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Size Spectra as a tool to understand structures and processes of aquatic communities
Full text linkAquatische Gemeinschaften sind stark körpergrößenstrukturiert mit einer exponentiellen
Abnahme der Häufigkeit der Individuen mit zunehmender Körpergröße, die als
Größenspektrum (SS) bezeichnet wird. Körpergrößenbasierte Ansätze bieten eine einfache und kostengünstige Methode zur Beantwortung komplexer ökologischer Fragestellungen in
aquatischer Forschung. Widersprüchliche Ergebnisse zu den wichtigsten Faktoren, die
Größenspektren beeinflussen unterstreichen jedoch die Notwendigkeit weiterer Studien.
Um einige dieser widersprüchlichen Schlussfolgerungen anzugehen, habe ich eine Reihe von
Fragen in den Bereichen Limnologie und Korallenriffökologie untersucht. In dieser
Dissertation wurden größenbasierte Ansätze wie SS verwendet, um zu untersuchen, (i) was die Größenverteilung von Zooplankton beeinflusst und ob Zooplankton-fressende Fische (topdown) oder Ressourcenverfügbarkeit und Umweltbedingungen (bottom-up) die SS der
Zooplanktongemeinschaft bestimmen, (ii) ob traditionelle Schleppnetze oder moderne
hydroakustische Methoden Fisch-SS zuverlässiger darstellen, und (iii) ob SS von Korallenriff-
Fischgemeinschaften und die strukturelle Komplexität der Korallen bzw. deren Beziehung
zueinander sich unter verschiedenen anthropogenen Stressoren verändert.
Zuallererst konnte ich zeigen, dass weder Top-down- noch Bottom-up-Kräfte stark die
Größenverteilung der Zooplanktongemeinschaft beeinflussten. Zooplankton SS scheinen
robust gegenüber Prädationseffekten zu sein, aber ein empfindlicher Indikator für die
Energieverfügbarkeit und Transfereffizienz im Nahrungsnetz des untersuchten Sees. Des
Weiteren konnten meine Studien bestätigen, dass hydroakustische Methoden die SS von
pelagischen Fischgemeinschaften zuverlässig darstellen, was sie zu einer kostengünstigen und minimalinvasiven Alternative zu traditionellen Fischentnahmemethoden macht. Ich konnte jedoch kein allgemeingültiges Muster hinsichtlich der Größenverteilung von
Korallenrifffischen und der strukturellen Komplexität der Korallen in Beziehung zu
unterschiedlichen anthropogenen Stressoren finden. Insgesamt zeigt die Dissertation das weite Anwendungsspektrum von SS, um Strukturen und
Prozesse in aquatischen Gemeinschaften und Fischfangmethoden zu untersuchen. Die hohe
Variabilität von Größenspektren und der Einfluss von Umweltbedingungen unterstreicht weiter die Wichtigkeit, Daten über einen langen Zeitraum einzubeziehen. Darüber hinaus
unterstreichen die Ergebnisse dieser Arbeit auch die Grenzen der Anwendung von SS, da für
die Beantwortung mancher ökologischer Fragestellungen artenspezifische Informationen, wie
Lebensraum- und Nahrungspräferenzen benötigt werden.Aquatic communities are highly body-size structured with an exponential decline of abundance with increasing body size, which is referred to as the size spectrum (SS). The importance of body size as a principal and simplifying framework within aquatic communities, has led to a high number of theoretical and empirical studies on energy fluxes in food webs and predatorprey interactions using Size Spectra. These size-based approaches offer a rather simple and inexpensive method to answer complex ecological questions. However, conflicting findings on the key drivers of SS highlight the need for further studies.
To address some of these conflicting conclusions, I investigated a range of questions within
the fields of limnology and coral reef ecology. In this thesis size-based approaches such as SS were employed to explore (i) what drives zooplankton size distribution and whether
zooplanktivorous fish (top-down) or resource availability and environmental condition
(bottom-up) determine zooplankton community SS, (ii) whether traditional midwater trawling
or modern hydroacoustic methods more reliably represent fish SS, and (iii) coral reef fish
community SS and habitat structural complexity and their relationship across site-specific
anthropogenic stressors. By analysing long term data, I first found that neither top-down or bottom-up forces drove the zooplankton community size distribution. Zooplankton SS seem robust against predation effects but a sensitive indicator for lake-wide energy availability and transfer efficiency in the food web. Then I found that hydroacoustic methods reliably represent pelagic fish community SS, making it a great alternative to traditional and more invasive fish removal sampling methods. Finally, I discovered that coral reef fish SS slope and structural complexity of the reef exhibited a significant negative relationship on two of the examined reef sites which are least exposed to anthropogenic disturbances. A consistent pattern of fish SS and reef complexity was missing, indicating that other environmental factors may also impact the assessed parameters. Overall, my studies show the range of applications of SS to effectively answer universal questions from trophic interactions and the importance of habitat characteristics in a community to a methodological comparison of fish sampling methods. The high variability of SS behaviour and the influence of environmental conditions further underlines the importance to include data on a large temporal scale. Community information, such as taxonomic identity and consideration of species-specific feeding and habitats preferences, for example, are still beneficial in some cases to answer ecologically questions extensively
Whole lake and mesocosm studies on the role of nutrients and zooplankton grazing in a system of shallow and deep lakes.
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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