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Search Results: 1 - 10 of 6448 matches for " Cordero Rivera Adolfo "
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CUANDO LOS áRBOLES NO DEJAN VER EL BOSQUE: EFECTOS DE LOS MONOCULTIVOS FORESTALES EN LA CONSERVACIóN DE LA BIODIVERSIDAD
CORDERO RIVERA,ADOLFO;
Acta Biológica Colombiana , 2011,
Abstract: human population is growing at rates that were unimaginable only a century ago, creating such pressure on resources, which will only decrease when the decline in birth rate stabilizes population. among these resources, wood is one of the most demanded. global consumption of wood is currently more than 3500 million m3, a rate multiplied by six since 1950. to meet this demand, we manage millions of hectares of forests and forest plantations, part of which are cut down each year. this logging determines drastic effects on forests, affecting the biodiversity associated and the ecosystems services provided to society. this work is a review of the structural and functional characteristics that differentiate forests and forest plantations, in spite of the confusion between both ecosystems by fao and the forest sector companies, which have coined the oxymoron “planted forests”. forest plantations are more productive than forests from the point of view of the volume of wood that can be obtained from them, and if well managed, could minimize the pressure on forests. however, they do not provide many services that forests do provide, especially in the case of monospecific plantations consisting of even aged individuals of exotic species that are managed intensively. some of the many techniques that combine the production of wood with the conservation of biodiversity are reviewed.
CUANDO LOS áRBOLES NO DEJAN VER EL BOSQUE: EFECTOS DE LOS MONOCULTIVOS FORESTALES EN LA CONSERVACIóN DE LA BIODIVERSIDAD
Cordero Rivera Adolfo
Acta Biológica Colombiana , 2011,
Abstract: RESUMEN La población humana crece a tasas que eran inimaginables hace sólo un siglo, creando tales presiones sobre los recursos, que sólo disminuirán cuando el descenso en la natalidad estabilice la población. Entre estos recursos, la madera es uno de los más demandados. Actualmente el consumo mundial de madera es de más de 3500 millones de m3, habiéndose multiplicado por seis desde 1950. Para responder a esta demanda, se gestionan millones de hectáreas de bosques y plantaciones forestales, que se talan en parte cada a o. Las talas determinan efectos drásticos en los ecosistemas forestales, afectando tanto a la biodiversidad asociada como a los servicios que dichos ecosistemas proporcionan a la sociedad. En este trabajo se hace una revisión de las características estructurales y funcionales que diferencian los bosques de las plantaciones, a pesar del intento de confusión entre ambos ecosistemas por parte de la FAO y de las empresas del sector, que han acu ado el oxímoron “bosques plantados”. Las plantaciones forestales son más productivas que los bosques desde el punto de vista del volumen de madera que se puede obtener de ellas, y si se gestionasen bien, podrían disminuir la presión sobre los bosques. Sin embargo, no pueden proporcionar muchos de los servicios que los bosques sí proporcionan, especialmente cuando se trata de plantaciones monoespecíficas constituidas por masas coetáneas de especies exóticas que son gestionadas de forma intensiva. Se repasarán algunas de las numerosas técnicas que permiten compatibilizar la producción de madera con la conservación de la biodiversidad. Palabras clave: bosques, plantaciones forestales, impactos ecológicos, conservación, silvicultura ecológica. ABSTRACT Human population is growing at rates that were unimaginable only a century ago, creating such pressure on resources, which will only decrease when the decline in birth rate stabilizes population. Among these resources, wood is one of the most demanded. Global consumption of wood is currently more than 3500 million m3, a rate multiplied by six since 1950. To meet this demand, we manage millions of hectares of forests and forest plantations, part of which are cut down each year. This logging determines drastic effects on forests, affecting the biodiversity associated with the services provided by these ecosystems to society. This work is a review of the structural and functional characteristics that differentiate forests and forest plantations, in spite of the confusion between both ecosystems by FAO and the forest sector companies, which have coined the oxymo
Evolution and ecology of Calopterygidae (Zygoptera: Odonata): status of knowledge and research perspectives
Córdoba-Aguilar, Alejandro;Cordero-Rivera, Adolfo;
Neotropical Entomology , 2005, DOI: 10.1590/S1519-566X2005000600001
Abstract: we review the studies of evolution and ecology in the calopterygidae. adults are easily distinguished for their pigmented wings and territorial behaviour. three genera have been well studied: hetaerina, calopteryx and mnais. larvae develop in riverine aquatic environments. selection operates at this stage to produce large muscle mass for adults. the adult spends some days until sexually ready. during this time, it feeds extensively to produce muscle fat for egg production and flight. however, gregarine parasites may ingest the fat reserves. males may use two mating tactics or strategies that may be genetically (mnais) or environmentally (calopteryx and hetaerina) determined: territoriality and nonterritoriality. in mnais, these strategies appear balanced in fitness terms. males of calopteryx, mnais and phaon show a precopulatory courtship that is not the case for hetaerina. male wing pigmentation seems to signal how good the male is to deal immunologically with parasites to females during the male courtship. during copulation, males displace the sperm the female has stored in the storage organs from previous matings. there is an enormous variation in male sperm displacement mechanisms and ability, and in genitalic morphology in both sexes. this variation possibly results from a coevolutionary game between the sexes to control stored sperm. after copulation, males guard females apparently to avoid that other males take the female in copulation. our review suggests sources for research in this family.
Turtle Carapace Anomalies: The Roles of Genetic Diversity and Environment
Guillermo Velo-Antón,C. Guilherme Becker,Adolfo Cordero-Rivera
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018714
Abstract: Phenotypic anomalies are common in wild populations and multiple genetic, biotic and abiotic factors might contribute to their formation. Turtles are excellent models for the study of developmental instability because anomalies are easily detected in the form of malformations, additions, or reductions in the number of scutes or scales.
Introgression and rapid species turnover in sympatric damselflies
Rosa A Sánchez-Guillén, Maren Wellenreuther, Adolfo Cordero-Rivera, Bengt Hansson
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-210
Abstract: In a principal component analysis of the microsatellite data, the first two principal components summarised almost half (41%) of the total genetic variation. The first axis revealed a clear separation of I. graellsii and I. elegans populations, while the second axis separated I. elegans populations. Admixture analyses showed extensive hybridization and introgression in I. elegans populations, consistent with I. elegans backcrosses and occasional F1-hybrids, suggesting hybridization is on-going. More specifically, approximately 58% of the 166 Spanish I. elegans individuals were assigned to the I. elegans backcross category, whereas not a single of those individuals was assigned to the backcross with I. graellsii. The mitochondrial genes held little genetic variation, and the most common haplotype was shared by the two species.The results suggest rapid species turnover in sympatric regions in favour of I. elegans, corroborating previous findings that I. graellsii suffers a mating disadvantage in sympatry with I. elegans. Examination of morph frequency dynamics indicates that hybridization is likely to have important implications for the maintenance of multiple female morphs, in particular during the initial period of hybridization.Hybridization and introgression are increasingly recognized as important factors in the evolution of plants, animals [1,2] and prokaryotes [3], and can lead to the creation of novel genotypes and phenotypes. Thus, the study of contemporary hybridization between species and the extent of genomic introgression between them provides an excellent opportunity to examine evolutionary processes such as adaptation, gene flow and, ultimately, speciation [4-6]. Determining the degree of genetic exchange between species may be of particular interest when studying recently diverged species, since they typically show incomplete reproductive barriers.Hybridization has an inherent spatial component, as the process requires direct contact between population
Environmental and Climatic Determinants of Molecular Diversity and Genetic Population Structure in a Coenagrionid Damselfly
Maren Wellenreuther,Rosa A. Sánchez-Guillén,Adolfo Cordero-Rivera,Erik I. Svensson,Bengt Hansson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020440
Abstract: Identifying environmental factors that structure intraspecific genetic diversity is of interest for both habitat preservation and biodiversity conservation. Recent advances in statistical and geographical genetics make it possible to investigate how environmental factors affect geographic organisation and population structure of molecular genetic diversity within species. Here we present a study on a common and wide ranging insect, the blue tailed damselfly Ischnura elegans, which has been the target of many ecological and evolutionary studies. We addressed the following questions: (i) Is the population structure affected by longitudinal or latitudinal gradients?; (ii) Do geographic boundaries limit gene flow?; (iii) Does geographic distance affect connectivity and is there a signature of past bottlenecks?; (iv) Is there evidence of a recent range expansion and (vi) what is the effect of geography and climatic factors on population structure? We found low to moderate genetic sub-structuring between populations (mean FST = 0.06, Dest = 0.12), and an effect of longitude, but not latitude, on genetic diversity. No significant effects of geographic boundaries (e.g. water bodies) were found. FST-and Dest-values increased with geographic distance; however, there was no evidence for recent bottlenecks. Finally, we did not detect any molecular signatures of range expansions or an effect of geographic suitability, although local precipitation had a strong effect on genetic differentiation. The population structure of this small insect has probably been shaped by ecological factors that are correlated with longitudinal gradients, geographic distances, and local precipitation. The relatively weak global population structure and high degree of genetic variation within populations suggest that I. elegans has high dispersal ability, which is consistent with this species being an effective and early coloniser of new habitats.
Trends in the evolution of ecology: “Spain is different”
A. Cordero Rivera
Web Ecology (WE) , 2003, DOI: 10.5194/we-4-14-2003
Abstract: During the last fifty years ecology has matured as a scientific discipline. In this paper I analyse the temporal development of the paradigm based on physical systems (the ecosystem paradigm), and the evolutionary ecology paradigm. I first analyse the contents of 61 textbooks to calculate the relative importance of ecosystem and evolutionary ecology in the training of new generations of ecologists. Results indicate that the evolutionary approach is becoming more important since 1980, and now most textbooks dedicate 10–20% of their pages to evolutionary concepts. In a second analysis I searched the names of ecology departments in universities around the world, and found out conspicuous differences between USA, where 43% of addresses associate ecology and evolution or behaviour on the same department, and Europe, where only 10% of ecology departments also include a reference to evolution or behaviour in their name. In both analyses Spain seems to follow only the ecosystem paradigm, because Spanish textbooks dedicate almost no pages to evolutionary concepts, and there is not a single university department that includes ecology and evolution. A further bibliometric study confirmed that Spanish ecologists prefer to publish their research in general ecology journals, and are under-represented in evolutionary ecology journals. I discuss the importance of historical factors on the development of paradigms of ecology, and the special case of Spain, likely due to the influence of pioneers working in oceanography, limnology and geography.
La política de consolidación de la seguridad democrática: balance 2006-2008
Atehortúa Cruz,Adolfo León; Rojas Rivera,Diana Marcela;
Análisis Político , 2009,
Abstract: the following lines are aimed at making a balance of the consolidation policy of the democratic security (pcsd for its acronym in spanish) in its first two years of application that is, between 2006 and 2008. for this, we turn to the analysis of the central policy topics: official statistics reviewing and comparing; registered results and impacts facing public opinion, current state of the war against the insurgency groups, the war against paramilitaries, forced displacement, the strategy against drugs, the human rights situation, and the accrual costs and investments. such topics are observed under the doctrinarian conception of the pcsd in general as well as in relation with its implications and concrete results.
La política de consolidación de la seguridad democrática: balance 2006-2008 The consolidation policy of the democratic security: balance 2006-2008
Adolfo León Atehortúa Cruz,Diana Marcela Rojas Rivera
Análisis Político , 2009,
Abstract: Los siguientes renglones tienen por objeto efectuar un balance de la Política de Consolidación de la Seguridad Democrática (PCSD) en sus dos primeros a os de aplicación, es decir, entre 2006 y 2008. Se acude, para ello, al análisis de las temáticas centrales de la política: revisión y contraste de las estadísticas oficiales; resultados e impactos registrados frente a la opinión pública, estado actual de la guerra contra los grupos insurgentes, el combate al paramilitarismo, el desplazamiento forzado, la estrategia contra las drogas, la situación con respecto a los derechos humanos y los costos e inversiones acumulados. Dichos temas son observados tanto en la concepción doctrinaria de la PCSD en general, como en relación con sus implicaciones y resultados concretos. The following lines are aimed at making a balance of the Consolidation Policy of the Democratic Security (PCSD for its acronym in Spanish) in its first two years of application that is, between 2006 and 2008. For this, we turn to the analysis of the central policy topics: official statistics reviewing and comparing; registered results and impacts facing public opinion, current state of the war against the insurgency groups, the war against paramilitaries, forced displacement, the strategy against drugs, the human rights situation, and the accrual costs and investments. Such topics are observed under the doctrinarian conception of the PCSD in general as well as in relation with its implications and concrete results.
Venezuela antes de Chávez:auge y derrumbe del sistema de "punto fijo"
Rojas Rivera Diana Marcela,Atehortúa Cruz Adolfo León
Anuario Colombiano de Historia Social y de la Cultura , 2005,
Abstract: Los siguientes renglones intentan bosquejar la historia reciente de Venezuela,desde el llamado Pacto de Punto Fijo, en 1958, hasta el golpe de estado fraguadopor Hugo Chávez Frías en 1992. La exposición comprende la caída de Marcos Pérez Jiménez, los perí
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