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Search Results: 1 - 10 of 56154 matches for " Miguel Martínez Ramos "
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The soil seed bank in abandoned tropical pastures: source of regeneration or invasion?
López-Toledo, Leonel;Martínez-Ramos, Miguel;
Revista mexicana de biodiversidad , 2011,
Abstract: we assessed the availability of both pioneer and non-native species in the soil seed bank of old-growth forest and recently abandoned pasture, to evaluate whether the soil seed bank in these pastures represents a source of regeneration of species from adjacent old-growth forest or of invasion by non-native species. our study was conducted at selva lacandona, chiapas, mexico. soil samples were randomly collected from 6 sites in old-growth forest, and 6 sites in abandoned pastures. seedlings from soil samples were identified and classified into pioneer, non-native (weeds/graminoids), and other forest species. pioneer species seeds were virtually absent in pastures, but represented ~30% of seeds in the forest. non-native species comprised ~99% of the soil seed bank in pastures. in the forest, soil seed bank density of weeds and graminoids decreased with increasing distance (up to 4 km) from agricultural fields, and comprised up to 25% (mean ± 1se= 16 ± 7) of the seed bank. our results show a near total elimination of pioneer species from the soil seed bank in pastures, and considerable invasion of the borders of the montes azules reserve by seeds of non-native species. thus, in the region studied, the soil seed bank in abandoned pastures represents a source of invasion by non-native species into old-growth forest rather than a potential source of forest regeneration.
The soil seed bank in abandoned tropical pastures: source of regeneration or invasion? El banco de semillas en pastizales tropicales abandonados: fuente de regeneración o de invasión?
Leonel López-Toledo,Miguel Martínez-Ramos
Revista mexicana de biodiversidad , 2011,
Abstract: We assessed the availability of both pioneer and non-native species in the soil seed bank of old-growth forest and recently abandoned pasture, to evaluate whether the soil seed bank in these pastures represents a source of regeneration of species from adjacent old-growth forest or of invasion by non-native species. Our study was conducted at Selva Lacandona, Chiapas, Mexico. Soil samples were randomly collected from 6 sites in old-growth forest, and 6 sites in abandoned pastures. Seedlings from soil samples were identified and classified into pioneer, non-native (weeds/graminoids), and other forest species. Pioneer species seeds were virtually absent in pastures, but represented ~30% of seeds in the forest. Non-native species comprised ~99% of the soil seed bank in pastures. In the forest, soil seed bank density of weeds and graminoids decreased with increasing distance (up to 4 km) from agricultural fields, and comprised up to 25% (Mean ± 1SE= 16 ± 7) of the seed bank. Our results show a near total elimination of pioneer species from the soil seed bank in pastures, and considerable invasion of the borders of the Montes Azules reserve by seeds of non-native species. Thus, in the region studied, the soil seed bank in abandoned pastures represents a source of invasion by non-native species into old-growth forest rather than a potential source of forest regeneration. Para evaluar si el banco de semillas en pastizales abandonados representa una fuente de regeneracion o de invasión por especies no-nativas para el bosque maduro se evaluó la presencia de especies pioneras y no-nativas en el banco de semillas de bosque maduro y pastizales recien abandonados en la selva lacandona, Chiapas, México. Se recolectaron muestras de suelo en 6 sitios de bosque maduro y de pastizales abandonados. Las semillas germinadas fueron identificadas y clasificadas en especies pioneras, no-nativas (malezas/graminoides) y otras especies de bosque. Las especies pioneras estuvieron virtualmente ausentes en los pastizales, pero representan ~30% de los registros en bosque maduro. Las especies no-nativas representan ~99% del banco de semillas en los pastizales. En el bosque maduro, el banco de semillas de malezas/graminoides decrece con el incremento de la distancia de campos agrícolas y representa hasta el 22% del banco de semillas. Nuestros resultados muestran una importante supresión de las especies pioneras en el banco de semillas de los pastizales y una considerable invasión de los bordes de la Reserva Montes Azules por semillas de especies no-nativas. En la región de estudio, el b
Sucesión ecológica y restauración de las selvas húmedas
Miguel Martínez Ramos,Ximena García Orth
Boletín de la Sociedad Botánica de México , 2007,
Abstract: Resumen: Las selvas húmedas han sufrido una intensa deforestación y degradación debido a las actividades antropogénicas. Grandes áreas antes cubiertas por estos bosques de elevada diversidad actualmente se encuentran transformadas en campos agropecuarios, bosques secundarios, campos degradados abandonados y, en menor proporción, remanentes aislados de selva. La teoría clásica de la regeneración natural en claros resulta insuficiente para el estudio de la sucesión y la restauración ecológica de selvas en los extensos campos deforestados. Se requieren nuevos principios ecológicos que permitan el desarrollo de tecnologías eficientes para la recuperación de selvas en campos degradados. El presente artículo desarrolla un esquema conceptual que considera el nivel de disponibilidad de propágulos de especies nativas y el grado de alteración ambiental (calidad de sitio) como dos ejes determinantes de la capacidad de regeneración de la vegetación de selva en campos degradados. La historia de uso del suelo es un promotor importante del estado de los ejes anteriores al modificar con un cierto nivel de intensidad, extensión y duración al ecosistema original. Nuestro marco conceptual identifica factores clave que es importante considerar en la restauración de campos degradados. Según nu e s t ro modelo, la tasa y la magnitud de la rege n e ración nat u ral (capacidad de regeneración) disminuyen con una reducción en la disponibilidad de propágulos (i.e. banco y lluvia de semillas, regeneración de avanzada, meristemos en raíces y tocones) y la disminución de la calidad sitio (por ejemplo, al aumentar la compactación y la fertilidad del s u e l o , y la abu ndancia de plantas exóticas). Dife rentes tipos de uso de suelo reducen diferencialmente la capacidad de rege n e ra c i ó n de la vegetación nativa. Por ejemplo, predecimos que la capacidad de regeneración en milpas abandonadas (las cuales reducen en mucho menor grado la disponibilidad de propágulos y la calidad de sitio) debería ser mayor que en pastizales ganaderos abandonados. Las predicciones se evalúan con información proveniente de la literatura y de un proyecto de investigación de largo plazo llevado a cabo en la región de La Selva Lacandona (Chiapas), México. Finalmente, se hace una reflexión sobre los costos asociados a la restauración y se ofrecen recomendaciones que pueden ayudar a promover la sucesión ecológica en campos degradados.
Applying Retrospective Demographic Models to Assess Sustainable Use: the Maya Management of Xa’an Palms
Andrea Martínez-Ballesté,Carlos Martorell,Miguel Martínez-Ramos,Javier Caballero
Ecology and Society , 2005,
Abstract: Xa’an palm (Sabal yapa) has been used to thatch traditional Maya houses for over 3000 years. In the Yucatan Peninsula, this palm has been introduced to pasturelands, maize fields (milpas), and homegardens. These and other traditional management systems are usually believed to be sustainable, but there is as yet little evidence to support this hypothesis. Demographic models have been used for this purpose, mainly focusing on population growth rate (λ). So far, retrospective analysis has not been applied, even though it examines how changes in the the life cycle of a species, caused by different management regimes, affect its λ. In this study, we assess whether ecologically sustainable use of xa’an occurs in homegardens, pasturelands, and milpas, and if so, how it is achieved. We constructed matrix population models for four populations of xa’an that were followed for 3 years, and then conducted a retrospective analysis on them. Management in homegardens seems to be oriented to increasing the availability of xa’an leaves, favoring the survival of seedlings, and increasing the density of harvestable-sized palms. However, in the milpa and the pastureland, the population size structure resembles that of unmanaged populations. Our λ values suggest that the traditional use of xa’an in all the studied management regimes is sustainable. Nevertheless, the processes that lead to sustainable use are different in each system, as shown by our retrospective analysis. Although fecundity contributes positively to λ only in homegardens, permanence and growth maintain palm populations at an equilibrium in the pastureland and in the milpa, respectively. Between-year climatic differences had a smaller impact on λ than management practices, which may vary from one year to another, leading to different balances in the sustainable use of the populations involved. Even though no significant differences were found in λ values, Maya achieve sustainable use of xa’an palm under diverse scenarios by managing the great plasticity of the species, as was revealed by the retrospective analysis. Hence, this approach proved to be effective, not only for assessing sustainable use, but also for understanding the factors that favor or limit it.
Gender differential on characteristics and outcome of leprosy patients admitted to a long-term care rural hospital in South-Eastern Ethiopia
Ramos José M,Martínez-Martín Miguel,Reyes Francisco,Lemma Deriba
International Journal for Equity in Health , 2012, DOI: 10.1186/1475-9276-11-56
Abstract: Introduction In previous studies, women are less aware of causation and symptoms of leprosy and have less access to health care coverage than men, thus contributing to their delay in seeking for treatment. We assess the gender differences in leprosy cases admitted to a rural referral hospital in Ethiopia for 7 and a half years. Methods Retrospective data of the leprosy patients admitted to referral hospital were collected using leprosy admission registry books from September 2002 to January 2010. Variables were entered in an Excel 97 database. Results During the period of study, 839 patients with leprosy were admitted; 541 (64.5%) were male, and 298 (35.6%) female. Fifteen per cent of female patients, and 7.3% of male patients were paucibacillary leprosy cases while 84.8% of female patients and 92.7% of males were multibacillary leprosy cases (p<0.001). Female leprosy patients were younger than male ones (median: 36 versus 44 years) (p<0.001). In the multivariate analysis, age (odds ratio [OR]: 0.97; 95% confidence interval [CI]: 0.96-0.98; p<0.001), admission for cardiovascular diseases (OR: 7.6, 95% CI: 1.9-29.3; p=0.004), admission for gastroenteritis (OR: 14.0; 95% CI: 1.7-117; p=0.02), admission from out patients clinic (OR: 2.04; 95% CI: 1.1-4.01; p=0.02), and mortality as final outcome (OR: 3.1, 95% CI: 1.2-8.0; p=0.02) were independently associated with female gender. Conclusions Female patients with leprosy admitted to hospital were younger, had a different profile of admission and a higher mortality rate than male ones.
Disponibilidad de esporomas de hongos comestibles en los bosques de pino-encino de Ixtlán de Juárez, Oaxaca
Garibay-Orijel, Roberto;Martínez-Ramos, Miguel;Cifuentes, Joaquín;
Revista mexicana de biodiversidad , 2009,
Abstract: wild edible mushrooms are non timber forest products whose sustainable use must have an ecological basis. in this work, we measured the availability of 81 edible mushrooms by means of their abundance, frequency, biomass production, temporal and spatial distribution of their fruiting bodies. these variables were integrated into an ecological importance index (iv) which describes sporome availability in the forest. the research was carried out during 2001 and 2002 in the pinus-quercus forests of ixtlán de juárez, oaxaca. the most abundant species were laccaria laccata var. pallidifolia, gymnopus confluens and laccaria vinaceobrunnea. laccaria laccata var. pallidifolia was the most productive species with an estimated total productivity of 2.21 kg/sampling site. only g. confluens and g. dryophilus were observed in all sampling dates, from june to october. species with the highest total availability were l. laccata var. pallidifolia, g. confluens, l. vinaceobrunnea and h. purpurascens. in the communal property of ixtlán, wild edible mushroom diversity is high (96 species); however, their availability is heterogeneous (from l. laccata var. pallidifolia iv = 0.7905, to helvella infula iv = 0.0055). within the forest, between sites relatively close to one another, species composition was different and their abundance and productivity were contrasting.
Estrés oxidativo, alimentación y suplementación antioxidante en patología ocular: historia breve y visión futura
Gutiérrez Maydata,Alfredo; Lavandero Espina,Aleida; Ramos Argilagos,Miguel E.; Martínez Nú?ez,Eligio;
Revista Cubana de Oftalmolog?-a , 2007,
Abstract: the eyes are at risk of suffering oxidative damage due to their high exposure to oxygen, a great deal of fatty acids in the retina and also to light, environmental pollutants and ultraviolet rays. the present paper discussed the evidence found about the possible role of oxidative damage in the pathogenesis of several eye diseases (glaucoma, cataract, diabetic retinopathy, macular degeneration) and the role of diet and antioxidant supplements in the prevention and treatment of such diseases. at present, the current recommendations cover the importance of a varied diet with high contents of fruits and vegetables, non-smoking, avoiding excessive exposure to the sun and ultraviolet radiations and a stict control of glycemic levels in diabetic patients as the most effective antioxidant strategy. the proven benefits of antioxidant supplements are being researched at present.
Sustainability of Mangrove Harvesting: How do Harvesters' Perceptions Differ from Ecological Analysis?
Laura López-Hoffman,Ian E. Monroe,Enrique Narváez,Miguel Martínez-Ramos
Ecology and Society , 2006,
Abstract: To harvest biological resources sustainably, it is first necessary to understand what "sustainability" means in an ecological context, and what it means to the people who use the resources. As a case study, we examined the extractive logging of the mangrove Rhizophora mangle in the Río Limón area of Lake Maracaibo, in western Venezuela. The ecological definition of sustainable harvesting is harvesting that allows population numbers to be maintained or to increase over time. In interviews, the harvesters defined sustainable harvesting as levels permitting the maintenance of the mangrove population over two human generations, about 50 yr. In Río Limón, harvesters extract a combination of small adult and juvenile trees. Harvesting rates ranged from 7–35% of small adult trees. These harvesting levels would be sustainable according to the harvester's definition as long as juvenile harvesting was less than 40%. However, some harvesting levels that would be sustainable according to the harvesters were ecologically unsustainable, i.e., eventually causing declines in mangrove population numbers. It was also determined that the structure of mangrove forests was significantly affected by harvesting; even areas harvested at low, ecologically sustainable intensities had significantly fewer adult trees than undisturbed sites. Western Venezuela has no organized timber industry, so mangrove logs are used in many types of construction. A lagging economy and a lack of alternative construction materials make mangrove harvesting inevitable, and for local people, an economic necessity. This creates a trade-off between preserving the ecological characteristics of the mangrove population and responding to human needs. In order to resolve this situation, we recommended a limited and adaptive mangrove harvesting regime. We also suggest that harvesters could participate in community-based management programs as harvesting monitors.
Estrés oxidativo, alimentación y suplementación antioxidante en patología ocular: historia breve y visión futura Oxidative stress, feeding and antioxidant supplementation in ocular pathology: brief history and future vision
Alfredo Gutiérrez Maydata,Aleida Lavandero Espina,Miguel E. Ramos Argilagos,Eligio Martínez Nú?ez
Revista Cubana de Oftalmolog?-a , 2007,
Abstract: Los ojos están en riesgo particular de da o oxidativo debido a su alta exposición al oxígeno, gran cantidad de ácidos grasos oxidables en la retina y su también alta exposición a la luz, los contaminantes ambientales y los rayos ultravioleta. En el presente trabajo se discuten las evidencias encontradas del posible papel del da o oxidativo en la patogenia de diversos trastornos oculares (glaucoma, cataratas, retinopatía diabética, degeneración macular); y de la dieta y la suplementación con antioxidantes en su prevención y tratamiento. De momento las actuales recomendaciones se inclinan a la importancia de una dieta variada, alta en frutas y vegetales, no fumar, evitar el exceso de exposición al sol y a las radiaciones ultravioletas y en los pacientes diabéticos mantener un estricto control de la glicemia como la estrategia antioxidante más efectiva, mientras se investigan los beneficios probados de suplementos antioxidantes. The eyes are at risk of suffering oxidative damage due to their high exposure to oxygen, a great deal of fatty acids in the retina and also to light, environmental pollutants and ultraviolet rays. The present paper discussed the evidence found about the possible role of oxidative damage in the pathogenesis of several eye diseases (glaucoma, cataract, diabetic retinopathy, macular degeneration) and the role of diet and antioxidant supplements in the prevention and treatment of such diseases. At present, the current recommendations cover the importance of a varied diet with high contents of fruits and vegetables, non-smoking, avoiding excessive exposure to the sun and ultraviolet radiations and a stict control of glycemic levels in diabetic patients as the most effective antioxidant strategy. The proven benefits of antioxidant supplements are being researched at present.
Presencia de Haematobia irritans (L)(Diptera:Muscidae) en ganado lechero estabulado de Aguascalientes, México: Informe preliminar
Carlos Cruz Vazquez,Irene Vitela Mendoza,Miguel Ramos Parra,Ma. Teresa Quintero Martínez
Veterinaria México , 1999,
Abstract: Con el objetivo de detectar la presencia de la mosca hematófaga Haematobia irritans en ganado bovino de la región lechera del estado de Aguascalientes, México, fueron seleccionados al azar 60 establos, los cuales se visitaron una vez por mes durante el periodo de mayo a julio de 1997; los establos mantienen al ganado, de raza Holstein, en confinamiento bajo el sistema de estabulación libre. En cada visita se eligieron al azar 10 vacas en producción, se sujetaron y con una trampa entomológica se colectaron moscas del dorso, costado y frente de las piernas, los especímenes se trasladaron al laboratorio para su posterior identificación taxonómica. Se encontró a Haematobia irritans en la totalidad de los establos y en el periodo de estudio; además se colectaron sobre el cuerpo de los animales ejemplares de Stomoxys calcitrans, Musca domestica, Fannia canicularis y Muscina stabulans. La presencia de Haematobia irritans en ganado lechero estabulado en una región semiárida es un hallazgo importante, aunado al hecho de que convive con Stomoxys calcitrans, especie hematófaga común en los establos. Se concluye que Haematobia irritans se encuentra presente y ampliamente distribuida parasitando al ganado bovino lechero estabulado de Aguascalientes.
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