WITHIN VINEYARD LANDSCAPE CONTROLS ON TEMPERATURE STRUCTURE AND VARIETAL RIPENING POTENTIAL IN THE UMPQUA VALLEY OF OREGON

Climate influences viticulture and wine production at various scales with the majority of attention given to regional characteristics that define the general varieties that can be grown and the wine styles that can be produced. However, within vineyard scale effects of climate can be substantial due to the control that landscape variations have on solar radiation and airflow. To better understand the effect of local weather and climate on terroir, the goal of this research was to examine within vineyard temperature variations. Temperature data was collected from 23 sites in a commercial 33 ha vineyard in the Umpqua Valley of Oregon over a five-year period during 2011-2016. Dormant period temperatures (Nov-Mar) varied by roughly 1°C across the 23 sites with the extreme minimum temperatures varying by just over 3°C. Spring temperatures (Apr-May) varied by roughly 2°C for the vineyard locations with frost occurrence varying as much as nine days in most years. During the summer (Jun-Aug) maximum temperatures varied more than minimum temperatures across the sites, while extreme maximums ranged nearly 5°C. During the ripening period (Sept-Oct) diurnal temperature ranges at the 23 sites averaged 20°C. Over all years and sites within the vineyard, the growing season heat accumulation averaged 1467 GDD but ranged from 1181 in the coolest year (2011) to 1705 in the warmest year (2015). The average range of GDD during these vintages shows that within vineyard variability in heat accumulation is 375 GDD. These variations in temperatures and heat accumulation are weakly correlated with elevation differences between the sites, however the combined effects of slope/aspect have more significant correlations with temperatures at these sites, especially minimum temperatures. As a result of the within vineyard differences in temperatures and heat accumulation, this commercial vineyard adequately ripens a range of cool to warm climate varieties including Albariño, Tempranillo, Viognier, Grenache, Syrah, Touriga Nacional, and others.