History of vegetation during the Holocene in the Courel and Queixa Sierras,Galicia, northwest Iberian Peninsula     

Luisa Santos  Juan Ramon Vidal Romani  Guy Jalut 《第四纪科学杂志》2000,15(6):621-632

Palynological studies undertaken in the mountainous regions of the northwest of the Iberian Peninsula are few in number and have been concerned largely with the second half of the Holocene. New pollen data from two Galician sierras, the Courel and Queixa Sierras, provide a 10000‐yr record of vegetation and climate change. In the Courel Sierra before 9750 yr BP, Laguna Lucenza (1420 m a.s.l.) reflects a period of open landscape covered by Poaceae and heliophilous plants, which may be correlated with the Younger Dryas. The onset of the Holocene is characterised by the expansion of oak woodland, prior to 9300 yr BP, following a short phase of birch along with the gradual decline of pine. The oak values reach a peak at 8350 ± 80 yr BP. Towards 8800 yr BP Corylus begins to expand, followed by Alnus (7500 yr BP) and Ulmus. During this period, the Fraga pollen assemblage (Queixa Sierra, 1360 m a.s.l.) indicates Betula woodland surrounding the site, masking the regional predominance of oak. After 5000 yr BP there is a gradual decrease in arboreal pollen values in both Sierras. Castanea appears in Laguna Lucenza (Courel Sierra) at 4075 ± 75 yr BP. There is widespread deforestation during the last 4000 yr. During this period the presence of large quantities of microcharcoal particles points to the occurrence of fire. The reduction in forest is associated with the arrival of cultivation at 4000 yr BP at low altitudes in the Queixa Sierra. At higher altitudes the first agricultural activity is dated at later than 2000 yr BP. This coincides with the first record of cereal cultivation at high altitude in the Courel Sierra. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Report of the Editors     

Julian E. Andrews  Brian G. Jones  A. Guy Plint 《Sedimentology》1999,46(1):211-213

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Earthquake loss estimation for the New York City Metropolitan Region   总被引：1，自引：0，他引：1  

Michael W. Tantala  Guy J.P. Nordenson  George Deodatis  Klaus Jacob 《Soil Dynamics and Earthquake Engineering》2008,28(10-11):812

This study is a thorough risk and loss assessment of potential earthquakes in the NY–NJ–CT Metropolitan Region. This study documents the scale and extent of damage and disruption that may result if earthquakes of various magnitudes occurred in this area. Combined with a detailed geotechnical soil characterization of the region, scenario earthquakes were modeled in HAZUS (Hazards US), a standardized earthquake loss estimation methodology and modeling program. Deterministic and probabilistic earthquake scenarios were modeled and simulated, which provided intensities of ground shaking, dollar losses associated with capital (the building inventory) and subsequent income losses. This study has also implemented a detailed critical (essential) facilities analysis, assessing damage probabilities and facility functionality after an earthquake. When viewed in context with additional information about regional demographics and seismic hazards, the model and results serve as a tool to identify the areas, structures and systems with the highest risk and to quantify and ultimately reduce those risks.  相似文献   

Acoustic Ray Tracing Comparisons in the Context of Geodetic Precise off-shore Positioning Experiments     

Pierre Sakic  Valérie Ballu  Wayne C. Crawford  Guy Wöppelmann 《Marine Geodesy》2018,41(4):315-330

The GNSS-Acoustics (GNSS-A) method couples acoustics with GNSS to allow the precise localization of a seafloor reference in a global frame. This method can extend on-shore GNSS networks and allows the monitoring of hazardous oceanic tectonic phenomena. The goal of this study is to test the influence of both acoustics ray tracing techniques and spatial heterogeneities of acoustic wave speed on positioning accuracy. We test three different ray tracing methods: the eikonal method (3D sound speed field), the Snell-Descartes method (2D sound speed profile), and an equivalent sound speed method. We also compare the processing execution time. The eikonal method is compatible with the Snell-Descartes method (by up to 10 ppm in term of propagation time difference) but takes approximately a thousand times longer to run. We used the 3D eikonal ray tracing to characterize the influence of a lateral sound speed gradient on acoustic ray propagation and positioning accuracy. For a deep water (? 3,000 m) situation, frequent in subduction zones such as the Lesser Antilles, not accounting for lateral sound speed gradients can induce an error of up to 5 cm in the horizontal positioning of a seafloor transponder, even when the GNSS-A measurements are made over the barycenter of a seafloor transponder array.  相似文献   

“This venue is brought to you by…”: the diffusion of sports and entertainment facility name sponsorship in urban Europe     

Jani Vuolteenaho  Matthias Wolny  Guy Puzey 《Urban geography》2019,40(6):762-783

ABSTRACT

Drawing on a database of 193 football (soccer) grounds and 115 indoor arenas, as well as press releases and media reports associated with them, this study charts the diffusion of sporting and entertainment facility name sponsorship across metropolises, cities, towns, and smaller settlements in six European contexts. Our results show the emergence of naming rights deals in the 1990s, their peak in the mid-2000s, and the current situation with a steadier growth of name sponsorship. Thus far, the corporate re-branding of venues has remained less prevalent in Italy, Norway, and Scotland than in England and Wales, Finland, and above all Germany. In financing newly built venues, however, the corporatized landmark language in focus has become a practically invariable part of local growth, austerity and (re)branding policies. Despite voices of resistance in all regions studied here, pressure towards the corporate renaming of even hereditary, communally endorsed football stadiums is increasingly being felt by municipal and private-sector venue owners.  相似文献   

Heat capacities of ordinary chondrite falls below 300 K     

Robert J. Macke  Cyril Opeil  Guy J. Consolmagno 《Meteoritics & planetary science》2019,54(11):2729-2743

Low‐temperature specific heat capacities of meteorites provide valuable data for understanding the composition and evolution of meteorites and modeling the thermal behavior of their source asteroids. By liquid nitrogen immersion, we measured average low‐temperature heat capacities for 60 ordinary chondrite falls from the Vatican collection. We further characterized the temperature dependence of ordinary chondrite by direct measurement of C_p(T) over the range 5–320 K for five OC falls, coupled by composition‐based models for 94 ordinary chondrites. We find that the heat capacity as a function of temperature for typical ordinary chondrites can be closely approximated by a third‐order polynomial in temperature. Furthermore, those polynomial coefficients can be estimated from the single‐value average heat capacity measurement. These measurements have important implications for the orbital and spin evolution of S‐ and Q‐type asteroids via the various Yarkovsky effects and the thermal evolution of meteorite parent bodies.  相似文献   

Effects of short flexible seagrass Zostera noltei on flow,erosion and deposition processes determined using flume experiments          下载免费PDF全文

Florian Ganthy  Laura Soissons  Pierre‐Guy Sauriau  Romaric Verney  Aldo Sottolichio 《Sedimentology》2015,62(4):997-1023

Innovative flume experiments were conducted in a recirculating straight flume. Zostera noltei meadows were sampled in their natural bed sediments in the field at contrasting stages of their seasonal growth. The aims of this study were: (i) to quantify the combined effects of leaf flexibility and development characteristics of Zostera noltei canopies on their interaction with hydrodynamics; and (ii) to quantify the role of Zostera noltei meadows in suspended sediment trapping and bed sediment resuspension related with changes in hydrodynamic forcing caused by the seasonal development of seagrasses. Velocity within the canopy was significantly damped. The attenuation in velocity ranged from 34 to 87% compared with bare sediments and was associated with a density threshold resulting from the flow‐induced canopy reconfiguration. The reduction in flow was higher in dense canopies at higher velocities than in less dense canopies, in which the reduction in flow was greater at low velocities. These contrasted results can be explained by competition between a rough‐wall boundary layer caused by the bed and a shear layer caused by the canopy. The velocity attenuation was associated with a two to three‐fold increase in bottom shear stress compared with unvegetated sediment. Despite the increase in near‐bed turbulence, protection of the sediment against erosion increased under a fully developed meadow, while sediment properties were found to be the main factor controlling erosion in a less developed meadow. Deposition fluxes were higher on the vegetated bed than on bare sediments, and these fluxes increased with leaf density. Fewer freshly deposited sediments were resuspended in vegetated beds, resulting in an increase in net sediment deposition with meadow growth. However, in the case of a very high leaf area index, sediment was mostly deposited on leaves, which facilitated subsequent resuspension and resulted in less efficient sediment trapping than in the less developed meadow.  相似文献   

The origin and disappearance of the late Pleistocene-early Holocene short-lived coastal wetlands along the Carmel coast, Israel     

Dorit Sivan  Noam Greenbaum  Guy Sisma-Ventura 《Quaternary Research》2011,76(1):83-92

The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The δ¹⁸O and δ¹³C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr.  相似文献   

Increasing impacts of climate change upon ecosystems with increasing global mean temperature rise     

Rachel Warren  Jeff Price  Andreas Fischlin  Santiago de la Nava Santos  Guy Midgley 《Climatic change》2011,106(2):141-177

In a meta-analysis we integrate peer-reviewed studies that provide quantified estimates of future projected ecosystem changes related to quantified projected local or global climate changes. In an advance on previous analyses, we reference all studies to a common pre-industrial base-line for temperature, employing up-scaling techniques where necessary, detailing how impacts have been projected on every continent, in the oceans, and for the globe, for a wide range of ecosystem types and taxa. Dramatic and substantive projected increases of climate change impacts upon ecosystems are revealed with increasing annual global mean temperature rise above the pre-industrial mean (ΔT_g). Substantial negative impacts are commonly projected as ΔT_g reaches and exceeds 2°C, especially in biodiversity hotspots. Compliance with the ultimate objective of the United Nations Framework Convention on Climate Change (Article 2) requires that greenhouse gas concentrations be stabilized within a time frame “sufficient to allow ecosystems to adapt naturally to climate change”. Unless ΔT_g is constrained to below 2°C at most, results here imply that it will be difficult to achieve compliance. This underscores the need to limit greenhouse gas emissions by accelerating mitigation efforts and by protecting existing ecosystems from greenhouse-gas producing land use change processes such as deforestation.  相似文献   

Nearshore Tsunami Inundation Model Validation: Toward Sediment Transport Applications     

Alex Apotsos  Mark Buckley  Guy Gelfenbaum  Bruce Jaffe  Deepak Vatvani 《Pure and Applied Geophysics》2011,168(11):2097-2119

Model predictions from a numerical model, Delft3D, based on the nonlinear shallow water equations are compared with analytical results and laboratory observations from seven tsunami-like benchmark experiments, and with field observations from the 26 December 2004 Indian Ocean tsunami. The model accurately predicts the magnitude and timing of the measured water levels and flow velocities, as well as the magnitude of the maximum inundation distance and run-up, for both breaking and non-breaking waves. The shock-capturing numerical scheme employed describes well the total decrease in wave height due to breaking, but does not reproduce the observed shoaling near the break point. The maximum water levels observed onshore near Kuala Meurisi, Sumatra, following the 26 December 2004 tsunami are well predicted given the uncertainty in the model setup. The good agreement between the model predictions and the analytical results and observations demonstrates that the numerical solution and wetting and drying methods employed are appropriate for modeling tsunami inundation for breaking and non-breaking long waves. Extension of the model to include sediment transport may be appropriate for long, non-breaking tsunami waves. Using available sediment transport formulations, the sediment deposit thickness at Kuala Meurisi is predicted generally within a factor of 2.  相似文献