The effect of wind on the performance of the grapevine

[摘要] ENGLISH ABSTRACT:Wind, as a component of the environment, contributes to the viticultural concept ofterroir in the South Western Cape region of South Africa. Many other componentsalso contribute to terroir (e.g. soil, altitude, direction of slope, etc.) and it is difficult toquantify the contribution of each. A good terroir promotes slow and complete ripeningof the berries. A vineyard on such a terroir produces good quality crops over time andthe effects of climatic extremes on the performance of the vine are limited by thisterroir.Although grapevines in the South Western Cape are exposed to strong synopticsoutherly and southeasterly winds during the growing season and sea breezes add tothe effect of wind in coastal areas, little is known about the effect of wind ongrapevine performance. This preliminary study was undertaken to obtain moreinformation on the effect of wind on some morphological and reproductivecharacteristics of Merlot nair. The aim was to obtain preliminary data which can serveas a basis for future studies on the effect of wind on grapevine performance.Important differences .in wind speed were measured spatially in a selected vineyardand exposure to wind was observed to result in essential viticultural differences. Theeffect of wind on vegetative parameters, canopy density, yield, berry composition andwine quality was investigated. Wind caused leaves on primary shoots of exposedvines to be smaller, but increased lateral growth in their fruiting zones. Shelteredvines had longer shoots but no significant differences were measured concerningcane diameter and pruning mass. Although it was expected that sheltered vineswould have denser canopies, similar canopy densities were measured for bothtreatments. Vines exposed to wind responded with decreased stomatal conductance.As a result, leaf temperature was affected, showing differences between shelteredand exposed vines. Sheltered vines had more bunches per vine but fewer berries perbunch. As a result, bunches of sheltered vines were smaller than those of exposedvines. No significant difference was observed concerning the yield under the twotreatments. The effect of wind on stomatal conductance had an essential impact onberry composition, thus directly influencing the quality of wine. Grapes from exposedvines showed a higher colour index. Berries from sheltered vines had significantlylower pH values and potassium concentrations and the malic acid content was lowerthan in berries from exposed vines.Wine from sheltered vines had more vegetative undertones in comparison with thestronger fruity character of exposed vines. A better acid balance, together withsuperior complexity (fullness/mouth feel), contributed to the better overall qualityidentified during the evaluation of wine produced from sheltered vines.

[发布机构] Stellenbosch University