The Influence of Climate and Soil Characteristics on Fruit Quality of Wine Grapes in New Zealand by So Pyay Thar

Introduction
Wine is one of the eldest beverages consumed throughout the world today (McGovern, et.al., 2000). It has been widely consumed for many years for its attractive aroma, exceptional taste as well as for social, recreational, ceremonial, medicinal and dietary purposes, etc. (Estreicher, 2004). Producing high quality grape wine has always been a challenge for many wine industries around the world. However, most of the winemakers agree that high-quality wine begins with the land and the natural environment of the region in which the grapes are grown (Goldammer, 2013).
NZ produces premium quality wine and its wine industry is growing rapidly (New Zealand wine industry, 2013). In order to produce premium high quality grapes for wine production, many factors need to be considered. Watson (2013) stated that success in high yielding, high quality grape wine production depends on not only the grape variety but also climate, soil characteristics, topography, vineyard site, viticulture practices and technology etc. Although there are various factors affecting the quality of wine grape, this literature review will focus on the climatic and soil characteristics which influence the grape wine quality in New Zealand.
The soil characteristics and climate has always had a significant impact on vineyard practices as recognized by viticulturists for centuries (Sluys, 2006). According to Smart et. al, (1985), all viticulturists agree on the conclusion that soil, climate and cultural management are the three most important sub-systems within the whole vineyard environment. An example of this relation among these sub-systems is given in figure 1. The concept applies that “soil, climate, and cultural practice have direct effects and alternations to canopy microclimate can have indirect effects by altering vine physiology” (Smart et al, 1985).

Figure 1. Conceptual model to show how soil, climate and vineyard management can affect the fruit composition directly or indirectly through canopy microclimate and vine physiology (Source: Smart et al, 1985; Weldon, 2003; Sluys, 2006)
The rest of the review is organized as follows; the next section describes the influence of climate on grape wine quality followed by detailed impacts of temperature, solar radiation, rainfall, wind and frost. Next the influence of soil characteristic including soil structure, soil texture, soil type, soil depth and soil pH are described and concluded with the discussion of the New Zealand wine industry.
Influence of Climate on Grape Wine Quality
The effect of climate on Agriculture is especially evident with the cultivation of grapevines (Jones, 2005). Likewise, Jackson (2001) stated that the grape vine is “one of the most responsive cultivated plants to the ever changing surrounding climatic conditions”.
The climate is affected by the altitude and latitude which in turns affect the ripening of the fruit. Between the latitudes of 30° to 50°, having a mean annual temperatures of 10°C and 20°C, grape cultivation occurs mainly (Jackson, 2001). Hence, most of the worlds’ wine producing regions are located between 30° and 50° latitude in both north and southern hemispheres (Neirynck, 2009). Berry (1990) stated that outside these latitudes there is either the problem of excessive heat or severe cold. The intensive heat can prevent the vine from a dormant resting stage and lead to burning of grapes and leaves reducing in quality by eliminating the aroma and color in the wine. On the other hand, severe chills can prevent the grapes from taking up sufficient sugar for full ripeness causing tart and over acidic wines. Therefore, it can be stated as a general rule that grapes can be grown for wine-making anywhere between 30° and 50°. According to Thropy (1971), New Zealand lies between 34° and 47°. The Bordeaux district, the home of the famous French clarets, lies approximately in the same latitude as Timaru (44°) in New Zealand. So, in general, New Zealand lies in the temperate zone.
There are many individual weather and climate factors that have a profound impact on the fruit maturity, grape growth and wine quality such as temperature, solar radiation, rainfall, wind, and frost (Zoecklein, 2010). As several classifications of climate exist for vine compatibility, wine growers have been concerned about climate for a longtime. There have also been various studies in which the weather and climate influence the quality of grapes to produce high quality wines (Fitzharris et. al, 1996; Ubalde et.al, 2010; Lorenzo, et. al., 2013). Due to these major influences, grapes possess the ability to ripen to optimum levels of sugar, acid and flavor maximizing the quality of wine grapes (Jones, 2005). Therefore, climate influences the rate of change in the grape during development and its composition at maturity.
The ideal climate for wine grape cultivation is found in those countries with warm summers which allow the fruit to ripen and cool winters which ensure the return of the sap to the roots after the maturing of the berries, thus giving the vine a rest. This temperate climate is the best for vine growth (Thropy, 1971).
New Zealand was once promoted as “the home of cool-climate wines” (Cooper, 2008). According to Jackson & Schuster (1994), the slow ripening of the grapes in cool autumn temperatures is the key advantage of cool-climate regions for wine quality as it slows down development leading to better balances and more aroma and flavors accumulation in the wine grape.
However, not every part of New Zealand is suitable for grape vine cultivation. According to Douglas (2000), New Zealand can be divided into three distinct climate zones for viticulture. The northern zone (from Northland to Hawke’s Bay) is characterized by plenty of heat and sunshine during the growing season and low frost risk, but also high humidity with an associated high disease risk. The central zone (Wairarapa, Nelson and Marlborough) is cooler, with fewer frost-free days but the highest sunshine hours in the country. The southern zone (Canterbury and Central Otago) has a low heat accumulation during the growing season and increased frost risk which are the major challenges faced by grape growers.
Temperature
Although there are many climatic factors influencing the grape vine and its development, the most essential factor for viticulture is temperature (Becker, 1985). The reason for this is because temperature determines the timing of the vine’s growth stages and grape ripening (Cooper, 2008).
Jones et.al (2005) stated that grape quality and viability is affected by temperature during the growing season in three stages. First is during vegetative stage where the temperature above 10°C initiates the growth and development of the grape vine and second is during flowering and throughout the growth of the berries can cause high great mortality, enzyme inactivation and partial or total failure of flavor ripening (Mullins et.al, 1992; Jones et.al, 2005). Third, a high diurnal temperature is required during the maturation stage for the beneficial synthesis of grape tannins, sugars, and flavors (Gladstones, 1992; Jones et.al, 2005).
Although the temperature requirement differs according to the growth stages of the grape vine, the optimal temperature range for grape cultivation is 25°C to 32°C (Jackson, 2001). Any temperature below this range can retard vegetative growth and above will reduce the photosynthesis rate by increasing respiration (Gladstone, 1992). Compared to Europe, during the peak growing season, most New Zealand wine regions are cooler at night delaying the ripening process which is believed to be an important factor in fruit quality (Cooper, 2008).
Solar Radiation
The sunlight can also affect the vine’s growth pattern (Berry, 1990). Grape anthocyanins increase with light intensity, while they decrease with temperature (Van Leeuwen, 2010). Since sugar is produced by photosynthesis, the amount of sunlight the plant receives will have an impact on the amount of sugar produced which in turn is concentrated in the fruit. (Bisson, 2008).
Although sunlight is essential for grape production and vine growth, excessive exposure to solar radiation can result in heat stress to vines and sunburn damage to berries. Sluys (2006) also found that berries can be damaged in the form of sunburn as temperature rise above 32° C. Such fruits may contain slightly higher quantities of tannins which can impair the fruit quality. Thorpy (1971) similarly reviews that wine produced from scorching and wilting vines is low in acid and tastes very syrupy.

Rainfall
In addition to temperature and solar radiation, an important factor in the production of grapes is the amount of rainfall and the humidity of the atmosphere. During growth and development stages, water availability to the grape vine is a major importance not only to the quantity but also to the quality of wine produced (Berry, 1990). Vines need sufficient rain to promote a healthy plant growth (Thorpy, 1971). On the other hand, although some rain is beneficial for grape development, excessive rain can retard ripening and encourage disease (Cooper, 2008). Van Leeuwen (2010) stated that the rainfall increases the pressure of diseases particularly downy mildew and grey rot. In addition to the threats of diseases, if rain occurs during the ripening period or before harvesting, it inhibits and delay ripening causing the quality of grapes to drop and may cause actual losses by splitting the berries (Thorpy, 197). Therefore, rainfall has both positive and negative impact on the quality of the grape wine.
According to Van Leeuwen (2010), most renowned wine growing regions have an annual rainfall between 300 and 1000 mm/year. In New Zealand, overall, growing season (October-April) rainfall decreases southwards from 562-673 mm in Auckland to 524 mm n Gisborne, 389-437 mm in Hawke’s Bay, 304-399 mm in Marlborough, and 274 mm in Central Otago (Cooper, 2008). Therefore less rainfall in New Zealand during the months of February, March and April, produces a higher quality wine. However, the challenge with rainfall for viticulture in New Zealand are the tropical cyclones arriving 3 or 4 times each year between December and March, bringing force winds and severe rain (New Zealand meteorological data, 2008).
Wind
Wind can also alter the microclimate of a vineyard (Sluys, 2006). Goldammer, T. (2013) describes that the air movement within dense vine canopies is reduced compared to canopies that are more open. It was stated that severe wind conditions can cause smaller berries with thicker skins, dry clusters limiting mold growth leading to enhanced evaporation which creates a greater losses of vine water (Bisson, 2008). Similarly, Jackson (2001) stated that “wind also promotes transpiration and therefore in dry conditions the growth of grapevine is retarded due to water loss”. On the other hand, increase wind speeds lead to higher rate of transpiration water use which may results in water stress (Sluys, 2006). Windblown soil particles can also damage young vines (White, 2003).

Frost
It has been stated that all the greatest vineyards are to be found in Champagne, Burgundy, Alsace, the Rheingau, the Moselle and Tokay. However, these places are subjected to frosts and extreme cold at times. Extreme cold in winter extending into spring has a disastrous effect on the burgeoning buds (Thropy, 1971).
Moreover, frost can damage the vine’s shoot and leaves and reducing the quality of grape (Cooper, 2008) thus causing a threat to grape growers. Jackson (2001) stated that serious frost events will cause severe damage to the fruit. In New Zealand, it was found that the major wine regions have a low to moderate incidence of frost with Napier in Hawke’s Bay with frost-free period of 306 days and Blenheim, in Marlborough (233 days) compared with Geisenheim, in Rheingau (197 days) and Bordeaux (214 days) (Fitzharris & Endlicher, 1996). The central zone (Wairarapa, Nelson and Marlborough) is cooler, with fewer frost-free days but the highest sunshine hours in the country. During the growing season, the southern zone (Canterbury and Central Otago) has a low heat accumulation and high frost risk which are the major challenges faced by grape growers (Cooper, 2008).

Influence of Soil Characteristics on Grape Wine Quality
The quality of grape depends not only on climatic parameters but also on the water-holding capacity of the soil (Leeuwen et al., 2004). Therefore, soil characteristic is another important factor in yielding high quality grapes for prize winning premium wines. It was stated by Berry (1990) that although the availability of water will depend on the rainfall, the structure and texture of the soil are also important to the vine because the size and shape of the soil particles will affect drainage, temperature regulations, and the distribution of the vine’s root system. Soil type and soil depth are also essential factors to consider as grape vines prefer a well-drained soil and can withstand drought better than most of the other fruits (Thorpy, 1971).
Van Leeuwen (2010) stated that although soil influences wine quality and style, great wines are produced worldwide on a wide range of soils. Soils in New Zealand normally exhibit low to moderate fertility, and since most vineyards are located on free-draining gravels, irrigation typically controls water uptake and availability. Some regions in New Zealand are known for producing premium types of a particular wine. For example, Marlborough is known for producing premium Sauvignon Blanc and Pinot Noir, Waipara for Riesling and Pinot Noir, and Hawkes Bay consistently produces award-winning red and red blends such as Merlot, Malbec, Syrah and some Cabernets. The vines grown in these regions are situated on gravels (Cooper, 2008).
Soil Structure
Good soil structure offers a favorable environment for the growth of root and soil organisms and is necessary for adequate aeration and drainage in vineyard soils (Gardner et.al., 1999). A desirable structure for vines provides optimal water and oxygen availability, which are fundamental for the growth of roots and soil organisms (White, 2009). The structure should be porous and not hard for roots to penetrate, allow ready exchange of gases and the flow of water, resist erosion, allowing the seedlings of cover crops in vineyards to emerge (White, 2003). Soil structure and consistence are responsible for the soil particles to be held together and also affect the strength of the soil, drainage, and the ease of root penetration (White, 2009).
Soil Texture
Soil texture (amount of gravel, sand, silt, and clay) influence the soil’s water holding capacity, drainage, and ease of cultivation (White, 2009). Wine quality was low on permanent water logging soils, leached soils and on deep soils developed on down hill colluviums but high on gravelly soils, sandy soils and heavy clay soils (Van Leeuwen, 2010). “Sandy soil have higher water holding capacity and the grape vines do not encounter water stress even in dry vintage but gravelly soil having lower water holding capacity are subjected to severe water stress while clay soils can cause moderate water deficits” (Van Leeuwen, 2004). Also, soil having too high clay content is compact preventing the vine roots from penetrating to the depths for essential nutrients and water (Neriynck, 2009). However, sandy soils will absorb a greater percentage of water but will retain a smaller percentage and dry out more rapidly in dry weather (Berry, 1990).
Imre & Mauk (2009) stated that More than 70% of vineyards in New Zealand are located on alluvium and gravels, and these free-draining subsurface have been the preferred location for vineyards for a long time.
Soil Type Van Leeuwen et al. (2004) studied the factors that have the greatest effect on the quality of the vine grape and subsequent effects on wine quality. The variables measured in their research were berry weight, berry sugar concentration, anthocyanin concentration and total acidity which have a direct influence on wine quality. It was stated that the soil type has a great influence on berry weight and berry sugar concentration and a significant effect on the anthocyanin concentration but a lesser extent on the acidity of the grape juice. Ubalde, et al., (2010) had also proved that berry weight was influenced by soil type.
The geological bedrock is an important factor in wine quality (Hancock and Huggett, 2004; Huggett, 2006). Although bedrock has been cited as an important influence on wine quality and flavor, good wines are grown on any geological base throughout the world (Cooper, 2008).
The color of soil affects the temperature of the soil; the darker the soil, the warmer the soil temperatures and the faster the maturation of the grapes (Neirynck, 2009).
Soil Depth
Soil depth affects the rooting depth and can cause water logging of the vine. Grape root systems have been known to penetrate to 5-6 m depth in gravelly and sandy soils. Some grape varieties like different soil depths, e.g. Chardonnay does better on deep soils, whereas Syrah does best on shallow soils (White, 2009).
Soil pH
Soil pH is an important factor as extremes in pH inhibit growth (White, 2009). pH values of below 5.5 or above 10 are too acidic or too alkaline to sustain grape growing activity (Neirynck, 2009). The presence of limestone indicates a neutral to alkaline pH, good soil structure and possible restriction in rooting depth (White, 2009).

Discussion
This review has described the influence of climate and soil characteristics to produce quality grape for successful wine. The climate, soil and geography of New Zealand have combined to produce high quality grapes giving the wine industry a comparative advantage and positioning New Zealand in the global wine market place. New Zealand has an internationally recognized reputation for its sauvignon blanc, cabernet sauvignon, pinot noir, pinot gris, chardonnay, riesling, merlot and methode traditionnelle sparkling wines (New Zealand Wine Industry, 2013).
New Zealand wine grape production has increased 3.5 times in the past decade and the wine exports by value are 33% of New Zealand’s horticultural exports (New Zealand Wine Grower Annual Report, 2013). However NZ wine will have to think of ways to maintain and improve its quality for a sustainable wine production, as the prevailing weather might also become a defining factor in the near future, with climate changes being a worldwide issue these days

Reference

Becker, N. J. (1985). Site selection for viticulture in cool climates using local climatic information. Proceedings International symposium on cool climate viticulture and enology, June 25-28, 1984, Oregon State University Agricultural Experiment Station, Technical Publication 7628, 20-34.
Berry, E. M. (1990). The importance of soil in fine wine production. Journal of Wine Research, 1(2), 179-194.
Bisson, L. F. (2008). Introduction to wine production. Retrieved from http://www. http://enologyaccess.org.
Cooper, M., & McDermott, J. (2008). Wine atlas of New Zealand / text by Michael Cooper; photography by John McDermott: Auckland, N.Z.: Hodder Moa, 2008. 2nd ed.
Dougherty, P. H. (2012). The geography of wine : regions, terroir and techniques. New York: Springer.
Douglas, C. (2000). Latitude limits of commercial viticulture in New Zealand (Master’s Thesis, University of Otago, Otago, New Zealand).
Estreicher, S. K. (2004). History of wine: Wine the past past 7,400 years. Retrieved from http://www1.mpi-halle.mpg.de/~md_simul/data/special-data/winehistory.pdf
Fitzharris, B. B., & Enducher, W. (1996). Climatic Conditions for Wine Grape Growing. New Zealand Geographer, 52(1), 1-11. doi: 10.1111/j.1745-7939.1996.tb00458.x
Gardner, C. M., Laryea, K. B., & Unger, P. W. (1999). Soil physical constraints to plant growth and crop production. Land and Water Development Division, Food and Agriculture Organization.
Gladstones, J. (1992). Viticulture and Environment.Winetitles, Adelaide.
Goldammer, T. (2013). Grape grower’s handbook: A complete guide to viticulture for wine production. Apex Publishing.
Hancock, J. M., & Huggett, J. M. (2004). The geological controls in Coonawarra. Journal of Wine Research, 15(2), 115-122. http://ir.canterbury.ac.nz/bitstream/10092/1338/1/thesis_fulltext.pdf Huggett, J. M. (2006). Geology and wine: a review. Proceedings of the Geologists' Association, 117(2), 239-247.
Jackson , D., Schuster, D., Tipples R. (2002). Canterbury grapes and wines 1840-2002. Christchurch: Shoal Bay Press.
Jackson, D. (2001). Monographs in cool climate viticulture No.2: Climate. Wellington: Gypsum Press.
Jackson, D., & Schuster, D. (1994). The production of grapes and wine in cool climate, 4th edn. Lincoln University Press, Christchurch, New Zealand.
Jones, G. V., White, M. A., Cooper, O. R., & Storchmann, K. (2005). Climate change and global wine quality. Springer, 73, 319-343. doi: 10.1007/s10584-005-4704-2.
Leeuwen, C. v. (2010). Terroir: the effect of the physical environment on vine growth, grape ripening and wine sensory attributes. In Reynolds, A. G. (Eds.), Viticulture and wine quality (managing wine quality). (pp. 273-315). Woodhead Publishing.
Leeuwen, C. v., Friant, P., Chone, X., Tregoat, O., Koundouras, S., & Dubourdieu, D. (2004). Influence of climate, soil and cultivar on Terrior. Annu Rev Entomol, 55(3), 207-217.
Lorenzo, M. N., Taboada, J. J., Lorenzo, J. F., & Ramos, A. M. (2013). Influence of climate on grape production and wine quality in the Rias Baixas, north-western Spain. Regional Environmental Change, 13(4), 887-896. doi: 10.1007/s10113-012-0387-1.
McGovern, P. E., Fleming, S. J., & Katz, S. H. (2000). The origins and ancient history of wine: Gordon and Breach: Amsterdam.
Mullins, M. G., Bouquet, A., & Williams, L. E. (1992). Biology of the grapevine. Cambridge University Press.
Neirynck, B. (2009). The grapes of wine: The fine art of growing grapes and making wine. New York: Square One Publisher, Garden City Publishers.
Sluys, S. L. (2006). Climatic influences on the grapevines: A study of viticulture in the Waipara Basin (Master’s Thesis, University of Cantebury, Christchurch, New Zealand). Retrieved from
Smart, R. E. (1985). Principles of grapevine canopy microclimate manipulation with implications for yield and quality. American journal of enology and viticulture (USA).
Thorpy, F. (1971). Wine in New Zealnad. Auckalnd, New Zealand: Collins Bros.
Ubalde, J. M., Sort, X., Zayas, A., & Poch, R. M. (2010). Effects of Soil and Climatic Conditions on Grape Ripening and Wine Quality of Cabernet Sauvignon. Journal of Wine Research, 21(1), 1-17. doi: 10.1080/09571264.2010.495851.
Watson, F. (2013). Analysis of factors affecting fruit quality for the 2007 growing season in a California Vineyard (Master’s Thesis, California State University Monterey Bay, California, United States). Retrieved from http://sep.csumb.edu/amws/theses/Castorani_Thesis_13217.pdf White, M. A., Jones, G. V., & Diffenbaugh, N. S. (2009). Climate variability, climate change, and wine production in the western United States. Utah, United States: University of Utah Press.
White, R. E. (2003). Soils for fine wine. New York: Oxford University Press.
Zoecklein, B.W. (2010). Practical methods of measuring grape quality. In Reynolds, A. G. (Eds.), Viticulture and wine quality (managing wine quality). (pp. 273-315). Woodhead Publishing.