A hierarchal terroir model for great lakes viticulture

Abstract

The terroir effect has been widely described as a hierarchy of many factors including those of climate, soil,  cultivar, and human influences.  Research into factors influencing the terroir effect in the Niagara Peninsula in Ontario, Canada using Chardonnay, Riesling, and Cabernet franc cultivars has concluded that there are substantial effects of bud hardiness (i.e. climate), soil texture, soil and vine water status, vine size, and crop load (i.e. human influence).  Observations in several Chardonnay vineyards (1998-2002) suggested that vine size was a major determinant of the terroir effect, insofar as high vine size zones were associated with high yields, berry weights, and titratable acidity.  In 2005-07 for ten Riesling vineyards, spatial variability of soil moisture and leaf water potential (ψ) were temporally stable within individual seasons as well as across seasons despite different weather patterns.  Low soil moisture and leaf ψ were consistently related to low yield, berry weight, vine size and high Brix and free/potential volatile terpenes (FVT/PVT).  Relationships between soil/vine water status and most metrics of vineyard performance were similar for Cabernet franc, and berry color, anthocyanins and phenols were associated with low soil/vine water status.  During 2010-12, twelve different vineyard blocks (six each of Riesling and Cabernet franc) were chosen to investigate the terroir of winter hardiness. Data were collected every 2 weeks during the growing season (soil moisture, leaf ψ), at harvest (yield components, berry composition), and three times during the winter (LT₅₀; the temperature at which 50 % of the buds die; bud death). Clear spatial trends were observed in each vineyard for soil moisture, leaf ψ, yield components, berry composition, and LT₅₀. GIS and statistical analysis revealed that both leaf ψ and berry weight could predict the LT₅₀ value, with strong positive correlations being observed between LT₅₀ and leaf ψ values in eight of the 12 vineyard blocks studied. In addition, vineyards in different appellations showed many similarities (Niagara Lakeshore, Lincoln Lakeshore, Four Mile Creek, Beamsville Bench). These results suggest that there is a spatial component to winter injury, as with other aspects of terroir.