Abstract:
The major focus of this dissertation was to explain terroir effects that impact wine
varietal character and to elucidate potential determinants of terroir by testing vine water
status (VWS) as the major factor of the terroir effect. It was hypothesized that consistent
water status zones could be identified within vineyard sites, and, that differences in vine
performance, fruit composition and wine sensory attributes could be related to VWS. To
test this hypothesis, ten commercial Riesling vineyards representative of each Vintners
Quality Alliance sub-appellation were selected. Vineyards were delineated using global
positioning systems and 75 to 80 sentinel vines per vineyard were geo-referenced for data
collection. During the 2005 to 2007 growing seasons, VWS measurements [midday leaf
water potential ('l')] were collected from a subset of these sentinel vines. Data were
collected on soil texture and composition, soil moisture, vine performance (yield
components, vine size) and fruit composition. These variables were mapped using global
information system (GIS) software and relationships between them were elucidated.
Vines were categorized into "low" and "high" water status regions within each vineyard
block and replicate wines were made from each. Many geospatial patterns and
relationships were spatially and temporally stable within vineyards. Leaf'l' was
temporally stable within vineyards despite different weather conditions during each
growing season. Generally, spatial relationships between 'l', soil moisture, vine size,
berry weight and yield were stable from year to year. Leaf", impacted fruit composition
in several vineyards. Through sorting tasks and multidimensional scaling, wines of
similar VWS had similar sensory properties. Descriptive analysis further indicated that
VWS impacted wine sensory profiles, with similar attributes being different for wines
from different water status zones. Vineyard designation had an effect on wine profiles,
with certain sensory and chemical attributes being associated from different subappellations.
However, wines were generally grouped in terms of their regional
designation ('Lakeshore', 'Bench', 'Plains') within the Niagara Peninsula. Through
multivariate analyses, specific sensory attributes, viticulture and chemical variables were
associated with wines of different VWS. Vine water status was a major contributor to the
terroir effect, as it had a major impact on vine size, berry weight and wine sensory characteristics.
