The use of local knowledge relating to vineyard performance to identify viticultural terroirs in stellenbosch and surrounds
A terroir can be defined as a grouping of homogenous environmental units based on the typicality of the products obtained. Identification and characterisation of terroirs depends on knowledge of environmental parameters, the functioning of the grapevine and characteristics of the final product, which must be placed in a spatial context. Field studies, resulting in point data, are considered necessary to investigate the functioning of the grapevine, but the use of representative sites to determine the response of the grapevine to its environment is time consuming and costly and limits terroir studies. We surveyed vineyard managers on their perceptions of the functioning of established Sauvignon blanc vineyards in the Stellenbosch Wine of Origin District. Comparison of data generated with these questionnaires to measured data in commercial vineyards suggested that the vineyard managers were able to characterise the performance of vineyards with respect to vigour, signs of drought stress and yield. Each vineyard was mapped and the responses were linked to modelled environmental variables. Classification and regression tree methodology indicated that the viticultural and oenological aptitude of a site was closely related to temperature, exposure to dominant winds, height above sea level and soil type. This data was used to construct decision trees, which could be applied to environmental data in a geographic information system to determine viticultural terroirs for production of Sauvignon blanc. Further study is required to test the validity of the delimitation with sensory analysis of commercial wines.