Canvis en el paisatge vegetal de les Illes Balears durant el final del Quaternari

A partir dels coneixements actuals es conclou que l'última glaciació i l'actual període postglacial ha tingut un caràcter distintiu a les Balears en el que concerneix a l'evolució del paisatge vegetal, sobretot tenint en compte altres zones properes de l'Europa occidental. Durant el Worm han existit períodes interestadials amb expansió de les comunitats forestals de caducifolis i termòfils i, sens dubte han romàs a alguna part de les Balears refugiats. Durant l'holocé inferior les illes Balears posseïen un paisatge vegetal amb Corylus, Buxus (que tindria el màxim protagonisme en el paisatge), Juniperus, Betula i Acer. L'Holocé superior es representat, a les Illes Balears, per un paisatge dominat per l'esclerofilia en el qual Olea te una gran importància en el paisatge.The present day knowledge allows to conclude that the landscape evolution during the last glacial period and the current postglacial period in the Balearic Islands have a distinctive character, in comparison with other zones from western Europe. During the WOrm, abundant interstadials periods with important expansions of deciduous trees and termophilous vegetation have been detected. These formations have remained in different refuge areas of the Balearic Islands. During the early Holocene, the Balearic Islands possessed a plant landscape made up by Corylus, Buxus (probably the most important taxon of the landscape), Juniperus, Betula and Acer. The latter Holocene in the Balearic Islands, is represented by a landscape dominated by the sclerophillous plants, with a great importance of Olea

Experimental demonstration of a magnetically induced warping transition in a topological insulator mediated by rare-earth surface dopants

Magnetic topological insulators (MTI) constitute a novel class of materials where the topologically protected band structure coexists with long-range ferromagnetic order, which can lead to the breaking of time-reversal symmetry (TRS), introducing a bandgap in the Dirac cone-shaped topological surface state (TSS). The gap opening in MITs has been predicted to be accompanied by a distortion in the TSS, evolving its warped shape from hexagonal to trigonal. In this work, we demonstrate such a transition by means of angle-resolved photoemission spectroscopy after the deposition of low concentrations of magnetic rare earths, namely Er and Dy, on the ternary three-dimensional prototypical topological insulator Bi$_2$Se$_2$Te. Signatures of the gap opening occurring as a consequence of the TRS breaking have also been observed, whose existence is supported by the observation of the aforementioned transition. Moreover, increasing the Er coverage results in a tunable p-type doping of the TSS. As a consequence, the Fermi level (E$_{\textrm{F}}$) of our Bi$_2$Se$_2$Te crystals can be gradually tuned towards the TSS Dirac point, and therefore to the magnetically induced bandgap; thus fulfilling two of the necessary prerequisites for the realization of the quantum anomalous Hall effect (QAHE) in this system. The experimental results are rationalized by a theoretical model where a magnetic Zeeman out-of-plane term is introduced in the hamiltonian governing the TSS band dispersion. Our results offer new strategies to control magnetic interactions with TSSs based on a simple approach and open up viable routes for the realization of the QAHE

The record of the latter glacial and interglacial periods in the Guadalquivir marshlands (Mari López drilling, S.W. Spain)

El estudio de un sondeo de 65 m en las marismas del Guadalquivir permite reconocer siete intervalos que reflejan cambios climáticos y eustáticos e intensa neotectónica durante tres periodos ¡nterglaciares (IS 71, 5 y i) y dos glaciares (IS 6-Riss-, IS 4, 3 y 2-WQrm). Se discute el valor de las 'vetas' como indicadores paleogeográficosPeer reviewe

A six thousand-year record of climate and land-use change from Mediterranean seagrass mats

The Mediterranean seagrass Posidonia oceanica maintains a biodiverse ecosystem and it is a world-wide important carbon sink. It grows for millennia, accumulating organic-rich soils (mats) beneath the meadows. This marine habitat is protected by the European Union; however, it is declining rapidly due to coastal development. Understanding its response to disturbances could inform habitat restoration, but many environmental impacts predate monitoring programs (years).This research explores the palaeoecological potential of Posidonia mats to reconstruct six thousand years of environmental change that could have affected Posidonia meadows and, in turn, left an imprint on the mats.Palynological, microcharcoal, magnetic susceptibility and glomalin-related soil protein (GRSP) analyses on Posidonia mats enabled us to detect climate- and human-induced environmental processes impacting on the seagrass during the Late Holocene.The pollen and microcharcoal records reconstructed anthropogenic disturbances attributed to agriculture. The record of GRSP shows that agrarian activities affected continental soil quality. Changes in magnetic susceptibility reveal that enhanced soil erosion was caused by both climate (major flooding events in the NW Mediterranean) and humans (cultivation) which impacted on the Posidonia mat. Finally, increased human impact is linked to eutrophication of coastal waters since Roman-Medieval times.Synthesis. This study shows that climate and land-use changes in the western Mediterranean resulted in enhanced loadings of terrigenous material to the coastal zone since the Late Holocene, likely disturbing the Posidonia meadows and their mat carbon accumulation dynamics. Under the current global change scenario in which CO2 emissions are projected to increase, restoring carbon sinks is a priority. Seagrass habitat restoration should consider not only the coastal perturbations, but also the continental ones at a catchment scale to preserve the socio-economic ecosystem services provided by seagrasses

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

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

The record of the lalter glacial and interglacial periods in the Guadalquivir marshlands (Mari López drilling, S.W. Spain)

El estudio de un sondeo de 65 m en las marismas del Guadalquivir permite reconocer siete intervalos que reflejan cambios climáticos y eustáticos e intensa neotectónica durante tres periodos interglaciares (IS 7?, 5 Y 1) Y dos glaciares (15 6-Riss-, 154, 3 Y 2-Würm). Se discute el valor de las 'vetas' como indicadores paleogeográficos

Record of anthropogenic environmental impact in the continental shelf north of Barcelona city

International symposium on applications of isotope techniques in studying past and current environmental changes in the hydrosphere and the atmosphere, 19-23 April 1993, Vienna, Austria.--10 pages, 4 figures, 1 tableThe continental shelf off the Barcelona coast receives polluted materials discharged by the Besós and the Llobregat rivers. A marine sediment core from the Besós river mouth in the inner prodelta (TG8) was dated by the analysis of excess 210Pb using a modified version of the CRS/MV method. The mean sedimentation rate was 1.74 ± 0.09 mm/year and its evo­lution showed a slow decrease from 1923 which became faster from 1962, in good agreement with the two most important periods o f industrial and demographic expansion in Catalonia. Heavy metals concentrations were determined by ICP-AES and showed high values in surface samples for Cr, Cu, Zn and Pb. The observed fluxes reflected well the industrial development of Catalonia, showing two important growth periods during the 1920s and the 1960s. Soot par­ticles were found in all samples by pollen analysis and showed the impact of the combustion of fossil fuel in cars and a nearby fuel oil/natural .gas power plan