1,721,097 research outputs found
Role of vegetation on fire contribution behaviour in Fennoscandia forests during the Holocene
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<p>The relationship between Holocene changes in Fennoscandia biomass burning (reconstructed by means of sedimentary charcoal records from lake and peat bogs) and main forest composition (based on pollen reconstructions from the same sites) divided into three different fire sensitivity classes is explored based on the hypothesis that fire-prone species are more abundant during periods characterized by higher fire disturbance, while fire-intolerant species dominate when biomass burning is low.</p><p>The overall patterns found across Fennoscandia suggest that there was low but increasing fire activity during the early Holocene, while a low and decreasing trend characterized the middle Holocene. During the late Holocene biomass burning increased, with a peak around 500 cal yr BP. This maximum is then followed by a downturn during the last centuries.</p><p>Generally, fire-prone species are strongly positively correlated with multi-millennial variability of biomass burning in Fennoscandia forests. A positive - but much weaker - relationship also exists between fire-tolerant species and long-term fire trends. On the contrary, a quite strong negative correlation is detected between biomass burning and fire-intolerant species.</p><p>The results presented in this large-scale analysis demonstrate that biomass burning was highly linked to fuel type (according to different fire sensitivity classes) during the Holocene, underlying the fact that all past fire-climate studies must consider key functional interactions between fuel type and long-term changes in fire regime.</p>
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The Changing Strength and Nature of Fire-Climate Relationships in the Northern Rocky Mountains, U.S.A., 1902-2008.
Full text linkTime-varying fire-climate relationships may represent an important component of fire-regime variability, relevant for understanding the controls of fire and projecting fire activity under global-change scenarios. We used time-varying statistical models to evaluate if and how fire-climate relationships varied from 1902-2008, in one of the most flammable forested regions of the western U.S.A. Fire-danger and water-balance metrics yielded the best combination of calibration accuracy and predictive skill in modeling annual area burned. The strength of fire-climate relationships varied markedly at multi-decadal scales, with models explaining < 40% to 88% of the variation in annual area burned. The early 20th century (1902-1942) and the most recent two decades (1985-2008) exhibited strong fire-climate relationships, with weaker relationships for much of the mid 20th century (1943-1984), coincident with diminished burning, less fire-conducive climate, and the initiation of modern fire fighting. Area burned and the strength of fire-climate relationships increased sharply in the mid 1980s, associated with increased temperatures and longer potential fire seasons. Unlike decades with high burning in the early 20th century, models developed using fire-climate relationships from recent decades overpredicted area burned when applied to earlier periods. This amplified response of fire to climate is a signature of altered fire-climate-relationships, and it implicates non-climatic factors in this recent shift. Changes in fuel structure and availability following 40+ yr of unusually low fire activity, and possibly land use, may have resulted in increased fire vulnerability beyond expectations from climatic factors alone. Our results highlight the potential for non-climatic factors to alter fire-climate relationships, and the need to account for such dynamics, through adaptable statistical or processes-based models, for accurately predicting future fire activity
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
Les plantes allochtones envahissantes de l’Archipel Crozet, Océan Austral
No full textThe present status of invasive vascular plants in the subantarctic Crozet Archipelagos has been assessed during a 14 months field study carried out from December 1988 to January 1990.
Four categories of invasive species were recognized, following the classification system of Walton and Smith (1973).
The whole of the Ile de la Possession was divided up into 666 quadrats of 500 x 500 m, all of them (except in a few unaccessible cliffs) being investigated by the author to assess the presence of allien plants. Short visits were also paid to Ile de l’Est and Ile aux Cochons. Among the ca 100 allochtonous plants recorded, only 12 can presently be considered as naturalized. Among them Caluna vulgaris is reported for the first time from Ile de la Possession.
The number of invasive vascular plants has greatly increased since the establishment of a permanent base on Ile de la Possession (1963), mostly through uncontroled import of seeds and compost for vegetable cultivation in glasshouses, and of grain for chicken feed. Such practices should be discontinued.Les îles subantarctiques ont subi de nombreuses perturbations résultant de l’introduction par l’homme d’espèces végétales et animales. Leurs paysages en furent dans certains cas profondément modifiés.
A la suite d’un séjour de 14 mois dans l’Archipel Crozet, l’auteur dresse le bilan des introductions végétales (> 100) en fonction du statut de chacune d’elles, en adoptant les catégories de Walton et Smith (1973). Douze espèces sont actuellement naturalisées, et peuvent être considérées comme envahissantes.
L’origine des introductions est discutée. Les établissements des chasseurs de phoques au XIXe siècle sont responsables de l’arrivée des premières espèces allochtones. Au XXe siècle, l’établissement de la Base permanente Alfred Faure sur l'île de la Possession en 1963 entraîna une très forte augmentation du nombre d’espèces introduites. Certains oiseaux et mammifères jouent par ailleurs un rôle dans la dispersion de certaines d’entre elles.
Certaines espèces allochtones provoquent une réorganisation des peuplements végétaux originels.Carcaillet Christopher. Les plantes allochtones envahissantes de l’Archipel Crozet, Océan Austral. In: Revue d'Écologie (La Terre et La Vie), tome 48, n°1, 1993. pp. 3-20
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