Valtellina (Sondrio, Northern Italy): a typical terroir for Nebbiolo grape

Located in the Central Alps of Italy, Valtellina is the main longitudinal valley in the Alpine chain, deeply cut by the Adda river, tributary of Como lake, the latter being one of the deepest canyons due to Messinian erosion (FINCKH, 1978). The E-W trending part of the valley is tectonically controlled, running parallel to the Periadriatic Lineament, the main fault of the entire Alpine edifice (LAUBSCHER, 1983; HEITZMANN, 1987; CNR, 1990). The geomorphology of this valley is characterized by a strong difference between the opposite slopes. The southern one, named Orobico, has a northwards exposure, while the northern one, named Retico (Rhaetian), has a southwards exposure and enjoys a strong solar radiance. Glacial erosion widened the valley and smoothed the bedrock up to 2,000 m a.s.l. Bedrock outcroppings clearly prevail in comparison with scattered, thin Quaternary deposits (BONSIGNORE et alii, 1971). The strong vertical relief from the alluvial plain of the Adda river to the adjacent mountain ridge (about 2,000 meters) is due to a combination of structural control, fluvial erosion and glacial overexcavation. The Rhaetian side is protected from the northerly winds and enjoys a microclimate that allows grape growing at a latitude of 46 degrees 10' and elevations ranging from about 300 up to 700 m a.s.l. (BELLONI & PELFINI, 1987; FAILLA et alii, 2004). Here the noblest italian wine grape (Nebbiolo) is cultivated on steep sunny slopes, on narrow terraces supported by stone walls. This ancient man-made landscape adds a typical note which takes part in characterization of Valtellina terroir. The bedrock is represented by strongly deformed metamorphic units of both Austroalpine and Southalpine domains, scatterly covered by thin glacial deposits. Nebbiolo offers some of the finest and prone to ageing wines in the world, in particular Barbaresco and Barolo from Piedmont Langhe, which has a typical exquisite bouquet ranging from goudron to violets to rose. As a wine grape, Nebbiolo is nevertheless very sensitive to both microclimate and pedological characteristics. Outside Piedmont area, Nebbiolo wine growing has generally denied satisfactory results, due to its selective micro-climatic requirements (ROBINSON, 1998). Nebbiolo, locally called Chiavennasca, has been cultivated in Valtellina since several centuries and is fully adapted to the local conditions. Vine-growing in Sondrio province is devoted to both local consumption (as for instance in Valchiavenna) and DOCG-DOC production (MURADA et alii, 2004; ZOIA, 2004). The DOCG and DOC qualified area is limited to the Rhaetian side of Valtellina, in an approximatively 45 km long belt which encompasses chief town Sondrio (MARIANI & COLA, 2004). Between 1998 and 2002 the DOCG production was about 21,500 hl produced in a 850 ha area.