Spatial variability in Ontario Riesling vineyards. II. Berry composition

Spatial variability of berry composition was studied over a 3-yr period in 10 Riesling vineyards in the Niagara Peninsula in Ontario. Vineyards were delineated using global positioning systems (GPS), and 75-80 sentinel vines were georeferenced within a sampling grid for data collection. During 2005-2007, vine water status measurements [leaf water potential (psi)] were collected biweekly from a subset of these sentinel vines. Data were collected on soil texture and composition, soil water content (SWC; %), leaf psi, and fruit composition. These variables were mapped using GIS software, and relationships between them were elucidated. Temporal stability in spatial patterns of soil texture and composition, SWC, leaf psi, soluble solids (Brix), titratable acidity, and monoterpenes were examined. Spatial trends in leaf psi and (or) SWC showed widespread evidence of temporal stability. Fruit composition variables were not as stable over a 3-yr period. Spatial trends in Brix were temporally stable in seven vineyards, free volatile terpenes were temporally stable in three vineyards, and potentially volatile terpenes were temporally stable in two vineyards. Consistent leaf psi zones were identified, and these were temporally stable despite different climatic conditions. Furthermore, some soil variables, and particularly vine water status, may contribute significantly to the terroir effect through their effects on vine size and fruit composition. For some vineyards, many viticulture and fruit composition variables were also temporally stable. There was evidence of strong spatial relationships between leaf psi and fruit composition, suggesting a strong relationship between berry composition and vine water status.