1,720,976 research outputs found
Interação solo-vegetação campestre:estudos de caso em diferentes escalas ecológicas
Get PDFEnquanto em regiões temperadas o conhecimento sobre a relação solo-vegetação é consolidado, nos trópicos e subtrópicos é preliminar. É urgente a necessidade de se determinar os fatores abióticos que controlam padrões vegetacionais visando dar suporte a estudos de recuperação e conservação. O presente estudo analisa a relação entre fatores abióticos e vegetação campestre na forma de três artigos científicos (capítulos I, II e III) e um artigo de revisão (capítulo IV). Nos primeiros três artigos, analisou-se a variância da vegetação em diferentes escalas ecológicas; e no artigo de revisão, discutiu-se de forma aplicada a variância de fatores bióticos e abióticos em resposta à degradação. Dessa forma, a presente tese objetivou responder as seguintes questões: (I) Que diferenças podem ser observadas dentro de uma mesma espécie quanto à funcionalidade e suas estratégias de alocação sob diferentes graus de disponibilidade de recursos?; (II) Quão variáveis são as propriedades físicas e químicas do solo em diferentes escalas espaciais; e existem propriedades dos solos que podem explicar com maior precisão a distribuição das espécies em diferentes escalas espaciais? (III) Que porcentagem de variância da vegetação pode ser explicada por propriedades pedológicas e climáticas; e quais características de solo e clima melhor explicam esses padrões de vegetação? No capítulo IV é apresentado um modelo conceitual sobre degradação dos campos e sua aplicação aos campos do Rio Grande do Sul (RS). Para responder as questões acima usei dados ao nível de espécie de campos calcáreos da Alemanha (capítulo I); dados ao nível de comunidade em seis áreas campestres do Rio Grande do Sul, sul do Brasil (capítulos II e III); e através da revisão de literatura relacionada à degradação, quanto à capacidade de recuperação dos campos do RS (capítulo IV). Os resultados evidenciaram que: (I) dentro de espécies ficaram evidentes duas estratégias frente à limitação de recursos, enquanto a resposta dos atributos aos diferentes tratamentos se mostrou constante; (II) a variação dos parâmetros do solo relaciona-se à escala espacial aplicada e a variância da vegetação geralmente responde a diferentes parâmetros de solo em diferentes escalas; (III) 45% da variância da vegetação entre biomas nos campos do RS foi explicada por características pedológicas e climáticas, sendo em grande parte governada pela precipitação anual e a porcentagem de saturação por alumínio do solo; e (IV) o modelo conceitual apresenta variações ao longo de dois eixos (biótico e abiótico) e poderá servir de suporte a estudos de conservação e recuperação de campos tropicais e suptropicais, bem como facilitar a tomada de decisões quanto ao manejo e conservação. Como conclusão geral, verificou-se que a vegetação campestre responde a variações ambientais em diferentes escalas espaciais e pode adotar diferentes estratégias para sobrepor filtros ambientais e processos de degradação. O entendimento da relação entre a vegetação e o meio abiótico é de grande importância para tomada de decisões quanto ao emprego de formas alternativas de manejo e conservação.Whereas in temperate regions the abiotic-biotic relationship is well-known, in the tropics and subtropics our understanding is still preliminary. There is an urgent need to determine abiotic factors that control vegetation patterns in order to give support to restoration and conservation approaches. The present thesis analyses the relationship between abiotic factors and grassland vegetation in three original research papers (chapters I, II and III) and a review paper (chapter IV). In the first three papers, vegetation variance in response to abiotic factors was analyzed at different ecological scales; and in the fourth, the variance in biotic and abiotic factors in response to degradation process was discussed with a more applied view. Thus in this thesis the aim is to answer the following questions: (I) Which differences can be found in functional plant traits and allocation strategies within species at different levels of water and nutrient availability?; (II) How variable are physical and chemical parameters in different spatial scales; and are there soil parameters that can more accurately explain plant distribution in different spatial scales? (III) How much of RS grassland vegetation variance can be explained by soil and climatic properties; and which climatic and soil properties better explain these vegetation patterns? In chapter IV a conceptual model of grassland degradation is presented and applied to Rio Grande do Sul (RS) grasslands. To address these questions I used species-level data in a calcareous grassland in Germany (chapter I); community-level data in six sites in RS, South Brazilian grasslands (chapter II and III); and a review of literature studies concerning RS grassland degradation and restorability (chapter IV). The results showed that: (I) at a intraspecific level, the study species showed two allocation strategies in relation to resource stress, while the responses of individual traits to the soil treatments were consistent across species; (II) soil parameters variation are related to the measurement scale applied and the vegetation variance often responds to different soil parameters at different scales; (III) climatic and soil properties explained 45% of vegetation variance between biomes in RS grasslands and the main factors controlling its variance are annual precipitation and percent aluminum saturation; and (IV) the conceptual model is displayed as biotic and abiotic changes along the axes and can serve as a general framework to study degradation and restorability of tropical and subtropical grasslands, and further it may facilitate decisions on alternative management and conservation. As a general conclusion, the grassland vegetation responds to changes in the environment in different scales and may use different strategies to overcome environmental selective forces and degradation process. The understanding of this relationship is of high importance to facilitate decisions on alternative management and conservation
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
Gênese, mineralogia e composição química de solos em um afloramento de serpentinito-estetito sob clima tropical úmido em Bom Sucesso, Brasil
No full textSerpentinite and steatite are metamorphic ultrabasic rocks, consisting of variable proportions of serpentine, talc and magnetite, among other unusual minerals. Soils derived from these rocks are typically unproductive due to excess Mg, low P content and high levels of heavy metals, but in tropical countries these soils are still poorly studied. This work aimed to understand the process of formation of eight steatite-serpentinite soils in the ultramafic complex of Morro das Almas, Bom Sucesso, Brazil, and to its mineral and geochemical composition. The soils were stratified into three basic types, in increasing degree of weathering: a) Lithic Udorthents (3 profiles); b) Oxic Dystrudepts (2 profiles); c) Acrudoxes (3 pedons). All soils presented high particle density, but low soil density due to the high packing void porosity associated to the granular structure. Soil pH and exchangeable Mg were relatively high, and there were low P and Al contents. Magnetic susceptibility increased strongly with the degree of weathering due to the concentration of magnetite. X-ray fluorescence analysis showed that Lithic Udorthents and Oxic Dystrudepts have high levels of total MgO (94 to 200 g kg-1) and higher Fe2O3 contents, while Acrudoxes are even more concentrated in Fe2O3, although they also have levels of MgO (6 to 30 g kg-1). The SiO2 and Al2O3 contents are relatively low, although silica is more concentrated in the Lithic Udorthents and Oxic Dystrudepts, poor in alumina, whereas alumina predominates over silica in the other soils. This unusual composition is due to the mineralogy of the granulometric fractions, including clays, which have an important amount of talc in Lithic Udorthents and Oxic Dystrudepts, with much lower presence of kaolinite and secondary oxides of Fe, whereas the other soils have massive concentrations of hematite. Serpentine was not found in soils, although present in the rock, and quartz occurs in low quantity in the sand, and probably. The high contentes allochtone of MgO are due to fragments of steatite-serpentinite preserved by an iron oxide crust, visible macro- and microscopically. High levels of Cr2O6 (up to 50 g kg-1 soil) suggest that part of the diffraction peaks attributed to hematite are due to chromite (FeCrO4), while higher NiO (up to 6 g kg-1 soil) was due to the substitution of Mg by Ni in the talc, forming garnierite and co-precipitation in Fe oxides. Slope and aspect strongly influence the formation of the soil and its composition, and this complex interaction results in varied formations of canyon cloud forest, semi-deciduous forest and savannas in a small area of 3.1 km2.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ)Serpentinito e esteatito são rochas ultrabásicas metamorfizadas, constituídas de proporções variáveis de serpentina, talco e magnetita, dentre outros minerais incomuns. Solos derivados dessas rochas são tipicamente improdutivos devido ao excesso de Mg, baixo teor de P e elevados níveis de metais pesados, mas em países tropicais esses solos são ainda pouco estudados. Este trabalho visou compreender o processo de formação de oito solos derivados de esteatito-serpentinito no complexo ultramáfico do Morro das Almas, em Bom Sucesso - MG, e avaliar sua composição mineral e geoquímica. Os solos foram estratificados em quatro tipos básicos, em grau crescente de intemperismo: a) Neossolos Litólicos (3 perfis); b) Cambissolos (2 perfis); c) Latossolos (2 perfis) e b) Plintossolo Pétrico (1 perfil). Todos os solos apresentaram elevada densidade de partículas, mas baixa densidade de solo, devido à elevada porosidade de empilhamento associada à estrutura granular. O pH e teor de Mg trocável foram relativamente elevados, e houve ainda baixos teores de P e Al. A suscetibilidade magnética aumentou fortemente com o grau de intemperismo, devido a concentração de magnetita. Análises de fluorescência de raios-X mostraram que os Neossolos e Cambissolos possuem altos teores de MgO total (94 a 200 g kg-1) e teores ainda maiores de Fe2O3, enquanto os Latossolos e Plintossolo são ainda mais concentrados em Fe2O3, embora também possuam teores significativos de MgO (6 a 30 g kg-1). Os teores de SiO2 e Al2O3 são relativamente baixos, embora a sílica seja mais expressiva nos Neossolos e Cambissolos, pobres em alumina, e nos Latossolos e Plintossolo a alumina predomina sobre a sílica. Tal composição incomum se deve à mineralogia das frações granulométricas, incluindo argilas, que possuem importante quantidade de talco nos Cambissolos e Neossolos, com presença bem menor de caulinita e óxidos secundários de Fe, enquanto os demais solos possuem concentrações expressivas de hematita. A serpentina não foi encontrada nos solos, embora presente na rocha, e o quartzo ocorre em baixa quantidade na areia, e provavelmente alóctone. O alto teor de MgO é devido a fragmentos de esteatito-serpentinito estarem preservados por uma crosta de óxido de ferro, visível macro- e microscopicamente. Altos teores totais de Cr2O6 (até 50 g kg-1 de solo) sugerem que parte dos picos de difração atribuídos à hematita se devem à cromita (FeCrO4), enquanto os teores de NiO (até 6 g kg-1 de solo) são provavelmente devidos à substituição de Mg por Ni no talco, formando garnierita e co-precipitação em óxidos de Fe. O declive e aspecto influenciam fortemente a formação do solo e sua composição, e essa interação complexa resulta em formações variadas de floresta ombrófila de cânion, floresta semi-decidual e cerrado numa área pequena de 3,1 km2
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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