Cambio global y ambiente lumínico en ecosistemas forestales mediterráneos:Consideraciones ecológicas e implicaciones para la gestión

10 páginas, 5 figuras y una tabla. Se recoge el trabajo en un cuadernillo titulado "Actas de la I Reunión sobre Ecología, Ecofisiología y Suelos forestales". En el apartado "Agradecimientos. Gracias a Teodoro Marañón, Juan Arroyo, Regino Zamora, José María Gómez, David Riaño, Emilio Chuvieco, Adrián Escudero, Federico Castillo, Bosco Imbert, Lucía Ramírez, Alba Valladares, Beatriz Guzmán-Asenjo y Libertad González por su colaboración en el trabajo de campo."La información cuantitativa sobre la radiación disponible en el sotobosque es crucial para la comprensión de multitud de aspectos relacionados con la ecología y dinámica del bosque. Dado que la gestión es en buena medida la gestión de la luz, la combinación de estudios sobre ecofisiología, heterogeneidad lumínica, dinámica forestal y cambio global representa un punto de encuentro entre la ecología y la gestión forestal, algo muy necesario em ecosistemas mediterráneos donde las incertidumbres son grandes y las predicciones poco optimistas. En este trabajo se presentan resultados sobre la heterogeneidad temporal y espacial de la luz en el sotobosque de diversas formaciones forestales ibéricas (encinares, alcornocales, pinares, abedulares y hayedos). En general se observa que las formaciones mediterráneas tiene una mayor estructura espacial y una mayor heterogeneidad lumínica que los bosques no mediterráneos, que la radiación disponible bajo un dosel es inversamente proporcional a la tolerancia a la sombra de las especies arbóreas que lo componen y que el número de destellos de sol disminuye con la radiación total que llega al sotobosque (i.e. los destellos se hacen largos e intensos). Las implicaciones de estos resultados se interpretan considerando la información disponible sobre las respuestas de las plantas a la combinación de sombra y sequía, y sobre el papel de la heterogeneidad abiótica en la coexistencia de especies. Se propone que el cambio global conduce a un sotobosque mas oscuro y lumínicamente homogéneo, lo cual unido al incremento de aridez irá dando lugar a bosques huecos, pobres en especies y con escasa capacidad de regeneración natural.La financiación procede de la red temática GLOBIMED, y de los proyectos ECOFIARB y TALMED del Ministerio de Ciencia y TecnologíaPeer reviewe

Ab Initio studies of the atomic structure and electronic density of states of pure and hydrogenated a-Si

We propose a method to simulate a-Si and a-Si:H using an ab initio approach based on the Harris functional and thermally amorphisized periodically continued cells with at least 64 atoms, and calculate their radial distribution functions. Hydrogen incorporation was achieved via diffusive random addition. The electronic density of states (DOS) is obtained using density functional theory with the aid of both the Harris-functional and Kohn-Sham-LDA approaches. Two time steps are used, 2.44 and 10 fs for the pure, and 0.46 and 2 fs for the hydrogenated, to see their effect on the topological and DOS structure of the samples. The calculated long time-step radial features of a-Si are in very good agreement with experiment whereas for a-Si:H the short time-step partial and total radial features agree well; for the long time-step simulation molecular hydrogen appears during annealing.The long time-step a-Si has a well defined gap with two dangling bonds, that clears and increases upon hydrogen addition and relaxation, as expected. The short time-step structures have more defects, both dangling and floating bonds, that are less characteristic of a good sample; however the radial structures of a-Si:H are in better agreement with experiment indicating that the experimental work was done on defective samples.Comment: 11 pages, RevTeX, 16 figures, submitted to Phys. Rev. B 16 June 200

Past, present and future methods of quantification in anatomical and ultrastructural studies of lichens

7 pages, figures, and tables statistics.This paper provides a general view of the state of the art in quantification methods for light and elctron microscopy, with especial reference to botany and lichenology.Peer reviewe

A Simulation Study on the Importance of Size‐related Changes in Leaf Morphology and Physiology for Carbon Gain in an Epiphytic Bromeliad

This study addresses the question of how size‐related changes in leaf morphology and physiology influence light absorption and carbon gain of the epiphytic bromeliad Vriesea sanguinolenta. A geometrically based computer model, Y‐plant, was used for the three‐dimensional reconstruction of entire plants and for calculation of whole plant light interception and carbon gain. Plants of different sizes were reconstructed, and morphological and physiological attributes of young and old leaves, and small and large plants were combined to examine the individual effects of each factor on light absorption and carbon gain of the plant. The influence of phyllotaxis on light absorption was also explored. Departure of measured divergence angles between successive leaves from the ideal 137·5° slightly decreased light absorption. The only morphological parameter that consistently changed with plant size was leaf shape: larger plants produced more slender foliage, which substantially reduced self‐shading. Nevertheless, self‐shading increased with plant size. While the maximum rate of net CO2 uptake of leaves increased linearly with plant size by a factor of two from the smallest to the largest individual, the potential plant carbon gain (based on total foliage area) showed a curvilinear relationship, but with similar numerical variation. We conclude that leaf physiology has a greater impact on plant carbon gain than leaf and plant morphology in this epiphytic bromelia

Influencia de tres dosis crecientes de biol en comparación con tres dosis crecientes de nitrógeno en la producción del cultivo de pepinillo (Cucumis sativus L.) para encurtido Cv. Palomar

Esta investigación se realizó en el Campus UPAO II, ubicado en la prolongación de la avenida Villareal S/N – Nuevo Barraza, distrito de Laredo, provincia de Trujillo, región La Libertad, de febrero a marzo del 2016. El objetivo fue determinar la influencia de tres dosis crecientes de Biol (1, 2 y 3 m 3 Biol/ha) y tres dosis crecientes de nitrógeno (100, 150 y 200 kg/ha) utilizando como fuente la urea, en la producción del cultivo de pepinillo (Cucumis sativus L.) Cv. Palomar para encurtido. El diseño experimental fue de Bloques Completamente al Azar (BCA), con 7 tratamientos y 4 repeticiones, y se realizó un análisis de varianza y la prueba de significación de Duncan al 0.05 de probabilidad. Los parámetros evaluados fueron altura de planta, número de hojas por planta, diámetro de tallo por planta, número de flores por planta, acumulación de biomasa fresca por planta, acumulación de biomasa seca por planta, a los 20, 40 y 56 días después de la siembra. También durante la cosecha, se evaluaron número de frutos por planta (según categorías) y rendimiento por hectárea. Los resultados demostraron que el rendimiento total de pepinillo (Cucumis sativus L.) Cv. Palomar para encurtidos respondió satisfactoriamente a la dosis de 200 kg N/ha, con 8782.81 kg/ha superando al testigo (sin aplicación) en 38.4 %. El mayor rendimiento total en aplicación de Biol se obtuvo con la dosis de 3 m3 Biol/ha con 7431.50 kg/ha superando al testigo en 27.2 %.This research was carried out in UPAO II Campus, located at Villarreal Avenue without number – New Barraza, district of Laredo, province of Trujillo, region La Libertad (Peru), from February to March 2016. The objective was to determine the influence of three increasing doses of Biol (1, 2 and 3 m 3 Biol/ha) and three increasing doses of nitrogen (100, 150 and 200 kg N/ha) on the yield of pickles (Cucumis sativus L.) Cv. Palomar. The experimental design was Randomized Complete Block, with 7 treatments and 4 replicates, and it was performed the variance analysis and Duncan significant test at 0.05 of probability. Plant Height, number of leaves per plant, stem diameter per plant, number of flowers per plant, accumulation fresh biomass per plant, and accumulation of dry biomass per plant were evaluated 20, 40, and 56 days after sowing. Number of fruits per plant (according to categories) and yield per hectare were also evaluated during harvesting. The results showed that the yield of pickles (Cucumis sativus L.) Cv. Palomar had satisfactory response to the dose of 200 kg N/ha, with 8782.81 kg/ha, over yielding the control (without application) in 38.4 %. The higher yield with Biol was obtained with the dose of 3 m3 Biol/ha with 7431.50 kg/ha up yielding control in 27.2 %.Tesi

Convergence in light capture efficiencies among tropical forest understory plants with contrasting crown architectures: a case of morphological compensation

10 páginas, 5 figuras y 4 tablasLeaf and crown characteristics were examined for 24 tree and herbaceous species of contrasting architectures from the understory of a lowland rainforest. Light-capture efficiency was estimated for the crowns of the different species with a three-dimensional geometric modeling program. Causal relationships among traits affecting light absorption at two hierarchical levels (leaf and whole crown) were quantified using path analysis. Light-capture and foliage display efficiency were found to be very similar among the 24 species studied, with most converging on a narrow range of light absorption efficiencies (ratio of absorbed vs. available light of 0.60– 0.75). Exceptionally low values were found for the climber vines and, to a lesser extent, for the Bromeliad Aechmea magdalenae. Differences in photosynthetic photon flux density (PFD) absorbed per unit leaf area by individual plants were mostly determined by site to site variation in PFD and not by the differences in crown architecture among individuals or species. Leaf angle, and to a lesser extent also supporting biomass, specific leaf area, and internode length, had a significant effect on foliage display efficiency. Potential constraints on light capture such as the phyllotactic pattern were generally offset by other compensatory adjustments of crown structure such as internode length, arching stems, and plagiotropy. The variety of shoot morphologies capable of efficiently capturing light in tropical forest understories is greater than initially thought, extending over species with very different phyllotactic patterns, crown architectures, leaf sizes, and morphologies.This research was supported by Mellon foundation/ Smithsonian Institution fellowships to FV and RWP, NSF Grant IBN 96-04424. Manuscript preparation was supported by a train and mobility grant given to FV by the Spanish Ministry of Education, Culture and Sports and a Professional Development Grant to JBS from the California State University.The authors thank Eduardo Sierra for help with the identification of the individuals studied, to Eloisa Lasso for help with data collection, and to Lourens Poorter for fitting criticisms. This research was supported by Mellon foundation/ Smithsonian Institution fellowships to FV and RWP, NSF Grant IBN 96-04424.Peer reviewe

Efectos de la disponibilidad de agua y nutrientes en el patrón de acumulación de carbohidratos en plántulas de tres especies de Quercus

6 páginas, 2 figuras y 2 tablasSe pretende estimar el efecto de un eventual cambio climático y edáfico sobre el patrón de almacenamiento de carbohidratos en plántulas de un año de tres especies leñosas mediterráneas del género Quercus. Para ello se han cultivado las plántulas bajo tres condiciones contrastadas de fertilidad y tres de riego, experimento no factorial, durante una estación de crecimiento. Se espera que en los medios menos fértiles se acumule carbono en forma de reservas debido a la limitación en el crecimiento por falta de nutrientes. Asimismo, en condiciones de riego bajo, aumente la concentración de glucosa para contribuir al ajuste osmótico de las hojas. Por último, esperamos que Q. faginea, la especie de crecimiento más rápido, invierta mayor cantidad de carbono en crecimiento y por tanto acumule menos almidón. Las concentración de almidón en raíz y tallo de Q. ilex y Q. coccifera fue inversamente proporcional al nivel de fertilización. La concentración de glucosa foliar mostró mayores concentraciones en las plántulas que experimentaron déficit hídrico. La especie que más carbohidratos almacenó fue Q. faginea. Nuestro estudio sugiere, que el efecto de un incremento de aridez sobre el almacenamiento de carbohidratos depende, no sólo de la especie, sino también de la fertilidad del suelo sobre el que se asiente.Universidad de Alcalá. Alcalá de Henares y Centro de Ciencias Medioambientales. CSICPeer reviewe

Species-specific water use by forest tree species: from the tree to the stand

Forests play a critical role in the hydrological cycle making the study of water use by trees and forest stands of prime importance in the global change context .Very negative effects of increasing and more intense droughts on forest vegetation have been described over the last decades. Symptoms of disease and decline have been associated with changed precipitation patterns in many forests particularly in European temperate and Mediterranean regions. Intra- and inter-specific differences in both physiology and morphology exert a large but not well understood influence on the water balance of forest ecosystems, further affecting their vulnerability to drought. Stand structure and composition influences rainfall interception, runoff and water fluxes of the whole ecosystem. Both expanding plantations of renovated interest for biofuel industry and natural and semi-natural forests must be managed in a sustainable way on the basis of their water consumption. We review the role of key drivers on forest water use such as species composition, tree canopy status of each of them and species specific sensitivity to soil water scarcity. Specifically we discuss the role of these factors for natural forest, but with references also to forest plantations. Water scarcity is expected to be one of the largest societal problems worldwide in the near future, so water use by natural and planted forest ecosystems has become a central subject in current research agendas.This work was supported by the INIA and Ministry of Economy and Competitiveness (grants SUM2008-00004-C03-01 and AGL2011-25365).Peer reviewe