Viticultural terroirs in Stellenbosch, South Africa. II. The interaction of Cabernet-Sauvignon and Sauvignon Blanc with environment
Aims: A terroir can be defined as a grouping of homogenous environmental units, or natural terroir units, based on the typicality of the products obtained. Terroir studies therefore require an investigation into the response of grapevines to the natural environment.
Methods and results: A network of plots of Sauvignon blanc and Cabernet Sauvignon were delimited in commercial vineyards in proximity to weather stations and their response monitored for a period of seven years. Regression tree methodology was used to determine the relative importance of the environmental and management related variables and to determine regression trees for each dependent variable. Excepting for scion clone, which had a high relative importance for bunch mass of Sauvignon blanc and yield to pruning mass index of Cabernet Sauvignon, no other nonenvironmental variable included in the analyses appeared to have a strong effect on grapevine performance and wine character. The performance of Cabernet-Sauvignon was related to the potassium content of the subsoil and climate (temperature and rainfall) of the season. The performance of Sauvignon blanc appeared to be related to soil texture, wind exposure and temperature of the site and season, both during the green berry growth stage and the month prior to ripening.
Conclusions: From the results presented, it appears that environmental parameters have an overriding effect on the performance of both Cabernet Sauvignon and Sauvignon blanc but that these two cultivars react differently to environmental stimuli.
Significance and impact of study: These results should contribute to the identification of viticultural terroirs with specific agronomic potential for Cabernet-Sauvignon and Sauvignon blanc.
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