- Title
- The influence of geology and soil characteristics on the fruit composition of winegrapes (Vitis vinifera cv: Shiraz), Hunter Valley, New South Wales - implications for regionality in the Australian wine industry
- Creator
- Rawson, Graeme Andrew
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2002
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Geographical identity of wines and wine regions is a potent marketing took that highlights the value and uniqueness of a particular product. Many Old World viticultural countries place great importance on the role of soil properties in determining geographical identity of wines. However this view has not gained currency in Australia, which does not have the density of plantings to highlight any soil influences on wine. It is relatively intuitive to suggest that soils have an influence on wine style and quality. After all, grapevines are grown in soils and are dependent upon them for support, nutrients and water. However, although there is a voluminous world literature declaring this relationship to be true, a meticulous examination of it points to the fact that the scientific evidence is scant and that very few studies could claim to have established clear links via truly repeatable, rigorous scientific methods. Much of what has been written is either biased by preconceived notions, journalistic licence, or flawed by an inattention to the complexity of the path from soil through root, vine and grape, to wine. Previous attempts at establishing relationships between soil geography and wine have been embroiled in the complexities of the definition of the French term 'terroir'. Examination is made of the world literature on terroir and the various attempts at classifying regions based on this sometimes tenuous concept. Literature related to the classification of wines based on their labaratory-determined constituents is also examined. By using a rigorously controlled geographical approach, this thesis attempts to "bridge the gap" between the wine industry's use and misuse of the concept of terroir and the detailed soil and plant physiological research which, although extremely valuable, has not often been readily transferable to the field situation. 11 soil locations were identified and described in the Pokolbin viticultural district that had distinctly different soil properties but were: a) planted to same grape variety (shiraz) with the same age and history; b) within the same mesoclimatic area; c) having identical soil and canopy management; and d) no irrigation influences. Thus all possible environmental influences on grape composition were controlled for except for soil variation. A wide range of juice and grape composition measures were obtained at harvest from each soil location, over three successive vintages, 1994, 1995 and 1996. These included yield parameters, juice composition, pigments, phenolics, glycosyl and mineral composition. Differences in grape composition were compared between soil locations and between years to gauge the relative influence of soil versus seasonal effects. Soil properties were examined in detail and used to help explain the variation in grape composition. It was found that significant variation in grape composition existed that could only have been attributed to soil variation. In many instances the soil location effects were significantly more influential than the vintage effect, even though the three seasons studied differed considerably in climatic conditions. Multivariate analysis of the grape composition data highlighted interactions between measures that were influenced by soil location effects. Interactions between calcium and magnesium in the grape were examined in more detail, and it was shown that a positive correlation exists between these two measures. This relationship is influenced and hidden by soil properties, namely the relative proportion of calcium and magnesium in soils. The broad implications of these results are discussed with relevance to site selection of vineyards and viticultural trials, the relative importance of soil chemistry in viticulture, irrigation management, and Geographical Indications in Australia.
- Subject
- geographical identity; wine regions; wine; regionality; Australian wine industry
- Identifier
- http://hdl.handle.net/1959.13/1312930
- Identifier
- uon:22486
- Rights
- Copyright 2002 Graeme Andrew Rawson
- Language
- eng
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