Estratégias de curto prazo para mitigação das alterações climáticas na viticultura mediterrânica (ClimVineSafe)

In Portugalthe wine-grape sector has a crucial economic, social and cultural relevance, especially in many inland regions of the country. One of those is the Alto Douro Wine Region, which is the oldest viticultural legal region in the world (from 1756). The cultural landscape of the Alto Douro combines the monumental Nature of the Douro River valley, which has steep slopes, poor and uneven soils, with the ancestral action of the Humankind. This intimate relation allowed the creation of an ecosystem of unique value recognized in 2001 by UNESCO as World Heritage. This region produces the world famous Port Wine and other remarkably good table wines. In economic terms, Port Wine accounts for more than 60% of the total value of wine export and just about 12% of the national wine volume production (IVV 2008).

In recent decades the grapevine/wine sector has been modernized, creating strict regulations to guarantee wine characteristics. By developing environmentally friendly management practices and controlling winemaking technologies, a positive effect on the improvement of the productivity and wine quality has been felt. However, in the main viticultural areas, such as the Douro Region, plants are often subjected to periods of severe drought associated with strong light and high temperature. Consequently, the vineyard experiences irreparable damage. In general, the leaf surface tends to decrease by scorching the leaves most exposed to direct sunlight, while in the remaining leaves the production of photoassimilates decreases significantly. Thus, the clusters, a part too exposed to direct sunlight, import less photoassimilates, with negative impacts on their phenological potential. Due to global climate change, it is increasingly accepted that future summer conditions in the Mediterranean countries will experience an increase in aridity, exacerbating the negative effects mentioned above. At the vine-growing regions, particularly in the Demarcated Douro Region (RDD), where part of the territory is already at maximum resistance to stress, this effect may compromise the economic and social viability.

As summer stress mitigation practices, some farms have invested in irrigation. However, given the high natural limitations in water resources and the rugged topography of the region, the systems of water capitation and distribution in large scale involve high costs and are environmentally unsustainable. Therefore, without disregarding the importance that vine irrigation can have on improving vine performance, it is crucial to develop mitigation alternatives, not only in economic terms, but also in terms of grape quality and environmental sustainability. Among these mitigation alternatives, there has been a major effort undertaken by the scientific community to study the effect of inorganic substances in the improvement of light microclimate and water relations of leaves. For the grapevine, the information on this subject is scarce and often inconclusive, mainly due to the numerous environmental and cultural variables implicated.

This project proposes to firstly, develop a statistical model that projects the impacts of climate change on several grapevine and wine parameters in the RDD, using the outputs of regional atmospheric circulation models for this purpose (in accordance with the IPCC scenarios) in association with historical series of climatic elements recorded in the region. This study will enable understanding into how the wine sector should readjust itself, in the short and long-term, in order to minimize climate change impacts.

Secondly, the role of the Bordeaux mixture (BM), Kaolin (K) (protector agents of leaves during periods of strong light and heat) and Silicon (Si) (a beneficial micronutrient in the physiological induction of tolerance to summer stress) as a short-term mitigation action will be assessed. In a first trial, which must be conducted in potted vines, we aim at determining the most effective dose of BM, K and/or Si in function of vine water status and phenological stage. In a second trial, to be carried out on commercial farms with at least three of the finest grape cultivars for Port and Douro wines, we intend on using the formulations that showed the best results in the previous trial. These experiments will use methodologies that investigate grapevine physiology behaviour, yield components and grape composition.

The tasks proposed in this project have the potential to produce relevant scientific production. The atmospheric modeling approach applied to vine growing is innovative in the Douro Region, in Portugal and in the Iberian Peninsula. The proposed mitigation practices have the potential to be extended to other Mediterranean wine regions once their technical and economic feasibility has been refined and scientifically demonstrated. They are also cultural practices that, with little modifications, can be applied to other Mediterranean perennial crops, such as almond and olive trees.