Variability in the content of coarse elements in a viticultural plot in the Graves appellation: relationship with geophysical data

The impact of viticulture on soil can be determined by comparing the biophysical properties that represent soil health at a particular site and depth with those same properties in soil considered to represent the ‘pre-vineyard’ state (the headland). Information gathered by this method shows the changes in soil properties following the change to viticulture depend on individual vineyard management and environment.

Under current climate change pressures, obtaining grapes with adequate acidity at harvest is one of the main challenges for growers, especially if the goal is producing sparkling wines. This issue arises from two main occurrences: i) higher temperatures enhance degradation of malic acid; ii) grape maturity may occur under suboptimal climatic conditions due to an advanced phenology.

This study aims to create an updated, agile viticultural climate index (similar to the Winkler Index) by performing in-depth analyses of current and historical data from industry partners in several major winegrowing regions. The Winkler Index was developed in the early twentieth century based on analysis of various grape-growing regions in California. The index uses heat accumulation (i.e. Growing Degree Days) throughout the growing season to determine which grape varieties are best suited to each region. As viticultural regions are increasingly subject to the complexity and uncertainty of a changing climate, a more rigorous, agile model is needed to aid grape growers in determining which cultivars to plant where. For the first phase of this study, 21 industry partners throughout Napa Valley shared historical phenology, harvest, viticultural practice, and weather data related to their Cabernet sauvignon vineyard blocks. To complement this data, berry samples were collected throughout the 2021 growing season from 50 vineyard blocks located throughout 16 American Viticultural Areas that were then analyzed for basic berry chemistry and phenolics. These blocks have been mapped using a Geographic Information System (GIS), enabling analysis of altitude, vineyard row orientation, slope, and remotely sensed climate data. Sampling sites were also chosen based on their proximity to a weather station. By analyzing historical data from industry partners and data specifically collected for this study, it is possible to identify key parameters for further analysis. Initial results indicate extreme variability at a high spatial resolution not currently accounted for in modern viticultural climate indices and suggest that viticultural practices play a major role. Using the structure of data collection and analyses developed for the first phase, this project will soon be expanded to other wine regions globally, while continuing data collection in Napa Valley.

Correlations between vineyard site and wine have, historically, been limited due to lack of uniformity in scion and rootstock clone and lack of controlled pilot-scale winemaking conditions, particularly temperature

La qualité des vins dépend de différents facteurs et procédés, notamment de la nature des terrains viticoles. Dans ce travail, nous avons cherché à établir les liens entre descripteurs pédologiques des parcelles et descripteurs sensoriels des vins. Sur la base de Classifications Ascendantes Hiérarchiques (CAH) et d’Analyses en Composante Principale (ACP), il a été possible d’établir des liens entre la nature des parcelles (sableuse, argileuse, sablo-graveuleuse) et certains descripteurs sensoriels des vins (chaleur, astringence, fruit noir) et plus globalement avec le type de vins élaborés.