Earth Sciences

ABSTRACT Coastal zones are suffering from severe changes. Dune systems are forecasted to be impacted severely by such changes. Since shifts in coastal dynamics may drive modifications in the floristic composition of plant communities, effective indicators of such changes are needed to support adaptive measures. We performe here an assessment of the relative efficiency of functional and phytosociological classifications in the analysis of structure and dynamics in foredune vegetation. Our results identified common signals but also highlighted some differences among results from different classifications with potential consequences for the monitoring of changes in dune ecosystems. The coincident signals provided by the analysed classification systems suggest that they are effective in capturing the major rules involved in the structure and dynamics of foredune vegetation. Since the disturbance regime in foredunes is mostly related to prevailing coastal dynamics, compositional shifts in phytosociological or functional spectra are thus useful in the establishment of reliable indicators and protocols to monitor changes in coastal zones. Résumé Les côtes souffrent aujourd'hui de plusieurs modifications. Les dunes peuvent être très dégradées par ces changements environnementaux. Dans la mesure où les modifications dans la dynamique côtière peuvent provoquer des changements dans la composition floristique des communautés végétales, des indicateurs sont nécessaires pour suivre de futures actions. Nous comparons ici l'efficacité de classifications fonctionnelles et phytosociologiques pour décrire la structure et la dynamique de la végétation des dunes blanches. Nos résultats ont identifié des indicateurs communs mais ont aussi signalé des différences entre les systèmes analysés avec des conséquences potentielles pour la surveillance des changements dans les écosystèmes dunaires. Comme le régime de perturbation dans ces dunes est principalement lié à la dynamique côtière, des modifications de la composition phytosociologique ou fonctionnelle des communautés offrent des outils pour identifier des indicateurs et des méthodes pour la surveillance des changements liés aux zones côtières.

Abstract: Close range digital photogrammetry, which involves the application of unmanned aerial vehicle (UAV), has been
used in a growing number of diverse applications across different scientific disciplines. Our objective was to use the mentioned
method in the survey of the contemporary geoecological conditions of the coastal area on the example of Portuguese northwest
coastal zone. The coastal zone can be subdivided into two geomorphological sectors: Sector 1, between the Minho River and the
town of Espinho, where the coastal segments consist of estuaries, sandy and shingle beaches with rocky outcrops, and Holocene
dune systems. The estuaries and the foredunes in particular are very degraded by human activities; and Sector 2, between
Espinho and the Mondego Cape, where coastal lagoons and Holocene dune systems occur. We chose two beaches for surveying
– Aguçadoura and Ramalha to which the drone swinglet CAM took the photos. We used the ground control software eMotion 2
to plan the flights over the study area and controlled the drone’s trajectory during flight. After processing the obtained images in
the program of AgisoftPhotoscanPro, we generated the 2D orthophotos and 3D digital elevation models (DEM) of the research
sections. At this stage of study we derived the above product without using the ground control points, or we used only the camera
GPS data. Based on these models the compilation of the large-scale maps of high resolution (1cm-5cm) will be possible in the
GISs for monitoring and management of the geoecological state of the mentioned beaches in case to precise the x, y and z values
of the models with the geodetic device of Differential GPSs in the selected ground control points (GCP).
Keywords: Unmanned Aerial Vehicle, Beach, Orthophoto, Digital Elevation Model, Accuracy

Question

Can very high-resolution colour orthophotography and digital surface models (DSMs) from an unmanned aerial vehicle (UAV) be effectively used for assessment of habitat extent and condition in fine-scale disturbance-dependent mosaics?
Location

Serra de Arga mountain range, a Natura 2000 protected site in the NW region of Portugal where drastic changes in pastoral activities have occurred over recent decades.
Methods

An UAV platform was used to collect very high-resolution (6 cm) images and to produce a DSM (10 cm). From these data, several features were extracted related to colour, band ratios, as well as texture features calculated from colour imagery and surface elevation. Based on a systematic sampling design, field data were collected for both training and validation of a supervised classifier. Extracted features and ground truth training data were combined to calibrate a pixel-based Random forest classifier, with the purpose of devising a habitat map for the entire study area. Map validation was performed to assess classification accuracy, and feature importance metrics were calculated.

Results

Validation results revealed good mean overall accuracy (0.89), with some performance decrease in situations of high interspersion of habitat types. The priority habitat type 6230* (Nardus grasslands), defining the vegetation matrix of the test site, obtained 0.96 and 0.91, considering, respectively, producer and user accuracy. In turn, priority habitat type 4020* (Atlantic wet heathlands) recorded 0.68 and 0.77. The obtained habitat map allowed measurement of the extent, description of the spatial arrangement and provided an indication of the conservation condition of target habitat types. Test results regarding the discrimination ability of different features highlighted the importance of surface elevation textures derived from the DSM, followed by band ratios textures and other more complex texture features calculated from colour imagery.

Conclusions

Overall, the developed methodology showed promising results for assessing the extent and condition of habitats of high conservation priority in fine-scale, dynamic vegetation mosaics. Future advances in the use of UAV platforms may play an important role in monitoring protected sites and fulfil legal reporting obligations of EU member states, while reducing the costs associated with intensive in-field assessments.

This work describes the use of Ground-penetrating Radar (GPR) surveys in the identification and mapping of subtle cultural remains, from Pego Late Bronze Age settlement, located near the city of Braga, in NW Portugal. Bronze Age settlements from NW Portugal are characterized by the presence archaeological structures such as storage pits, postholes and trenches. These subtle structures have a very low dielectric contrast, making them quite difficult to detect in GPR surveys. In the case of Pego Site, previous investigations using conventional archaeological techniques, during a rescue excavation, partially revealed a residential area, a necropolis, and a stockade foundation trench that encircle the whole settlement. Different GPR prospection approaches were performed using GSSI Sir 3000 System, with 400 MHz antennae, with the objective of identify and define the borders between the different areas of human occupation inside the settlement. For the GPR survey, a grid-based approach wi...

Trabalhos de emergência durante a construção de uma moradia permitiram a escavação parcial do monumento megalítico do Carreiro da Quinta (Laje, Vila Verde, Braga). Atendendo à sua implantação espacial, ao registo de escavação e ao estudo dos materiais recolhidos, avançam-se algumas interpretações. um machado e uma ponta de seta em matérias-primas alógenas e uma forma cerâmica datáveis do neolítico situam a construção do mo- numento naquele período. Fragmentos cerâmicos de recipientes campaniformes e um número considerável de recipientes e fragmentos cerâmicos datáveis da idade do Bronze apontam para a profusa reutilização do local entre o III e o II milénios a. C. Formas cerâmicas históricas terão resultado, quer de reutilizações, quer de violações do monumento.

A dialogue between signs and matter in the rock carvings of Fornelos (Viana do Castelo, North-Western Portugal) is made. This kind of methodological approach is important as a way of interpretation the rock art. Some considerations are made about horses, horse-riders and one antropomotphic figure  engraved in this particular boulder.

The aim of this chapter is to present the dialogue that exists between the morphology of granite outcrops, the geoforms of these outcrops and the motifs engraved or inscribed in them. It is assumed that the outcrops were not an inert material or a simple surface for carvings but instead active agents that contributed to the meaning of these places. One case study, which clearly an anthropomorph were engraved. The space chosen for the carving of these signs, the orientation for the audience, while at the same time it seems to tell a real or a mythical narrative. Here, horses only a few would return, probably a rite of passage of the Late Bronze Age or Iron Age inhabitants.

... REE and HREE abundances are generally higher in swamp-lake than in floodplain sediments. The majority of the REE in floodplain sediments is hosted by Y and Th-bearing minerals and illite; in swamp-lake sediments is also probable an association with organic matter. ...