Browsing by Author "Silvestre, J."
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- Can soil water content be used as a predictor of predawn leaf water potential for deficit irrigation scheduling? A case study at Alentejo wine regionPublication . Egipto, R.; Costa, J. M.; Silvestre, J.; Chaves, M.M.; Lopes, C. M.Context and purpose of the study: Water and heat stress impose new challenges to irrigation management in the Mediterranean areas. This reality has a major impact on the vineyard ecosystem, particularly on the scarce water resources of the Alentejo region (South Portugal). To mitigate this problem, irrigation management should focus on optimizing yield and fruit quality per volume of water applied. This work aims to discuss the use of predawn leaf water potential and soil water status relationships as a decision tool for irrigation management taking as basis data from a field trial where two deficit irrigation strategies were compared
- Economic growth and individual satisfaction in an agent-based economyPublication . Silvestre, J.; Araújo, Tanya; St. Aubyn, MiguelMacro and micro-economic perspectives are combined in an eco- nomic growth model. An agent-based modeling approach is used to develop an overlapping generation framework where endogenous growth is supported by work- ers that decide to study depending on their relative (skilled and unskilled) indi- vidual satisfaction. The micro perspective is based on individual satisfaction: an utility function computed from the variation of the relative income in both space and time. The macro perspective emerges from micro decisions, and, as in other growth models of this type, concerns an important allocative social decision the share of the working population that is engaged in producing ideas (skilled work- ers). Simulations show that production and satisfaction levels are higher when the evolution of income measured in both space and time are equally weighted.
- A fito-monitorização como ferramenta de apoio à gestão da rega deficitária na vinha - estudo de caso no AlentejoPublication . Egipto, R.; Barriguinha, A.; Silvestre, J.; Carvalho, N.; Neto, M.; Costa, M.; Lopes, C.M.Na produção de uvas para vinhos tintos é reconhecida a importância da obtenção de um stresse hídrico moderado de forma a permitir um balanço equilibrado entre crescimento vegetativo e reprodutivo e, consequentemente, bons rendimentos de elevada qualidade. Em vinhas regadas, a obtenção deste stresse moderado e sua correcta adequação à fase fenológica da videira, exige uma gestão cuidada das designadas “Estratégias de Rega Deficitária” para a qual é necessário conhecer, em tempo real, o maior número possível de indicadores, desde os indicadores ambientais (variáveis climáticas e teor de humidade do solo) aos indicadores da planta (aparência da vegetação e indicadores fisiológicos). No âmbito do projecto europeu Innovine (FP7/2007- 2013, nº 311775) a empresa Agri-Ciência, em colaboração com o ISA e ITQB, desenvolveu um sistema de monitorização, integração e análise dinâmica e em tempo real de dados obtidos de fontes diversas (clima, solo e planta). Várias ilhas de sensores foram instaladas numa vinha da Herdade do Esporão, em Reguengos de Monsaraz, num ensaio de avaliação do impacto de duas estratégias de rega deficitária em duas castas tintas (Touriga Nacional e Aragonez). Foi desenvolvido um painel digital “dashboard”, para recolha, processamento, análise e disponibilização da informação quer referente às ilhas de sensores quer aos dados da estação meteorológica, permitindo visualizar e manipular os dados recolhidos em tempo real. O conjunto de dados obtidos foi utilizado para estudo das relações entre as variáveis ambientais (clima e solo) e parâmetros fisiológicos (potencial hídrico foliar e temperatura da folha e bagos) de forma a gerar indicadores/ modelos passíveis de serem integrados num sistema de apoio à decisão para condução da rega deficitária da vinha. Neste trabalho apresentam-se e discutem-se algumas das relações encontradas
- Phloem carbon isotopic signature as a valuable tool to assess physiological adjustments among European grapevine varieties under a Mediterranean climatePublication . Jacinto, J.; Jesus, J.G.; Damásio, M.; Silvestre, J.; Máguas, C.; Antunes, Victor A. C.Wine production is being threatened by climate change, particularly in the Mediterranean region. Thus, more knowledge on vineyards’ well-functioning and adjustments to drought conditions is essential. We aimed to understand how grapevine varieties from different European origins, under the same climatic context, respond to water stress and whether the climatic origin plays a role in their water-use efficiency (WUE). With that in mind, we assessed the carbon isotopic signatures (δ13C) in berry juice and phloem of 172 white and red grapevine varieties grown in Herdade do Esporão (Alentejo, Portugal) from five different climatic origins in two different rainfed water treatments: with full and no irrigation. Our findings indicate that there is a 13C enrichment in both berry juice and phloem under water stress, regardless of the climatic origin of the grapevine varieties. This suggests that the plants exhibited greater stomatal regulation and tighter control over water loss during drought conditions. Also, we found a positive correlation between berry juice and phloem δ13C signatures that is maintained under limited water conditions (i.e., non-irrigated rainfed condition: NI-rf). Six clusters, based on δ13C patterns in NI-rf, were obtained and the varieties that showed the higher WUE listed. The patterns of δ13C drought-adjustments (differences among water-treatments) were dependent on specific varieties capacity to acclimate, and the varieties that were grouped as the ones with high WUE in NI-rf also showed greater δ13C drought-adjustments. These results highlight a range of WUE adjustments, revealed through phloem isotopic analysis, being phloem δ13C signature a complementary and promising proxy to assess grapevine varieties’ drought acclimation capacity. Our study reinforces vineyard plasticity and great adaptative ability, transversal to several grapevine varieties with different climatic origins. The results provided might be a complementary support to identify the varieties that are potentially more physiologically equipped under drought, and to further explore their vitality and grape quality under sustainable water-management scenarios.
- The impact of the winery's wastewater treatment system on the winery water footprintPublication . Saraiva, A.; Rodrigues, G.; Mamede, H.; Silvestre, J.; Dias, I.; Feliciano, M.; Oliveira e Silva, P.; Oliveira, M.In the Mediterranean region, water scarcity has already prompted concern in the wine sector due to the strong impact it has on vineyard productivity and wine quality. Water footprint is an indicator that takes account of all the water involved in the creation of a product and may help producers to identify hotspots, and reduce water consumption and the corresponding production costs. In recent years several studies have been reported on wine water footprint determination, but mostly focused on the viticulture phase or assuming no grey water footprint at the winery since it has a treatment system. In the framework of the WineWaterFootprint project a medium-size winery was monitored, with direct measurements, regarding determination of the blue and grey components of water footprint. The determined winery water footprint ranged from 9.6 to 12.7 L of water per wine bottle of 0.75 L, the wastewater produced being responsible for about 98%, which means that the grey component cannot be disregarded. The developed scenarios show that a potential reduction of 87% in winery water footprint can be obtained with almost no investment. The challenge of reducing the grey footprint is not in technology development, but rather in the proper maintenance and monitoring of treatment systems
- Transpiration reduction as an answer to water stress: models versus measurements for irrigated olive trees in South PortugalPublication . Lourenço, S.; Conceição, N.; Losada, H.P.; Silvestre, J.; Siqueira, J.; Santos, F.; Rolim, J.; Ferreira, Maria IsabelThe so-called stress functions, allowing quantification of transpiration or evapotranspiration reduction, as an answer to water deficit stress (stress coefficient, Ks), are useful tools for irrigation scheduling. It is known that this coefficient depends on several variables and parameters, such as evapotranspiration rate, root patterns/density and soil properties. However, the most common Ks models with practical applicability do not include some of these factors and the experimental work on this matter is not abundant. A well-known model proposed in the FAO 56 manual uses two parameters: the allowable depletion (p) and the total available soil water (TAW) in the root zone, the input variable being the soil water depletion (SWD). We discuss the application of this model in olive trees under specific natural conditions. Two studies were conducted in Alentejo, South Portugal (2011 and 2017), in one intensive and one super intensive drip irrigated olive orchards (Olea europaea 'Arbequina'). Transpiration reduction was obtained from sap flow measurements. For both experiments, Ks was related to the estimated SWD. The experimental relationship was compared with modelling outputs. Experimental results show that, in both experiments, the Ks FAO 56 model only fits using parameters such as p= 0.05 and TAW = 350 mm. The suggested p in that manual is 0.7. Furthermore, for such soils, anisotropic canopy and small wetted area (drippers), 350 mm is much more than first approach estimates would suggest. The results can be related with the root system functioning and resilience of olive trees
- Using soil and canopy temperature to support efficient management of irrigated vineyardsPublication . Costa, J. M.; Egipto, R.; Lopes, Carlos; Silvestre, J.Extreme heat and drought events are becoming more frequent and erratic in Mediterranean Europe. Better comprehension of spatial and temporal dynamics of heat fluxes and thermal microclimate in vineyards can support vineyard’s management and minimize the impact of climate variability. Field experiments were carried out in South Portugal with two red cvs. Touriga Nacional and Aragonez (syn. Tempranillo) under deficit irrigation. Canopy temperature (Tc) is a robust predictor of plant water status, especially when measured under more stressful conditions. In parallel, soil temperature (TS) had a positive influence on TC especially at the cluster zone