Ecología de la germinación de la semillas de Pinus sylvestris L. en el límite sur de su distribución

Seed germination of Pinus sylvestris L. in south eastern Spain was studied under field and growth chamber conditions to assess the effect of the most representative microhabitats of these forests. Under growth chamber conditions, germination was high (almost 95%) in the litter from all microhabitats. Germination under field conditions was highest (up to 95%) in shade-free microhabitats and therefore higher soil temperature (e.g. areas of bare soil and meadows), and lowest (down to 62%) in microhabitats with dense canopy shade and thus lower soil temperature (e.g. under the canopy of pines and under the canopy of juniper). Nevertheless, germination was high also in shaded microhabitats in a year with high rainfall during the germination period, supporting the hypothesis that germination was determined by a combination of appropriate levels of soil temperature, moisture, and light intensity. In contrast, biotic speciesspecific characteristics of the microhabitat were not relevant. Germination may thus reach high percentages in all the microhabitats of the understory during rainy years that ensure appropriate soil moisture during the germination period. However, during dry years germination will concentrate in sunny microhabitats because they reach higher soil temperature early in the season before soil desiccation. These patterns have implications for forest management and stand regeneration via direct seeding.Se analiza la germinación de las semillas de pino silvestre en el límite sur de su distribución (Sierra Nevada) mediante experimentos de campo y de laboratorio en una muestra de diez microhábitats que representan la mayoría de los lugares en los que se encuentran las semillas tras la dispersión en estos bosques. En condiciones de laboratorio, las semillas mostraron una alta tasa de germinación (en torno al 95%) en la hojarasca de todos los microhábitats. En el campo las semillas mostraron una tasa de germinación mayor (en torno al 95%) en microhábitats directamente expuestos al sol y por tanto con mayor temperatura (e.g. suelo sin vegetación y prados de herbáceas) y una menor tasa bajo plantas con copa espesa que generan un microhábitat sombreado y con menor temperatura (bajo copa de pinos adultos y bajo copa de enebros). No obstante, durante un año lluvioso la tasa de germinación en microhábitats sombreados se incrementó considerablemente, sugiriendo que la germinación está controlada por una combinación adecuada de radiación, humedad y temperatura. Por el contrario, no se detectó ningún efecto biótico relacionado con el microhábitat, como alelopatía. La germinación de las semillas de pino silvestre en estos bosques puede por tanto alcanzar valores altos en todos los microhábitats durante años con primavera lluviosa que asegure la confluencia de humedad y temperatura apropiada en el suelo. Sin embargo, en años con primaveras más secas la germinación se concentrará en microhábitats con alta radiación, ya que la mayor temperatura del suelo permitirá una rápida germinación antes de que se produzca la desecación del sustrato. Estos patrones deben tenerse en cuenta a la hora de planificar la regeneración del bosque mediante la siembra de semillas

Tailoring activated carbons for the development of specific adsorbents of gasoline vapors

The specific adsorption of oxygenated and aliphatic gasoline components onto activated carbons (ACs) was studied under static and dynamic conditions. Ethanol and n-octane were selected as target molecules. A highly porous activated carbon (CA) was prepared by means of two processes: carbonization and chemical activation of olive stone residues. Different types of oxygenated groups, identified and quantified by TPD and XPS, were generated on the CA surface using an oxidation treatment with ammonium peroxydisulfate and then selectively removed by thermal treatments, as confirmed by TPD results. Chemical and porous transformations were carefully analyzed throughout these processes and related to their VOC removal performance. The analysis of the adsorption process under static conditions and the thermal desorption of VOCs enabled us to determine the total adsorption capacity and regeneration possibilities. Breakthrough curves obtained for the adsorption process carried out under dynamic conditions provided information about the mass transfer zone in each adsorption bed. While n-octane adsorption is mainly determined by the porosity of activated carbons, ethanol adsorption is related to their surface chemistry, and in particular is enhanced by the presence of carboxylic acid groups.This work is supported by the MICINN-FEDER, project CTM2010-18889

Uso de matorrales como plantas nodriza en ambientes nediterráneos: evaluación de una nueva técnica de repoblación forestal

Common techniques currently used for reforestation in Spain consider the pre-existing vegetation (mainly shrubs) as a source of competition for trees, and consequently it is generally eliminated before planting. Nevertheless, it has been demonstrated that woody plants can facilitate the establishment of understory seedlings in environments that, like the Mediterranean area, are characterized by a pronounced dry season. In this study, we experimentally analyze the usefulness of shrubs as nurse plants for reforestation considering a broad gradient of environmental conditions, such as altitude, aspect, annual rainfall, nurse plant and target species. Seedlig survival was boosted under the canopy of shrubs in relation to a traditional reforestation technique, while seedling growth was not hampered. The results show therefore that the use of shrubs as nurse plants is a viable technique for reforestation in Mediterranean environments, which in addition offers both economic and ecologic advantages.Los matorrales suelen considerarse como una fuente de competencia con los plantones sembrados, por lo que en las repoblaciones forestales que se llevan a cabo en España son generalmente eliminados antes de la siembra. Sin embargo, numerosos estudios indican que en los ambientes mediterráneos los matorrales pueden proteger a los plantones de la desecación, incrementando su supervivencia. Desde esta perspectiva, durante el período 1997-2003 llevamos a cabo repoblaciones experimentales en la provincia de Granada, considerando un amplio gradiente de condiciones ambientales, de especies repobladas y de matorrales nodriza, con objeto de evaluar la plantación bajo la copa de matorrales como una técnica alternativa de repoblación que mejore las técnicas convencionales. Los resultados obtenidos muestran que la técnica es viable, incrementando considerablemente la supervivencia de los plantones (hasta 6,2 veces respecto a las técnicas convencionales) sin reducir su crecimiento. La técnica ofrece además ventajas ecológicas y económicas respecto a las metodologías convencionales, por lo que proponemos que debe usarse extensivamente en las repoblaciones forestales realizadas en la España mediterránea

The use of functionalized carbon xerogels in cells growth

In the present study carbon xerogels are used for the first time to study the fibroblast cell growth. For that, carbon xerogel microspheres are synthesized and thereafter functionalized with carbon nanofibers followed by the 1,3-dipolar cycloaddition of azomethine ylides (the so called \u201cPrato reaction\u201d) or the addition of aryl diazonium salts (the so called \u201cTour reaction\u201d) to improve its wettability. The presence of nanofibers produces a huge improvement of the functionalization degree (59 versus 372 \u3bcmol/g for pristine carbon spheres and carbon spheres with 30% of carbon nanofibers, respectively) in spite of the blockage of the carbon spheres porosity caused after the nanofibers growth. This improvement was explained on the base of the increase of the number of probable active sites for the addition reactions (C[dbnd]C bonds) and the accessibility to these active sites (accessible surface area) by the presence of nanofibers. These high functionalization degrees reflect a promising potential of these materials in biomedical applications. Toxicity results obtained using a fibroblast cell line showed that samples are biocompatible for this kind of cells and that the presence of carbon fibers on the surface of the spheres increases the cells proliferation in a high extend reaching in some case values around 150% regarding the control. This study evidences that carbon aerogels could be interesting materials in biological applications, an unexplored field for this type of materials, being biocompatible, favouring the proliferation of cells and achieving high functionalization degrees

Applying plant facilitation to forest restoration in Mediterranean ecosystems: a meta-analysis of the use of shrubs as nurse plants

11 pages, 4 figures, 1 table, 75 references. We thank the Consejería de Medio Ambiente, Junta de Andalucía, and the Direction of the National Park of Sierra Nevada for permission to field work, constant support and facilities. We are also especially grateful to Empresa de Transformación Agraria S.A. (TRAGSA) for carrying out the experimental reforestation. We thank Sergio de Haro and several students for field assistance. David Nesbitt looked over the English version of the manuscript.After a millenarian history of overexploitation, most forests in the Mediterranean Basin have disappeared, leaving many degraded landscapes that have been recolonized by early successional shrub-dominated communities. Common reforestation techniques treat these shrubs as competitors against newly planted tree seedlings; thus shrubs are cleared before tree plantation. However, empirical studies and theory governing plant– plant interactions suggest that, in stress-prone Mediterranean environments, shrubs can have a net positive effect on recruitment of other species. Between 1997 and 2001, we carried out experimental reforestations in the Sierra Nevada Protected Area (southeast Spain) with the aim of comparing the survival and growth of seedlings planted in open areas (the current reforestation technique) with seedlings planted under the canopy of preexisting shrub species. Over 18 000 seedlings of 11 woody species were planted under 16 different nurse shrubs throughout a broad geographical area. We sought to explore variation in the sign and magnitude of interactions along spatial gradients defined by altitude and aspect. In the present work, we report the results of a meta-analysis conducted with seedling survival and growth data for the first summer following planting, the most critical period for reforestation success in Mediterranean areas. The facilitative effect was consistent in all environmental situations explored (grand mean effect size d1 5 0.89 for survival and 0.27 for growth). However, there were differences in the magnitude of the interaction, depending on the seedling species planted as well as the nurse shrub species involved. Additionally, nurse shrubs had a stronger facilitative effect on seedling survival and growth at low altitudes and sunny, drier slopes than at high altitudes or shady, wetter slopes. Facilitation in the dry years proved higher than in the one wet year. Our results show that pioneer shrubs facilitate the establishment of woody, late-successional Mediterranean species and thus can positively affect reforestation success in many different ecological settings.This study was supported by a PFPU-MECD grant to L. G. and PFPI-MCYT to E. B. and projects FEDER 1FD97-0743-CO3-02 and REN 2001- 4552-E from MCYT.Peer reviewe