Search Results (15)

The study of marine and terrestrial palynomorphs in fluviomarine environments has been successfully used in combination with different geophysical approaches to understand high-resolution relative sea-level oscillations and to reconstruct the environmental changes affecting estuaries and adjacent inland ecosystems. However, erosion during the postglacial marine transgression frequently causes sedimentary discontinuities or may lead to the redeposition of ancient upland sediments, including secondary, recycled and rebedded pollen. Therefore, a robust seismic and chronological control of the sedimentary facies is essential. In addition, studies of modern pollen sedimentation and its relationship to contemporaneous vegetation are valuable for obtaining a more realistic interpretation of the sedimentary evidence. To explore the significance of the experimental evidence obtained and to support the interpretation of sedimentary records from the same basin, we analysed a large set of modern pollen data from the Ría de Vigo (NW Iberia). The pollen samples derived from different sedimentary environments were compared with the local and regional vegetation cover. Pollen evidence from the various limnetic systems studied allows the identification of major vegetation types in the basin. However, in all the cases, the reconstructed relative pollen contributions of each vegetation unit are often distorted by the overrepresentation of certain anemophilous pollen types, the underrepresentation of some entomophilous species, and the specific taphonomy of each site of sedimentation. The ability of the seabed pollen evidence to represent the modern deciduous and alluvial forests, as well as the saltmarsh vegetation onshore, increases in the shallowest points of the ria (shallower than −10 m). Conversely, pastures and crops are better represented at intermediate depths (shallower than −30 m), while scrubland vegetation is better represented in samples at more than 20 m below modern sea level. It is concluded that shallow seabed pollen can provide information on the main elements of the modern vegetation cover of the emerged basin, including the main elements of the vegetation cover. However, the selection of the most suitable subtidal sites for coring, combined with pollen data from several environmental contexts, is critical for achieving an accurate reconstruction of the changing conditions of the emerged basin over time. Full article

In the Atlantic region of northern Spain, heat extremes were historically rare, but in recent decades, they have become more intense and persistent. This article characterizes heat events in Asturias (NW Spain) between 2001 and 2023, focusing on their frequency, intensity, and duration, as well as their temporal trends. Additionally, it explores the synoptic patterns linked to these episodes to enhance understanding of their occurrence and evolution over the study period. The research is based on official meteorological records, and it distinguishes between officially declared heatwaves (DHs) and significant heat events (SHEs) identified through regional press reports. This methodology enables the study to capture a broader spectrum of heat-related impacts. During the study period, 17 episodes were documented (11 DHs and 6 SHEs). The frequency, intensity, and duration of heat events have significantly increased, particularly since 2016, standing the last two years (2022 and 2023). Both DHs and SHEs have progressively shifted toward the early and late periods of the astronomical summer, with some events occurring during spring and autumn in the second half of the study period (years 2017, 2022, and 2023). Three atmospheric patterns have been identified as responsible for extreme heat episodes; Type 1 (warm tropical continental air masses, combined with atmospheric stability) is responsible for 10 of the episodes. Furthermore, urban areas and main river valleys were the most affected areas, while coastal regions remained largely unaffected. This research aims to contribute to a broader understanding of how heatwaves are evolving in a temperate climate area under the influence of global warming, providing insights to inform and improve adaptation strategies for mitigating their impacts. Full article

This study analyses the Roman hydraulic system linked to Las Médulas gold mining complex in Northwest Iberia. The research includes a detailed mapping and assessment of the hydraulic network, which extends over 1110 km, using advanced geomatic techniques and an innovative script for tracing canals implemented in Matlab. The study reveals previously unidentified canals, improves existing cartographic representations, and addresses water sourcing and canal distribution uncertainties. It identifies 41 canals distributed between La Cabrera and El Bierzo regions, (33 and 8, respectively), with 14 canals supplying water to Las Médulas. Our study also provides evidence that this canal system had a wider purpose than simply supplying the mining works at Las Médulas. Furthermore, the findings presented here challenge established assumptions about the system’s water sources and offer new insights into how this outstanding canal system was built. Thus, this work not only provides a detailed map of the Las Médulas hydraulic system but also constitutes a model for an effective methodological approach for studying similar ancient hydraulic systems worldwide. Full article

Mountains matter. Rural subsistence communities living in areas with high biodiversity, such as mountains, are hotspots of ecological knowledge. However, modern lifestyles may threaten this unique cultural heritage. Our study aimed to document and analyze information on plants used to fulfill the everyday needs of the people in three rural communities in NW Portugal. Fieldwork was carried out for a period of one year and information was collected through face-to-face semi-structured interviews. A total of 98 species, belonging to 46 families, were identified, and 142 vernacular names were recorded. Ethnobotanical richness was similar among the studied communities. The five most frequently cited species were: Pterospartum tridentatum, Erica arborea, Ruta graveolens, Zea mays and Chamaemelum nobile. Phanerophytes and hemicryptophytes comprise nearly 81% of the list. The top three uses categories (total 14) were: medicine, fuel and ritual. Digestive, skin and respiratory symptoms were the most often conditions treated with plants. Medicinal plants were used fresh and dried, mostly as infusions. The insights gathered here are important for the preservation of the cultural heritage of the local communities. Moreover, the data are of considerable scientific interest because it provides the fundaments for future studies that aim to validate/invalidate specific uses. Full article

Understanding species–habitat relationships is essential for ecosystem-based conservation. This study explores the significance of habitat characteristics and complexity for demersal and benthopelagic communities within a patchwork of coastal habitats, including rocky seabed, macroalgae formations, sandy bottoms, and a combination of rock and sand areas. Species and habitats were surveyed along the north-west (NW) Iberian continental shelf area of Viana do Castelo using baited remote underwater video stations (BRUVS). We found significant differences (p < 0.05) in species assemblages across habitats, with rocky substrates showing the highest diversity and abundance. Sand habitats showed the lowest species richness and abundance, underscoring the importance of habitat complexity to support marine life. Our study also emphasises the role of specific species in shaping the communities, identifying key species such as Trisopterus luscus, Diplodus vulgaris, and Ctenolabrus rupestris as the three most abundant in the region and significant contributors to the observed dissimilarities between habitats. By elucidating the impact of habitat complexity on marine life, our results offer essential baseline data, which serve as a kick-start point to inform sustainable management and conservation strategies for the long-term health and productivity of these vital ecological systems in the North-East Atlantic. Full article

Integrating fire into land management is crucial in fire-prone regions. To evaluate the effectiveness and efficiency of prescribed fire (PF), we employed the REMAINS model in NW Iberia’s Transboundary Biosphere Reserve Gerês-Xurés. We tested three levels of prescribed fire treatment effort for shrubland and grassland, employing three spatial allocation strategies: random distribution, prioritization in high-wildfire-risk zones, and creating fuel breaks by utilizing the existing road network. These approaches were assessed in isolation and in combination with three land-use scenarios: Business-as-usual (representing rural abandonment trends), High Nature Value farmland (reversing farmland abandonment), and Fire-Smart forest management (promoting fire-resistant landscapes). Our results confirm that PF is effective in reducing future wildfires (reductions up to 36%), with leverage values ranging from 0.07 to 0.45. Strategic spatial allocation, targeting wildfire-risk areas and existing road networks, is essential for maximizing prescribed fire’s efficiency (leverage effort of 0.32 and 0.45; i.e., approximately 3 ha of PF decrease subsequent wildfire by 1 ha). However, the PF treatments yield the best efficiency when integrated into land-use policies promoting ‘fire-smart’ landscapes (reaching leverage values of up to 1.78 under policies promoting ‘HNVf and ‘fire-smart’ forest conversion). These recommendations strengthen wildfire prevention and enhance landscape resilience in fire-prone regions. Full article

We compared climate–growth relationships (1956–2013) of two natural pedunculate oak (Quercus robur L.) stands with different water-holding capacities growing at the species distribution limit of the Mediterranean Region in NW Iberia. For this, tree-ring chronologies of earlywood vessel size (separating the first row from the other vessels) and latewood width were obtained. Earlywood traits were coupled to conditions during dormancy, whereby an elevated winter temperature appears to induce a high consumption of carbohydrates, resulting in smaller vessels. This effect was reinforced by waterlogging at the wettest site, whose correlation to winter precipitation was strongly negative. Soil water regimes caused differences between vessel rows, since all earlywood vessels were controlled by winter conditions at the wettest site, but only the first row at the driest one; radial increment was related to water availability during the previous rather than the current season. This confirms our initial hypothesis that oak trees near their southern distribution boundary adopt a conservative strategy, prioritizing reserve storage under limiting conditions during the growing period. We believe that wood formation is highly dependent on the balance between the previous accumulation of carbohydrates and their consumption to maintain both respiration during dormancy and early spring growth. Full article

An 8500-year record of high-resolution pollen, non-pollen palynomorph, microscopic charcoal and selected geochemical data (Ti, Zr and Pb) is presented from an ombrotrophic mire from the Xistral Mountains, Galicia, North-West Iberia. The results suggest that vegetation changes over the last eight millennia are primarily the result of human disturbance, fire and climate change. Climate and fire were the main factors influencing vegetation development during the early to mid-Holocene, including a short-lived decline in forest cover c. 8.2 cal. ka BP. Changes associated with the 4.2 and 2.8 cal. Ka BP events are less well defined. Human impact on vegetation became more pronounced by the late Holocene with major periods of forest disturbance from c. 3.1 cal. ka BP onwards: during the end of Metal Ages, Roman period and culminating in the permanent decline of deciduous forests in the post-Roman period, as agriculture and metallurgy intensified, leading to the creation of a cultural landscape. Climate change appears to become less influential as human activity dominates during the Late Holocene. Full article

This paper addresses an experimental approach to the archaeological study of Roman camps in NW Iberia using ground-penetrating radar (henceforth GPR). The main goal is to explore the capabilities of GPR to extract datasets from ephemeral features, such as temporary camps or siege works, among others. This information aims to maximise the data available before excavation, orienting it to areas that could provide good results in terms of feature detection and contrast between soil matrix and archaeological deposits. This paper explores the potential of the GPR approach and volumetric data visualisation to improve our understanding of four ephemeral sites: Alto da Raia (Montalegre, Portugal–Calvos de Randín, Spain), Sueros de Cepeda (Villamejil, Spain), Los Andinales (Villsandino, Spain), and Villa María (Sasamón, Spain). Despite the focus of this paper, other survey techniques (namely LiDAR, aerial photography, and magnetometry) were used in combination with GPR. Further excavation of the sites provided ground truthing for all data remotely gathered. Full article

Findings of Iron Age metallurgical activities related to tin metal and mining are very rare. In the present work, we present a detailed study of the Outeiro de Baltar hillfort, dated to the Late Iron Age/Early Roman period, located in a place where 20th century tin mining work took place. Elemental and microstructural analysis by portable, micro and wavelength dispersive X-ray fluorescence spectrometry (pXRF, micro-XRF and WDXRF) and scanning electron microscopy with energy dispersion spectrometer (SEM-EDS) showed that metallurgical debris found at the archaeological site is related to tin smelting and binary and ternary bronze productions. Analysis of the artefacts of diverse typologies found at the site showed that a variety of metals and alloys were in circulation and use. Samples of tin ores (cassiterite) from the region were analyzed for comparison with an archaeological tin slag from the site. The analytical results point to the production of tin metal using local cassiterite and the production of bronze by directly adding cassiterite into a smelting process. Furthermore, data of remote sensing (airborne Light Detection and Ranging (LiDAR) and historical aerial imagery) and Geographical Information System (GIS) mapping were combined with archival mining documentation and maps to retrieve a landscape context for the site. The study showed that the place of the Outeiro de Baltar hillfort (NW Iberia) was mined periodically over time. Full article

The San Finx W–Sn ore deposit is located in the Spanish province of A Coruña (Galicia, NW Spain). Geologically, it occurs in the Galicia-Trás-os-Montes zone which is one of the innermost zones of the Iberian Variscan collisional belt. This ore deposit is characterized by NE–SW trending quartz-dominated veins with centimeter-size hübnerite and cassiterite. This research focuses on one sector of this deposit known as Buenaventura. The aim of this work is to present a mineralogical and petrological characterization of the ore-bearing veins, their host rocks and associated hydrothermal alteration. The vein mineralogy is mainly quartz, muscovite, K-feldspar, apatite and scarce fluorite. The ore minerals are hübnerite, scheelite and cassiterite with columbite and ilmenorutile-struverite inclusions, together with sulfides, mainly chalcopyrite and arsenopyrite, and, in less abundance, molybdenite, löllingite, pyrrhotite, sphalerite, stannite, pyrite, Bi-Pb-Ag sulfosalts and native bismuth. The main host-rocks are micaschist and paragneiss and two types of pegmatites, homogeneous pegmatites and banded aplite-pegmatites with columbite. The host rocks are affected by four types of hydrothermal alterations: tourmalinization, greissenization, feldspathization and silicification. The more widespread alteration is the feldspathization in which the protolith is replaced by massive albite and K-feldspar with fibrous habit, accompanied by apatite, chlorite, rutile, magnetite, hematite, chalcopyrite and sphalerite. In addition, there are highly deformed areas with a complex alteration rich in K-feldspar and sulfides, mainly chalcopyrite, minerals of the stannite group and sphalerite and, in less abundance, bismuthinite, native bismuth, galena and pyrite. This deposit shares features in terms of geological setting, hydrothermal alteration and ore assemblages with exogreisen systems formed in the cupolas of highly fractionated granites in collisional settings. Full article

Upwelling and downwelling processes play a critical role in the connectivity between offshore waters and coastal ecosystems, having relevant implications in terms of intense biogeochemical activity and global fisheries production. A variety of in situ and remote-sensing networks were used in concert with the Iberia–Biscay–Ireland (IBI) circulation forecast system, in order to investigate two persistent upwelling and downwelling events that occurred in the Northwestern (NW) Iberian coastal system during summer 2014. Special emphasis was placed on quality-controlled surface currents provided by a high-frequency radar (HFR), since this land-based technology can effectively monitor the upper layer flow over broad coastal areas in near-real time. The low-frequency spatiotemporal response of the ocean was explored in terms of wind-induced currents’ structures and immediacy of reaction. Mean kinetic energy, divergence and vorticity maps were also calculated for upwelling and downwelling favorable events, in order to verify HFR and IBI capabilities, to accurately resolve the prevailing surface circulation features, such as the locus of a persistent upwelling maximum in the vicinity of Cape Finisterre. This integrated approach proved to be well-founded to efficiently portray the three-dimensional characteristics of the NW Iberian coastal upwelling system regardless of few shortcomings detected in IBI performance, such as the misrepresentation of the most energetic surface dynamics or the overestimation of the cooling and warming associated with upwelling and downwelling conditions, respectively. Finally, the variability of the NW Iberian upwelling system was characterized by means of the development of a novel ocean-based coastal upwelling index (UI), constructed from HFR-derived hourly surface current observations (UI_HFR). The proposed UI_HFR was validated against two traditional UIs for 2014, to assess its credibility. Results suggest that UI_HFR was able to adequately categorize and characterize a wealth of summer upwelling and downwelling events of diverse length and strength, paving the way for future investigations of the subsequent biophysical implications. Full article

The isotopic composition of precipitation provides insight into the origin of water vapor, and the conditions attained during condensation and precipitation. Thus, the spatial variation of oxygen and hydrogen stable isotope composition (δ_p) and d-excess of precipitation was explored across the Iberian Peninsula for October 2002–September 2003 with 24 monitoring stations of the Global Network of Isotopes in Precipitation (GNIP), and for October 2004–June 2006, in which 13 GNIP stations were merged with 21 monitoring stations from a regional network in NW Iberia. Spatial autocorrelation structure of monthly and amount weighted seasonal/annual mean δ_p values was modelled, and two isoscapes were derived for stable oxygen and hydrogen isotopes in precipitation with regression kriging. Only using the GNIP sampling network, no spatial autocorrelation structure of δ_p could have been determined due to the scarcity of the network. However, in the case of the merged GNIP and NW dataset, for δ_p a spatial sampling range of ~450 km in planar distance (corresponding to ~340 km in geodetic distance) was determined. The range of δ_p, which also broadly corresponds to the range of the d-excess, probably refers to the spatially variable moisture contribution of the western, Atlantic-dominated, and eastern, Mediterranean-dominated domain of the Iberian Peninsula. The estimation error of the presented Iberian precipitation isoscapes, both for oxygen and hydrogen, is smaller than the ones that were reported for the regional subset of one of the most widely used global model, suggesting that the current regional model provides a higher predictive power. Full article

The Galician coast (NW Spain) is a region that is strongly influenced by the presence of low pressure systems in the mid-Atlantic Ocean and the periodic passage of storms that give rise to severe sea states. Since its wave climate is one of the most energetic in Europe, the objectives of this paper were twofold. The first objective was to characterize the most extreme wave height events in Galicia over the wintertime of a two-year period (2015–2016) by using reliable high-frequency radar wave parameters in concert with predictions from a regional wave (WAV) forecasting system running operationally in the Iberia-Biscay-Ireland (IBI) area, denominatedIBI-WAV. The second objective was to showcase the application of satellite wave altimetry (in particular, remote-sensed three-hourly wave height estimations) for the daily skill assessment of the IBI-WAV model product. Special attention was focused on monitoring Ophelia—one of the major hurricanes on record in the easternmost Atlantic—during its 3-day track over Ireland and the UK (15–17 October 2017). Overall, the results reveal the significant accuracy of IBI-WAV forecasts and prove that a combined observational and modeling approach can provide a comprehensive characterization of severe wave conditions in coastal areas and shows the benefits from the complementary nature of both systems. Full article

In 2012, there were exceptional blooms of D. acuminata in early spring in what appeared to be a mesoscale event affecting Western Iberia and the Bay of Biscay. The objective of this work was to identify common climatic patterns to explain the observed anomalies in two important aquaculture sites, the Galician Rías Baixas (NW Spain) and Arcachon Bay (SW France). Here, we examine climate variability through physical-biological couplings, Sea Surface Temperature (SST) anomalies and time of initiation of the upwelling season and its intensity over several decades. In 2012, the mesoscale features common to the two sites were positive anomalies in SST and unusual wind patterns. These led to an atypical predominance of upwelling in winter in the Galician Rías, and increased haline stratification associated with a southward advection of the Gironde plume in Arcachon Bay. Both scenarios promoted an early phytoplankton growth season and increased stability that enhanced D. acuminata growth. Therefore, a common climate anomaly caused exceptional blooms of D. acuminata in two distant regions through different triggering mechanisms. These results increase our capability to predict intense diarrhetic shellfish poisoning outbreaks in the early spring from observations in the preceding winter. Full article