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La invasión de especies exóticas de espacios naturales constituye un problema de conservación a nivel global. En la Reserva Ecológica Siboney-Juticí, Leucaena leucocephala es considerada como una de sus principales amenazas para la conservación del bosque semideciduo micrófilo. El objetivo de este estudio es caracterizar la riqueza y estructura del bosque semideciduo micrófilo en áreas con diferentes niveles de cobertura de Leucaena leucocephala en dicha reserva. Para el estudio se establecieron 15 parcelas de 400 m2 en tres niveles de cobertura de la especie invasora: ABSM-NI (bosques sin perturbación), ABSM-PI (40-60 % de cobertura de Leucaena leucocephala) y ABSM-TI (70 % de cobertura de Leucaena leucocephala). Se estimó el número de individuos por especie y su presencia en cada uno de los estratos, además se consideró la altura de las especies leñosas. Por cada uno de los niveles estudiados se determinó la riqueza específica, la abundancia relativa de las especies y la composición florística por estratos; así como las similitudes florísticas entre cada uno de los niveles. En ABSM-NI se registraron 55 especies, en ABSM-PI 51 y en ABSM-TI 43. En los tres niveles de cobertura se mantuvieron los estratos (arbóreo, arbustivo, herbáceo) y las lianas. En ABSM-TI no se registraron epífitas. La mayor similitud biológica fue entre ABSM-PI y ABSM-TI; muchas de las especies compartidas son ruderales y colonizan áreas con algún tipo de perturbación. La principal transformación estuvo en la composición y abundancia de las especies en la medida que aumenta la cobertura de la especie invasora. En ABSM-TI incrementó la riqueza específica y la abundancia/cobertura de especies propias de vegetación secundaria, en detrimento de otras especies típicas del bosque. En los sitios de mayor cobertura de la especie invasora ocurre una disminución de la composición específica y altura del estrato arbóreo. En este sitio también se observó un aumento de la composición específica de los estratos arbustivo y herbáceo. Las epífitas solo se registraron en ABSM-NI y ABSM-PI.

Abstract This experimental study evaluates the energy performance and climatic changes of a cascade cooling system operating with the R134a/R744 pairs (cooling capacity of 4.5‐6 kW) and R438A/R744. In both cases, the low‐temperature refrigerant, R744, operated under subcritical conditions. The experimental apparatus basically consists of two vapor‐compression cycles coupled by a plate cascade condenser. Two operational variables, from R744 cycle, were controlled: the degree‐of‐superheat and the compressor frequency. The experiment was initially assembled to pair R134a/R744. Subsequently, the R134a refrigerant charge in the high‐temperature cycle was replaced by R438A, on a drop‐in basis. The two systems, R134a/R744 and R438A/R744, were compared for similar cooling capacities and cold chamber air temperatures. Results showed that the energy consumption of the high‐temperature compressor, operating with R438A, was higher than R134a for all tests. As a result, the COP values for R438A/R744 were 30% lower than those for R134a/R744. The greenhouse gases emissions of the two systems were evaluated using the total equivalent warming impact factor, TEWI, whose value for the R438A/R744 pair was approximately 29.5% higher, compared with R134a/R744. Since R438A was originally designed to substitute R22, a few comparative tests were carried out with the latter, always with R744 as the low‐temperature cycle working fluid.

The studies of flora and vegetation that have been carried out in El Retiro Natural Reserve have been limited to some of its sectors, so there is still no information about the structure of its vegetation formations and the relationship between them. Therefore, the objective of this research was to characterize the vegetation of this protected area. The following aspects were analyzed: dominant species, stratification and distribution in all vegetation types. A more detailed map of the distribution of vegetation formations in the area was obtained. Seven vegetation types were identified, of which secondary shrubland in semi-deciduous microphyllous forest ecotypes and secondary shrubland in coastal and pre-coastal shrubland ecotypes were new vegetation records for the reserve. The coastal and pre-coastal scrub and the semi-deciduous microphyllous forest were the richest vegetation formations in terms of number of species and endemics. In the analysis of biological similarity, they were the most similar.

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The fire represents one of the most severe disturbance agents altering the communities’ characteristics. The objectives of the research are to determine the magnitude of the change of plants species diversity generated by a fire at the microphyll semideciduos forest of the natural reserve El Retiro, as well as their recovery capacity through the time. Forthat, two 20 x 20 m plots were established at the conserved and burned area, spaced at a distance of 20 m each other. The plots of the burned area were examined three times at the 2013 and 2014, and the results were presented in four sample stage. The variables were the richness, recruitment and relative abundance of the species, which wereanalyzed by means of abundance-range curves, similarity index and multivariate analysis. 72 species were determined, of which 17 are endemics and 16 are new record forthearea. The burned area contain the biggest species richness, emphasized for its dominance at the beginning of the recovery, the herbs Bothriochloa pertusa, Cynodondactylon and Waltheria indica,and the succulent Agave underwoodii, with a highpotential of vegetative resproute. The number and the species composition, and so the biological similarity between the burned and conserved area, were increasing considerably beginning from 12 months of monitoring, which indicate a rapid process of recovery of the burned forest, characterized mainly by the mshrubs and epiphytes dominance.

Los ofidios constituyen el segundo grupo en importancia dentro de los reptiles en las Antillas, pero la ecología de sus especies no ha sido muy estudiada. El propósito de este trabajo es dar a conocer algunos aspectos de la historia natural de cuatro especies de ofidios de Cuba (familias Dipsadidae y Tropidophiidae), acumulados durante ocho años de observación en 27 localidades y 11 tipos de hábitats. Las cuatro especies viven en una amplia diversidad de hábitats, incluyendo algunos con alta influencia humana. La especie de menor plasticidad ecológica fue Tropidophis wrighti, la que se encontró solo en el 45.4% de los hábitats y tuvo menor tolerancia por los ambientes antropizados. Todas las especies usan mayormente microhábitats terrestres, pero Cubophis cantherigerus y T. melanurus utilizan, en alguna medida, los substratos arbóreos. Dos especies (las de la familia Dipsadidae) tienen actividad diurna y parecen ser heliófilas, mientras que las otras dos (las de la familia Tropidophiidae) parecen tener poca actividad diurna y pueden considerarse como especies umbrófilas. Se detectaron dos agrupaciones morfológicas que parecen tener bases filogenéticas, ya que están poco relacionadas con el microhábitat o la alimentación.

This experimental study evaluates the energy performance and climatic changes of a cascade cooling system operating with the R134a/R744 pairs (cooling capacity of 4.5‐6 kW) and R438A/R744. In both cases, the low‐temperature refrigerant, R744, operated under subcritical conditions. The experimental apparatus basically consists of two vapor‐compression cycles coupled by a plate cascade condenser. Two operational variables, from R744 cycle, were controlled: the degree‐of‐superheat and the compressor frequency. The experiment was initially assembled to pair R134a/R744. Subsequently, the R134a refrigerant charge in the high‐temperature cycle was replaced by R438A, on a drop‐in basis. The two systems, R134a/R744 and R438A/R744, were compared for similar cooling capacities and cold chamber air temperatures. Results showed that the energy consumption of the high‐temperature compressor, operating with R438A, was higher than R134a for all tests. As a result, the COP values for R438A/R744 were 30% lower than those for R134a/R744. The greenhouse gases emissions of the two systems were evaluated using the total equivalent warming impact factor, TEWI, whose value for the R438A/R744 pair was approximately 29.5% higher, compared with R134a/R744. Since R438A was originally designed to substitute R22, a few comparative tests were carried out with the latter, always with R744 as the low‐temperature cycle working fluid. [ABSTRACT FROM AUTHOR]

Resumen Se caracterizaron la composición florística y la estructura horizontal del bosque semideciduo micrófilo de la reserva ecológica Siboney-Juticí, perteneciente a la reserva de la biosfera Baconao, en el suroriente de Cuba. Se procesaron los datos correspondientes a diez parcelas de 20 m × 50 m, donde a cada individuo se le midió la altura y el diámetro a 1,30 m del suelo. Se calculó el área basal, las abundancias, las frecuencias y las dominancias absolutas y relativas, además del índice de Valor de Importancia por especie y familia. A las matrices de datos se les aplicó el Análisis de Coordenadas Principales como método de ordenación. En el bosque se analizaron 3206 individuos correspondientes a 54 taxones infragenéricos y 27 familias, además se anotaron otras plantas acompañantes. Las especies con mayor número de individuos fueron Coccoloba diversifolia, Bursera simaruba, Sideroxylon salicifolium, Gymnanthes lucida, Nectandra coriacea, Eugenia axillaris y E. monticola, que son las de mayor índice de Valor de Importancia y con tendencia a asociarse entre sí. Se observaron regularidades estructurales y de diversidad entre las parcelas. El estrato arbóreo es denso pero bajo, con escasos emergentes.

Copyright of Rodriguésia is the property of Revista Rodriguesia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)