Possible effects of climate change on the early development of pea, broad bean, maize and sunflower in Mediterranean areas.

In Mediterranean-type climates crop yield depends strongly on the early development of individual plants. Extreme variations of soil temperature close to the surface of bare soils and fast changes of soil water content due to irregular rainfall and high evaporative demand reduce the success of germination, emergence and early leaf production, reducing crop productivity. According to IPCC Fourth Assesment report, climate change in Southern Europe “is projected to worsen hygrometric and thermal conditions (high temperature and drought) and to reduce water availability” and, consequently, to decrease general crop productivity. The aim of this study was to evaluate the thermal conditions in the top soil layer under different climate change scenarios, and their effects on the early development of some representative crops of Mediterranean agriculture (pea, broad bean, maize and sunflower). For this purpose, soil temperatures near the surface of a Luvisol and a Vertisol during the usual sowing season of winter (October) and summer crops (April) were compared to those recorded in the air above ground, to forecast future values. The impact of simulations on the speed, size and dispersion of germination, emergence and early leaf production was estimated using values of bioclimatic parameters of the crops (cardinal temperatures and thermal times for different phases of establishment) found in the literature. In both seasons, monthly mean temperatures at soil top layer were significantly greater (*P<0.05) than those found in the air above ground. However, the relationships between air and top soil temperatures were different in both soils and in both seasons. Summer crops seem to be less affected by an increase in temperature than winter crops. Otherwise, the former seem to be more affected by a decrease in soil water availability than the later. In addition, final emergence, speed of emergence and leaf production of the different species will be more affected by global warming than the dispersion around the most likely thermal times. The magnitude of these effects depends also on the magnitude of warming

Litter layer influence on the thermal regime of a sandy soil under a pine forest in mediterranean Portugal

Decomposition of needle litter is a relevant process in applied ecology, namely in the nutrient dynamics of forested ecosystems. Soil temperature strongly influences soil microbian activity. Temperature profiles of a sandy soil (Haplic Podzol) under a pine forest were measured at several depths down to 16 cm, with and without litter layer. Daily cycles were analysed by means of Fourier series. Daily cycles were studied based on data from four days defined according to soil water content. The daily periodic variations of soil temperature follow closely the time-course of solar irradiance. Daily course of soil temperature is generally well described by the two first Fourier harmonics. The litter layer acts as a thermal insulator, reducing soil temperature gradients and amplitudes and increasing damping depth, particularly in dry soil

Leaf area expansion and dry matter accumulation during establishment of broad bean and sorghum at different temperatures and soil water contents in two types of soil in mediterranean Portugal

Crop establishment is a major factor determining crop productivity in the field and is strongly controlled by soil temperature and soil moisture. Fast leaf expansion and dry matter accumulation during crop establishment are required for an adequate establishment. Leaf area expansion and accumulation of dry matter during the establishment of broad bean (Vicia faba L.) and sorghum (Sorghum vulgare L.) were studied at different soil temperatures and soil moisture contents in a Vertisol (Lisboa) and a Luvisol (Évora) from November 1993 to November 1996. Soil temperature was measured at 2 and 4 cm depth with thermocouples, air temperature was measured with a ventilated psychrometer and soil moisture was measured using the gravimetric method. Leaf area was estimated non-destructively. Above ground seedling dry matter was weighed after oven drying at 65ºC. Data analysis was based on the thermal time concept. For each crop no significant differences were found on leaf area at establishment in both soils under favourable water conditions, but significant differences were found on seedling dry matter. In moist soils, leaf area of both species increased linearly with accumulated temperature and dry matter increased exponentially with accumulated temperature. Low soil water during establishment reduced leaf expansion and dry matter accumulation of both crops, mainly if it occurred before seedling emergence. In mediterranean type climates meteorological extremes of low rainfall associated to high temperatures are expected to be more frequent on the wake of global climate change, reducing crop establishment and productivity

Considering Human Aspects on Strategies for Designing and Managing Distributed Human Computation

A human computation system can be viewed as a distributed system in which the processors are humans, called workers. Such systems harness the cognitive power of a group of workers connected to the Internet to execute relatively simple tasks, whose solutions, once grouped, solve a problem that systems equipped with only machines could not solve satisfactorily. Examples of such systems are Amazon Mechanical Turk and the Zooniverse platform. A human computation application comprises a group of tasks, each of them can be performed by one worker. Tasks might have dependencies among each other. In this study, we propose a theoretical framework to analyze such type of application from a distributed systems point of view. Our framework is established on three dimensions that represent different perspectives in which human computation applications can be approached: quality-of-service requirements, design and management strategies, and human aspects. By using this framework, we review human computation in the perspective of programmers seeking to improve the design of human computation applications and managers seeking to increase the effectiveness of human computation infrastructures in running such applications. In doing so, besides integrating and organizing what has been done in this direction, we also put into perspective the fact that the human aspects of the workers in such systems introduce new challenges in terms of, for example, task assignment, dependency management, and fault prevention and tolerance. We discuss how they are related to distributed systems and other areas of knowledge.Comment: 3 figures, 1 tabl

Effects of Irrigation and Tree Spacing on Soil and Air Temperature Profiles of Olive Orchards

Changes on the climate of the boundary layer occur when a vegetation cover above a bare soil is introduced, namely on temperatures and humidity profiles, above and under soil surface. Since air and soil temperatures affect crop growth and development and also soil moisture, they have been used as driving variables in numerous crop growth and development models as well as in those referred to soil mineralization, evaporation, transpiration, etc. The aim of this work was to evaluate (a) the soil thermal behavior in two olive orchards (Olea europaea sp. europaea), both grown on soils with little profile development (Regosol and Cambisol) and subject to drip irrigation but with different spacing between trees, and (b) the air thermal profile over olive rows. Experiments were performed from April to June 2012 in Southern Portugal. Soil and air temperatures were measured by thermocouples. The two orchards changed spatial distribution of soil surface temperature, soil temperature profiles and air temperature within the canopy, either on a daily or hourly basis. Olive tree spacing and irrigation affected both the soil thermal behavior and air thermal profiles. Tree spacing affected the horizontal gradients established along the interrows (intensity and rhythm). Irrigation reduced hourly and daily mean soil surface temperatures and daily thermal amplitudes of both profiles. Differences were also found on damping depths of the thermal wave estimated for the driest and the wettest profiles. Along the row, the effect of shading seems to overlap that of irrigation in a hourly basis

The Montado agroforestry system microclimatic specificity in the context of global change

The effects of oak trees on microclimatic parameters in Quercus rotundifolia Lam. woodland in the Alentejo, Southern Portugal, are reported. Results show that oak tree create a marked differentiation in the grass matrix, between open and undercanopy areas. Compared to open areas, it presents lower soil moisture beneath the oak canopy, lower soil temperatures and lower photosynthetically active radiation (PAR). Soil temperatures outside trees canopy were generally higher than undercanopy areas, reaching twice its values during the winter. The decrease of soil water content is more rapid in areas outside the trees canopy action, but the replenishment starts early and is faster in those areas. PAR intercepted by tree canopy is greater than 60%, and affects dramatically herbaceous production. Different climatic conditions due to the presence of the tree, associated with greater variability in chemistry environment undercanopy, if combined with the IPCC forecasts for Mediterranean region, pose new challenges in the management of the montado areas

Identificação eletrónica, assinatura e serviço de confiança

A generalização do uso de comunicações eletrónicas em todas as esferas das atividades humanas traz a necessidade de uma nova perspetiva legal. Esta necessidade é particularmente sentida a nível da União Europeia com o objetivo assumido de construir um mercado digital único e fiável. O Regulamento 910/2014 foi estabelecido como o principal quadro jurídico europeu destinado a harmonizar o entendimento de instrumentos como identificação eletrónica, autenticação eletrónica, serviços eletrónicos e também outros serviços de confiança da sociedade de informação, como selos eletrónicos, carimbos, serviços de entrega registrada eletrónica e autenticação de sites. No seu conjunto, o Regulamento 910/2014 visa estabelecer um quadro jurídico comum que permitisse aos cidadãos europeus tirarem pleno partido dos serviços digitais num ambiente técnica e juridicamente seguro.The generalization of the use of electronic communications in all spheres of human activities brings along a need for a new legal perspective. This need is particularly felt at European Union level with the assumed aim of building a trustable Digital Single Market. Regulation 910/2014 was set as the main European legal framework aimed at harmonizing the understanding of instruments such as electronic identification, electronic authentication, electronic services, and other trust services of information society, such as electronic seals, electronic time stamps, electronic registered delivery services and website authentication. In the whole, Regulation 910/2014 is intended to establish a common legal framework allowing European citizens to take full advantage of digital services in a technically and legally secure environment

Controlo de qualidade dos dados de posicionamento em reflexão sísmica de muito alta resolução

The quality control is a very important operation in the seismic data acquisition surveys and its main goals are to assess the quality of the acquired data, to detect problems during acquisition and finally to guarantee that the data has the required quality to be accepted for further processing, or if it must be rejected. The time spent in operations makes its cost to grow up and therefore the QC must be done efficiently and as early as possible., It is critical that the most relevant factors that can seriously compromise the data are evaluated onboard. Navigation quality control is extremely important because the navigation errors can contribute to the feathering effect that by itself is one of the main rejections criteria. On the other hand, the quality of the positioning data can have strong influence on the seismic resolution, as it is used to calculate positioning for every reflection point. Thus, wrong positioning data affect offsets computing and can move the reflection midpoints to erroneous position causing a discrepancy between the actual geology and the seismic section obtained. This causes errors in the exact location of boulders and the identification of other in-depth hazards that threat the optimization of wind turbine installations, which is one of Geosurveys goals in this type of surveys. The main sources of these problems are related to the bad functioning of GPS antennas used in the acquisition system and other systematic problems such as geometry assignment. There are typical errors which affect the geometry such as distance measurement between lead buoy center and first channel, distance measurements and assignment between channels in the different streamer sections. The solution proposed in this work consists on the development of effective methods to diagnose these types of problems, where through a graphical scheme it becomes possible to detect different types of positioning errors and their causes. The method developed in the scope of this work was based on the quality control of the offsets calculated with the positioning data and the direct arrivals time. With this information it was possible to establish a classification criterion for the positioning data according to its quality, to calculate the errors and obtain indicators about its source of error, always considering that the various factors have different influences on the errors and some problems appear more frequently than others. Based on this, rejection criteria for data with positioning errors was established and solutions were tested in the software packages RadExPro and Kingdom Suite, in order to evaluate the effect of these errors on the seismic volumes.O controle de qualidade é uma operação muito importante durante as campanhas de aquisição de dados sísmicos. Tem como objetivo avaliar a qualidade dos dados adquiridos, detetar problemas ocorridos durante a aquisição, e finalmente assegurar que os dados têm a qualidade necessária para serem aceites ou se devem ser rejeitados. O tempo de operação tem consequências diretas sobre os custos e, por esta razão, esta é uma operação que deve ser feita rapidamente. Assim, devem ser avaliados os fatores mais relevantes que podem comprometer seriamente a qualidade dos dados. O controle de qualidade da navegação é de extrema importância, visto que os erros de navegação contribuem para o feathering, que por sua vez constitui um dos principais critérios de rejeição. Por outro lado, a qualidade da navegação ou dos dados de posicionamento pode afetar fortemente a resolução sísmica pelo facto de serem usados para a determinação das posições das reflexões. Assim, dados de posicionamentos errados afetam os cálculos dos offsets e podem deslocar os pontos médios de reflexões para posições erradas, provocando uma discrepância entre a geologia real e a secção sísmica obtida. Deste modo, fica mais difícil a localização exata de blocos rochosos e a identificação de outros perigos em profundidade que colocam em risco a otimização das instalações das turbinas eólicas, trabalhos que a Geosurveys tem vindo a realizar. As principais causas na origem destes problemas estão relacionadas com o mau funcionamento das antenas GPS usadas no sistema de aquisição, e outros problemas sistemáticos, como a atribuição de geometria. Existem erros típicos que afetam a geometria, tais como o erro na medição da distância entre o centro da antena da lead buoy e o primeiro canal, e erros na medição e atribuição das distâncias entre canais para as diferentes secções dos streamers. A solução proposta neste trabalho passou pelo desenvolvimento de métodos eficientes para diagnóstico destes tipos de problemas, onde através de padrões gráficos se torna possível detetar diferentes tipos de erros de posicionamentos e as respetivas causas. O método desenvolvido baseou-se no controle de qualidade dos offsets calculados com os dados de posicionamento e no tempo de chegada das ondas diretas. Com essas duas informações foi possível estabelecer um critério de classificação dos dados de posicionamento quanto à sua qualidade, calcular os erros e obter indícios sobre a sua origem, levando sempre em consideração que os vários fatores têm diferentes influências sobre os erros e que alguns problemas são mais frequentes que outros. Com base neste procedimento, foram estabelecidos critérios de rejeição de dados com erros de posicionamento. As soluções obtidas foram testadas no software RadExPro e Kingdom Suite de modo a avaliar o efeito que esses erros têm sobre a sísmica.Mestrado em Engenharia Geológic

Radiação Líquida e Fluxo de Energia à superfície de um Solo Mediterrâneo Pardo (Pmg)

O fluxo de energia no solo é um componente importante do balanço de energia na interface solo-atmosfera. As variações do fluxo de energia (G) e da radiação líquida (Rn) à superfície de um solo Mediterrâneo Pardo (Luvissolo Háplico) foram analisadas para diferentes dias-tipo e para um ciclo anual completo. Usaram-se para o efeito placas de fluxo de calor (medição de G), um pirradiómetro de balanço (medição de Rn) e termopares (medição da temperatura do solo). Os valores medidos de G foram comparados com os estimados a partir da simulação da temperatura do solo com recurso a séries de Fourier (2 harmónicas). Discute-se a influência da humidade do solo, da nebulosidade e da insolação astronómica nas variações de G e de Rn ao longo do dia e na razão G/Rn