1,720,976 research outputs found
Ryser et al 2019
No full textThis data package includes the files needed to reproduce the data and analyses of the following paper: The biggest losers: habitat isolation deconstructs complex food webs from top to bottom, Ryser, Remo, Häussler, Johanna, Stark, Markus, Brose, Ulrich, Rall, Björn C., Guill, Christia
Maintaining ecological stability for sustainable economic yields of multispecies fisheries in complex food webs
Get PDFFish stocks are increasingly overexploited due to the growing global demand for seafood. As these species are embedded in complex food webs, traditional single-species management plans should be replaced by models that integrate multi-species fisheries with economic market feedbacks into complex food webs to promote sustainable resource use. Here, we develop such a dynamic model involving three open-access fisheries in a complex food web. Systematically comparing six fishing scenarios, we find that targeting low or high trophic levels risks reducing basal biomass or triggering trophic cascades that undermine first ecological stability (food web biomass and persistence) and then sustainability of economic returns (total sustainable catch and revenue). High sustainable economic returns combined with low negative ecological impacts occur when similar mid-trophic level species are caught in multispecies fisheries. We conclude that complex systems analysis can help design ecosystem-based management strategies to achieve a sustainable food supply for the world
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
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
Synthesis of spatial and trophic networks and their response to global change
Get PDFIncreasing human demands for production and goods continuously leads to the loss and fragmentation of habitat and eutrophication and threatens biodiversity. Organisms that comprise biodiversity interact with each other and depend on each other and thus, biodiversity is organised in complex interaction network. On the one hand, food-web research has addressed how trophic interactions shape local communities and how global change drivers such as eutrophication affects them. On the other hand, metacommunity research has been focused on spatial distributions and geographic drivers of local and regional biodiversity and how global change drivers such as habitat fragmentation species communities. These two realms have, however, mostly been separate. In this thesis, I present a meta-food-web model that synthesizes local trophic interactions and interpatch dispersal. This model employs species body masses as an interlinking trait that creates food webs and trophic dynamics through predator-prey body mass ratios and spatial networks through species dispersal capacities. With the meta-food-web model, I uncover mechanisms shaping biodiversity that only arise as a consequence of the synthesis of spatial and trophic interactions. The perspective from meta-food-webs reveals that the effect of global change drivers such as eutrophication and habitat fragmentation are highly context dependent and their effect depends on food-web and landscape structures. Furthermore, I show that interacting global change drivers can create non-linearities in biodiversity responses. Thus, this thesis provides a tool and theory derived hypotheses to shed light on consequences of global change and on what may be important to conserve biodiversity
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
The environment to the rescue: can physics help predict predator–prey interactions?
No full textABSTRACT Understanding the factors that determine the occurrence and strength of ecological interactions under specific abiotic and biotic conditions is fundamental since many aspects of ecological community stability and ecosystem functioning depend on patterns of interactions among species. Current approaches to mapping food webs are mostly based on traits, expert knowledge, experiments, and/or statistical inference. However, they do not offer clear mechanisms explaining how trophic interactions are affected by the interplay between organism characteristics and aspects of the physical environment, such as temperature, light intensity or viscosity. Hence, they cannot yet predict accurately how local food webs will respond to anthropogenic pressures, notably to climate change and species invasions. Herein, we propose a framework that synthesises recent developments in food‐web theory, integrating body size and metabolism with the physical properties of ecosystems. We advocate for combination of the movement paradigm with a modular definition of the predation sequence, because movement is central to predator–prey interactions, and a generic, modular model is needed to describe all the possible variation in predator–prey interactions. Pending sufficient empirical and theoretical knowledge, our framework will help predict the food‐web impacts of well‐studied physical factors, such as temperature and oxygen availability, as well as less commonly considered variables such as wind, turbidity or electrical conductivity. An improved predictive capability will facilitate a better understanding of ecosystem responses to a changing world
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