La hiérarchisation des Coteaux du Languedoc: une application concrète du zonage vitivinicole

Wine is one of the most consumed and appreciated beverages in the world. Due to the growing attention paid to consumer health, there is a continuous search for sustainable alternatives to common additives (such as sulfur dioxide) used to preserve wine. An example is represented by chitosan, the main derivative of chitin, approved for the treatment of must and wine since 2009 by the “international organization of vine and wine” (OIV/OENO 338a/2009) and by the european commission (EC Reg. No. 606/2009).

Vine diseases have a strong impact on vineyards sustainability, which in turns leads to strong economic consequences. Among those diseases, Flavescence dorée spreads quickly and is incurable, which led in France to the setup of a mandatory pest control implying the systematic use of pesticides and the prospection and uprooting of every infected plants. Remote sensing could be a very powerful tool to optimize prospection as it allows to produce quickly accurate maps over large areas. Recent studies have shown that high spatial resolution (10cm/pixel) multispectral images acquired from UAVs allow to map Flavescence dorée in vineyards using leaves discolorations [e.g. Albetis et al., Remote Sensing, 2017].

The Valpolicella area (Veneto Region, Italy) is famous for its high quality wines: Amarone and Recioto, both obtained from partial post-harvest dehydrated red grapes. The main cultivars used for these wines are Corvina and Corvinone. In this Region hundreds of years ago a particular training system (Pergola, cordon/cane with horizontal shoot-positioning) was developed. In the last 20 years the Guyot have been introduced in the area; now Pergola and Guyot are equally widespread in the Valpolicella area. In two different environmental conditions (hill and floodplain) two vineyards, one for each type of training system, were studied along two years (2011-2012).

The presence of undesirable compounds in wines, such as ota, biogenic amines and pesticides residues, affects wine quality and can cause health problems for the consumer. Additionally, an excess of tannins can produce an undesirable increase in the astringency and bitterness of the wine, so tannins are also a target for reduction. The main tool that a winemaker has to reduce their content in the wine is fining. However, some of the fining agents commonly used in the winery can cause allergies or even increase the protein content in the wine, increasing the turbidity.

Viticulture is entangled with weather and climate. Therefore, areas currently suitable for grape production can be challenged by climate change. Winegrowers in Italy already experiences the effect of climate change, especially in the form of warmer growing season, more frequent drought periods, and increased frequency of weather extremes.
The aim of this study is to investigate the impact of climate variability and change on grape yield in Italy to provide winegrowers the information needed to make their business more sustainable and resilient to climate change. We computed a specific range of bioclimatic indices, selected by the International Organisation of Vine and Wine (OIV), and correlated them to grape yield data. We have worked in collaboration with some wine consortiums in northern and central Italy, which provided grape yield data for our analysis.
Using climate variables from the E-OBS dataset we investigate how the bioclimatic indices changed in the past, and the impact of this change on grape productivity in the study areas. The climate impact on productivity is also investigated by using high-resolution convection-permitting models (CPMs – 2.2 horizontal resolution), with the purpose of estimating productivity in future emission scenarios. The CPMs are likely the best available option for this kind of impact studies since they allow a better representation of small-scale processes and features, explicitly resolve deep convection, and show an improved representation of extremes. In our study, we also compare CPMs with regional climate models (RCMs – 12 km horizontal resolution) to assess the added value of high-resolution models for impact studies. Further development of our study will lead to assessing the future suitability for vine cultivation and could lead to the construction of a statistical model for future projection of grape yield.