1,721,303 research outputs found
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
Ecology of the Black-faced Sheathbill on Marion Island
No full textAs the pace of climate change has begun to accelerate so too has it become clear that the
direct impacts thereof are likely to have profound consequences for many island systems.
Moreover, it has also been suggested that climate change will exacerbate the effects of
many invasive species, so further impacting both diversity and ecosystem functioning.
Forecasts for such interactions have been most pronounced for the Southern Ocean islands,
which are home to a wide variety of endemic species. This thesis is about such interactions
and their specific impacts on a key endemic, the black-faced sheathbill (Chionis minor) on
the Prince Edward Islands.
Of increasing concern is how invasive rodent populations in the Southern Ocean may
be responding to global climate change, as ameliorating conditions on these islands are
forecast to decrease thermal and resource restrictions on rodents. However, firm evidence
for changing rodent populations in response to climate change, and demonstrations of
associated impacts on the terrestrial environment, are entirely absent for the region. In
Chapter 2 of this thesis, these relationships are explored for invasive house mice (Mus
musculus) on Marion Island. Using spatially explicit capture-recapture modeling, it is
determined that mouse populations across a range of habitats have increased over time.
Owing to an extended breeding season, made possible by ameliorating conditions brought
on by climate change, the total number of mice on the island at annual peak density more
than doubled over the past decade. It is also demonstrated that mice directly reduce
invertebrate densities, with biomass losses up to two orders of magnitude in some habitats.
Because of the importance of invertebrates to nutrient cycling on the island, such changes
are likely to have significant ecosystem-level impacts.Submitted in partial fulfilment for the degree Doctor of Philosophy in Zoolog
Iimbovane Outreach Project: Vegetation data
No full textThe Iimbovane outreach project investigates the abundance and diversity of ants along two extensive transects through the Fynbos and Succulent Karoo biomes of South Africa. It is a long term project initiated in 2005 by Principal Investigator Prof. S.L. Chown, Stellenbosch University. Data collection is carried out learners on a biannual (spring and autumn) basis.To provide information on the vegetation at the sites where ants were collected
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
AMR Bird observation data (avian assemblages in alien acacia thickets)
No full textBird observation data: Site, date of observation, point number at which observation was made, species name (common and latin), distance to bird, Roberts VII species number, feeding guild, nesting type, foraging substrate, weather during observation.dataset contains bird observations needed to analysize bird density, species richness, biomass and BSF
The extent, impacts and management of ungulate translocations
No full textThe worldwide movement of biota is of substantial concern for the conservation of biodiversity. The movement of species takes place at three different scales. These are translocations of indigenous species within their natural distribution ranges, the translocation of species outside their natural distribution ranges within geopolitical boundaries (i.e. extralimital introductions) and the translocation of species outside geopolitical boundaries and their natural distribution ranges (i.e. extraregional introductions). Ungulates are extensively translocated at each of these scales and each scale of translocation is expected to have different impacts on biodiversity. Ungulates are translocated for conservation purposes such as reintroducing species to places where they have previously gone extinct and to mitigate inbreeding in small, isolated populations. Ungulates are also extensively translocated for economic and recreational reasons, such as for sport hunting. Translocations for sport hunting include indigenous, extralimital and extraregional species. Concerns for translocations of indigenous species are largely for the loss of genetic diversity through the mixing of genetically distinct populations, and concerns for extralimital and extraregional translocations are for impacts on indigenous biodiversity such as through herbivory, competition, hybridization and disease transmission. This thesis investigates the extent of ungulate introductions globally and at a finer resolution in South Africa. It investigates the pathways, drivers and impacts of ungulate introductions and it also investigates the use of surrogates for genetic distinctiveness for advising the translocation of indigenous ungulates. The study finds that ungulate translocations have been extensive and have lead to the homogenization of ungulate assemblages in countries globally and at a quarter-degree grid-cell resolution in South Africa. Zoos were identified as a potential introduction pathway for extraregional ungulates globally and in South Africa extraregional introductions have made ungulate assemblages more different; whereas large numbers of extralimital introductions have made ungulate assemblages more similar. The homogenization of ungulate species in South Africa has increased with time, due to increased numbers of translocations, particularly of extralimital species. In South Africa translocations have most recently been made to high-income areas with high human population density and high livestock density; whereas in the 1960s ungulates were introduced to areas species poor for indigenous ungulates and marginal for livestock. In South Africa, long distance translocations of indigenous species extralimitally has resulted in extensive range expansions of a magnitude greater than predicted range changes as a result of predicted climate change. When the use of surrogates of genetic distinctiveness for advising translocations was investigated for Africa, the East African rift valley was found to be important in delineating genetic distinctiveness and translocations across this feature should be prevented. Major rivers in Africa also showed potential for delineating genetic distinctiveness in ungulates, but relevant phylogeographic data are needed to confirm this. Sufficient evidence for the impacts of non-indigenous ungulates on biodiversity both in South Africa and globally is lacking despite substantial concern for their impacts. It is suggested that to demonstrate the impacts of non-indigenous ungulates exclosure and enclosure experiments should be used and population declines in indigenous species should be shown.Ph
Cederberg Climate Data 2002-2018
No full textThe Coast to Karoo Transect investigates the abundance and diversity of ants and beetles along an altitudinal gradient in the Cederberg mountains of the Western Cape, South Africa. It is a long term project, initiated in 2002 by Prof. S.L. Chown, Stellenbosch University. Data collection is carried out on a biannual (spring and autumn) basis.To monitor changes in invertebrate assemblages, focusing on ants and beetles. Temperature data are collected with i-buttons and a Hobo data logger
Fresh and dry ant body mass along the Cederberg "Coast-to-Karoo" transect
No full textFresh and dry body mass of ants collected along an altitudinal gradient in the Greater Cederberg Biodiversity Corridor (the CIB's Coast-to-Karoo transect).Quantification of intra- and inter-specific variation in body mass across a wide range of sites. This project was by the Chown research group
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
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