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Relationship between the geology, soil assessment, and terroir of Gewürtztraminer vineyards: A case study in the Dolomites of northern Italy

Ferretti, Carlo G.
Catena 2019 v.179 pp. 74-84
Vitis, biochemical pathways, carbonates, case studies, fruits, grapes, magnesium, manganese, minerals, orchard soils, physical properties, product quality, quaternary soils, root systems, sediments, silicates, villages, vines, vineyards, wines, Alps region, Italy
The study of the geological identity of rare vineyards introduces new classification approaches for the geological natural environment, which is sometimes underestimated in agriculture. This research examines the geological features related to quaternary soil sediments in the Italian Alps, near the village of Tramin. The local winemakers have constantly encountered differences between vineyards over the decades, such as growth of vines and quality of the grapes and wine, even in Gewürtztraminer vineyards close to each other. A detailed geological territorial study with more precise classification at the vineyard scale would therefore be significant, because it could explain the source of these differences. A new term for this approach, Vineyard Geological Identity (VGI), has been coined. The purpose is to standardize the geological information and enhance scientific comparisons between vineyards, but it is also useful for vintners as they attempt to obtain scientific confirmation for their personal observations or for supporting the territorial subdivision provided by the wine's product quality specification. Our findings show a very marked variability of sediments in the study area and how the more recent geological processes are directly related to their varied chemical and mineralogical distributions. Many dolomitic or silicate soil sediments marked by different history, and therefore with different chemical and physical properties, lie adjacent in a very restricted territory. Some of the analysed vineyards are evidently siliciclastic, whereas others are mostly carbonate. In adjacent vineyards, the content of carbonate mineral can range from 36.3% to 0.6%. A marked alternation of layers with different mineralogy can typify the sediment layers where the grapevine root systems grow. The Mn and dolomitic Mg mean concentration were 1.1 mg/kg and 343 mg/kg, respectively, in strictly siliciclastic layers compared with 6.9 mg/kg and 1081 mg/kg in the more carbonate layers. Several minerals characterize the different sediments, and relations between some of them and the fruit orchard soil reaction classes were found. Further studies should verify direct links with the biochemical processes related to the variable mineral macronutrients observed. A correct geopedological classification and mapping of both the sediments and related soils are essential to eliminate incongruities in the interdisciplinary data.