1,721,030 research outputs found
Decontextualizing big data for a better perception of macroecology
Full text linkFish species are charismatic subjects widely used for ecological assessment and modelling. We investigated the influence of electrofishing in an attempt to illuminate the extent to which datasets might be merged together. Three American Midwestern regions in Ohio were chosen as study area and the changes in the size-biomass spectra of more than 2000 fish assemblages were analysed. These communities behaved differently according to the sampling method in conjunction to the morphology of the investigated streams and rivers, as shown by decreasing predatory species and lowering of allometric slopes. There are here several lines of evidence indicating that the chosen sampling method, as determined by different habitats, acts as a pitfall and strongly influences the allometry of fish spectra. In the ongoing data-rich era, our results highlight that macroecological investigations, often performed by machine-learning systems without considering the different procedures adopted to collect original data, can easily produce artefactual allometric scalings
Data from: Contextualizing macroecological laws: A big data analysis on electrofishing and allometric scalings in Ohio, USA
No full textWe investigated the influence of different electrofishing methods on allometric scaling features of fish assemblages in lotic environments. The ultimate aim was to elucidate to which extent the structure of fish assemblages is predictable by the three-quarter power law theory. Water bodies across the state of Ohio, USA, provided a suitable data set to analyze the size–biomass spectra of 2051 fish assemblages. For the first time, 41,070 allometric field observations were screened according to sampling methods (i.e., longline, tote barge, boat) adopted for sampling collection. Allometric patterns varied considerably in relation with the sampling method, in turn imposed by the local hydrology and morphology of the investigated water courses, as shown by the lowering of scalings from boatable to wadeable systems. There are several lines of evidence indicating that the chosen type of electrofishing acts as a pitfall for size spectra. Using individually weighted body-mass values as independent predictor of spectra we show that the specific sampling methodology required by the physical characteristics of different lotic habitats influence the allometric outcomes, a novel result that makes universality of community power laws not as straightforward as supposed until now
Detrital Dynamics and Cascading Effects on Supporting Ecosystem Services
No full textTop-down trophic cascades are well known in many autotrophic systems, yet their role in heterotrophic food webs is less clear. We collated data from 78 investigations and applied meta-analysis to evaluate the strength of detrital trophic cascades in freshwater and terrestrial food webs. Predators exerted significant, indirect controls on detrital resources, in line with theoretical predictions, whereas this was not the case for omnivores, suggesting that detritivory prevailed over predation and disrupted trophic cascades. Significant relationships were observed for both types of consumer in terms of their responses to detrital quality: specifically, unimodal curves across C:N and N:P gradients were the best fits for predators, whilst cascade strength responses to detrital quality were saddle shaped. These insights suggest that while predatory strategy is determining cascades within detrital-based systems, resource quality has bottom-up role effects on predators and on preferential consumption by omnivores. As such, these environmental responses seem to mirror some provisioning and supporting services; our findings are discussed within conceptual frameworks related to ecological stoichiometry and ecosystem services
Contextualizing macroecological laws: A big data analysis on electrofishing and allometric scalings in Ohio, USA
No full textWe investigated the influence of different electrofishing methods on allometric scaling features of fish assemblages in lotic environments. The ultimate aimwas to elucidate to which extent the structure of fish assemblages is predictable by the three-quarter power law theory. Water bodies across the state of Ohio, USA, provided a suitable data set to analyze the size–biomass spectra of 2051 fish assemblages. For the first time, 41,070 allometric field observations were screened according to sampling methods (i.e., longline, tote barge, boat) adopted for sampling collection. Allometric patterns varied considerably in relation with the sampling method, in turn imposed by the local hydrology and morphology of the investigated water courses, as shown by the lowering of scalings from boatable to wadeable systems. There are several lines of evidence indicating that the chosen type of electrofishing acts as a pitfall for size spectra. Using individually weighted body-mass values as independent predictor of spectrawe show that the specific sampling methodology required by the physical characteristics of different lotic habitats influence the allometric outcomes, a novel result that makes universality of community power laws not as straightforward as supposed until now
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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