[Show abstract][Hide abstract] ABSTRACT: Wine production is strongly affected by weather and climate and thus highly vulnerable
to climate change. In Portugal, viticulture and wine production are an important
economic activity. In the present study, current bioclimatic zoning in Portugal (1950-
2000) and its projected changes under future climate conditions (2041-2070) are
assessed through the analysis of an aggregated, categorized bioclimatic index (CatI) at
a very high spatial resolution (near 1 km). CatI incorporates the most relevant
bioclimatic characteristics of a given region, thus allowing the direct comparison
between different regions. Future viticultural zoning is achieved using data from 13
climate model transient experiments following the A1B emission scenario. This data is
downscaled using a two-step method of spatial pattern downscaling. This downscaling
approach allows characterizing mesoclimatic influences on viticulture throughout
Portugal. Results for the recent past depict the current spatial variability of Portuguese
viticultural regions. Under future climate conditions, the current viticultural zoning is
projected to undergo significant changes, which may represent important challenges
for the Portuguese winemaking sector. The changes are quite robust across the
different climate models. A lower bioclimatic diversity is also projected, resulting from a
more homogeneous warm and dry climate in most of the wine regions. This will lead to
changes in varietal suitability and wine characteristics of each region.
Full-text · Article · Feb 2014 · Regional Environmental Change
[Show abstract][Hide abstract] ABSTRACT: In Douro Region (Northeast Portugal) grapevines are often exposed to severe water stress in the summer. During 11 years (2002 - 2012) a study was conducted in a commercial vineyard with cv. Touriga Nacional x 196-17 growing under three water regimes, non-irrigated (NI) and two irrigation strategies (WR1-30% ETc and WR2-60% ETc). The site has a Mediterranean-type climate with average annual rainfall of 560 mm. The water application starts when the predawn leaf water potential (Ψpd) reach the value of -0.3MPa (late June / mid-July according the years), and stop near 2 weeks before the harvest. Leaf gas exchange and chlorophyll fluorescence measurements were performed only in2009 and 2011. Berry ripening was followed weekly, and at harvest, yield, vigour, pruning weight per vine was determined in 20 samples, and fruit composition using a 200 berry samples, for analysis of soluble solids, pH, titratable acidity, phenols and total anthocyanin’s.Results showsthat predawn leaf water potential reached several times values below -1.2 MPa, with negative consequences in the photosynthetic productivity. Both irrigation levels had a positive significant effect on leaf gas exchange, yield, shoot weight and berry weight, with an increase in sugar content and a reduction in acidity, while no significant effects were registered on pH, phenols or anthocyanin’s. Thresholds in predawn water potential for monitoring deficit irrigation strategies can be oriented between the values -0.4 MPa ≥ Ψpd ≥ -0.6 MPa between veraison and harvest.
[Show abstract][Hide abstract] ABSTRACT: The Douro Region is located in Northeast Portugal, within the Douro river basin, surrounded by craggy mountains that confer it characteristic Mediterranean-likeclimate. This region spreads over a total area of approximately 250,000 ha, of which 45,000 are under vine, and it is divided into three sub-regions: Baixo Corgo (BC), Cima Corgo (CC) and Douro Superior (DS). The westernmost BC is the smallest region and
it gets the most rainfall. The easternmost DS is the largest of the three sub-regions and it is the most arid region. Especially in this region, grapevine cultivars are exposed to conditions of severe water stress during the summer period, which strongly affects their behavior. In order to mitigate these effects, vine growers introduced the irrigation in their vineyards. However, given the multiple characteristics of the topography, soil,
variety and rootstocks and the water resources scarcity, the knowledge of the amount and frequency of the irrigation has been one of the most pertinent issues in the region.
The use of expedite methodologies to assess the water status is essential for vine growers in the near future. The study was conducted between 2002 and 2010, in a commercial vineyard with cultivar Touriga Nacional at Qtª dos Aciprestes (CC and DS interface), growing under 3 water availability regimes: non-irrigated and irrigated (60% and 30%) of the potential evapotranspiration. In this study were used methodologies to
evaluate the leaf and stem water potential and the yield and quality parameters. In several years the photosynthetic productivity was also determined. The main results showed that grapevines experienced a severe water stress with levels of water potential below of the general references. On the other hand, the predawn water potential was confirmed as a powerful tool to evaluate inter and inter-annual variations
in grapevine behavior. Also, high levels of irrigation had a strong impact in yield, while a moderate irrigation increased sugar and in some years the anthocyanins contents.
[Show abstract][Hide abstract] ABSTRACT: The water status of vines is one of the main factors which influence the quality of grapes and wines. Climate change, with an increase of mean temperatures and evapotranspiration, generates an important drought during the vegetative cycle induced by a strong and early water deficit, principally in southern Europe. This situation calls for an evolutionary adaptation of cultural practices and therefore, irrigation is increasingly used to avoid the serious problems of yield and quality decrease of the grape harvest. According to the above, during the 2010 season a trial was conducted in the Douro Region in order to implement an irrigation strategy to control water status in a Touriga Nacional vineyard with a qualitative objective. Two situations were compared: an irrigated treatment (I) with a non-irrigated control (NI). The I vines were irrigated with frequencies and water amounts varying in accordance to measurements of predawn leaf water potential (Ψpd) in order to maintain plants water status complying to values of Ψpd ≥ -0,4 MPa during the period between flowering and veraison (f-v), and -0,4 MPa ≥ Ψpd ≥ -0,6 MPa between veraison and harvest (v-h). These thresholds were chosen according to literature and previous experience of the working group. Ψpd was measured weekly during the growing period and water was applied to the soil by drip irrigation. At harvest, sugar, pH, total acidity, anthocyanins, anthocyanin extraction index and berry weight were analyzed. Results showed that in order to keep water status of I plants on the desired threshold, was necessary to apply a total of 60 mm of water during the season (20 mm in f-v period and 40 mm during v-h period) distributed in 10 times (4 during f-v and 6 in v-h ) with water quantities varying between 4 and 8 mm each. The average Ψpd values of I plants were -0,29 MPa in f-v period and -0,37MPa in v-h, while Ψpd values of NI plants were significantly lower (-0,44MPa in f-v and -0,74 MPa in v-h, considered as a strong water stress). At harvest date, anthocyanin content and their extraction rate were significantly higher in irrigated plants (+32% and +35% respectively more than the control), and there were no differences in other parameters analyzed. This study shows that excessive water stress, usual in many vineyards of Douro region, can affect the quality of grapes and wine of Touriga Nacional vines, and a well-timed irrigation, based on accurate and reliable methods to avoid excesses, allows for optimizing water usage, while improving the vineyard’s performance.