Dissertation (PhD(Agric)) -- Stellenbosch University, 2005. / ENGLISH ABSTRACT: Due to increased consumer demand for products labelled by origin, and the
requirement that these labels are a guarantee of both quality and product character,
there is an increasing global focus on delimitation of denominations of origin. The
integrity of denominations of origin and their defensibility can be ensured through the
use of terroirs as a basis for delimitation.
The aims of this study were to establish the dominant environmental criteria that
affect the viticultural behaviour and wine character of two important cultivars
(Cabernet Sauvignon and Sauvignon blanc) in the Stellenbosch Wine of Origin
District, to use an appropriate methodology to identify viticultural terroirs in this district
based on these criteria and with the use of a geographic information system, and
finally to use these viticultural terroirs to identify denominations of origin within the
same area.
A terroir can be defined as a grouping of homogenous environmental units, or
natural terroir 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 the characteristics of the final product. Field
studies, resulting in point data, are necessary to investigate the functioning of the
grapevine but in order for this information to be of use within zoning studies it must
be placed in a spatial context.
As a first phase in data acquisition, the Stellenbosch Wine of Origin District was
characterised and natural terroir units were identified using existing digital data and a
geographic information system. A natural terroir unit (NTU) can be defined as a unit
of land that is characterised by relatively homogenous topography, climate,
geological substrate and soil. A total of 1389 NTUs were identified in the
Stellenbosch Wine of Origin District (84 537 ha). The identified NTUs were
homogenous with respect to terrain morphological unit, altitude, aspect and soil type.
Each of the identified units was further described with respect to the extent of the
expected sea breeze effect and, for certain of the soil types, the associated parent
material.
As a second phase of data acquisition, a network of plots of Sauvignon blanc and
Cabernet Sauvignon were delimited in commercial vineyards in proximity to weather
stations and their viticultural and oenological response monitored for a period of
seven years.
Regression tree analyses were performed on the complete data set and the
relative importance of the environmental and management related variables
determined 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 non-environmental variable included in the
analyses appeared to have a strong effect on grapevine performance and wine character. The performance of Cabernet Sauvignon was affected by the potassium
content of the subsoil and the climate of the season. The performance of Sauvignon
blanc appeared to be related to soil texture, wind exposure and temperature, both
during the green berry growth stage and the month prior to ripening. 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.
A knowledge-driven model used the rules generated in the regression tree
analyses to directly classify natural terroir units with respect to expected response of
Cabernet Sauvignon and Sauvignon blanc in the Stellenbosch Wine of Origin District.
The natural terroir units were thus grouped into terroir units that were homogenous
with respect to predicted viticultural and oenological response for each cultivar.
The use of representative sites to determine the response of the grapevine to its
environment is time consuming and costly and limits terroir studies to research
related investigations. Vineyard managers were therefore surveyed with respect to
the functioning of established Sauvignon blanc vineyards in the Stellenbosch Wine of
Origin District in an attempt to obtain the necessary data. Comparison of the 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 trees were 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. These terroirs,
although fewer, were comparable to those generated using field data.
Data gathered during terroir studies, and the identified viticultural terroirs for
Cabernet Sauvignon and Sauvignon blanc, were used to revisit the boundaries of the
Stellenbosch Wine of Origin District and the Simonsberg-Stellenbosch ward.
Modifications were proposed based on expected wine characteristics. Boundaries for
two new wards in the Helderberg basin were proposed. It was also possible to
identify vineyards within a ward for the production of terroir specific wines. / AFRIKAANSE OPSOMMING: Toenemende verbruikersaanvraag vereis produkte waarvan die etikette nie net die
oorsprong aandui nie, maar ook kan dien as ‘n waarborg vir die produk se kwaliteit
en kenmerkendheid. Hierdie tendens verklaar die toenemende wereldwye fokus op
afgebakende areas van oorsprong. Die integriteit van die afgebakende areas van
oorsprong sowel as hul verdedigbaarheid kan gewaarborg word deur terroirs as basis
vir afbakening te gebruik.
Die doelstellings van die studie was om die oorheersende omgewingseienskappe
wat wingerdprestasie en wynkarakter van twee belangrike cultivars, naamlik
Cabernet Sauvignon en Sauvignon blanc, in die Stellenbosch Wyn van
Oorsprongsdistrik bemvloed, te bepaal; tweedens om ‘n toepaslike metodologie te
gebruik om terroirs in die die distrik te bepaal wat gebaseer is op die geidentifiseerde
omgewingseienskappe met die gebruik van ‘n geografiese inligtingstelsel; en, ten
slotte, om hierdie terroirs vir wingerbou te gebruik om afgebakende areas van
oorsprong in dieselfde omgewing te identifiseer.
‘n Terroir kan gedefinieer word as ‘n samestelling van homogene
omgewingseenhede, of natuurlike terroir-eenhede (NTE), wat gebaseer word op die
kenmerkende eienskappe van die produkte wat daaruit verkry word. Identifisering en
karakterisering van terroirs sal afhang van kennis van die omgewingsparameters, die
funksionering van die wingerdstok en die eienskappe van die finale produk.
Veldstudies waaruit puntdata verkry word, is noodsaaklik om die funksionering van
die wingerdstok te ondersoek. Dit is egter noodsaaklik om eers hierdie inligting in
ruimtelike konteks te plaas alvorens die inligting vir soneringstudies gebruik kan
word.
As 'n eerste fase van datagenerering, was die Stellenbosch Wyn van
Oorsprongsdistrik gekarakteriseer en NTE’s geidentifiseer deur gebruik te maak van
bestaande digitale data en ‘n geografiese inligtingstelsel. ‘n NTE kan gedefinieer
word as ‘n landseenheid wat gekarakteriseer word deur ‘n relatiewe homogene
topografie, klimaat, geologiese substraat en grondtipe. ‘n Totaal van 1389 NTE’s is
geidentifiseer in die Stellenbosch Wyn van Oorsprongsdistrik (84 537 ha). Die
geidentifiseerde NTE’s was homogeen met betrekking tot die terrein morfologiese
eenheid, hoogte bo seespieSI, hellingsaspek en grondtipe. Elk van die
geidentifiseerde eenhede was verder beskryf volgens die omvang van die seewindinvloed
en, vir toepaslike grond tipes, die geassosieerde moedermateriaal.
As ‘n tweede fase van datagenerering is ‘n netwerk van persele van Cabernet
Sauvignon en Sauvignon blanc afgebaken binne bestaande kommersiele wingerde in
die nabyheid van weerstasies. Hul wingerd- en wynkundige respons is vir ‘n periode
van sewe jaar gemonitor.
Regressieboomanalises is gebruik om die volledige stel data te analiseer en om
die relatiewe belang van omgewings- en bestuurspraktykverbonde veranderlikes te bepaal. Die bostokkloon (wat 'n hoe relatiewe belang vir die trosmassa van
Sauvignon blanc en die oes- tot snoeimassa verhouding van Cabernet Sauvignon
het) is die enigste van die nie-omgewingsparameter wat ‘n sterk invloed op
wingerdprestasie of wynkarakter blyk te he. Die prestasie van Cabernet Sauvignon is
beTnvloed deur die kaliuminhoud van die ondergrond sowel as die seisoensklimaat.
By Sauvignon blanc het dit voorgekom of die prestasie verband hou met
grondtekstuur, windblootstelling en temperatuur tydens die groen fase van korrelgroei
sowel as die maand voor rypwording. Alhoewel dit blyk uit die resultate dat
omgewingsparameters 'n oorheersende invloed op die prestasie van beide Cabernet
Sauvignon en Sauvignon blanc uitoefen, reageer die twee cultivars verskillend op
omgewingsprikkels.
‘n Kennisgedrewe model waarvan die riglyne uit resultate van die
regressieboomanalise saamgestel is, word gebruik om NTE direk te klassifiseer ten
opsigte van die verwagte respons van Cabernet Sauvignon en Sauvignon blanc in
die Stellenbosch Wyn van Oorsprongsdistrik. Die NTE is dus gegroepeer om terroir
eenhede te vorm wat homogeen was ten opsigte van die verwagte wingerd- en
wynkundige respons vir elke cultivar.
Die gebruik van verwysingspersele om die respons van die wingerdstok teenoor
sy onmiddelike omgewing te bepaal, is tydrowend en duur en beperk sodoende
terroir studies tot navorsing. Gevolglik is ‘n opname onder wingerdbestuurders
gemaak om inligting oor die prestasie van Sauvignon blanc in die Stellenbosch Wyn
van Oorsprongsdistrik in te win en sodoende die nodige data te verkry. Na
vergelyking van die ingewinde data, wat uit die opname verkry is, met gemete data
vanaf kommersiele wingerde, kon afgelei word dat wingerdbestuurders by magte is
om die prestasie van wingerde ten opsigte van groeikrag, tekens van droogtestres en
opbrengs te karakteriseer. Elke wingerd is gekarteer en die respons is gekoppel aan
die gemodeleerde omgewingsparamters. Klassifikasie en regressiebome is gebruik
om besluitnemingsmodelle saam te stel wat toegepas kon word op omgewingsdata in
‘n geografiese inligtingstelsel om terroirs vir die produksie van Sauvignon blanc te
bepaal. Hierdie terroirs, alhoewel minder, was vergelykbaar met die wat gegenereer
was met behulp van veldstudies.
Data verkry met terroirstudies, sowel as gei'dentifiseerde terroir-eenhede, was
gebruik om die grense van die Stellenbosch Wyn van Oorsrongsdistrik en die
Simonsberg-Stellenbosch wyk te herbepaal. Voorgestelde modifiserings was
gebaseer op verwagte wyneienskappe. Grense vir twee nuwe wyke in die
Helderbergkom is voorgestel. Dit was ook moontlik om wingerde binne ‘n wyk te
identifiseer vir die produksie van terroir-spesifieke wyne.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50533 |
| Date | 04 1900 |
| Creators | Carey, Victoria Anne |
| Contributors | Archer, E., Barbeau, G., Saayman, D., Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology. Institute for Wine Biotechnology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 201 p. : ill. |
| Rights | Stellenbosch University |
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