Evaluation of thermal regime of <em>Vitis vinifera</em> L. var. Melon during winter time in Québec

Abstract

The production of wine is a recent endeavour in Québec. In 1996, 95 p. cent of the commercial vineyards were found in the Eastern Townships and Montérégie regions, where climate puts severe constraints on viticulture. Very low winter time temperatures can occur and it is important to match vine hardiness to climate reality. This can be accomplished by plant selection and/or by application of variety of phytoprotective measures. Field measurements of the thermal regime of different parts of vines (Vitis vinifera L. var. Melon) are reported here. Intratissular temperatures were recorded semi-continuously using fine (A WG n° 40) thermocouples and datalogger system. Measurements were recorded throughout the winters 1993-1994 in a vineyard near Sherbrooke, Québec. The measurements show that snow is very important factor ameliorating root-zone temperatures. Snow is also very important to keeping the aerial parts of the plant at temperatures well above their winter hardiness. Temperatures of 0°C to 4°C were recordeding snow cover parts of the plants even at ambient air temperatures near -30°C. During cold spells, following periods of melt with complete removal of the snow cover, cooling was notes down to a depth of 60 cm in the soil and the aerial parts of the plants closely followed the air temperatures. By contrast, if the cold front marking the end of the melting event was accompanied by snowfall, such extreme cooling did not occur. Even just a few centimeters of snow had very important thermal effects. Our results suggest that noble grapes, which give a more interesting wine, but which are less hardy than their hybrid counterparts, can survive in Québec, provided they remain snow covered. A snow cover of only about 10 cm would suffice to protect the vines. Active management of snow cover conditions by means of snow fences, or even by production of artificial snow, may be useful venues to investigate.

Keywords

• Winter hardiness
• snow cover
• extreme temperatures
• frost protection
• thermal rate