursuing consistency.  Tippetts likens the viticulturist pursuing this path to a manufacturer who utilizes a set of raw materials and a well-established methodology to produce a consumer-friendly product.  "The potential greatness of the ends is neglected as a result of too much focus on the means."

Viticultural science, according to Mr. Tippetts, provides the basis for a continuing "unbalancing" of the vineyard environment; a cyclical, long-term degradation of the vineyard which almost guarantees reduced fruit quality.  This cycle was initiated when it was discovered that chemical fertilizers could improve the productivity of farmlands.  According to Mr. Tippett, fertilizers are salts and they cause the plants to take in more water, a situation which improves growth and productivity in the short term but saps the plant's energy, rendering it more susceptible to attack from parasites and other pests.  Pesticides are then applied to eradicate these pests (which they do until the pests adapt) but they also deplete the soil of its nutrients while also stressing the broader environment.

Viticulturists who are considering biodynamic viticulture want to make better wine, according to Mr. Tippets, and in order to accomplish that goal, they see the need to treat their vineyard differently. The implication here is that biodynamic viticulture is that path to better wines.

Looking at Mr. Tippetts' arguments, I give him credit for the implication throughout that wine is made in the vineyard.  It is a position that I hold.  Beyond that, however, I take issue with a number of his positions and assertions.  First, I thought that it was rather bold of Mr. Tippett to provide a blanket indictment of viticultural schools and practicing viticulturists as being co-conspirators in a plan to drive us all to banal wines.  He spent most of the article making the case against modern viticulture but was less-than-convincing in making a case for the biodynamic alternative.

Second, in some of his forays, he likened viticulturists to agriculturists, damning the latter practitioners with "faint" praise.  Third, Mr. Tippett asserts that viticulturist who want to make better wine realize that they have to treat their vineyards differently.  The implications here are that (i) only a subset of viticulturists want to make better wine and (ii) biodynamic viticulture is "the" vehicle for treating your vineyard differently (in so doing ignoring alternatives such as organic vitculture, for example).

I applaud Mr. Tippett for his advocacy of biodynamic viticulture but (i) he could have taken a more "pro"-active approach and (ii) his arguments do not necessarily point to biodynamic viticulture as the answer.


©Wine -- Mise en a byme

The science of viticulture: Soils and vineyard site selection

The vineyard site is a key variable in the production of high-quality grapes, which is, itself, a key requirement for the production of high-quality wine.  In the absence of an existing vineyard, the viticulturist has to seek out a site on which the wine grapes will be planted.  I have detailed the climatological and topographic requirements for such a vineyard in recent posts and will devote this instance to soils, the final -- and second only to climate -- site-selection requirement.

According to Wolf and Boyer (Vineyard Site Selection, Virginia Cooperative Extension), the best vineyard soils "permit deep and spreading root growth" and provide a moderate supply of water year-round.  Mark Chien (Soil and Site Selection Considerations for Wine Grape Vineyards, Pennsylvania State University) posits that wine grapes do best in moderately fertile soils that are unsupportive of vigorous vine growth.  What are the soil characteristics that will permit "deep and spreading root growth" and year-round access to water?  Those characteristics are presented in descending order of importance in the table below.

The most important requirements, according to the table, are internal water drainage and water-holding capacity.  Geologic permeability (the capability of a porous rock or sediment to permit the flow of fluids through its pore spaces -- Dictionary.com) is seen by Wolf and Boyer as perhaps the most important consideration in a candidate vineyard's soil.  Chien sees well-drained soils as a  common denominator among all great vineyard sites.  These soils "strike a balance between adequate depth and drainage and water-holding capacity" and vines deployed therein will have adequate water access during the summer and can rapidly drain water from the soils in the event of rainfall during the grape-ripening period.  Vineyards sited on convex land patterns are preferable to those on concave landforms in that the former shed surface water while the latter import water as well as soils which erode from higher ground.

Vineyard soil fertility is one of those cases where more is not necessarily better. Adequate amounts of the appropriate nutrients are required to support proper growth of the vine, fruit development, and fruit maturity.  Fertile soils are generally rich in organic material and moisture.  In that grapevines are naturally vigorous, vines grown in highly fertile vineyards will produce abundant canopies and fruit but the fruit will be mediocre because of limited access to the sun and the vine having spread its resources too thinly. Most high-quality vineyards are sited on low-/moderate-fertility soils.

The next soil feature mentioned in the table is effective rooting depth.  The roots of the vine plant: i) anchor the vine; ii) absorb water and nutrients; iii) store nutrients that nourish the plant during dormancy; and iv) produce hormones that control plant functions. The vine deploys a three-part root structure to meet these varied needs.  First, quick-growing, short-lived roots deployed close to the service are tasked with moisture collection. Second, subterranean roots provide the anchoring function.  The principal roots are tasked with nutrient delivery and storage.  According to UCDavis, about 60% of the root structure of a vine plant can be found in the first two feet of the surface but individual roots can grow as deep as 20 feet depending on soil permeability, the level of the water table, and the rootstock variety.

Soil texture refers to the nature, size, shape, orientation, and arrangement of particles.  In the soil-type page I show that sand, silt, and clay have standalone properties which are transformed when the soils are combined.  Clay forms flexible elastic bridges between soil particles to maintain soil structure and preserve porosity.  Pebbles and rocks in clay-rich soils break up the soil, providing pathways for water and root penetration.  Deep, rich soils will provide high-vigor growth and large, watery grapes.

Soil pH is a measure of the acidity (3.5 to 6.5) or alkalinity (7.4 to 9.0) of soil which, through its influence on nutrient solubility and micro-organism activity, affects the number and types of nutrients in the soil.  Soil pH between 6.0 and 6.8 is considered optimal for vine plant growth as most of the needed nutrients and micro-organisms are available in that range.  Alkaline or acidic soils can be treated to bring them closer to optimal.

Adequate amounts of the appropriate nutrients are required to support proper growth of the vine, fruit development, and fruit maturity.  The table below shows the mineral requirements of the vine plant, the role of each mineral, acceptable ranges of each mineral in the soil, and the impact of mineral deficiency on the vine.

Source: Compiled from LGRGP.org and others

The key factors in nutrient availability are soil type, soil composition, and root structure.  Soil type dictates the quality of nutrients present and the adequacy of water drainage.  The soil-type page shows the different types of soil that are of interest to the viticulturist.  The optimal soil type has a moderate content of low cation exchange capability (CEC) clay (Clay minerals act as harbors for nutrients because the positive ions of the nutrients are trapped by the negative charge of the clay minerals.  The abundance and types of minerals determine whether the clay is classed as low- or high-CEC.).  Soil composition affects root growth and development and the availability of nutrients for soil uptake.  The roots of the vine plant, among other things, absorb water and nutrients and store the nutrients that nourish the plant during dormancy.  The principal roots of the plant are tasked with nutrient delivery and storage.

By this time the viticulturist will have been exposed to enough information to select a vineyard site which will have a better than even chance of producing high-quality grapes.  All of the pertinent questions about climate, aspect, slope, elevation, and soils have been raised and a path to high quality has been carved out.  The next task will be setting up the vineyard on the selected site.

© Wine -- Mise en abyme

The science of viticulture: Climate and site selection

Quality grapes are a precursor of quality wine and the science of viticulture has developed and evolved with a single goal in mind: the delivery of high-quality wine grapes to the winery.  The quality of wine grapes produced in a specific harvest is not only a function of that year's harvest conditions.  Rather, it is the result of a combination of factors which, together, represent the full scope of viticultural science.  I will cover most of the inherent elements of viticultural science in a series of posts as a part of my investigation of the source of grape-derived odors.

There are three major areas of concern for the viticulturist as he/she sets about the task of delivering quality grapes to the winery door: (i) selecting the site which will best ensure goal attainment; (ii) setting up the vineyard with the appropriate elements such that cost-effective goal-attainment is promoted; and (iii) implementing a cost-effective, repeatable vineyard management regime which is reflective of the operating conditions.  Within these major considerations there are a number of sub-elements where the rubber really meets the road and I will focus our coverage of the topic on these areas beginning with today's writeup on climatic considerations in site selection.

The site selected for a new vineyard will determine the amount and quality of fruit produced, the resources required to manage the vineyard, and, ultimately, the profitability of the vineyard.  Selecting a site for a new vineyard is generally a compromise between a number of factors.  For example, most of the exceptional vineyard sites in the world have been under vine for many a year, leaving less-than-perfect options available for the aspiring vineyard owner.  Second, most prospective vineyard owners are drawn to sites that are readily accessible to them and this limiting facor comes with a given climate.  And so on.  Site selection is thus the process of making an optimal choice within the bounds provided bythe needs of the wine grapes, the available site options, and associated limiting factors. 

Source: Compiled from arcserver2.iagt.org

The key site-selection factors for consideration are climate and site physical characteristics.  Climate, according to Dr. Tony Wolff (Lecturer and Viticulturist, Virginia Tech) and John D. Boyer, is the average course of weather in a region over an extended period as measured by temperature, precipitation, and wind speed, among other variables (Vineyard Site Selection, Virginia Cooperative Extension).  Weather is itself defined as the state of the atmosphere at a specific point in time using the same variables as referenced in the climate definition above.  The climate of a grape-growing region will determine, to a large extent -- and all things being equal -- both the grape varieties that can be grown and the styles of wine that can be produced.  For example, Syrah appears to flourish in warm climates while Riesling does best in cold.  That is not to say that these varieties cannot be grown outside of these environments; that is to say, however, that varietal typicity is compromised when these varieties are grown outside of their "zones."

As it relates to the wine regions of the world, the ideal climates for vitis vinifera are Mediterranean and marine west-coast climates which are both characterized by mild, wet winters and warm, dry summers.  The mild winters promote long-term survivability of the vines (and increased quality of the juice as the vines age) and the wetness provides a reservoir of water that the vine roots can tap into during the grape maturation cycle.  The warm, dry summers provide the heat and light that are the engines of vegetative and crop growth while keeping at bay the threat of rot and flavor dilution that would accompany summer/fall rains.

Source:www.buywineonline.co.uk

In viticulture, three separate aspects of climate are normally considered: macro-climate, meso-climate, and micro-climate.  Macro-climate refers to climatic effects over large (hundreds to thousands of miles) geographic areas and are either continental or the aforementioned maritime.  Continental climates are modified by large land masses and are characterized by hot summers and cold winters.  Maritime climates, on the other hand, are modified by proximate large bodies of water which heat up and cool down at a slower rate than does the adjoining land mass.  This scientific fact results in the warming of winter winds as they blow over a warmer body of water and the warming of landside vineyards as the winds make landfall.  This warming could act to extend the growing season and minimize the potential vine impact of winter low-temperature events. On the other side of the coin, warm spring air blowing in over the still-cold water will be cooled down and will retard the development of landside vineyards, minimizing their potential for damage from spring frosts.

Meso-climate covers a much smaller area than does macro-climate and is generally the scale at which site decisions are made.  It is at this level that that the physical aspects of the surroundings -- elevation, slope, aspect -- can temper broader macro-climatic effects.  The climatic effects of these physical elements will be covered when they are discussed individually.

Micro-climate are the conditions that exist in the vineyard from the soil upward into the vine canopy and, as such, is more relevant when the land is under vine than in the site-selection phase.

One of the key grape needs is adequate sunlight and heat to allow both the fruit and the vegetative aspects of the plant to mature.  The progression of the grape through its various stages of maturity is influenced by the ambient temperature with research indicating that growth of the grapevine begins when temperature exceeds 10℃.  A measure -- growing degree days (GDD) -- has been developed to measure the accumulation of heat (as measured by temperature) in excess of 10℃ over a growing season.  Extensive research has yielded the following GDD parameters which can be used as input in the site-selection dialogue.

Source: Compiled from oregonviticulture.net

These then are the broader climatic considerations for the viticulturist in selecting a site for a new vineyard for the production of quality wine grapes.  The physical characteristics that should be evaluated will be covered in the next post on viticultural science.


© Wine -- Mise en abyme