1,720,966 research outputs found
Patterns of Density and Production in the Community Forests of the Sierra Madre Occidental, Mexico
No full textThe Mexican Sierra Madre Occidental (SMO) represents a region where hundreds of plant species reach the limits of their northern or southern range. The SMO also features a unique cultural diversity, and many communities living within the forest or in its close vicinity depend on the products and services that these forests provide. Our study was based on a large set of remeasured field plots placed in the forests of Durango which are part of the SMO. Using hierarchical clustering, three distinctly different forest types were identified based on structural differences and the relation between stem density and basal area. Maximum forest densities were estimated using a 0.975th quantile regression. Forest production (expressed as current periodic volume increment per unit of area and time) was estimated based on number of stems, forest density, mean height, and forest diversity. Forest density is the principal factors affecting periodic volume production. The discussion presented recommendations for the sustainable use of this unique natural resource. Maintaining minimum levels of residual density is key to ensuring the continued viability of the forests of the Mexican SMO. Future research is needed to identify optimum residual structures, productive residual densities, and desirable levels of biodiversity
Efecto de la altitud, pendiente y exposición geográfica en la distribución de helechos arborescentes
No full textBackground and Aims: Knowledge of the topographic characteristics of a site is important to understand the local diversity and for proper monitoring of the response of plants with high conservation interest to climate change or land use change. The objective was to examine the distribution pattern of four tree fern species in function of elevation above sea level, exposure, and slope along an altitudinal continuum.Methods: The effect of altitude, slope and geographic exposure on the distribution of Alsophila firma, Cyathea bicrenata, Cyathea myosuroides and Sphaeropteris horrida was studied in La Chinantla, northern Oaxaca, Mexico. The hypothesis of homogeneity of proportions to the change of topo-graphic factors was verified by the Chi square test and the degree of incidence with polynomial functions.Key results: Significant differences between the proportions of each species as a function of each topographic variable were observed. On average, the slope showed an index of significance 43.48 times greater than geographic orientation and 2.50 times greater than elevation above sea level. We observed similarities between the partial niche of Cyathea bicrenata and Alsophila firma, but dissimilarities between Alsophila firma and Cyathea myosuroides.Conclusions: The distribution of tree fern proportions at the local level is discontinuous and non-uniform, attributable to the action of the predomi-nant local factors, mainly topography. Heterogeneous topography leads to highly random distribution patterns of the species studied.Antecedentes y Objetivos: El conocimiento de los rasgos topográficos de un sitio es importante para comprender la diversidad local y monitorear la respuesta de las plantas de alto interés de conservación al cambio climático o al cambio de uso de suelo. El objetivo de este trabajo fue examinar el patrón de distribución de cuatro especies de helechos arborescentes en función de la altitud, la exposición y la pendiente a lo largo de un continuo altitudinal.
Métodos: Se estudió el efecto de la altitud, pendiente y exposición geográfica en la distribución de Alsophila firma, Cyathea bicrenata, Cyathea myosuroides y Sphaeropteris horrida, en La Chinantla, al norte de Oaxaca, México. La hipótesis de homogeneidad de proporciones a los factores topográficos se verificó con la prueba de Chi cuadrada y la magnitud de incidencia mediante funciones polinómicas.
Resultados clave: Se observaron diferencias significativas entre las proporciones de cada especie en función de cada variable topográfica. En promedio, la pendiente mostró un índice de importancia 43.48 veces más que la orientación geográfica y 2.50 veces más que la altitud. Se observaron similitudes entre el nicho parcial de Cyathea bicrenata y de Alsophila firma, pero disimilitudes entre Alsophila firma y Cyathea myosuroides.
Conclusiones: La distribución de proporciones de los helechos arborescentes a nivel local es discontinua y no uniforme, atribuible a la acción de los factores locales predominantes, principalmente a la topografía. Una topografía heterogénea propicia patrones de distribución más aleatorios
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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