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Briofite degli stagni temporanei della Sardegna: biodiversità, ecologia e distribuzione.
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Bryoflora of temporary ponds in the Mediterranean Basin: hints for management and conservation
No full textIn the Mediterranean region temporary ponds are classified among the most biologically and biogeographically interesting ecosystems. Despite the important ecological functions of bryophytes in those fragile environments, they are neglected or undervalued in most management actions. We surveyed the bryoflora composition and distribution within 33 Mediterranean temporary ponds in Sardinia (Italy). The bryoflora is composed by 139 taxa, (119 Bryophyta, 19 Marchantiophyta and 1 Antocerothophyta), accounting for 28% of the total Island bryoflora. Among those, Petalophyllum ralfsii, Cephaloziella calyculata and Fossombronia pusilla are critically endangered and Riccia huebeneriana and Hypnum revolutum var. revolutum, are reported for the first time in Sardinia. Three belts were recognized in temporary ponds: a central belt, an intermediate belt, and an outer belt. Species showed a spatial pattern within the temporary ponds, from species Pottiaceae and Brachytheciaceae, with the life strategy colonist and perennial, to species Ricciaceae with life strategy annual shuttle. Species as Scleropodium touretti and Tortella squarrosa are significantly associated with the outer belt, however the Riccia canaliculata is significantly associated with the central belt, because it occurs in these belt only. Those information are useful to build up a scientifically sound knowledge useful for future effective conservation actions
Analysis of bryophyte’s spores in Mediterranean temporary ponds
No full textThe persistence and abundance of most of the species in an area are the result of a dynamic balance between the duration of the habitat and the ability of species to colonize such environments through the production and dispersion of spores. This study presents a preliminary analysis of bryophyte’s spores from the pauli of the Giara of Gesturi (C Sardinia). The Giare (average altitude 550 m a.s.l.) are basaltic plateaus that rise unexpectedly from the plain of the country, as huge natural fortresses. Several authors have studied the population dynamics of some bryophytes confined to fragmented and temporary habitat (1, 2, 3) and, in particular, studies conducted by Herben & Söderström (4) show that the most important factor that regulates the survival of the species is the ability to form new colonies on substrates fragmented. The aim of this study is to determine what are the species that show a better fitness for survival and adaptation in Mediterranean temporary ponds, in order to evaluate the conservation status. In Europe, Mediterranean temporary ponds are indicated as priority natural habitats under the Habitats Directive 92/43/EEC (5): in those habitats bryophytes are recognized to have an important ecological function. Thirthy soil samples were collected in November (rainy season) in three ponds until the depths of 7 cm. The samples were taken and subdivided in seven portions, which were collected for obtaining an ex situ germination of spores, at the Botanical Garden of University of Cagliari. The results showed the capacity of some genus and two species to germinate in ex-situ conditions: Bryum sp., Pohlia sp., Tortula sp., Fossombronia sp., Riccia canaliculata Hoffm. and Archidium alternifolium (Hedw.) Mitt. It is possible to observe as these bryophytes are the most recurring in the study area, showing a better fitness for survival and adaptation to these environments.
1) W.S.C. Gurney and R.M. Nisbet (1978) American naturalist, 112, 1075-1090.
2) J. Roughgarden and Y. Iwasa (1986) Theoret. Popul. Biol., 29, 235-61.
3) L. Fahrig and J. Paloheimo (1988) Theoret. Popul. Biol., 34, 194-213.
4) T. Herben and L. Söderström (1992) Biological conservation, 59, 121-126.
5) Directive 92/43/CEE. (1992) Journal officiel de Communautés europénnes L 206:7
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
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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