North-eastern Sardinia Research Articles

Continuous vs. discontinuous garnet growth in mylonitic micaschists from northeastern Sardinia, Italy: Evidence from LA-ICPMS trace element mapping

Garnet with complex, discontinuous zoning is a common occurrence in metamorphic terrains, and the relationship between major and trace element zoning can provide insight into the metamorphic evolution of the host rock. Mylonitic micaschists along the Posada-Asinara Shear Zone in the Axial Zone of the Sardinia Variscan chain contain garnet porphyroblasts, enveloped by the S2 schistosity, with distinct core and rim domains. A large garnet porphyroblasts was investigated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS) mapping. The major element compositional variation follows a bell-shaped zoning, with Ca and Mn contents progressively decreasing, and Fe and Mg increasing, from the core to the outer rim. LA-ICPMS mapping revealed a thin and sharp annular enrichment zone in Y, Sc, Dy, Ho, Er, Tm at the mantle-rim boundary. The trace element (TE) compositional profiles show a central enrichment area for HREE (Tm, Yb, Lu). This enrichment decreases progressively, as a function of atomic number, for Er, Ho and Dy. Elements with even lower atomic number (Tb, Gd, Eu and Sm), are depleted in this central domain, but their content increases in broad shoulders towards the garnet rim. The position of these lateral shoulders migrates progressively rimwards with decreasing atomic number. The REE distribution, trend and behavior in the growth zones of the garnet is an example of TE control during a continuous growth ruled by diffusion-limited REE uptake. The Y + HREE annular enrichment zone, interpreted as resulting from a decrease in the garnet growth rate, reflects a short-lived episode in the garnet growth history.

Retrospective study of lameness in beef cattle in northeastern Sardinia, Italy.

Lameness is one of the most prevalent diseases affecting dairy and beef cattle, resulting in decreased animal performance, decreased animal welfare, and substantial economic loss. In extensive beef cattle farming, the risk factors for this multifactorial disease are largely unexplored. This study aims to conduct a preliminary epidemiological survey of risk factors in beef cattle in extensive breeding, evaluate the farmer's perception of lameness, and determine the recurrence frequency of the pathologies under investigation in treated animals. The study was conducted in Sardinia, Italy. The population of the study consisted of 14379 cattle from 230 farms. An ad hoc questionnaire was developed to collect all the necessary data. A strong association was found between breed and the occurrence and recurrence of lameness (p < 0.0001). In addition, the Country of origin of both bulls and cows was found to be correlated with the incidence of lameness (p < 0.0001 and 0.0001, respectively). Farmers who indicated on the questionnaire that lameness was not important on their farm had more animals with recurrences (p < 0.0001) than other farmers. The veterinarian's treatment choice differed significantly by farmer concern (p = 0.007) and was associated with less disease recurrence (p < 0.0001), resulting in greater farmer satisfaction (p < 0.007). Pure cow breed, French bull origin, and farmer's age were detected as significant predictors of lameness issues, with pure cow breed and French bull origin having the strongest associations (p = 0.009). Even though the results of this study are preliminary, they indicate that breed selection is crucial in extensive beef farms to reduce lameness prevalence. In addition, it would be reasonable to train breeders to prevent and diagnose lameness early in order to collaborate with veterinarians to prevent recurrence.

Classification of the Sardinian pine woodlands

Mediterranean pine woodlands are one of the most common wooded vegetation types across the Mediterranean Basin and are included in two habitats of European interest as they have great conservation importance. We studied the woodlands of the class Pinetea halepensis dominated by Pinus halepensis, P. pinaster, and P. pinea in Sardinia (Italy) with the aim to clarify their syntaxonomic position. We compiled a dataset of 66 original vegetation relevés, complemented with the holotypes of similar vegetation types formerly described for Italy and Corsica (France). We classified P. halepensis woodlands, native to the Island of San Pietro, to the association Erico arboreae-Pinetum halepensis. We classified P. halepensis woodlands growing on limestones of the south-western coast of Sardinia to the new association Smilaco asperae-Pinetum halepensis and woodlands typical of coastal dunes to the new association Asparago horridi-Pinetum halepensis. We also described the north-eastern Sardinia P. pinaster woodlands as the new association Arbuto unedonis-Pinetum pinastri, of which we recognised two new subassociations, typicum and cephalantheretosum longifoliae, ecologically distinguished by the xerophilous and mesophilous conditions, respectively. Furthermore, we classified P. pinea woodlands, putatively native only to stabilised sand dunes of south-western Sardinia, in the new association Querco calliprini-Pinetum pineae. This study represents the first complete survey and classification of Sardinian pine woodlands, allowing a better understanding of their ecology, floristic composition and differences with other Mediterranean pine woodlands.

Aliens in changing seascapes: a newly reported non-native sacoglossan (Mollusca, Heterobranchia) in the western Mediterranean Sea

We report the discovery of the Indo-Pacific sacoglossan Elysia nealae Ostergaard, 1955 from northeastern Sardinia (Central Tyrrhenian Sea). This is the first record of this species in the western Mediterranean Sea and only the second for the whole of the Mediterranean Sea following a report from Cape Epanomi, Greece. We discuss the identification of this species as well as the expansion of its geographical range. Data on the ecology and behavior of E. nealae leads us to hypothesize that the increase in the Mediterranean&amp;rsquo;s water temperature due to climate change has favored this non-native species and contributed to its expanded distribution.

Late Valanginian sponge spicules from north-eastern Sardinia (Italy)

The knowledge of siliceous sponges of Early Cretaceous age is generally scarce. An interesting assemblage of late Valanginian spicules from NE Sardinia is described. It comprises 21 taxa within two classes, Demospongiae and Hexactinellida. The fauna, which is associated with very abundant radiolarians, seems to be an admixture of morphotypes likely belonging to taxa which have no modern counterparts and spicules identical to those occurring in modern species, such as dischelae of Coelodischela cf. massa, amphitriaenes of Samus cf. anonymus, sterrasters of Geodia sp., and selenasters of Placospongia sp. The fossil record of most of the morphotypes observed in the assemblage dates back to Jurassic or even Triassic. The presence of spicules that belong to shallow-water sponges as well as to forms that inhabit today wide depth ranges, suggests that this Early Cretaceous assemblage lived at depths around 200 m.

Garnet-Rich Veins in an Ultrabasic Amphibolite from NE Sardinia, Italy: An Example of Vein Mineralogical Re-Equilibration during the Exhumation of a Granulite Terrane

A complex system of mono- and polymineralic centimeter-thick veins occurs within the ultrabasic amphibolites of Montigiu Nieddu hill in northeastern Sardinia, and they are filled with garnet, amphibole, chlorite, and epidote. Some garnet-rich veins are margined by an amphibole layer at the interface with the host rock and/or show replacement of epidote concentrated in the vein core. Together with homogeneous matrix garnet (Grt1), millimetric, euhedral, and strongly zoned garnet porphyroblasts occur within these veins. The estimated pressure–temperature conditions (P = 1.0–1.7 GPa, T = 650–750 °C) for the formation of Grt1 match the metamorphic peak and early exhumation derived previously for the host rocks and confirm that the garnet veins also formed under high-pressure (HP) conditions. The igneous protolith of the host rocks experienced HP metamorphism in a subduction zone and underwent exhumation in an exhumation channel. The vein system in the ultrabasic amphibolites formed by cyclic hydrofracturing as rapid and transient events such as crack-seal veining. The growth of multiple vein-filling mineral assemblages indicates the formation of separate vein-producing cycles.

New insights into Early Iron Age connections between Sardinia and Etruria: Archaeometric analyses of ceramics from Tavolara

The island of Tavolara off the coast of northeastern Sardinia (Italy) was intermittently occupied from Neolithic to modern times, and recent excavations at the site of Spalmatore di Terra have revealed the presence of Villanovan ceramics on the island dating to the 9th century BCE (according to the traditional chronology). Contacts between Etruria and Sardinia during the Early Iron Age are well documented by the recovery of Nuragic vessels and metal objects in Etrurian burial contexts, but the presence of Villanovan artefacts in Sardinia is comparably rare. Indeed, discoveries from Spalamatore di Terra represent the first evidence of Villanovan ceramics in Sardinia, likely originating from Tyrrhenian Etruria.To investigate the provenance of the ceramics found at Spalamatore di Terra, a representative sample of these materials was chosen to be studied through a combination of petrographic and geochemical characterisation. A particular emphasis was placed on the Villanovan materials that were most abundant, but a selection of Nuragic sherds was also included. The results of these analyses are significant in that they reveal a surprisingly diverse range of ceramic fabrics that can be linked to Etruria, thus providing insights into Tavolara’s place within a broader trans-marine network of interaction.

Coralligenous assemblages differ between limestone and granite: A case study at the Tavolara-Punta Coda Cavallo Marine Protected Area (NE Sardinia, Mediterranean Sea)

The Tavolara-Punta Coda Cavallo Marine Protected Area (North-eastern Sardinia, western Mediterranean Sea) includes, in a restricted area, substrates of different lithology. In fact, the Tavolara Island is characterized by limestone (high carbonate content), while the nearby Molara Island and the Molarotto islet are granitic (high quartz content). These peculiar features create a suitable condition to test the hypothesis that the taxonomic richness of the Mediterranean coralligenous communities could be also driven by the lithological characteristics of the substrate.Differences, in terms of recurrences of the macrobenthic sessile species, mainly macroalgae, sponges, anthozoans and bryozoans, of the coralligenous communities settled on limestone and granite, were investigated by image analysis. 240 photos on standard surfaces and four video transects were taken in 12 sites at comparable depth (40–50 m) but characterized by a different lithology. Multivariate analyses highlighted significant differences among sites, characterized by carbonate and granitic substrates. In general, limestone proved to be more suitable for the development of a thick differentiated coralligenous basal layer and showed a marked heterogeneity. Among structuring species, the gorgonian Eunicella cavolini was more recurrent on limestone than on granite, while the sponges Sarcotragus foetidus, Axinella polypoides and Axinella spp. were significantly more abundant on granite.Results suggest that a number of mechanisms could be involved to explain the observed patterns, such as a selective capacity of several sessile organisms, towards substrate, with ultimate repercussions on the structure of the whole coralligenous assemblage.

Habitat selection and density of the Barbary partridge in Sardinia, Mediterranean Sea

The Barbary partridge is one of the four species of Alectoris found in Mediterranean Basin. Its range is restricted to Sardinia, northwestern Africa, Gibraltar, and Canary Islands. It is classified as SPEC3 because its population is declining; nonetheless, its ecology is poorly known. Our aims were to define the habitat factors linked to the species presence, and which affects the breeding density in northeastern Sardinia. Data were collected in the breeding seasons 2012 and 2013 carrying out 376 listening points in 34 study sites representative of the typical landscapes of the island. The habitat selection was assessed by generalized linear model with binomial error distribution following an information theoretic approach. In particular, the environmental variables concerning the land use cover, the landscape configuration, and the topography of the points with the species presence were compared with an equal number of availability points. The densities were estimated by distance sampling, and then, we formulated two multiple linear regressions, one for each year, relating densities with the environmental variables. The analyses showed that the species inhabits shrublands, garrigue, and meadows on slopes faced to east, especially between the sea level and 200 m, avoiding forests and northwestern slopes. In 2012 and 2013, we estimated 22.9 and 5.1 pairs per km2, respectively. It is likely that this change in densities is related to a lower singing activity of the males due to the bad weather conditions in the spring 2013.

Using verified citizen science as a tool for monitoring the European hornet (Vespa crabro) in the island of Sardinia (Italy)

The European hornet, Vespa crabro L. (Hymenoptera: Vespidae), is a eusocial insect native to Eurasia that was accidentally introduced in the island of Sardinia (Italy) in 2010. This alien generalist predator could impact on native insect species through predation or competition by modifying interspecific relations in sensitive island ecosystems. As part of the Interreg project ALIEM, the present work regarded the first monitoring activity of the European hornet conducted in Sardinia by means of verified citizen science. The main goals of this study were to define the distribution area of the wasp in 2018 and evaluate the profile and the performance of citizen scientists. Our results showed that V. crabro is mainly located in north-eastern Sardinia and that the hotspot was probably the commercial port of Olbia. Furthermore, data provided by contributors were very accurate and none of the parameters considered to define the participants (age, gender, education level, job category) was a true predictor of a volunteer’s ability to recognise the wasp. In conclusion, this small-scale study suggests that citizen scientists could be a valuable aid to monitor already-established alien species and could be part of a surveillance network for early detection of other potentially invasive alien species not yet introduced in Sardinia, such as the yellow-legged hornet, Vespa velutina, which is already present in northern Italy.

Ancient and recent sponge assemblages from the Tyrrhenian coralligenous over millennia (Mediterranean Sea)

The demosponge siliceous spicules, entrapped in the Mediterranean coralligenous bioherms, are a good tool for reconstructing the sponge ancient communities across time, also allowing a comparison with the current biodiversity. The aim of this paper has been the description of the ancient sponge assemblages of the coralligenous bioherms grown up in the Tavolara-Capo Coda Cavallo Marine Protected Area (northeastern Sardinia, Tyrrhenian Sea) between 5800 and 3700 YBP and its comparison with the living sponge community. On the base of radiocarbon age determinations, it was possible to estimate that these bioherms cover a span of time ranging from the Holocene Climatic Optimum until the Bronze Age Crisis. Their growth rates, 0.21–0.24 mm year−1, were of the same order of estimations conducted around the Mediterranean. The Tavolara ancient sponge diversity was compared with those found in ancient accretions from Ligurian Sea and Ionian Sea. Our results supported the already-described general trend, supporting the hypothesis that the genus richness in the coralligenous bioherms was driven by climatic vicissitudes. Nevertheless, our data strongly indicated that the sponge diversity is also related to the conditions of the coralligenous structures: in the accretions characterized by an active growth of coralline algae the number of sponge genera is similar to those recorded in the ancient assemblages while in coralligenous where the accretion is stopped the number of sponge genera strongly decreases probably due to the competition with frondose macroalgae.

Hitch-hikers of the sea: concurrent morphological and molecular identification of Symplegma brakenhielmi (Tunicata: Ascidiacea) in the western Mediterranean Sea

We report here one of the first records of the non-indigenous colonial ascidian Symplegma brakenhielmi (Michaelsen, 1904) in the western Mediterranean Sea. Colonies of this invasive species have been collected in 2014 and 2018 along North-eastern Sardinia coasts (Olbia, Italy). Further colonies have been observed in 2016 in the Mar Piccolo basin (Gulf of Taranto, Italy). Both areas are strongly influenced by anthropogenic activities such as commercial shipping and aquaculture, suggesting these human-mediated pathways the most likely vectors of introduction. In both areas, the colonies present two different color phenotypes, the yellow and the red type, with the yellow coloration never found before in the Mediterranean Sea. Morphological and DNA barcode analyses of the collected specimens show that both these color types belong to the same species. Phylogenetic and species delimitation analyses based on the DNA barcode confirm our identification as S. brakenhielmi, but also indicate a surprisingly high similarity with published sequences of other two species, including the co-generic species Symplegma rubra Monniot, 1972. Morphological and molecular examination of a large number of samples of these species would be need in the near future to clarify this issue.

Geomorphology of the continental shelf of Tavolara Island (Marine Protected Area ‘Tavolara-Punta Coda Cavallo’ – Sardinia NE)

ABSTRACT In this document a geological – geomorphological map in scale 1: 25,000 is presented. The study area is located inside the Protected Marine Area Tavolara – Punta Coda Cavallo, in north-eastern Sardinia. The study was done through integrated analysis of multibeam bathymetric and very high-resolution side scan sonar data, acquired in an area of 163 km2 with the purpose of mapping the main biocoenoses and with particular reference to the coralligenous bioconstructions and the distribution of Posidonia oceanica. The interpretative hypotheses, based on the analysis of geophysical data, have been validated through diving surveys. This map represents a fundamental knowledge base and it constitutes an important technical-scientific support for long-term planning and management of the studied seabed.

Integration of Conservation Measures Concerning Natura 2000 Sites into Marine Protected Areas Regulations: A Study Related to Sardinia

This study defines and discusses a spatial planning approach, which can be integrated into conservation measures, regarding the sites of the Natura 2000 Network—established under the provisions of Directive No. 92/43/EEC (the “Habitats” Directive), and Directive No. 2009/147/EC (the “Birds” Directive)—into the regulations of marine protected areas. The protected marine area of the Island of Tavolara and Cape Coda Cavallo, located in North-Eastern Sardinia (which is overlapped by a Natura 2000 Site) is the spatial context for the implementation of the proposed methodology. The comprehensive outcome of this study, that is, the implementation of the proposed spatial planning approach into regulations regarding the previously mentioned protected marine areas, is particularly relevant for the scientific and technical debate on spatial planning. This debate is related to protection of nature and natural resources, since the issue of integration of the conservation measures related to Natura 200 Network, into regulations of protected areas, is an open question, which needs further consideration and insights.

Small-scale spatial variation of soil organic matter pools generated by cork oak trees in Mediterranean agro-silvo-pastoral systems

The aim of this study was to assess the role of cork oak (Quercus suber L.) trees on the small-scale variation of soil organic matter (SOM) pools in an agro-silvo-pastoral system under Mediterranean semi-arid conditions in northeastern Sardinia, Italy. Six cork oak trees were selected in a wooded grassland (30% tree ground cover). For each tree, and along two opposite transects (NE and SW), floor litter and soil (20-cm depth) were sampled at five points starting next to the trees' trunk and ending beyond the tree crown projection. Soil organic matter quality was characterized by measuring the content of water extractable organic matter (WEOM), free particulate SOM (POMf), occluded aggregates particulate SOM (POMo), and mineral-associated SOM (MOM). Carbon (C) input from floor litter was larger in the sampling points under the tree crown projection than in those beyond the tree crown. The C content of SOM pools differed among sampling positions regardless of the transect orientation, decreasing from the trunk to the positions beyond the tree crown projection, from 24.1 to 15.7gCkg−1 for MOM, and from 9.9 to 5.7gCkg−1 for the sum of WEOM, POMf and POMo. The C in MOM next to the tree trunk was above the saturation level sensu Hassink and Whitmore (1997), but below saturation beyond the tree crown projection. The nitrogen (N) distribution showed a similar trend. These results indicate that in these agro-silvo-pastoral systems, oak trees generate hot spots of soil C storage, by controlling the rate of C inputs via litterfall. Hence, conservation strategies designed to maintain cork oak trees in grasslands will also contribute to maintain a high stock of C stored and a resilient, multipurpose system.

Organic carbon pools and soil biological fertility are affected by land use intensity in Mediterranean ecosystems of Sardinia, Italy

Soil quality is mainly studied from the chemical and physical point of view, whereas soil biochemical and microbiological parameters are relatively more scarcely explored to assess the effect of management practices. This study aimed to evaluate soil organic carbon (SOC) and its pools; soil microbial activity parameters; and the Biological Fertility Index (BFI), in six land uses characteristics of the Mediterranean basin in north-eastern Sardinia. These land uses differed in management intensity and consisted of: tilled vineyard (TV), no tilled grassed vineyard (GV), former vineyards (FV), hay crop and pasture (HC and PA), cork oak forest (CO).Significant differences among ecosystems were found in most cases in (SOC), the related pools (total extractable carbon, humic and fulvic acids, not humified, not extractable), humification parameters (degree, rate and index of humification), and soil microbial activity (microbial carbon, respiration, metabolic quotient, and mineralization quotient). Pasture and cork oak forest showed in average a better soil quality for most biochemical and microbial parameters in comparison with the other ecosystems. The index of soil biological fertility (BFI) was higher under cork oak forest which is supposed to be the most sustainable ecosystem in the long term in this environment, able to maintain soil biological fertility and microbial diversity.

Geomorphic response to an extreme flood in two Mediterranean rivers (northeastern Sardinia, Italy): Analysis of controlling factors

A high-magnitude, low-frequency flash flood affected two ungauged rivers (northeastern Sardinia, Italy) on 18 November 2013. This study investigates the response of channel reaches in a Mediterranean environment featuring different morphological settings (i.e., alluvial, semialluvial, and bedrock boundaries) with the aims of (i) detecting the morphological effects of this large flood and (ii) analyzing a range of morphological and hydraulic variables as potential controlling factors of channel response. Channel widening was the dominant geomorphic response observed, and it occurred at different magnitudes among the study subreaches. Within individual subreaches, channel width increased from 1.1 to 6.2 times the pre-flood width. A significant trend in channel widening is observed, especially in alluvial subreaches where the narrowest channels were prone to enlarge more compared to the widest channels. Considerable erosion of valley sides also occurred in confined and partly confined semialluvial and bedrock subreaches. A range of parameters influenced the geomorphic role of the flood, and a series of selected morphological and hydraulic controlling factors showed robust correlations with changes in channel width, although correlations were stronger in alluvial subreaches. Analysis and documentation of channel response and its variability through different morphological settings is crucial to provide a basis from which to forecast future river sensitivity to geomorphic adjustment to high-magnitude floods and improve flood management strategies.

Factors influencing wild boar damage to agricultural crops in Sardinia (Italy).

Crop damage by wildlife is a frequent source of human–wildlife conflict. Understanding which factors increase the risk of damage is crucial to the development of effective management strategies. The aims of this study were to provide a general description of agricultural damage caused by wild boar Sus scrofa meridionalis over a 7-year period in North-eastern Sardinia (Mediterranean Italy), and to formulate a predictive model of damage risk. We recorded a total of 221 cases of wild boar damage, with economic losses amounting to 483,982 Euros. Damage events mostly involved vineyards, meadows and oat fields, and were characterized by a peak incidence in summer and early autumn, and a minimum in spring. Damaged fields were characterized by an increasing presence of permanent crops, a decreasing presence of woodlands, maquis and urban areas, and a reduced distance from shelter areas (forests and shrublands). The analysis of spatiotemporal variation of boar-induced damage and the identification of factors that augment the risk of damage provides essential information for contributing to the development of a more effective plan for managing wild boar populations.

Benthic foraminiferal assemblages from shallow-water environments of northeastern Sardinia (Italy, Mediterranean Sea)

Thirteen samples were collected from three coastal bays of northeastern Sardinia (Gallura). Bays are areas of mixed siliciclastic-carbonate sedimentation. Seagrasses and algae, widely distributed in the shallow-water environments, contribute to the carbonate factory. Near-shore benthic foraminifers (111 species, 50 genera), occurring in the shallower water areas of Posidonia oceanica, were taxonomically identified and the assemblages were investigated by statistical analysis to determine if any groups of samples or species correlate with a specific sub-environment. Dominant taxa are phytophilous and three main assemblages were identified: the Lobatula lobatula/Elphidium crispum assemblage and Lobatula lobatula/Peneroplis pertusus assemblage are linked to the distribution of P. oceanica, whereas the Peneroplis/Quinqueloculina assemblage reflects oligotrophic conditions and a mixed algal/Posidonia substrate. Taxonomic abundance and diversity appear to be mainly controlled by the type of phytal substrate.

Uranium distribution in the Variscan Basement of Northeastern Sardinia

ABSTRACTWe present a detailed map of uranium distribution and its uncertainties in the Variscan Basement of Northeastern Sardinia (VBNS) at a scale of 1:100,000. An area of 2100 km2 was investigated by means of 535 data points obtained from laboratory and in situ gamma-ray spectrometry measurements. These data volume corresponds to the highest sampling density of the European Variscides, aimed at studying the genetic processes of the upper crust potentially triggered by an enrichment of radiogenic heat-producing elements. For the first time, the Kriging with Variance of Measurement Error method was used to assign weights to the input data which are based on the degree of confidence associated with the measurements obtained using different gamma-ray spectrometry techniques. A detailed tuning of the model parameters for the adopted Experimental Semi-Variogram led to the identification of a maximum distance of spatial variability coherent to the observed tendency of the experimental data. We demonstrate that the obtained uranium distribution in the VBNS, characterized by several calc-alkaline plutons emplaced within migmatitic massifs and amphibolite-facies metamorphic rocks, is an excellent benchmark for the study of ‘hot’ collisional chains. The uranium map of VBNS, and in particular the Arzachena minor pluton, confirms the emplacement model based on the recognition of the different petrological associations characterizing the Variscan magmatic processes in the Late Paleozoic. Furthermore, the presented model of the uranium content of the geological bedrock is a potential baseline for future mapping of radon-prone areas.