1,720,965 research outputs found
Microtopography-Induced Differentiation of Moss Synusiae in Wet Grasslands Covering a Karst Plain in Central Italy (Pian Grande, Central Apennines)
No full textThis study examines the relationships between the occurrence of epigeic moss assemblages in different grasslands and the microhabitats (pits, dolines, brooks and mounds) occurring in a karst, almost flat basin. The bryophytes tend to form specific synusiae in grassland communities that cover particular microhabitats differentiated on the basis of microtopography. Except for pits and mounds, all other microhabitats are clearly distinguishable in terms of bryophyte composition. The most discriminant species between the moss synusiae of dolines, brooks and pits are Drepanocladus aduncus, Fontinalis antipyretica and Polytrichum commune, respectively. The mounds have no differential species and are poorly distinguished from pits based only on the low cover of Polytrichum commune. A combined soil acidity-moisture gradient determined by both land microtopography and surface water runoff is responsible for the good compositional distinctiveness of dolines and brooks from pits and mounds. A relatively broad section of this gradient is occupied by the niche of Calliergonella cuspidata, which could be the indicator of a different synusia occurring in microhabitats with ecological conditions intermediate between dolines and brooks. A weaker gradient of soil organic matter content accounts for the distinction of pits from dolines and brooks in the species multidimensional space. Overall, there is a good Agreement between the structure of epigeic bryophyte assemblages and the corresponding type of vascular plant communities developed in the same karst habitat, which supports the hypothesis of their dependence and the methodological approach of integrated releve ́s in phytocoenosis sampling
Ricerche geobotaniche nella torbiera di Fiavè (1986-2018)
No full textRicerche geobotaniche nella torbiera di Fiavé (1966-2018). Comparazione di ricerche floristico-geobotaniche, distribuzione della vegetazione e flora in un cinquantennio
Do species incidence matrices reflect different degrees of plant community integration?
No full textBackground and aims – Assuming the asymmetrical hump model of the stress-gradient hypothesis, higher degree of species aggregation in floristically similar communities is expected under conditions of stronger environmental severity. Methods – Several species incidence-based metrics were calculated for two large, homogeneous matrices pertaining to predefined community types: weed assemblage of trampled sites (S-P) and nutrient-rich pastures (F-A). For each metric and matrix, a standard effect size (SES) was estimated through a null model with fixed species frequencies and equiprobable sites. Key results – All metrics related to co-occurrence, nestedness and clustering of species range boundaries have significant SES in both matrices, but they are all larger in S-P. No significant checkerboardness was detected in S-P, whereas F-A displays non-random segregation patterns that are exclusively due to species turnover. The core species effect is positive but not significant in S-P, and the between-site pairwise similarities present a monotonic distribution. The higher SES of coherence and the significant SES of homotoneity in F-A make it more clearly delineated as a syntaxon. In fact, between-site pairwise similarities are significantly higher in F-A and their distribution approaches a reversed J-shape. Conclusions – The stronger species association and nestedness patterns revealed in weed assemblages are consistent with the hypothesis of higher community integration in harsh environments. However, the species-rich and productive grassland communities appear overall more structured. Regular and moderate disturbances produced by herbivores may be an important requisite for plant community organisation according to the core-satellite species hypothesis in fertile habitats. Although not a test for inferring underlying ecological processes, the joined use and comparison of complementary, species incidence-based metrics represents a useful exploratory tool for distinguishing between various patterns of species assembly, at least for relatively homogeneous, presence-absence matrices of different plant community types
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Manual de interpretare a habitatelor Natura 2000 din România [Romanian Manual for Interpretation of EU Habitats]
No full textThe book is an attempt to select and interpret European habitats present in Romania, focusing on biodiversity conservation, environmental protection and legislation. Manualul este fructul unui proiect PHARE privind implementarea retelei Natura 2000 in Romania si se doreste a fi un ghid pentru identificarea acestor habitate. Manual is the fruit of a PHARE project on the implementation of the Natura 2000 network in Romania and is intended as a guide for identifying these habitats. Lucrarea se adreseaza celor care vor contribui la implementarea retelei Natura 2000, personalului agentiilor de mediu si tuturor celor interesati. The book is addressed to those who will contribute to the implementation of Natura 2000 environmental agency staff and all those interested
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Get PDFWe 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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