Reseñas bibliográficas

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Condicionantes de la respuesta vegetal al cambio climático. Una perspectiva paleobiolágica.

RESUMEN. Condicionantes de la respuesta vegetal al cambio climático. Una perspectiva paleobiolágica. Este artículo proporciona una revisión de las pautas y procesos de cambio vegetal en relación con el cambio climático, así como sobre la cuestión del equilibrio clima-vegetación y sus condicionantes, desde una perspectiva paleobiológica basada fundamentalmente en secuencias polínicas. En la escala evolutiva, la mayor parte de los eventos de migración, extinción de especies y reorganización de la estructura ecológica se describen adecuadamente como respuestas tipo umbral bióticamente condicionadas. Se constata una gran resistencia a la invasión de las comunidades establecidas, siendo de mayor relevancia la historia biológica de los grupos que el propio sentido del cambio climático en orden a establecer los grupos dominantes después de cada crisis. El nexo entre la biología evolutiva y la biogeografía lo proporcionan los estudios paleoecológicos a escala orbital. Durante los ciclos climáticos del Cuaternario, hubo dispersión de poblaciones, extinciones locales y desagregación de comunidades. A esta escala, el clima ejerce un control a largo plazo sobre el cortejo florístico disponible, dentro de las limitaciones que impone la historia evolutiva regional. Hay que destacar el carácter no lineal de las respuestas de la vegetación en cada una de las tres frecuencias de control astronómico. Ante los cambios climáticos acaecidos desde la última glaciación, la vegetación ibérica se ha mostrado a menudo inerte durante milenios y a veces reactiva en la escala de centurias o incluso décadas. Las respuestas abruptas pueden condicionarse a factores no climáticos, muy a menudo cambios en el regimen de fuegos. La cuestión del equilibrio es, simplemente, un problema de escala. En este sentido, el control del cambio vegetal se deslizaría sutilmente desde lo climático a lo biótico conforme disminuimos la escala temporal y/o espacial. A la hora de interpretar los cambios en la composición, estructura y distribución de comunidades vegetales, las oscilaciones climáticas abruptas representan accidentes históricos que, eventualmente, pueden llegar a ser más relevantes que las tendencias climáticas a largo plazo.Palabras clave. Paleoecología, palinología, hiogeografía histórica, vegetación, cambio climático, EspañaABSTRACT. Vegetation response to climatic change. A palaeobiological perspective. This paper reviews the patterns and processes of vegetation change in response to climatic factors, and the question of climate- vegetation equilibrium from a palacoecological perspective. At an evolutionary temporal scale, processes such as migration, species extincion, and reorganization of the ecological structure are adequately described by biotically-conditioned threshold responses. Established communities exhibit great resistance to invasion, being pre-adaptive traits of higher importance than the direction of climate change in determining the dominant group after each environmental crisis. Palaeoecological studies at the orbital scale provide a link between evolutionary and ecological processes. The Quaternary climate variation induced dispersion of plant populations, local extinctions and disaggregation of plant communities. Climate exerted control on long-term species pool within the constraints imposed by regional evolutionary history. Vegetation responses to astronomic forces were characteristically non linear. Iberian plant communities have often behaved inertial to climate changes occurring since the last glacial maximum. Sometimes, however, they have been very sensitive, providing century- to decadal-scale responses. Abrupt vegetation changes may be related with non-climatic factors, principally changes in the fire regime. The question of climate-vegetation equilibrium is a scale problem, where the control of vegetation changes would shift from climatic to biotic controls as the temporal and spatial scales are shortened. While interpreting compositional, structural and distributional changes in plant communities, abrupt climatic changes may represent historical accidents eventually more relevant than long-term climatic trends.Key words. Palaeoecology, palynology, historical biogeography, vegetation, climatic change, Spai

Macroevolución en plantas vasculares.

RESUMEN. Macroevolución en plantas vasculares. Se revisan los sistemas jerarquizados de evolución vegetal, desde una perspectiva paleoecológica y con énfasis en los controles del nivel superior para las plantas vasculares. Este nivel supone la existencia de breves episodios de intensa radiación, seguidos por largas fases de estabilización y declive taxonómico. El registro fósil sugiere que no han existido extinciones masivas entre las plantas terrestres, en el sentido en que ésta expresión se emplea para la evolución de animales, es decir, la existencia de fuertes pérdidas de biodiversidacl en períodos breves de tiempo geológico comparados con la vida media de las especies. Durante los episodios de estrés ambiental, las plantas han reaccionado haciendo valer sus capacidades de migración, recolonización, desplazamiento competitivo y, en suma, reorganizando la estructura ecológica o fitogeográfica. A un nivel taxonómico elevado, la mayoría de los grandes grupos exhiben un importante componente de supervivencia (fósiles vivientes). El único estrés al que no han podido escapar parece haber sido el de tipo abiótico y extrínseco que supone el incremento atmosférico del dióxido de carbono durante los eventos de superpluma asociados a las pulsaciones tectónicas. De entre estas, aquellas constatables para el Ordovícico Medio-Silúrico (460- 430 Ma), Devónico Medio-Carbonífero Inferior (375-350 Ma), Jurásico (150 Ma) y Cretácico Inferior (120-80 Ma), se correlacionan con fases de incremento rápido en la especiación y con la aparición de nuevos proyectos reproductores, a saber embriófitos, espermatófitos, gimnospermas actuales y angiospermas respectivamente. El artículo concluye considerando las opciones dialécticas de la radiación difusiva frente a la hipótesis adaptacionista, el papel de la preadaptación y la evolución de la complejidad.Palabras clave. Evolución, paleobottinica, paleoecología, plantas terrestres, extinciones masivas, preadaptación, pulsaciones tectónicas.ABSTRACT. Macroevolution in vascular plants. Here we review hierarchical, evolutionary model systems for vascular plants from a palaeoecological perspective, with emphasis in the controls for the highest tier.This involves the existence of rapid events of radiation, followed by enduring phases of stabilization and taxonomic declining. The fossil record fails to recognize mass extinctions among terrestrial plants, at least in the sense adopted for the evolution of animals, namely, short periods of geological time involving strong losses of biodiversity if compared with average lifetimes of the extinct species. During stages of environmental stress, the vascular plants have exploted their capabilities to migration, recolonization, and competitive displacement; shortly, reorganization of the ecological and fitogeographic structure. At high taxonomic levels, most groups exhibit persistence, inertia, and survival rather than extinction, demonstrably through the existence of a number of living fossils among the main clades. The only environmental factor to which plants could not escape was extrinsic abiotic stress in the form of increasing atmospheric CO, during superplumes associated to tectonics pulsations. In fact, those dated at the Mid-Ordovician u; Silurian (460- 430 Ma), Mid-Devonian to Lower Carboniferous (375-350 Ma), Jurassic (150 Ma), and Lower Cretaceous (120-80 Ma), correlate with phases of rapid speciation within the principal reproductive groups, namely embriophytes, seed plants, gymnosperms, and angiosperms respectively. We conclude discussing related issues of palaeoecological concern, such as diffusive versus adaptive hypotheses of radiation, the role of preadaptation in plant evolution, and the long-term patterns of complexity.-Key words. Evolution, palaeobotany, palaeoecology, land plants, mass extinctions, preadaptation, pulsation tectonics

Steppes, savannahs, forests and phytodiversity reservoirs during the Pleistocene in the Iberian Peninsula

A palaeobotanical analysis of the Pleistocene floras and vegetation in the Iberian Peninsula shows the existence of patched landscapes with Pinus woodlands, deciduous and mixed forests, parklands (savannah-like), shrublands, steppes and grasslands. Extinctions of Arctotertiary woody taxa are recorded during the Early and Middle Pleistocene, but glacial refugia facilitated the survival of a number of temperate, Mediterranean and Ibero-North African woody angiosperms. The responses of Iberian vegetation to climatic changes during the Pleistocene have been spatially and temporarily complex, including rapid changes of vegetation in parallel to orbital and suborbital variability, and situations of multi-centennial resilience or accommodation to climatic changes. Regional characteristics emerged as soon as for the Middle Pleistocene, if not earlier: Ericaceae in the Atlantic coast indicating wetter climate, thermo-mediterranean elements in the south as currently, and broad-leaf trees in the northeastern. Overall, steppe landscapes and open Pinus woodlands prevailed over many continental regions during the cold spells of the Late Pleistocene. The maintenance of a high phytodiversity during the glacials was linked to several refuge zones in the coastal shelves of the Mediterranean and intramountainous valleys. Northern Iberia, especially on coastal areas, was also patched with populations of tree species, and this is not only documented by palaeobotanical data (pollen, charcoal) but also postulated by phylogeographical models

Biomass-modulated fire dynamics during the last glacial-interglacial transition at the central pyrenees (Spain)

Understanding long-term fire ecology is essential for current day interpretation of ecosystem fire responses. However palaeoecology of fire is still poorly understood, especially at high-altitude mountain environments, despite the fact that these are fire-sensitive ecosystems and their resilience might be affected by changing fire regimes. We reconstruct wildfire occurrence since the Lateglacial (14.7. cal. ka BP) to the Mid-Holocene (6. cal. ka BP) and investigate the climate-fuel-fire relationships in a sedimentary sequence located at the treeline in the Central Spanish Pyrenees. Pollen, macro- and micro-charcoal were analysed for the identification of fire events (FE) in order to detect vegetation post-fire response and to define biomass-fire interactions. mean fire intervals (mfi) reduced since the Lateglacial, peaking at 9-7.7. cal. ka BP while from 7.7 to 6. cal. ka BP no fire is recorded. We hypothesise that Early Holocene maximum summer insolation, as climate forcing, and mesophyte forest expansion, as a fuel-creating factor, were responsible for accelerating fire occurrence in the Central Pyrenees treeline. We also found that fire had long-lasting negative effects on most of the treeline plant communities and that forest contraction from 7.7. cal. ka BP is likely linked to the ecosystem's threshold response to high fire frequencies.This research has been funded by the projects DINAMO (CGL2009-07992) (funding EGPF — grant ref. BES-2010-038593 and MSC), DINAMO2 (CGL2012-33063), ARAFIRE (2012 GA LC 064), GRACCIE-CONSOLIDER (CSD2007-00067). GGR was funded by the Juan de la Cierva Program (grant ref. JCI2009-04345) and JAE-Doc CSIC Program, LLM was supported by a postdoctoral MINT fellowship funded by the Institute for the Environment (Brunel University), AMC is a Ramón y Cajal fellow (ref: RYC-2008-02431), APS holds a grant funded by the Aragon Government (ref. 17030G/5423/480072/14003) and JAE holds a grant funded by the Basque Country Government (BFI-2010-5)

Mountain strongholds for woody angiosperms during the Late Pleistocene in SE Iberia

Mediterranean mountains played an essential role during glacial periods as vegetation refugia. The SE Iberia Late Pleistocene woody angiosperm fossil and floristic evidences are reviewed in the context of phylogeographical studies aiming to identify (i) spatial patterns related to woody angiosperms glacial survival, (ii) structural and functional characteristics of montane refugia, and (iii) gaps in knowledge on the woody angiosperm patterns of survival in Mediterranean mountains. The distribution of palaeobotanical data for SE Iberia refugia has been found to be taphonomically biased due to the scarcity of available and/or studied high-altitude Late Pleistocene sites. However, Siles Lake data together with floristic inference provide evidences for woody angiosperms’ survival in a high-altitude Mediterranean area. The main features boosting survival at montane contexts are physiographic complexity and water availability. Phylogeography studies have mainly been conducted at a continental scale. Although they cohere with palaeobotanical data to a broad scale, a general lack of sampling of SE Iberian range-edge populations, as well as misconceptions about the origin of the populations sampled, impede to infer the proper location of woody angiosperms’ mountain refugia and their importance in the post-glacial European colonisation. We conclude that floristic, geobotanical, palaeobotanical, ethnographical and genetic evidence should be merged to gain a deeper understanding on the role played by Mediterranean mountains as glacial refugia in order to explain the current distribution of many plants and the large biodiversity levels encountered in Mediterranean mountain areas. This is hallmark for effective and efficient conservation and management

Gravitational waves in dynamical spacetimes with matter content in the Fully Constrained Formulation

The Fully Constrained Formulation (FCF) of General Relativity is a novel framework introduced as an alternative to the hyperbolic formulations traditionally used in numerical relativity. The FCF equations form a hybrid elliptic-hyperbolic system of equations including explicitly the constraints. We present an implicit-explicit numerical algorithm to solve the hyperbolic part, whereas the elliptic sector shares the form and properties with the well known Conformally Flat Condition (CFC) approximation. We show the stability andconvergence properties of the numerical scheme with numerical simulations of vacuum solutions. We have performed the first numerical evolutions of the coupled system of hydrodynamics and Einstein equations within FCF. As a proof of principle of the viability of the formalism, we present 2D axisymmetric simulations of an oscillating neutron star. In order to simplify the analysis we have neglected the back-reaction of the gravitational waves into the dynamics, which is small (<2 %) for the system considered in this work. We use spherical coordinates grids which are well adapted for simulations of stars and allow for extended grids that marginally reach the wave zone. We have extracted the gravitational wave signature and compared to the Newtonian quadrupole and hexadecapole formulae. Both extraction methods show agreement within the numerical errors and the approximations used (~30 %).Comment: 17 pages, 9 figures, 2 tables, accepted for publication in PR

Reconstructing the impact of human activities in a NW Iberian Roman mining landscape for the last 2500 years

This article was made available through the Brunel Open Access Publishing Fund.Little is known about the impact of human activities during Roman times on NW Iberian mining landscapes beyond the geomorphological transformations brought about by the use of hydraulic power for gold extraction. We present the high-resolution pollen record of La Molina mire, located in an area intensely used for gold mining (Asturias, NW Spain), combined with other proxy data from the same peat core to identify different human activities, evaluate the strategies followed for the management of the resources and describe the landscape response to human disturbances. We reconstructed the timing and synchronicity of landscape changes of varying intensity and form occurred before, during and after Roman times. An open landscape was prevalent during the local Late Iron Age, a period of relatively environmental stability. During the Early Roman Empire more significant vegetation shifts took place, reflected by changes in both forest (Corylus and Quercus) and heathland cover, as mining/metallurgy peaked and grazing and cultivation increased. In the Late Roman Empire, the influence of mining/metallurgy on landscape change started to disappear. This decoupling was further consolidated in the Germanic period (i.e., Visigothic and Sueve domination of the region), with a sharp decrease in mining/metallurgy but continued grazing. Although human impact was intense in some periods, mostly during the Early Roman Empire, forest regeneration occurred afterwards: clearances were local and short-lived. However, the Roman mining landscape turned into an agrarian one at the onset of the Middle Ages, characterized by a profound deforestation at a regional level due to a myriad of human activities that resulted in an irreversible openness of the landscape. © 2014 The Authors

ANÁLISIS POLÍNICO DE LOS YACIMIENTOS ARQUEOLÓGICOS CERRO DEL ALCÁZAR DE BAEZA Y ERAS DEL ALCÁZAR DE ÚBEDA (JAÉN)

Here we present the palynological study from two archaeological sites placed at Jaén province, dating from the Fourth to the Second millennia B.C. In both sites, known as Cerro del Alcázar de Baeza and Eras del Alcázar de Úbeda, a progressive deterioration of the environment is acknowledged. Agriculture impact, at local level, is proposed as the main factor acting on this process.Presentamos el análisis palinológico de dos secuencias arqueoestratigráficas localizadas en la comarca natural de La Loma, Jaén. Nos referimos a los yacimientos del Cerro del Alcázar de Baeza y de las Eras del Alcázar de Úbeda, con una cronología comprendida entre el IV y el II Milenios a.n.e. En ambos sitios de estudio se ha documentado un proceso de degradación ambiental que se iniciaría durante el Calcolítico y se traduciría en una clara apertura del paisaje con pérdida de recursos forestales. A nivel local, se propone el impacto de la agricultura sobre el medio como factor desencadenante de este proceso