1,720,955 research outputs found
Ecology and sustainable management of African mahoganies and other selected timber species in northeastern Congo Basin, Democratic Republic of Congo
Full text linkThis thesis reports on a study that assessed management options for African mahoganies and other major timber species in the Ituri region through analyses of regeneration ecology and the performance of these species in disturbed and undisturbed forests, and the impacts of selective logging and shifting cultivation on forest structure, tree diversity and composition. The main hypotheses tested were: (1) insufficient seed availability and dispersal limit seedling recruitment in logged forests; (2) soil disturbance promotes seedling establishment; (3) single tree harvesting provides insufficient light levels for the successful recruitment of African mahoganies; and (4) the combined effects of selective logging and agriculture result in severe degradation and impoverishment of natural forests. The first three hypotheses were tested using a factorial split-plot experiment involving seed addition, litter removal, and canopy cover (gap vs. understory). The fourth hypothesis was evaluated by comparing forest structure, tree diversity and composition between secondary and mature forest stands in logged and unlogged forests. In addition, long-term ecological data were used to examine whether size distributions and wood density were correlated with the life history parameters of common timber species in the region. These findings suggest that intensive silviculture, perhaps involving the use of shifting cultivation in a taungya-like system, appear necessary to achieve sustainable management of African mahoganies and other disturbance-adapted timber species. In this context, biodiversity conservation will likely be assured by the zoning of forests into multiple-use, timber production and strict protection areas. The results showed that timber species in the Ituri region varied widely in their regeneration requirements and their performance in natural forests. There was a strong dispersal limitation effect on seedling establishment and seed addition greatly increased seedling recruitment. Litter removal did not improve seedling establishment. However, the combined occurrence of canopy gaps and litter removal offered the best conditions for seedling survival and growth. Secondary forests had lower diversity of large trees than mature forests and the dominant species of mature forest were poorly represented in them. The regeneration of African mahoganies was 10 times greater in secondary forests than in adjacent mature forest stands.Ph.D
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Forest structure, species diversity and spatial patterns of trees in monodominant and mixed stands in the Ituri Forest, Democratic Republic of Congo
Full text linkTwo rectangular 10-ha plots (200 x 500 m) were established in each of the two main forest types of the Ituri Forest, Democratic Republic of Congo (formerly Zaire). The description of stand structure and species diversity, the comparison of the two forest types, and the evaluation of the effects of canopy dominance on species richness were the main goals of the study. All shrubs and trees >1 cm dbh, and lianas >2 cm dbh were measured, tagged, mapped to the nearest half-meter, and identified. Stem density, basal area, species richness and spatial dispersion of species were determined. Statistical comparisons were performed using analysis of variance and the chi-square test. The density of trees >1 cm dbh was higher in mixed forest (8112 stems ha-1) than in monodominant forest (6844 stems ha-1). Density of stems >10 cm dbh was 438 ha-1 and 358 ha-1 in mixed and monodominant stands, respectively. Monodominant stands, with 98 stems >30 cm dbh ha-1, had more large trees than mixed stands (77 stems ha-1). Basal area was 37.7 m2 ha-1 and 32.6 m2 ha-1 for trees >1 cm dbh and >10 cm dbh in monodominant forest, and 33.2 m2 ha-1 and 26.2 m2 ha-1 in mixed forest, respectively. Mean number of species per hectare was 178, 56, and 14 at 1 cm dbh, 10 cm dbh and 30 cm dbh, respectively, in monodominant forest; in the same order, mean species richness per hectare was 170,68 and 27 in mixed forest. The density of Gilbertiodendron dewevrei, the dominant tree species of the monodominant stands, had a strong negative correlation with the species richness of trees >30 cm dbh. The vast majority of species exhibited significant clumping at all scales of analysis. No species had a significant regular dispersion pattern in the 10-ha plots. Small trees were more clumped than large trees and rare species were more clumped than more common species. Compared to many other tropical moist forests, the Ituri Forest was less diverse
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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