Helder Fraga

Future scenarios for viticultural zoning in Europe: ensemble projections and uncertainties

Optimum climate conditions for grapevine growth are limited geographically and may be further challenged by a changing climate. Due to the importance of the winemaking sector in Europe, the assessment of future scenarios for European viticulture is of foremost relevance. A 16-member ensemble of model transient experiments (generated by the ENSEMBLES project) under a greenhouse gas emission scenario and for two future periods (2011–2040 and 2041–2070) is used in assessing climate change projections for six viticultural zoning indices. After model data calibration/validation using an observational gridded daily dataset, changes in their ensemble means and inter-annual variability are discussed, also taking into account the model uncertainties. Over southern Europe, the projected warming combined with severe dryness in the growing season is expected to have detrimental impacts on the grapevine development and wine quality, requiring measures to cope with heat and water stress. Furthermore, the expected warming and the maintenance of moderately wet growing seasons over most of the central European winemaking regions may require a selection of new grapevine varieties, as well as an enhancement of pest/disease control. New winemaking regions may arise over northern Europe and high altitude areas, when considering climatic factors only. An enhanced inter-annual variability is also projected over most of Europe. All these future changes pose new challenges for the European winemaking sector.

Understanding climate change projections for precipitation over western Europe with a weather typing approach

Precipitation over western Europe (WE) is projected to increase (decrease) roughly northward (equatorward) of 50°N during the 21st century. These changes are generally attributed to alterations in the regional large-scale circulation, e.g., jet stream, cyclone activity, and blocking frequencies. A novel weather typing within the sector (30°W–10°E, 25–70°N) is used for a more comprehensive dynamical interpretation of precipitation changes. A k-means clustering on daily mean sea level pressure was undertaken for ERA-Interim reanalysis (1979–2014). Eight weather types are identified: S1, S2, S3 (summertime types), W1, W2, W3 (wintertime types), B1, and B2 (blocking-like types). Their distinctive dynamical characteristics allow identifying the main large-scale precipitation-driving mechanisms. Simulations with 22 Coupled Model Intercomparison Project 5 models for recent climate conditions show biases in reproducing the observed seasonality of weather types. In particular, an overestimation of weather type frequencies associated with zonal airflow is identified. Considering projections following the (Representative Concentration Pathways) RCP8.5 scenario over 2071–2100, the frequencies of the three driest types (S1, B2, and W3) are projected to increase (mainly S1, +4%) in detriment of the rainiest types, particularly W1 (−3%). These changes explain most of the precipitation projections over WE. However, a weather type-independent background signal is identified (increase/decrease in precipitation over northern/southern WE), suggesting modifications in precipitation-generating processes and/or model inability to accurately simulate these processes. Despite these caveats in the precipitation scenarios for WE, which must be duly taken into account, our approach permits a better understanding of the projected trends for precipitation over WE.

Integrated Analysis of Climate, Soil, Topography and Vegetative Growth in Iberian Viticultural Regions

The Iberian viticultural regions are convened according to the Denomination of Origin (DO) and present different climates, soils, topography and management practices. All these elements influence the vegetative growth of different varieties throughout the peninsula, and are tied to grape quality and wine type. In the current study, an integrated analysis of climate, soil, topography and vegetative growth was performed for the Iberian DO regions, using state-of-the-art datasets. For climatic assessment, a categorized index, accounting for phenological/thermal development, water availability and grape ripening conditions was computed. Soil textural classes were established to distinguish soil types. Elevation and aspect (orientation) were also taken into account, as the leading topographic elements. A spectral vegetation index was used to assess grapevine vegetative growth and an integrated analysis of all variables was performed. The results showed that the integrated climate-soil-topography influence on vine performance is evident. Most Iberian vineyards are grown in temperate dry climates with loamy soils, presenting low vegetative growth. Vineyards in temperate humid conditions tend to show higher vegetative growth. Conversely, in cooler/warmer climates, lower vigour vineyards prevail and other factors, such as soil type and precipitation acquire more important roles in driving vigour. Vines in prevailing loamy soils are grown over a wide climatic diversity, suggesting that precipitation is the primary factor influencing vigour. The present assessment of terroir characteristics allows direct comparison among wine regions and may have great value to viticulturists, particularly under a changing climate.

Statistical modelling of grapevine phenology in Portuguese wine regions: observed trends and climate change projections

Phenological models are considered key tools for the short-term planning of viticultural activities and long-term impact assessment of climate change. In the present study, statistical phenological models were developed for budburst (BUD), flowering (FLO) and veraison (VER) of 16 grapevine varieties (autochthonous and international) from the Portuguese wine-making regions of Douro, Lisbon and Vinhos Verdes. For model calibration, monthly averages of daily minimum (Tmin), maximum (Tmax) and mean (Tmean) temperatures were selected as potential regressors by a stepwise methodology. Significant predictors included Tmin in January–February–March for BUD, Tmax in March–April for FLO, and Tmin, Tmax and Tmean in March–July for VER. Developed models showed a high degree of accuracy after validation, representing 0·71 of total variance for BUD, 0·83 for FLO and 0·78 for VER. Model errors were in most cases

Modeling Phenology, Water Status, and Yield Components of Three Portuguese Grapevines Using the STICS Crop Model

Viticulture plays a key role in Portuguese economic growth. The possibility of obtaining early predictions of viticultural parameters, such as phenology, water status, yield, and potential wine characteristics, are of great value for growers and will influence the viticultural chain. The present study is a first approach to adapt the Simulateur mulTIdisciplinaire pour les Cultures Standard (STICS), a dynamic crop model, to Portuguese winegrowing conditions and grapevine varieties. Several site-specific parameters for climate, soil, and management practices were assessed. Varietal-specific parameters were measured from vineyards in the Douro and Lisboa winegrowing regions of Portugal. Three of the most important varieties in the country (Aragonez, Touriga-Franca, and Touriga-Nacional) were targeted for model calibration. Overall, the STICS crop model was successful in simulating yield, phenological stages, and water stress, but not alcohol content. The relatively high model accuracy will improve the performance of vineyard operations and winemaking practices, such as organizing harvests, vineyard intervention scheduling, irrigation procedures, and strategic planning of wineries. STICS may be feasible as a decision support tool for short- and long-term strategic planning in Portuguese viticulture, particularly taking into account the projected impacts of climate change. The efficiency gains obtained from the use of this crop model by wine industry stakeholders is expected to increase the competitiveness and sustainability of the wine sector in Portugal.

Examining the relationship between the Enhanced Vegetation Index and grapevine phenology

Abstract Monitoring the main grapevine phenological stages is a key procedure for optimizing vineyard activities and improving yield and quality attributes. Remote sensing may be an effective and practical monitoring tool, as data from on-board satellite sensors can measure vegetative growth. In the current study, a 12-year time series of four main phenophases (budburst, flowering, veraison and harvest) were obtained from an experimental vineyard located in Lisbon (Portugal). LANDSAT surface reflectances were used to calculate the Enhanced Vegetation Index (EVI) and derived metrics. Both time series were then analysed. Results show statistically significant relationships between vegetation metrics and phenological timings and intervals, such as the linkage between the peak greenness and flowering/veraison. The current study highlights the applicability of remote sensing to monitor grapevine phenology in both retrospective and real-time, bringing an added-value to the winemaking sector.

Daily prediction of seasonal grapevine production in the Douro wine region based on favourable meteorological conditions

Background and Aims The cooperative wineries of the Douro demarcated region (DDR) have a major socio-economic role within the winemaking sector. The existing network of regional wineries provides an organisational basis for the wine market of the DDR, contributing to the sustainability of the sector. Given this strategic importance, the present research aims to develop an innovative grape production model (PGP) targeted at regional wineries. Methods and Results For the development of the PGP model, the relationships between daily historic meteorological conditions and grape production for three wineries within the DDR (Mesao Frio, Favaios and Freixo de Espada a Cinta) were analysed. The model runs on a daily time step, comparing the thermal/hydric conditions in a given year against the average conditions in high and low production years. Results establish site-specific linkages between favourable (unfavourable) weather conditions and high (low) grapevine production. Relatively, cool pre-flowering temperature and relatively warm conditions during berry development tend to favour wine production. Furthermore, higher production is typically found in years with higher than average precipitation level until flowering. The correlation between PGP model outputs and grapevine production at the three wineries ranges from 0.68 ≤ r ≤ 0.84. Conclusions Decision makers from the DDR may indeed take advantage of the information provided by the PGP model. Daily updated knowledge of potential grape production enables wineries to timely plan and optimise harvest and postharvest procedures. Significance of the Study The PGP model may be regarded as a useful tool to implement cost-effective winery management, thus bringing added value to stakeholders and decision makers of the Portuguese winemaking sector.

Improvement of grapevine physiology and yield under summer stress by kaolin-foliar application: water relations, photosynthesis and oxidative damage

Knowledge about short-term climate change adaptation strategies for Mediterranean vineyards is needed in order to improve grapevine physiology and yield-quality attributes. We investigated effects of kaolin-particle film suspension on water relations, photosynthesis and oxidative stress of field-grown grapevines in the Douro region (northern Portugal) in 2012 and 2013. Kaolin suspension decreased leaf temperature by 18% and increased leaf water potential (up to 40.7% in 2013). Maximum photochemical quantum efficiency of PSII was higher and the minimal chlorophyll fluorescence was lower in the plants sprayed by kaolin. Two months after application, net photosynthesis and stomatal conductance at midday increased by 58.7 and 28.4%, respectively, in treated plants. In the same period, kaolin treatment increased photochemical reflectance, photosynthetic pigments, soluble proteins, soluble sugars, and starch concentrations, while decreased total phenols and thiobarbituric acid-reactive substances. Kaolin application can be an operational tool to alleviate summer stresses, which ameliorates grapevine physiology and consequently leads to a higher yield.

Modelling climate change impacts on early and late harvest grassland systems in Portugal

Abstract. Climate change projections for Portugal showed warming and drying trends, representing a substantial threat for the sustainability of forage production in perennial grassland. The objective of the present study was to assess climate change impacts on seasonal dry matter yield (DMY) in three locations (North-west-, Central-inner and South-Portugal) with different climatic conditions, for two grassland production systems deviating in growing season length, either early cuts in spring (ES) or late cuts in summer (LS). Impacts were estimated using the STICS (Simulateur mulTIdisciplinaire pour les Cultures Standard) crop model, by comparing a historical baseline period (1985–2006) with simulated projections over future periods (2021–2080). For this purpose, the STICS crop model was driven by high-resolution climate data from a coupled Global Climate Model/Regional Climate Model chain. As a result, we obtained that, during the baseline period, DMY of LS was consistently much higher than that of ES in all three locations. For LS, significant reductions in mean DMY were forecasted during 2061–2080, ranging from mild (–13%) in the north to severe (–31%) in the south of Portugal. In contrast, seasonal DMY was largely maintained for ES among sites until 2080, benefiting from low water deficits, the expected atmospheric CO2 rise and the forecasted temperature increase during cool season. Thus, the yield gap was projected to gradually decrease between the two regimes, in which mean DMY for ES was foreseen to exceed that of LS over 2061–2080 in the southern site. Moreover, ES was projected to have very low exposure to extreme heat and severe water stresses. Conversely, LS, subjected to high summer water deficit and irrigation needs, was projected to experience increased summertime water stress (9–11%) and drastically increased heat stress (33–57%) in 2061–2080, with more pronounced heat stress occurring in the south. Frequency of occurrence of extreme heat stress was projected to gradually increase in summer over successive study periods, with a concomitant increased intensity of DMY response to inter-annual variability of heat stress during 2061–2080. Heat stress tended to be more important than water stress under the prescribed irrigation strategy for LS, potentially being the main limiting factor for summertime DMY production under climate change scenario.