1,720,975 research outputs found
Carpobrotus acinaciformis vs Carpobrotus edulis: Are there any differences in their impact on coastal dune plant biodiversity?
No full textCoastal sand dunes are widely acknowledged as fragile and dynamic ecosystems. Among the several threats affecting the native biodiversity of these systems, invasive plants are one of the most troubling ones. The genus Carpobrotus has been recognized as one of the most abundant invasive genera along the Mediterranean coast, particularly in coastal sand dunes. In Italy, two taxa belonging to this genus have been identified: C. edulis and C. acinaciformis. Given that the taxonomic identification of these two species is still subject of debate, we investigate whether there are differences concerning their ecology in terms of their impact on native plant communities in central Italy coastal dunes. To do so, we analyzed their relative impact on species richness, diversity and relative abundance. Vegetation sampling was carried out through paired-plots, comparing invaded to non-invaded plots. Although our results show a general decrease in native species richness in all the invaded plots, there were no significant differences between the richness and diversity of the native communities invaded by C. edulis and that of the communities invaded by C. acinaciformis, although slight differences on native species’ relative cover was observed. In addition, we observed a higher occurrence of C. edulis in the areas closer to the seashore. We conclude that even though there are no meaningful differences in the impacts of the two taxa on native biodiversity, further analyses are needed to exclude potential differences in their relative ecological adaptations to the changing abiotic conditions found along the coastal zonation
Studying local species assemblages of salt-affected vegetation for monitoring Natura 2000 habitats
No full textThis study aims to characterize saline habitats of the Tuscan coast based on the Natura 2000 Habitats Directive 92/43/ECC. These habitats include Atlantic salt meadows (1330), Mediterranean salt meadows (1410) Mediterranean and thermo-Atlantic halophilous scrubs (1420), and Mediterranean salt steppes (1510). We compiled vegetation data from a total of 418 plots carried out during our own fieldwork (N = 157) and published scientific literature (N = 261). We performed a Linear Discriminant Analysis to associate species to habitats and used the phi coefficient of association to identify diagnostic species of each habitat. For each habitat, we provide a regional syntaxonomic framework, constant species, cover coefficients, diagnostic species (phi) and “typical species”. We identified groups of species, that we called “local assembly of typical species”, composed by species with a phi coefficient > 20 and/or a cover coefficient > 50 that can be used to identify the habitats and to monitor their conservation status at the local level. This study revealed differences in the “local assembly of typical species” among habitats, characterized by fewer species in habitats 1420 and 1510, and many species in habitats 1410 and 1310. Our results showed that the habitat 1510 was recognizable only for the high cover value of Limonium narbonense and, at least in Tuscany, its syntaxonomic attribution to the order Limonietalia is uncertain. We tested this approach only for a few habitats, but a broader applicability based on other habitats is desirable
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Long‐term dynamics of coastal dune landscapes and habitat diversity: Insights from a quarter century of resurveys in Castelporziano Presidential Estate
No full textCoastal dunes are dynamic ecosystems vulnerable to human impact. Traditional monitoring relies on costly field surveys, but high-resolution satellite imagery offers an efficient alternative. This study integrates remote sensing (RS) and field data to analyze vegetation and landscape changes over 25 years in the highly protected Castelporziano Presidential Estate. We examined three habitat groups—Herbaceous Dune Vegetation (HDV), Woody Dune Vegetation (WDV), and Broadleaf Mixed Forest (BMF)—using 58 resurveyed plots and land cover maps. Landscape dynamics and vegetation compositional changes were assessed, and temporal patterns were calculated for three buffer sizes (25, 75, and 125 m), using Bray–Curtis dissimilarity and differences in landscape metrics. Random forest models evaluated the relationship between landscape and vegetation compositional changes. The results revealed a reduction in artificial surfaces, greater vegetation encroachment, and clear signs of natural succession. HDV exhibited a shift toward grassland species, reflecting ongoing changes in vegetation composition. WDV experienced the most pronounced compositional change, while BMF showed signs of structural homogenization. Habitat proportion emerged as the strongest predictor of compositional changes, especially at the finest scale. These findings confirm the value of combining RS and field data for long-term monitoring and provide useful insights for managing coastal dune habitats
Spatial patterns of coastal dune plant diversity reveal conservation priority hotspots in and out a network of protected areas
Full text linkEffective conservation planning requires identifying priority hotspots to allocate resources. To preserve biodiversity, it is crucial to consider α, and γ-diversity and protect ecologically unique sites, which can host uncommon and irreplaceable species assemblages that would be lost if only species-rich sites were protected. Coastal dunes, hosting highly specialized plant communities, are among the most threatened ecosystems worldwide. In this study, we identified conservation priority hotspots to assess the effectiveness of the network of protected areas in coastal dunes of Tuscany (central Italy), using data on plant communities collected in 506 plots. We additively partitioned -diversity in its and components, observing a significant variation at all spatial levels only for dune species. In terms of -diversity, we found that Northern protected sites were richer in dune species, while synanthropic and alien species were equally present inside and outside protected areas. By partitioning the total -diversity into its components (replacement and richness difference), we found a prevalence of replacement for dune species, indicating the most unique sites as the ones to favor for conservation. Unique sites were identified through Local Contributions to Beta-Diversity and their conservation value was determined by their species composition and the relationship with landscape variables. Unique sites with high conservation value were only partly protected, while some protected sites were altered and required restoration. Our approach proved effective for identifying the most unique sites, indicating some issues in the existing protected network, while providing valuable information on sites to prioritize for future conservation actions
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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