The Relationship Between Terroir and The Phenology of Barossa Shiraz

ABSTRACTBackground and AimsVine phenology results from the interaction between the genotype, environment and management, with implications for fruit, and wine composition. The impact of weather, site and management practices, underlying elements of terroir, impacting the timing of key phenological stages were explored across the Barossa Zone (GI).Methods and ResultsVine phenology was assessed in three zones of 24 vineyards over three vintages using the E-L scale before veraison, and total soluble sugars (TSS) in berries during ripening. We explored the associations between weather, plant traits and viticultural variables, and development in four periods: pre-budburst, budburst-flowering, flowering-veraison and veraison-maturity. The spatial structure of the timing of phenological events suggested three main groups of vineyards. This structure followed gradients in topography and soils across the landscape, and were maintained despite the effect of the season (vintage). On average, differences between early and late groups of vineyards were 13 days at budburst, 20 days at flowering and 24 days at TSS = 24 °Brix. Phenology responded mainly to temperature until flowering, and to temperature and canopy size from flowering to maturity. The strength of the relationship between the duration of the period and temperature ranked pre-budburst (r2= 0.94) > budburst-flowering (r2= 0.40) > veraison-maturity (r2= 0.17). Duration of pre-budburst and budburst-flowering periods was shortened at 6 d °C-1, compared to 2 d °C-1for veraison-maturity. The duration from veraison to maturity increased with yield (r2= 0.29,Pa< 0.0001).ConclusionsThe spatial variation in development was maintained despite vintage effects and management practices. Variation in temperature due to topography and elevation were the major drivers of vine phenological development until flowering. During ripening, development was driven by temperature and carbon capture and partitioning.Significance of the StudyThis is the first attempt to show spatial variability on phenology across the Barossa Valley GI. The observed switch on drivers on phenology during development from temperature-driven processed before flowering to resource-dominated processes during ripening have implications for modelling and vineyard management.