Terroir 1996 banner
IVES 9 IVES Conference Series 9 Thermal conditions during the grape ripening period in viticulture geoclimate. Cool night index and thermal amplitude

Thermal conditions during the grape ripening period in viticulture geoclimate. Cool night index and thermal amplitude

Abstract

c L’objectif du travail est de caractériser le régime thermique, notamment la fraîcheur,, des nuits et l’amplitude thermique au cours de la maturation, au niveau du climat viticole mondial, sur une base des données de 100 régions viticoles dans 30 pays, obtenue par l’intermédiaire de l’Organisation Mondiale de la Météorologie – OMM. Plusieurs indices climatiques viticoles ont été calculés: l’Indice de Fraîcheur des Nuits – IH (°C), l’Indice Héliothermique de Huglin – IH (°C) et l’Indice de Sécheresse – IS (mm) du Système de Classification Climatique Multicritères Géoviticole, et l’amplitude thermique moyenne en août et septembre Aa-s (0C). Egalement, sur la période véraison-récolte – v-r (moyenne des 30 jours précédant la date de récolte, estimée sur la base d’un Indice Héliothermique de HUGLIN égal à 1.900 – approximatif pour la maturation du Cabernet-Sauvignon) : la fraîcheur des nuits (FNv-r), la température moyenne de l’air (Tv-r), la température maximale de l’air (Txv-r) et l’amplitude thermique (Av-r). Les résultats montrent que IH est corrélé avec Tv-r (r=0,79) et avec Txv-r (r=0,80). IH représente donc bien les conditions thermiques générales de la période de maturation en ce qui concerne la température moyenne et maximale de l’air. Mais IH n’est pas corrélé ni avec Aa-s ni avec Av-r. Par contre, IF est corrélé avec Aa-s (r = -0,70) et FNv-r est corrélé avec Av-r (r = -0,69). Cette corrélation doit justifier, en partie, l’usage assez courant de l’amplitude thermique comme indicateur de bonnes conditions thermiques de maturation pour les régions qui présentent des valeurs élevées. Mais ce raisonnement peut amener à des caractérisations erronées. Le travail met en évidence, également, l’importance de considérer le bilan hydrique des régions (IS) dans l’analyse du régime thermique sur la qualité du raisin. On peut conclure que pour avoir une bonne caractérisation du régime thermique en période de maturation il faut considérer la fraîcheur des nuits (IF étant un bon indicateur de FNv-r moyen des régions, avec un r = 0,80**), caractérisation qui peut être améliorée avec l’information des températures maximales et de l’amplitooe thermique en période de maturation du raisin. Les éléments présentés peuvent servir à améliorer les indices climatiques pour estimer le potentiel qualitatif du raisin des différentes régions viticoles, notamment en complément de IF.

The thermal conditions during the grape ripening period are important variables related to colour of the grapes, anthocyanins, polyphenols and flavour of the wine. The main purpose of this work was to characterise the thermal conditions, especially the night coolness and the thermal amplitude during maturation, in the geoclimate of the world vine culture. A database of 100 grape-growing regions of 30 countries obtained from the World Meteorology Organisation (WMO) was used. Some climatic indexes were calculated: Cool Night Index – IF (°C), Huglin’s Heliothermal Index -IH (°C) and Dryness Index -IS (mm), from the Multicriteria Climatic Classification System for World Viticulture, and the thermal amplitude in August and September Aa-s (°C). Over véraison-harvest period-v-r (mean of the 30 days before harvesting date, estimated on the basis of IDJGLIN Heliothermal Index equal to 1,900 – approximately value to ripen Cabernet-Sauvignon) similar indexes were obtained: the cool night (FNv-r), the mean air temperature (Tv-r), the maximal air temperature (Txv-r) and the thermal amplitude (Av-r). The results showed that IH is positively correlated with Tv-r (r=0.79), Txv-r (r = 0.80) and IF (r = 0.67). Therefore, IH represents well the general thermal conditions during maturation period, specially concerning the mean and the maximal air temperature. However, IH was correlated neither with Aa-s nor to Av-r. IF was negatively correlated with Aa-s (r = – 0.70) and FNv-r was negatively correlated with Av-r (r = -9.69). The correlation to some extent explains the current use of the thermal amplitude to predict good ripening thermal conditi0ns for those regions that show high values. As here we have described, this thinking may give incorrect results. This work has also showed the inportance to consider the water balance of the regions (IS) in the effect of the thermal conditions in grape quality. We conclude that the characterisation of the thermal conditions during the ripening period do need the cool night index (in this case, IF is a good index to provide the mean FNv-r of the regions, r = 0,80**). Factors other than cool night which influence this characterisation are both maximal air temperature and thermal amplitude data. The elements presented in this work, in addition to IF, may improve the climatic indexes to be used to predict the qualitative potential of grapes from different regions.

 

DOI:

Publication date: February 15, 2022

Issue: Terroir 2002

Type: Article

Authors

Jorge TONIEITO (1) and Alain CARBONNEAU (2)

(1) EMBRAPA, Rua Livramento, 515 – 95700-000 Bento Gonçalves, Brésil
(2) AGRO Montpellier, 2, Place P. Viala, 34060 Montpellier, Cedex 1, France

Keywords

indice de fraîcheur des nuits, amplitude thermique, Système CCM Géoviticole, zonage, qualité
cool night index, thermal amplitude, MCC System for World Viticulture, zoning, quality

Tags

IVES Conference Series | Terroir 2002

Citation

Related articles…

Mapping and tracking canopy size with VitiCanopy

Understanding vineyard variability to target management strategies, apply inputs efficiently and deliver consistent grape quality to the winery is essential. However, despite inherent vineyard variability, the majority are managed as if they are uniform. VitiCanopy is a simple, grower-friendly tool for precision/digital viticulture that allows users to collect and interpret objective spatial information about vineyard performance. After four years of field and market research, an upgraded VitiCanopy has been created to achieve a more streamlined, technology-assisted vine monitoring tool that provides users with a set of superior new features, which could significantly improve the way users monitor their grapevines. These new features include:
• New user interface
• User authentication
• Batch analysis of multiple images
• Ease the learning curve through enhanced help features
• Reporting via the creation of colour maps that will allow users to assess the spatial differences in canopies within a vineyard.
Use-case examples are presented to demonstrate the quantification and mapping of vineyard variability through objective canopy measurements, ground-truthing of remotely sensed measurements, monitoring of crop conditions, implementation of disease and water management decisions as well as creating a history of each site to forecast quality. This intelligent tool allows users to manage grapevines and make informed management choices to achieve the desired production targets and remain profitable.

How can historical cultivars mitigate the effects of climate change?

IFV, INRAe and the national network “Partenaires de la Sélection Vigne” representing 37 organizations from the different wine regions, have been working increasingly closely over the last 2 decades towards the preservation of the French varietal patrimony. There are approximately 600 patrimonial varieties according to INRAe and SupAgro Montpellier experts, including ancient cultivars (400) and intravarietal crossbreeds obtained since the 19th century. In the context of a drastic reduction in such varieties from the mid 1980’s in favor of mainstream varieties, it was essential to carry out an inventory of old vines and vineyards. INRAe Vassal collection plays a key role here as it holds the largest diversity available, along with a rich bibliography and herbariums, offering us the opportunity to document and double check the identity of a cultivar, consolidating the expertise of ampelographers. The work is carried out in several stages, from verifying the existence of a variety in a small region, through to rehabilitation. During this session, the authors present the process that leads to the official registration of a variety. After this, IFV selection center takes over to initiate the process of selection and propagation. A specific focus within regions such as the Alps, Champagne and the South-West will provide details of the full procedure. Bia, Bouysselet, Chardonnay rose, Mecle and the aptly named Tardif, are some of the cultivars that have followed this procedure. Furthermore, a recent regulation established by INAO on “varieties of interest for adaptation purposes” might boost uptake by growers. Since 2006, 36 historical cultivars have been registered. Most of these have been neglected in the past due to late maturity, lack of sugar and high titratable acidity at harvest time. Such characteristics are today considered as positive qualities, not only in mitigation of the effects of climate change, but also as an opportunity for restoring diversity…

Climate and the evolving mix of grape varieties in Australia’s wine regions

The purpose of this study is to examine the changing mix of winegrape varieties in Australia so as to address the question: In the light of key climate indicators and predictions of further climate change, how appropriate are the grape varieties currently planted in Australia’s wine regions? To achieve this, regions are classified into zones according to each region’s climate variables, particularly average growing season temperature (GST), leaving aside within-region variations in climates. Five different climatic classifications are reported. Using projections of GSTs for the mid- and late 21st century, the extent to which each region is projected to move from its current zone classification to a warmer one is reported. Also shown is the changing proportion of each of 21 key varieties grown in a GST zone considered to be optimal for premium winegrape production. Together these indicators strengthen earlier suggestions that the mix of varieties may be currently less than ideal in many Australian wine regions, and would become even less so in coming decades if that mix was not altered in the anticipation of climate change. That is, grape varieties in many (especially the warmest) regions will have to keep changing, or wineries will have to seek fruit from higher latitudes or elevations if they wish to retain their current mix of varieties and wine styles.

Climate change impacts: a multi-stress issue

With the aim of producing premium wines, it is admitted that moderate environmental stresses may contribute to the accumulation of compounds of interest in grapes. However the ongoing climate change, with the appearance of more limiting conditions of production is a major concern for the wine industry economic. Will it be possible to maintain the vineyards in place, to preserve the current grape varieties and how should we anticipate the adaptation measures to ensure the sustainability of vineyards? In this context, the question of the responses and adaptation of grapevine to abiotic stresses becomes a major scientific issue to tackle. An abiotic stress can be defined as the effect of a specific factor of the physico-chemical environment of the plants (temperature, availability of water and minerals, light, etc.) which reduces growth, and for a crop such as the vine, the yield, the composition of the fruits and the sustainability of the plants. Water stress is in many minds, but a systemic vision is essential for at least two reasons. The first reason is that in natural environments, a single factor is rarely limiting, and plants have to deal with a combination of constraints, as for example heat and drought, both in time and at a given time. The second reason is that plants, including grapevine, have central mechanisms of stress responses, as redox regulatory pathways, that play an important role in adaptation and survival. Here we will review the most recent studies dealing with this issue to provide a better understanding of the grapevine responses to a combination of environmental constraints and of the underlying regulatory pathways, which may be very helpful to design more adapted solutions to cope with climate change.

Revealing the Barossa zone sub-divisions through sensory and chemical analysis of Shiraz wine

The Barossa zone is arguably one of the most well-recognised wine producing regions in Australia and internationally; known mainly for the production of its distinct Shiraz wines. However, within the broad Barossa geographical delimitation, a variation in terroir can be perceived and is expressed as sensorial and chemical profile differences between wines. This study aimed to explore the sub-division classification across the Barossa region using chemical and sensory measurements. Shiraz grapes from 4 different vintages and different vineyards across the Barossa (2018, n = 69; 2019, n = 72; 2020, n = 79; 2021, n = 64) were harvested and made using a standardised small lot winemaking procedure. The analysis involved a sensory descriptive analysis with a highly trained panel and chemical measurement including basic chemistry (e.g. pH, TA, alcohol content, total SO2), phenolic composition, volatile compounds, metals, proline, and polysaccharides. The datasets were combined and analysed through an unsupervised, clustering analysis. Firstly, each vintage was considered separately to investigate any vintage to vintage variation. The datasets were then combined and analysed as a whole. The number of sub-divisions based on the measurements were identified and characterised with their sensory and chemical profile and some consistencies were seen between the vintages. Preliminary analysis of the sensory results showed that in most vintages, two major groups could be identified characterised with one group showing a fruit-forward profile and another displaying savoury and cooked vegetables characters. The exploration of distinct profiles arising from the Barossa wine producing region will provide producers with valuable information about the regional potential of their wine assisting with tools to increase their target market and reputation. This study will also provide a robust and comprehensive basis to determine the distinctive terroir characteristics which exist within the Barossa wine producing region.