3. The Growing Environment Flashcards
How much sunlight does the vine need for photosynthesis?
At least one third of full sunshine.
Hence, fog can slow photosynthesis, but an average cloudy day will not.
How do solar radiation levels decrease in intensity before reaching the earth’s surface?
Solar radiation is absorbed (held by water droplets, dust and ozone) and scattered as it travels through the Earth’s atmosphere, decreasing its intensity.
How does the earth’s curvature influence solar radiation levels in regions at high latitudes?
Nearer the poles solar radiation must travel through a larger section of atmosphere to reach the Earth’s surface. It also means that the radiation hits the Earth at a low angle, so the radiation is spread over a larger area (it is more diffuse).
If all other factors are equal, this generally means solar radiation is less intense at higher latitudes.
How does the earth’s curvature influence solar radiation levels in regions at low latitudes?
At the Equator the radiation travels through a smaller section
of atmosphere and hits the Earth’s surface at a larger angle (nearer perpendicular), so that solar radiation here is more powerful.
How does a high latitude influence daylight hours?
High latitude regions have longer daylight hours in the summer and shorter daylight hours in the winter. This permits a longer duration of time over which photosynthesis can take place in the growing season.
Why is grape production rare at latitudes below 30°C?
Regions nearer the Equator are usually too hot during the day. Vines transpire to regulate their temperature and if water is not readily available, this can cause water stress. Grapes can also suffer from sunburn.
Why is grape production rare at latitudes higher 50°C?
Regions near the poles are simply not warm enough during the growing season (despite long daylight hours) for enough sugar to accumulate in the grapes.
How much does temperature change with altitude?
Temperature falls by approximately 0.6°C (1.1°F) over every 100 m increase in altitude.
Why is sunshine more intense at high altitudes than low latitudes?
Because solar radiation travels through less atmosphere to reach the surface.
What is ultra-violet radiation?
Radiation with a lower wave-length than visible sunlight.
What helps promote anthocyanin and tannin synthesis in high altitudes?
More intense levels of sunshine and ultra-violet radiation
What is diurnal range?
The difference between day and night temperatures.
Why do high altitude sites typically have a higher diurnal range?
The ground absorbs energy from solar radiation during the day and releases energy into the atmosphere during the night.
At high altitudes the air is thinner and holds less moisture and therefore heat rapidly escapes, leading to relatively cool night-time temperatures.
Why do sites at lower altitudes typically have lower diurnal range?
The ground absorbs energy from solar radiation during the day and releases energy into the atmosphere during the night.
At lower altitudes the air in the atmosphere (particularly the water vapour) absorbs some of this energy, meaning some heat is retained at night
Why does the importance of aspect and slope steepness increase at high latitudes?
Solar radiation hits the Earth at a low angle at high latitudes. In the context of the vine growth cycle, the angle is lowest in the spring and autumn (compared to the summer).
The slope increases the angle (nearer to perpendicular) at which the solar radiation hits the Earth’s surface, hence increasing the intensity of heat and light.
A good slope and aspect in cool climates located at high latitudes can ensure the full and even ripening of grapes.
What are the advantages of east-facing slopes?
Slopes facing east benefit from morning sunshine that can heat up the atmosphere when air and soil temperatures are at their lowest. This can extend the hours of vine growth and grape ripening each day, especially in cool climates.
The grape canopy, which can be covered with dew in the morning, also dries out earlier in east-facing vineyards, reducing the spread of fungal disease, which is beneficial for grape quality and yields.
What must a grower consider before planting vines on a west-facing slope?
Slopes that face west receive the afternoon sun and may become too hot, especially in warm climates, and risk of sunburnt grapes is increased.
However, in areas with coasts to the west, e.g. California and Western Australia, cool afternoon sea breezes may alleviate this.
Other than heat and light, what are the benefits of planting vines on slopes?
- Shallower, poorer soils and better drainage
- Shelter from winds and rain
- Protection from frosts (air movement down the slope prevents frosts from forming)
What are the two main disadvantages of planting vines on a slope?
Soil erosion and the inability to use machinery on steep slopes can be problematic.
How do nearby bodies of water influence temperature?
Water heats up and cools down more slowly than land.
**During the day ** The water and the air above a body of water remains relatively cool and lowers the average temperature in the local area. Air directly above dry land heats up more quickly than that above the water, and this warm air rises. Cool air from above the water is drawn to the land to replace the warm air as it rises, resulting in cool, humid afternoon breezes.
During the night The water retains the warmth gained during the day, whereas, without solar radiation, the land loses heat relatively quickly. The warmth of the body of water keeps the local area warmer.
The same effect can be experienced over the year, with large bodies of water giving cooler summers and milder winters.
Give two examples of how ocean currents can moderate temperatures.
Margeaux, Bordeaux and Willamette Valley, Oregan are both at 45° latitudes. One produces cabernet sauvignion (late ripening) and one produces pinot noir (early ripening).
Bordeaux’s climate is warmed by the Gulf Stream, an ocean current flowing from the Gulf of Mexico.
Oregan’s temperature is cooled by the California current, which flows from the northern pacific.
How does El Nino start?
El Niño starts when warm water in the western Pacific Ocean moves eastwards along the Equator towards the Caribbean.
How does El Nino affect regions located in the eastern Pacific Ocean?
The eastern Pacific Ocean becomes warmer than average and this tends to cause high levels of rainfall and risk of hurricanes in South America and California. Rainfall can disrupt pollination and fruit set and lead to excessive water availability, which can increase vegetative growth and hinder ripening. And hurricanes clearly have a destructive influence.
However, El Niño brings warmer than average temperatures and drier conditions
to the more northerly states of Washington and Oregon.
How does El Nino affect regions located in the western Pacific Ocean?
On the western side of the Pacific Ocean in Australia, El Niño tends to cause warmer temperatures and drought conditions, which can cause extreme vine stress and vine damage.
How often does El Nino occur?
El Niño events typically occur once every 3–7 years, with extreme El Niño events being rarer. It is thought, however, that these extreme events are becoming more frequent as a part of climate change.
How does La Nina start?
La Niña is caused when the eastern Pacific Ocean is cooler than average.
How does La Nina affect regions in the eastern Pacific ocean?
La Nina tends to result in cooler, wetter conditions in Washington and Oregon, but warmer, drier conditions in California and South America
How does La Nina affect regions in the western pacific ocean?
La Niña causes wetter and cooler conditions in Australia
In what ways do bodies of water influence heat and sunlight available to wine growing regions?
- Moderating effect. Bodies of water are slow to warm up and cool down.
- Ocean currents
- Water surface can reflect solar radiation
- El Nino and La Nina in the Pacific Ocean
How to winds affect vineyards and wine growing regions?
- Winds can cool or warm regions (for example, the cold Mistral in the Rhone Valley, and the warm Zonda in Mendoza.
- Winds and breezes can reduce the occurence of humid, stagnant air in the vine canopy that encourages the development of fungal disease.
- Wind increases evapotranspiration of the vine, meaning vines water needs may be higher in windy areas. (If water isn’t readily available, wind can lead to water stress).
- Strong winds can cause damage to vines and vineyard trellising.
What can be implemented in the vineyard to minimise the damage caused by strong winds?
Rows of trees can be planted at the edge of the vineyard to act as wind breaks (these can compete with the vines for nutrients and water).
Fences can also be used, but are less aesthetic and require maintenance.
What factors of the soil influence the warmth of the vineyard?
The drainage of the soil, texture and colour.
Why is it desirable for cool-climate vineyards to have free-draining soils?
Soils that drain freely, for example sandy or stony soils, warm up more quickly in the spring than damp soils. Rising soil temperature encourages the breakdown of starch in the roots, which stimulates budburst and shoot growth.
What are two factors to consider when planting vines in free-draining soils?
Although free-draining soils are typically beneficial in cool climates, there is a risk of early budburst, which increases the risk of harmful spring frosts damaging young buds and shoots.
Warm soils also encourage root growth, which means the vines can absorb more water and nutrients.
How do light coloured soils influence temperature?
Light coloured soils can reflect some energy from solar radiation to the lower parts of the canopy (which may recieve little light). This can increase photosynthesis and grape ripening in cool and cloudy climates or where late-ripening grapes are used.
In warm climates, light coloured soils can increase temperatures in the warmest part of the day.
How do dark colour soils influence temperature?
Dark-coloured soils, such as some of those from volcanic origin (e.g. as found in Etna), absorb more energy and re-radiate most of it when temperatures are cooler, for example at night. This can be useful, especially in cool climates or for late-ripening grapes, allowing the development of colour and degradation of acid to continue during the night.
How do stony soils influence temperature?
Stony soils, especially if the underlying soil is slightly damp, are also very effective at absorbing heat and releasing it at night. This is because stone and water are good conductors compared to air.
What is mist and fog? How do they form?
Mists are formed by tiny drops of water collecting in the air just above an area of ground or water. They are usually formed when warm air is rapidly cooled, causing water vapour in the air to condense. This may occur, for example, at night when warm air over a body of water meets cooler conditions above the land.
Fog is dense mist.
How do mist, fog and clouds influence the heat and light available to the vineyard?
Depending on the density of the mist, fog or amount of cloud cover, sunlight can be limited to such an extent that photosynthesis is reduced. With less solar radiation, temperatures can be lower, particularly if morning fog or cloud delays the time at which the morning sun begins to warm the land. Where mists, fogs and cloudy conditions are regular, this can slow down sugar accumulation and acid degradation in the grapes, which may be beneficial in warm regions or when growing early-ripening grape varieties.
Why is a high diurnal range considered beneficial in warm and hot climates?
In these climates, a relatively cool period during the night can slow the respiration of malic acid and be beneficial for the formation of anthocyanins (day-time temperatures are too hot).
Why is a low diurnal range considered to be favourable in cool to moderate climates?
A low diurnal range may be favourable so that night-time temperatures still allow ripening (e.g. acid degradation, anthocyanin synthesis) to continue, which may be needed for grapes to ripen sufficiently.
How does a region’s diurnal range influence a grape’s aroma compounds?
It is thought that night-time temperatures can have some influence on aroma compounds. For example, warmer night temperatures are associated with a greater breakdown of methoxypyrazines, which may be important in cool climates, and cooler temperatures are associated with a greater retention of some other compounds, such as rotundone.
What are the natural factors that affect temperature and sunlight?
- Latitude
- Altitude
- Slopes and aspect
- Proximity to water
- Wind
- Characteristics of the soil
- Mist, fog and clouds
+ diurnal range, however this is associated with latitude and altitude.
How much rainfall do vines typically need per year?
500mm in cool climates
750mm in warm climates
Why do vines need water?
- Turgidity (keeping the vine from wilting)
- Photosynthesis
- Temperature regulation
- Uptake of nutrients (water acts as a solvent for nutrients in the soil)
What is transpiration?
Water vapour diffuses out of the stomata (tiny pores) on the underside of vine leaves. The loss of water from the cells in the leaf causes water to be pulled upwards from the soil, through the roots and the above-ground parts of the vine.
What happens when the stomata is open?
Open stomata allow the free exchange of water vapour out of the vine and also let carbon dioxide and oxygen diffuse in and out of the leaves. If the vine has sufficient water, it can keep its stomata open all day.
Why would stomata close or partially close? What can this lead to?
A lack of water causes the vine to close its stomata partially, an effort to conserve water.
Closed stomata can also reduce or stop photosynthesis due to the lack of carbon dioxide entering the leaves.
What are the risks of closed stomata?
Closed stomata reduces or even stops photosynthesis.
As photosynthesis is the way that the plant makes sugars for energy, this causes the vine’s growth to be stunted and ripening to slow down. Extreme cases of water stress can lead to leaf loss and vine death.
