Pinot noir yield prediction in a variable cool climate

Tasmania, located in southern Australia, has a very cool and variable climate with vineyards located in areas with mean January temperature (MJT) ranging from 14.5 to 16.5 °C and annual rainfall ranging between 450 mm and 1050 mm. Climate-induced variability in yield, for key varieties grown in Tasmania can vary between 3.5 and 10.0 tonnes per hectare. Preliminary analysis of Pinot Noir and Chardonnay over an eleven-year period (1990-2000), found that climate events played an important role at recognised periods of sensitivity in the grapevine growth cycle. The objective of this preliminary study was to explore relationships and build a data set to enable the development of a yield prediction model for cool, and inherently variable, climates. Vine reserve analysis was conducted in an attempt to better predict yield. A block of spur pruned MV6 Pinot Noir was monitored for two seasons and yield, yield components and vine reserves measured and weather data collected. Principal component analysis (PCA) showed negative associations between yield and vine starch reserves, and yield and rainfall. Strong positive associations were observed between yield component data and temperature and rainfall at flowering and degree days but not with rainfall during initiation and throughout the growing season. This study advances our understanding of the role of vine reserves that will ultimately lead to the development of a robust yield prediction model for cool climate viticulture.