Viticulture and winemaking are important socioeconomic sectors in many European regions. Climate plays a vital role in the terroir of a given wine region, as it strongly controls canopy microclimate, vine growth, vine physiology, yield, and berry composition, which together determine wine attributes and typicity. New challenges are, however, predicted to arise from climate change, as grapevine cultivation is deeply dependent on weather and climate conditions. Changes in viticultural suitability over the last decades, for viticulture in general or the use of specific varieties, have already been reported for many wine regions. Despite spatially heterogeneous impacts, climate change is anticipated to exacerbate these recent trends on suitability for wine production. These shifts may reshape the geographical distribution of wine regions, while wine typicity may also be threatened in most cases. Changing climates will thereby urge for the implementation of timely, suitable, and cost-effective adaptation strategies, which should also be thoroughly planned and tuned to local conditions for an effective risk reduction. Although the potential of the different adaptation options is not yet fully investigated, deserving further research activities, their adoption will be of utmost relevance to maintain the socioeconomic and environmental sustainability of the highly valued viticulture and winemaking sector in Europe.

9 pagesInternational audienceBackground and Aims: Late frosts are a significant risk to grape production in frost-prone viticultural regions. Increasing air temperature because of climate change is likely to advance grape budburst and last frost events in spring. So far, it is unclear whether one trend will be more pronounced than the other, and hence, whether the risk of late frost damage will increase or decrease. The aim of this work was to investigate the future frost risk in the Luxembourgish winegrowing region by assessing the effect of simulated future climate conditions on the timing of budburst and last frost date. Methods and Results: Late frost risk was assessed by combining: (i) a phenological model for budburst of the grapevine (DORMPHOT); and (ii) ensemble-based projections of future air temperature. Analyses indicated that increasing spring temperature will advance the timing of budburst and the date of the last frost. This advancement, however, will be more pronounced for last frost events than for budburst. Conclusions: Modelled projections showed that the frequency of spring frost damage in the Luxembourgish winegrowing region will decrease, without completely excluding them for the near (2021-2050) or the far future (2069-2098). Significance of the Study: The application of a combination of a phenological model for grape budburst and ensemble-based projections of future air temperature enables the assessment of the future late frost risk in a frost-prone viticulture region

Extreme heat events or heatwaves can be particularly harmful to grapevines, posing a major challenge to winegrowers in Europe. The present study is focused on the application of the crop model STICS to assess the potential impacts of heatwaves over some of the most renowned winemaking regions in Europe. For this purpose, STICS was applied to grapevines, using high-resolution weather, soil and terrain datasets from 1986 to 2015. To assess the impact of heatwaves, the weather dataset was artificially modified, generating periods with anomalously high temperatures (+5 °C), at specific onset dates and with specific episode durations (from five to nine days). The model was then run with this modified weather dataset, and the results were compared to the original unmodified runs. The results show that heatwaves can have a very strong impact on grapevine yields. However, these impacts strongly depend on the onset dates and duration of the heatwaves. The highest negative impacts may result in a decrease in the yield by up to −35% in some regions. The results show that regions with a peak vulnerability on 1 August will be more negatively impacted than other regions. Furthermore, the geographical representation of yield reduction hints at a latitudinal gradient in the heatwave impact, indicating stronger reductions in the cooler regions of Central Europe than in the warmer regions of Southern Europe. Despite some uncertainties inherent to the current modelling assessment, the present study highlights the negative impacts of heatwaves on viticultural yields in Europe, which is critical information for stakeholders within the winemaking sector for planning suitable adaptation measures.

Common cumulative degree day models used to forecast grape growth stages often are only of local validity, restricted to a limited number of phenological stages, or do not take into consideration that the forcing effect of temperature is limited at higher temperatures. A new model was developed to simulate all 26 phenological stages (according to the BBCH scheme; Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) of Vitis vinifera L. Müller-Thurgau between budburst and harvest. Sixty time series of grape phenology from four European countries were used to set up and validate the model. Three cumulative degree day models (starting with budburst: BBCH 09) with one, two, or three optimized temperature threshold values were compared. The incorporation of an upper threshold temperature, above which a further increase of the temperature will not accelerate plant development, and of a heat threshold, above which a further increase of the temperature leads to a development deceleration, significantly improved the accuracy of the model compared to previous cumulative degree day approaches. The threshold triplet 5ºC, 20ºC, and 22ºC for lower (base), upper, and heat threshold temperature, respectively, allowed the most precise forecast. In 70.5 or 95.8% of the cases, phenological stages were correctly predicted in 3 or 7 days (assuming daily mean temperatures of 20ºC), respectively, around the predicted cumulative degree day. The model can be used for a range of applications in viticultural research and practical viticulture and could further be parameterized for other varieties.

Aim: Grape (Vitis vinifera L.) phenology is mainly temperature-driven. Consequently, the shift in thermal conditions due to climate change is supposed to have a distinct influence on grape phenology, grape maturity and wine typicity. This study aims to investigate (i) the future phenological development, as well as (ii) the consequences on the temperature conditions in specific phenophases under the conditions of the Luxembourg grapegrowing region.Methods and Results: A budburst model and a phenological model were combined with an ensemble of ten regional climate change projections for Luxembourg. Analyses comparing four 30-year time spans (reference period: 1971-2000; present: 2001-2030; near future: 2031-2060; far future: 2061-2090) demonstrated that each of the 27 phenological stages according to BBCH code is projected to be reached significantly earlier than in the reference period. According to these projections, the length of phenophases at the early stages is not affected, whereas the ripening period length is significantly shortened. The air temperature increase in the ripening period (far future compared to reference period: + 4.6 °C to + 5.3 °C) is projected to be markedly higher than in the annual averages (+ 2.6 °C).Conclusions: Since (i) air temperatures are generally projected to increase in the future and (ii) the ripening period will take place earlier (usually in the warmer parts of the season), climate change is implicating a two-fold impact on air temperature increase in the ripening period.Significance and impact of the study: This two-fold impact potentially threatens the wine typicity of the traditional grapegrowing regions and therefore calls for specific adaptation strategies.