Clima e terroir in due diverse aree delle Alpi italiane : la Valle di Susa (Piemonte) e la Val d'Adige (Trentino)

This work examines the relation between climate and viticulture in two different areas of the italian Alps: the Upper Susa Valley (Piedmont region), where the wine «Valsusa» is produced, and the Adige Valley (Trentino region), where the wine «Teroldego Rotaliano» is produced. Climatic data were analyzed from a group of four automatic stations of the net of Climatic-Hydrographic Sector of Regione Piemonte and three stations of Adige Agriculture Institute network, in the period 1990-2003. According to the thermal zonation of vineyards areas by Winkler and Amerine, the Upper Susa Valley is included in the «cold» zone (Winkler Index <1371), while the lower Susa Valley is in the «cold-temperate» zone (1371 < Winkler Index < 1648). The Adige Valley bottom is placed in the «cold-temperate» zone while the slopes at elevation over 300 m are included in the «cold» zone. The continentality Gams index reveals different conditions: a constant decrease in the Susa Valley with increasing elevation and an opposite trend in the Adige Valley. This result points out the relevance of topoclimatic conditions in terms of wine quality. In the Adige Valley, also the Amann hygrothermic index, which increases with elevation up to the vineyard cultivation, confirms the topoclimatic complexity of this area. From a thermometric point of view the limit of vineyards is characterized by i) yearly average temperature of 8,5-9,0°C in the Susa Valley and 11,0-11,5°C in the Adige Valley; ii) yearly average sum with base 10°C from April to September of 850-900°C a day, a much lower value with respect to the standard of 1000°C (FRIBOURG & SCARPATI, 1989); iii) average temperatures of 7,5-8,0°C at budding (April) in Susa valley and 11,5-12°C in Adige valley; iv) average temperatures at blossoming (June) of 16,0°C in the Susa Valley and 19,0 in the Adige Valley; v) maximum of 5/6 days of frost from April to May in the Susa Valley and only 2/3 in the Adige Valley. A yearly average relative humidity of 65% is the threshold between stations where it is possible to grow grapes or not. The persistence of the snow layer doesn't seem instead to influence directly the possibilities to use the ground to grow grapes.