892 resultados para SUBSTANTIA-NIGRA
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Las concentraciones migratorias y postnupciales de cigüeña negra han sido objeto de estudio en 22 localidades de las provincias de Ciudad Real, Cáceres y Badajoz (centro y oeste de España). Entre 2003 y 2006 se visitaron periódicamente distintos tipos de humedales con presencia habitual de la especie durante los pasos migratorios, desde el 21 de julio hasta el 10 de octubre. En 174 de las 339 visitas realizadas se detectó la presencia de cigüeña negra. El número promedio registrado de ejemplares por bando resultó de 11,3 ejemplares. Las fechas en que se contabilizaron más individuos, tanto en valores absolutos como relativos, correspondieron al período del 11 al 20 de septiembre. La mayor parte de los ejemplares datados (69,1%) resultaron adultos (plumaje de más de 3 años de edad), seguidos por jóvenes del año (20,2%) e inmaduros-subadultos (10,6%, 2-3 años de edad). A lo largo de todo el período migratorio se mantuvo constante la proporción de edades, salvo en el mes de octubre, cuando se incrementó la presencia aves juveniles. Durante las horas centrales del día se registró el mayor número relativo de aves sedimentadas en los humedales estudiados. Entre las 13:00 h y las 16:00 h (GMT + 2h) se censó el 62,7% de las cigüeñas negras presentes. Alrededor de la mitad de los individuos (52,5%) emplearon las áreas de concentración estudiadas para descansar y sestear.
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PREDICT POTENTIAL DISTRIBUTION. Spatial and temporal evolution of the species under different climate scenarios. Generation of habitat suitability models (HSM) high degree of uncertainty and limitations. The importance of their validation has been stressed. In this work we discuss the present potential distribution of P. sylvestris and P. nigra in the Iberian Peninsula by using MaxEnt, and evaluate the influence of the different environmental variables. Our intention is to select a set of environmental variables that explains better their current distribution, to achieve the most accurate and reliable models. Then we project them to the past climatic conditions (21 to 0 kyrs BP), to evaluate the outputs with existing palaeo-ecological data.
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The presence of Pinus nigra in central Spain, where its natural populations are very rare, has led to different interpretations of the current vegetation dynamics. Complementary to the available palynological evidence, macroremains provide local information of high taxonomic resolution that helps to reconstruct the palaeobiogeography of a given species. Here we present new macrofossil data from Tubilla del Lago, a small palaeolake located at the eastern part of the northern Iberian Meseta. We identified 17 wood samples and 71 cones on the basis of their wood anatomy and morphology, respectively. S ome of the fossil samples were radiocarbon dated (~4.230-3210 years cal BP). The results demonstrate the Holocene presence of P. nigra in the study area, where it is currently extinct. This evidence, together with other published palaeobotanical studies, indicates that the forests dominated by P. nigra must have had a larger importance on the landscape prior to the anthropogenic influence on the northern Iberian Meseta.
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In recent years, challenged by the climate scenarios put forward by the IPCC and its potential impact on plant distribution, numerous predictive techniques -including the so called habitat suitability models (HSM)- have been developed. Yet, as the output of the different methods produces different distribution areas, developing validation tools are strong needs to reduce uncertainties. Focused in the Iberian Peninsula, we propose a palaeo-based method to increase the robustness of the HSM, by developing an ecological approach to understand the mismatches between the palaeoecological information and the projections of the HSMs. Here, we present the result of (1) investigating causal relationships between environmental variables and presence of Pinus sylvestris L. and P. nigra Arn. available from the 3rd Spanish Forest Inventory, (2) developing present and past presence-predictions through the MaxEnt model for 6 and 21 kyr BP, and (3) assessing these models through comparisons with biomized palaeoecological data available from the European Pollen Database for the Iberian Peninsula.
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El presente proyecto se centra en el estudio de la influencia que ejerce el contenido de humedad en la madera sobre mediciones realizadas mediante diversos ensayos no destructivos (NDT – Non Destructive Tests-). El objetivo es encontrar la relación entre el contenido de humedad de la madera de varias especies del género Pinus (Pinus nigra Arn, Pinus radiata D.Don. y Pinus sylvestris Ait.) y los resultados de diferentes NDT (penetrómetro, resistencia al arranque de tornillos y velocidad de propagación de ondas inducidas y ultrasonidos), y en caso de existir, tratar de elaborar un modelo o factor de corrección que nos permita tener en cuenta dicha influencia en futuros NDT.
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Pie de imp. tomado del colofón
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Stress-induced mutations may play an important role in the evolution of plants. Plants do not sequester a germ line, and thus any stress-induced mutations could be passed on to future generations. We report a study of the effects of heat shock on genomic components of Brassica nigra Brassicaceae. Plants were submitted to heat stress, and the copy number of two nuclear-encoded single-copy genes, rRNA-encoding DNA (rDNA) and a chloroplast DNA gene, was determined and compared to a nonstressed control group. We determined whether genomic changes were inherited by examining copy number in the selfed progeny of control and heat-treated individuals. No effects of heat shock on copy number of the single-copy nuclear genes or on chloroplast DNA are found. However, heat shock did cause a statistically significant reduction in rDNA copies inherited by the F1 generation. In addition, we propose a DNA damage-reppair hypothesis to explain the reduction in rDNA caused by heat shock.
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Folio-sized leaf with a handwritten Latin exercise titled, "Idea Substantia incorporea est aeque clara ac corporea."
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.