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Ecological significance of seed traits in the genus Macaranga
Get PDFAccording to the regeneration niche hypothesis, the transition from seeds to seedlings is critical in determining plant distribution patterns. This initial stage of recruitment may be strongly influenced by seed mass via effects on the sensitivity to light quality and soil moisture availability for germination, and via susceptibility to predators and pathogens. In this study ten Macaranga species (Euphorbiaceae) varying in seed mass and adult crown illumination were used as a study system to test hypotheses linking seed mass to light and soil moisture requirements for germination, investment in seed chemical and physical defense, and seed persistence in the soil. Empirical measurements of germination and seed persistence in the soil were made at Lambir Hill National Park in Borneo, and coupled with analyses of the physical and chemical defense characteristics of seeds. I found that seed mass in Macaranga was significantly correlated with germination response to light quality represented by the ratio of red to far-red light. Previously reported opposing relationships between seed mass and light requirements for germination between temperate (negative relationship) and tropical taxa (positive relationship) were found to be robust, indicating contrasting selection on germination responses across biomes. In contrast, seed mass was not associated with soil moisture requirements for germination in Macaranga and two additional pioneer species. Nonetheless, soil moisture requirements for germination of species from Lambir were higher than those previously reported for species from seasonal tropical forest. Macaranga also exhibited strong interspecific variation in physical and chemical defensive traits. Overall, there was no evidence for a trade-off between investment in seed physical versus chemical defense; however, seed physical defenses were more important than chemical defenses in predicting the duration of seed persistence in the soil. While phenolic concentrations used in chemical defense were generally lower in seeds than leaves, certain phenols were expressed in higher fraction in seeds than leaves, and may be important in defending seeds from natural enemies that primarily attack seeds. Finally, among Macaranga species, variation in soil moisture requirements for germination and in the investment in seed physical defenses was most strongly associated with adult crown-illumination. Interspecific differences in germination requirements and defensive traits found in this study emphasize the importance of regeneration niche differentiation as a contributing factor to species coexistence in diverse plant communities.Item withdrawn by Mark Zulauf ([email protected]) on 2013-06-04T19:51:10Z
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Capsule development, seed germination and dormancy of Luehea seemannii (Tiliaceae) in two forests in Panama 2008
No full textPre-dispersal seed predation can greatly reduce crop size and affects recruitment success. In addition, fungi have been directly implicated in post-dispersal seed losses, but successful fungal infection may depend on initial damage to seeds by seed predators. The objectives of this study were (1) to quantify pre-dispersal seed predation and fungal infection in a Neotropical tree species, Luehea seemannii, that produces dehiscent fruits and wind-dispersed seeds, and (2) to link pre-dispersal effects on seed quality to seed survival in the soil. To examine how seed predators and fungi influence seed losses, mesh exclosures, fungicide and the combination of both treatments were applied to separate branches in the canopy of trees in Gamboa and Parque Natural Metropolitano, Panama. To determine if treatments affect seed viability and survival in the soil, half of the seeds collected from each treatment were buried for four weeks in forest soils and subsequently germinated before and after the breaking of dormancy. Data include number of aborted and damaged capsules in the canopy and germination of seeds before and after burial
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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