Continuous human presence without extensive reductions in forest cover over the past 2500 years in an aseasonal Amazonian rainforest          下载免费PDF全文

Thomas J. Kelly  Ian T. Lawson  Katherine H. Roucoux  Timothy R. Baker  Euridice N. Honorio‐Coronado  Timothy D. Jones  Santiago Rivas Panduro 《第四纪科学杂志》2018,33(4):369-379

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GIS‐based Calibration of MassMov2D     

Monia Elisa Molinari  Massimiliano Cannata  Santiago Begueria  Christian Ambrosi 《Transactions in GIS》2012,16(2):215-231

MassMov2D is a numerical model for simulating runout and deposition of landslide phenomena over a complex topography that is implemented in the free GIS PCRaster. This research aims at improving the mechanism of MassMov2D calibration and verifying its capability of representing complex landslides. In this article the authors present the enhancement of the MassMov2D code due to the introduction of the Nash‐Sutcliffe coefficient for model efficiency calculation; this enables the replacement of the inefficient ‘trial and error’ approach used for sensitivity analysis and calibration with a semi‐automatic procedure. During this research the improved code was tested in a case study located on the Canaria Valley (Switzerland) where a complex landslide occurred. An optimal set of parameters were calculated for evaluating the effects of a possible further slope failure. The availability of a unique dataset of high resolution digital elevation models just before and after the collapse allowed precise evaluation of the sensitivity and calibration of the model with the new procedure. The results demonstrate that this model is capable of reproducing the observed deposits even though some model limitations were identified in steep slope areas. Finally the study presents the expected scenario due to a future landslide.  相似文献   

Sensitivity of two Iberian lakes to North Atlantic atmospheric circulation modes     

Armand Hernández  Ricardo M. Trigo  Sergi Pla-Rabes  Blas L. Valero-Garcés  Sonia Jerez  Mayte Rico-Herrero  José C. Vega  Margarita Jambrina-Enríquez  Santiago Giralt 《Climate Dynamics》2015,45(11-12):3403-3417

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Consistency Problems in the Improvement of the IAU Precession–Nutation Theories: Effects of the Dynamical Ellipticity Differences     

Alberto Escapa  José M. Ferrándiz  Tomás Baenas  Juan Getino  Juan F. Navarro  Santiago Belda–Palazón 《Pure and Applied Geophysics》2016,173(3):861-870

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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   

What can gene flow and recruitment dynamics tell us about connectivity between European hake stocks in the Eastern North Atlantic?     

Alfonso Pita  Santiago Cerviño 《Continental Shelf Research》2011,31(5):376-387

Systematic genetic analyses of fish populations allow the testing of temporal stability in their genetic structures and better understanding their pattern of connectivity. In this study the pattern of gene flow between the two Atlantic stocks of the European hake has been examined for the period 2000-2002. Present analyses indicate that a large genetic homogeneity existed among all Atlantic populations in that period, and that a systematic grouping occurred between Porcupine Bank samples and Cantabric ones. This scenario is congruent with an inter-annual gene flow from central grounds of the northern stock (Porcupine and Great Sole) to Iberian grounds inhabited by the southern stock. Additionally, estimated migration figures were in agreement with the good recruitments observed in the southern stock after 2003 despite the spawning biomass was at its historical minimum. Altogether these results highlight the central role of Porcupine bank and Great Sole in making sustainable both stocks and advocate the integrative management of this hake fishery by means of a multidisciplinary assessment.  相似文献   

Primary and diagenetic isotopic signals in fossils and hemipelagic carbonates: the Lower Jurassic of northern Spain     

Idoia Rosales  Santiago Quesada  & Sergio Robles 《Sedimentology》2001,48(5):1149-1169

Stable isotope and trace element analyses of 230 Jurassic (Pliensbachian–Toarcian) samples from northern Spain have been performed to test the use of geochemical variations in fossils (belemnites and brachiopods) and whole‐rock hemipelagic carbonates as palaeoceanographic indicators. Although the succession analysed (Reinosa area, westernmost Basque–Cantabrian Basin) has been subject to severe thermal alteration during burial diagenesis, the samples appear to be well preserved. The degree of diagenetic alteration of the samples has been assessed through the application of integrated petrographic, chemical and cathodoluminescence analyses. It is demonstrated that brachiopods and whole‐rock carbonates, although widely used for palaeoceanic studies, do not retain their primary marine geochemical composition after burial diagenesis. In contrast, there is strong evidence that belemnite rostra preserve original isotopic values despite pervasive diagenesis of the host rock. Well‐preserved belemnite shells (non‐luminescent to slightly luminescent) typically show stable isotope values of +4·3‰ to –0·7‰δ¹³C, +0·7‰ to –3·2‰δ¹⁸O, and trace element contents of <32 μg g^–1 Mn, <250 μg g^–1 Fe, >950 μg g^–1 Sr and Sr/Mn ratios >80. This study suggests that the degree to which diagenesis has affected the preservation of an original isotopic composition may differ for different low‐Mg calcite fossil shells and hemipelagic bulk carbonates, behaviour that should be considered when marine isotopic signatures from other ancient carbonate rocks are investigated. Multiple non‐luminescent contemporaneous belemnite samples passed the petrographic and geochemical tests to be considered as palaeoceanic recorders, yet their δ¹³C and δ¹⁸O values exhibited moderate scatter. Such variability is likely to be related to the palaeoecological behaviour of belemnites and/or high‐frequency secular variations in sea‐water chemistry superimposed on the long‐term isotopic trend. A pronounced positive carbon‐isotope excursion (up to +4·3‰) is documented in the early Toarcian serpentinus biozone, which correlates with the Toarcian δ¹³C maximum reported in other European and Tethyan regions.  相似文献   

On Dry Deposition Modelling of Atmospheric Pollutants on Vegetation at the Microscale: Application to the Impact of Street Vegetation on Air Quality     

Jose-Luis Santiago  Alberto Martilli  Fernando Martin 《Boundary-Layer Meteorology》2017,162(3):451-474

A Reynolds-averaged Navier–Stokes model is used to investigate the impact of urban canopy vegetation on air quality, with particular emphasis on the comparison between the positive effect induced by deposition versus the negative effect due to a reduction of ventilation. With this aim, a series of simulations over a simplified urban geometry with different vegetation designs are carried out. The problem is tackled at two scales. From the mesoscale point of view, the relevant variable is the total deposition flux of pollutant as a function of the pollutant concentration above the canopy (e.g. the “mesoscale” deposition velocity). This is assessed within the Monin–Obukov similarity theory framework, and a modification of the classical formulation is proposed based on the numerical results. At the microscale, the distribution of concentration within the urban canopy is investigated for the different configurations. The main conclusion is that the height of the vegetation and the magnitude of the microscale deposition velocity are key parameters that determine which of the two effects (deposition or reduction of ventilation) prevails.  相似文献   

High-proper-motion white dwarfs and halo dark matter     

Santiago Torres  Enrique García-Berro  reas Burkert  Jordi Isern 《Monthly notices of the Royal Astronomical Society》2002,336(3):971-978

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Changes in land cover and shallow landslide activity: A case study in the Spanish Pyrenees   总被引：8，自引：3，他引：5  

Santiago Beguería   《Geomorphology》2006,74(1-4):196-206

The Pyrenees, like many other mountain areas in Europe, have experienced depopulation and land abandonment during the 20th century. This has encouraged vegetation recovery in formerly occupied areas, including reforestation to promote woodland. The objective of this study is to analyse the effects of these changes on shallow landsliding, a process responsible for erosion and land degradation in many mountain areas. A sequence of aerial images reveals a slight decrease in the landslide occurrence rate in the last half of the 20th century and a parallel increase in the landslide extinction rate, i.e. the rate at which evidence of landslide activity is removed by vegetation colonisation. A logistic regression routine was used to assess the influence of land use and vegetation recovery in the occurrence of shallow landslides. The result shows that the former arable fields on the valley slopes still facilitate landsliding, even after land abandonment and revegetation by shrubs or trees. A shift in the topographic location of landslides was also detected, pointing to an increased importance of water redistribution in the slopes after prolonged rainfall periods.  相似文献