Chronology of tropical dry forest regeneration in Santa Rosa, Guanacaste, Costa Rica. I. Edaphic characteristics. We characterized soil chemical and physical properties in eight tropical dry forest (TDF) successional sites along a time sequence (10, 15, 20, 40, 60 and >100 years) in Santa Rosa, Costa Rica. Seventeen soils were identified, described, and classified in six orders. Most soils were classified as Entisols and Vertisols, but Mollisols, Alfisols, Inceptisols and Ultisols were also present. All soils showed good fertility that did not constrain species richness. High edaphic variation seemed the result of complex interactions among the pyroclastic origin of Santa Rosa ignimbritic plateau (SRIP), the lithological composition and acidity of ignimbritic rocks, the strong seasonality in rainfall, intense hydric and aeolic erosion, topographic variations within the SRIP, and past human intervention. Correlations performed on soils classified as Entisols (<60 cm deep) showed a depletion of soil cations (Ca, Mg, K, Na and CEC) during the first 20 years of forest regeneration, that later recovered in mature TDF sites. Organic matter content did not change significantly along the TDF chrono-sequence. Substantial increments in macro-pores and soil hydraulic conductivity were observed, probably resulting from higher root biomass and turnover in older successional sites. Soil available water and meso-pore abundance were negatively correlated with TDF successional age. Our results indicate that edaphic chan ges observed along TDF regeneration might have been due to annual fires in pastures and young TDF sites, addition of decaying litter and fine roots as regeneration progressed, milder microclimate conditions during late regeneration in mature TDF sites, increased nutrient cycling, and the predominance of sandy loam textures among the soils examined. These changes in the soil environment with succession may have physiological and phenological consequences on the species appearing at different stages of TDF regeneration. Rev. Biol. Trop. 57 (3): 801-815. Epub 2009 September, 30. Keywords: Santa Rosa National Park, soils, chemical properties, physical properties, seasonally dry tropical forests, pastures, forest succession.Los bosques tropicales estacionalmente secos (BTS) de Meso América contienen una alta riqueza estructural y funcional (Murphy & Lugo 1986, Medina 1995, proveen numerosos servicios ambientales (Maas et al. 2005), y constituyen un modelo para la restauración ecológica y el estudio de la regeneración de los ecosistemas tropicales (Janzen 2000). Estas zonas de vida han sido las predilectas para el desarrollo de importantes asentamientos humanos a través del tiempo, lo que ha causado enormes perturbaciones ecológicas; los BTS son actualmente un mosaico de fragmentos de bosques sucesionales secundarios (Kramer 1997). En la actualidad, los BTS continúan sometidos a presiones superiores a las enfrentadas por sus contrapartes, los bosques tropicales lluviosos (Janzen 1986), y el éxito de los ...
La revista está indexada en los directorios:LATINDEX , REDALYC, IRESIE, CLASE, DIALNET, DOAJ, E-REVIST@S, La revista está incluida en los sitios: REDIE, RINACE, OEI, MAESTROTECA, PREAL , HUASCARAN , CLASCOResumen: En este trabajo, proponemos métodos para la ejecución y evaluación cuantitativa de ejercicios participativos en la enseñanza de las ciencias naturales, diseñados bajo los principios del constructivismo, trasladando el protagonismo de los profesores a los estudiantes. Los métodos implementan principios epistemológicos, ontológicos y conceptuales actuales, propios del constructivismo cibernético de segundo orden, sustentado técnicamente en los hallazgos recientes de la Psicología cognitiva aplicada a la Educación, y los ajustan a las condiciones locales del proceso de enseñanza-aprendizaje. Los ejercicios facilitan el aprendizaje y la práctica del método científico utilizado en las ciencias naturales, específicamente en el contexto de las ciencias agrícolas, y promueven el desarrollo de habilidades técnicas y la adquisición de competencias personales. Además se promueve la práctica de la investigación científica, la formulación de hipótesis, la indagación y el uso de procedimientos para la adquisición, la sistematización y el análisis de datos, y permite la transferencia de conocimientos fundamentales a los ámbitos cotidianos. Proponemos la evaluación de estas técnicas didácticas mediante la aplicación de la V heurística o epistémica, los mapas conceptuales, las pruebas de pre test-test-post test, y las curvas de aprendizaje. Palabras clave: AGRONOMÍA/ BIOLOGÍA/ COMPETENCIAS OPERACIONALES/ DIDÁCTICA/ CONSTRUCTIVISMO CIBERNÉTICO DE SEGUNDO ORDEN/ MÉTODO CIENTÍFICO/Abstract: We propose new methodologies to implement and evaluate participatory exercises as aids in the teaching and learning of natural sciences; these exercises transfer teacher protagonism in the classroom to a collaborative learning process developed with the students. These methodologies deploy modern epistemological, ontological and conceptual principles, born by second-order cybernetic constructivism, technically supported by the most recent findings of cognitive psychology, as applied to the local educational process. The exercises facilitate the understanding and application of the scientific method in natural sciences, and promote the development of other technical and personal skills and competences. The protocols also promote the practice of scientific research, formulation of hypotheses, and the use of procedures to acquire, systematize, and analyze data. In addition, allows the easy transference of basic knowledge to daily situations. We propose that the effectiveness of traditional versus new, contructivism-based educational methods, may be evaluated quantitatively using tools such as the heuristic or epistemic V, conceptual maps, pre test-test-post test, and leaning curves.
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