1,721,322 research outputs found
Heathland responses to nitrogen deposition : exploring the role of habitat management and soil biochemistry
Get PDFElevated levels of nitrogen deposition are altering the normal functioning of seminatural
ecosystems around the world. Of concern in Europe are the nitrogen driven
changes occurring to (semi)-natural ecosystems such as obrotrophic bogs, upland
moors and lowland heathland. Lowland heathland is a particularly vulnerable
oligotrophic habitat, with a narrow climatic optimum that restricts the remaining
fragmented patches to a small corner of highly populated northwestern Europe.
Increased nitrogen availability reduces the competitiveness of characteristic heathland
plants, such as Calluna vulgaris, that are adapted to situations where nitrogen is the
limiting nutrient. Resulting changes such as accelerated productivity, increased
herbivore and frost damage, and changes in the nutrient limitation status of heathlands
can lead to invasion by nitrophilous graminoid species, but this process may be
dependent on (1) the intensity and duration of elevated nitrogen inputs, (2) the relative
availability of other nutrients and (3) conservation management intended to reduce
overall nutrient levels.
The present study investigated the effects of nitrogen deposition in N and P limited
vegetation, and in heathlands around the UK that are experiencing anthropogenically
enhanced background levels of nitrogen deposition. Physical and biochemical
parameters of vegetation, litter and soil were used as indicators. A long-term fieldscale
manipulation study at Thursley Common, Surrey was used to quantify the effect
of nitrogen inputs to an N limited system and, in particular, determine how these
effects were modified by a gradient of management intensity, and an unplanned
wildfire. The process of vegetation recovery, following a cessation of nitrogen inputs was also investigated. The effects of nitrogen deposition to P limited heathland were
investigated using heathland mesocosms. Two nationwide heathland surveys
investigated how the effect of nitrogen deposition within a gradient of background
deposition in England was modified by environmental factors, such as geology or soil
type. The first survey examined the effect of stand age (and management) on
responses to nitrogen deposition. The second survey focused on the physical and
biochemical responses to nitrogen deposition in Calluna, litter, bryophytes and soil to
quantify its impact on heathlands across England.
The Thursley nitrogen manipulation investigation showed clear ongoing responses in
rates of canopy development and shoot growth to nitrogen deposition, which were
reduced by increasing levels of management intensity. Historical nitrogen inputs in
the recovery experiment continued to significantly increase rates of Calluna canopy
development 9 years after inputs had ceased. These effects were re-invigorated by the
unplanned wildfire. The mesocosm experiment indicated that P limited heathlands are
susceptible to the detrimental effects of nitrogen deposition, particularly, altering
shoot phenology and increasing drought stress. Both the nationwide surveys indicated
that, at a national scale, heathland vegetation and soil biochemical indices are
responsive to background nitrogen deposition levels within (and exceeding) the
critical load range, despite environmental influences, such as geology and soil type
which were also found to have significant effects on these parameters
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
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
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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