Temperature variability inside a wine production area and its effect on vine phenology and grape ripening. An example from the Saint-Emilion-Pomerol

Abstract

AIM: the aim of this study was to develop a method for fine-scale temperature zoning. The effect of temperature variability on vine phenology and grape composition was assessed in the production area of Saint-Emilion, Pomerol and their satellite appellations (Bordeaux, France).

METHODS: 90 temperature sensors were set up inside the vine canopy over an area of 19,233 ha, including 12,200 ha of vineyards. Hourly temperatures were recorded from 2012-2018. Vine phenology and grape ripening were monitiorred on 60 plots, close to temperature sensors. Vine water and nitrogen status were assessed by measuring, respectively, δ13C and yeast available nitrogen on grape must.

RESULTS: A spatial model, based on temperatures recorded by the sensors and environmental co-variables derived friom a digital elevation model, was developped to produce daily temperature maps over the study area. The effect of temperature on vine physiology was assessed. Significant variability was observed over the area for budbreak (19 days), flowering (9 days), véraison (13 days) and sugar ripeness (25 days). Sugar/acid ratio increased with higher temperatures and water deficit and decreased with higher vine nitrogen status.

CONCLUSIONS: A methodology was developped for fine scale temperature mapping inside a wine production area. The effect of temperature was assessed on vine development and grape ripening. This study shows that temperature variability is one of the major drivers of the terroir effect.