Human‐affected disturbances in vegetation cover and peatland development in the late Holocene recorded in shallow mountain peatlands (Central Sudetes,SW Poland)     

Bartłomiej Glina  Małgorzata Malkiewicz  Łukasz Mendyk  Adam Bogacz  Przemysław Woźniczka 《Boreas: An International Journal of Quaternary Research》2017,46(2):294-307

The aim of this study is to assess the impact of biotic and abiotic factors on peatland formation in the Central Sudetes (central Europe) during the late Holocene. The research methodology adopted allowed us to determine whether vegetation development and shallow peatland formation were affected by human activity. Knowledge of past changes might be useful in evaluating recent and future changes, and to avoid pitfalls in the present management of peatland ecosystems. A palaeoecological research study of four peatlands was conducted in the Sto?owe Mountains (Central Sudetes, SW Poland). The results showed that these shallow peatlands originated in the middle to late Holocene (from 3301 BC to AD 1137). Palaeoecological records reflect continuous human impact on vegetation development and peat accumulation from the Middle Ages to the present (late Holocene). The strongest agrarian settler activity is observed in the High Middle Ages (AD 1200–1500). The human‐induced or wildfires observed in the late Holocene were an integral component of peatland ecosystems in the Central Sudetes. Moreover, palaeoecological analysis (sphagnum spores decline) and radiocarbon dating (AD 1870) confirmed drainage of the study area in the 19th century, which greatly affected the vegetation communities.  相似文献   

The Phase A study of the ESA M4 mission candidate ARIEL     

Ludovic Puig  Göran Pilbratt  Astrid Heske  Isabel Escudero  Pierre-Elie Crouzet  Bram de Vogeleer  Kate Symonds  Ralf Kohley  Pierre Drossart  Paul Eccleston  Paul Hartogh  Jeremy Leconte  Giusi Micela  Marc Ollivier  Giovanna Tinetti  Diego Turrini  Bart Vandenbussche  Paulina Wolkenberg 《Experimental Astronomy》2018,46(1):211-239

ARIEL, the Atmospheric Remote sensing Infrared Exoplanet Large survey, is one of the three M-class mission candidates competing for the M4 launch slot within the Cosmic Vision science programme of the European Space Agency (ESA). As such, ARIEL has been the subject of a Phase A study that involved European industry, research institutes and universities from ESA member states. This study is now completed and the M4 down-selection is expected to be concluded in November 2017. ARIEL is a concept for a dedicated mission to measure the chemical composition and structure of hundreds of exoplanet atmospheres using the technique of transit spectroscopy. ARIEL targets extend from gas giants (Jupiter or Neptune-like) to super-Earths in the very hot to warm zones of F to M-type host stars, opening up the way to large-scale, comparative planetology that would place our own Solar System in the context of other planetary systems in the Milky Way. A technical and programmatic review of the ARIEL mission was performed between February and May 2017, with the objective of assessing the readiness of the mission to progress to the Phase B1 study. No critical issues were identified and the mission was deemed technically feasible within the M4 programmatic boundary conditions. In this paper we give an overview of the final mission concept for ARIEL as of the end of the Phase A study, from scientific, technical and operational perspectives.  相似文献   

Critical tissue copper residues for marine bivalve (Mytilus galloprovincialis) and echinoderm (Strongylocentrotus purpuratus) embryonic development: conceptual, regulatory and environmental implications     

Rosen G  Rivera-Duarte I  Chadwick DB  Ryan A  Santore RC  Paquin PR 《Marine environmental research》2008,66(3):327-336

Critical tissue copper (Cu) residues associated with adverse effects on embryo-larval development were determined for the Mediterranean mussel (Mytilus galloprovincialis) and purple sea urchin (Strongylocentrotus purpuratus) following laboratory exposure to Cu-spiked seawater collected from San Diego Bay, California, USA. Whole body no-observed-effect-residues (NOER) were similar, with means of 21 and 23mugg(-1)dw, for M. galloprovincialis and S. purpuratus, respectively. Mean whole body median effect residues (ER50) were 49 and 142mugg(-1)dw for M. galloprovincialis and S. purpuratus, respectively. The difference in ER50s between species was reduced to a factor of <2 when expressed as soft tissue residues. Coefficients of variation among whole body-ER50s were 3-fold lower than median waterborne effect concentrations (EC50) for both species exposed to samples varying in water quality characteristics. This suggests that tissue concentrations were a better predictor of toxicity than water concentrations. The CBRs described herein do not differentiate between the internal Cu concentrations that are metabolically available and those that are accumulated and then detoxified. They do appear, however, to be well enough related to the level of accumulation at the site of action of toxicity that they serve as useful surrogates for the copper concentration that affects embryonic development of the species tested. Results presented have potentially important implications for a variety of monitoring and assessment strategies. These include regulatory approaches for deriving saltwater ambient water quality criteria for Cu, contributions towards the development of a saltwater biotic ligand model, the conceptual approach of using CBRs, and ecological risk assessment.  相似文献   

Hydrologic Sensitivity of Global Rivers to Climate Change   总被引：12，自引：1，他引：12  

Bart Nijssen  Greg M. O'Donnell  Alan F. Hamlet  Dennis P. Lettenmaier 《Climatic change》2001,50(1-2):143-175

Climate predictions from four state-of-the-art general circulation models (GCMs) were used to assess the hydrologic sensitivity to climate change of nine large, continental river basins (Amazon, Amur, Mackenzie, Mekong, Mississippi, Severnaya Dvina, Xi, Yellow, Yenisei). The four climate models (HCCPR-CM2, HCCPR-CM3, MPI-ECHAM4, and DOE-PCM3) all predicted transient climate response to changing greenhouse gas concentrations, and incorporated modern land surface parameterizations. Model-predicted monthly average precipitation and temperature changes were downscaled to the river basin level using model increments (transient minus control) to adjust for GCM bias. The variable infiltration capacity (VIC) macroscale hydrological model (MHM) was used to calculate the corresponding changes in hydrologic fluxes (especially streamflow and evapotranspiration) and moisture storages. Hydrologic model simulations were performed for decades centered on 2025 and 2045. In addition, a sensitivity study was performed in which temperature and precipitation were increased independently by 2 °C and 10%, respectively, during each of four seasons. All GCMs predict a warming for all nine basins, with the greatest warming predicted to occur during the winter months in the highest latitudes. Precipitation generally increases, but the monthly precipitation signal varies more between the models than does temperature. The largest changes in the hydrological cycle are predicted for the snow-dominated basins of mid to higher latitudes. This results in part from the greater amount of warming predicted for these regions, but more importantly, because of the important role of snow in the water balance. Because the snow pack integrates the effects of climate change over a period of months, the largest changes occur in early to mid spring when snow melt occurs. The climate change responses are somewhat different for the coldest snow dominated basins than for those with more transitional snow regimes. In the coldest basins, the response to warming is an increase of the spring streamflow peak, whereas for the transitional basins spring runoff decreases. Instead, the transitional basins have large increases in winter streamflows. The hydrological response of most tropical and mid-latitude basins to the warmer and somewhat wetter conditions predicted by the GCMs is a reduction in annual streamflow, although again, considerable disagreement exists among the different GCMs. In contrast, for the high-latitude basins increases in annual flow volume are predicted in most cases.  相似文献   

ROBUST: The ROle of BUffering capacities in STabilising coastal lagoon ecosystems     

Rutger de Wit  Lucas J. Stal  Bente Aa. Lomstein  Rodney A. Herbert  Hans van Gemerden  Pierluigi Viaroli  Victor-Ugo Cecherelli  Francisco Rodríguez-Valera  Marco Bartoli  Gianmarco Giordani  Roberta Azzoni  Bart Schaub  David T. Welsh  Andrew Donnelly  Ana Cifuentes  Josefa Antn  Kai Finster  Lise B. Nielsen  Anne-Grethe Underlien Pedersen  Anne Turi Neubauer  Marina A. Colangelo  Sander K. Heijs 《Continental Shelf Research》2001,21(18-19)

“Buffer capacities” has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that “buffering capacities” can be depleted progressively, and, therefore, we make a distinction between current and potential “buffering capacities”. We have applied this concept to understand the limited “local stability” in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant–microbe interactions in the seagrass meadows.  相似文献   

Influence of geological factors on seismic ground-motions (seismic microzoning of Prague)     

Jiří Zahradník  Vlastislav Červený  Vladimír Barták  Reviewer V. Kárník 《Studia Geophysica et Geodaetica》1981,25(4):343-355

Summary Seismic microzoning of Prague was performed using geological data and seismic response (ground shaking) computations. The Prague territory was covered by a square grid, each square 250 m×250 m being characterized by a simplified geological cross-section from the Earth's surface to the bedrock boundary. The data were obtained from detailed engineering-geological maps 1:5000. The geological cross-sections were transformed into a set of layered models, specified by the thicknesses of individual layers and corresponding compressional and shear-wave velocities, densities and parameters of the causal absorption. The seismic responses were computed by the matrix method. The main amplitude and frequency characteristics of the responses are demonstrated in the form of microzoning maps. The maps do not depend on the specific type of seismic excitation. They make it possible to predict the relative amplification of P and S waves, with respect to the bedrock outcrop, all over the city.  相似文献   

Correlation between microbiological and chemical parameters of some hydrothermal springs in New Mexico, USA     

Bart omiej Rzonca  Dirk Schulze-Makuch 《Journal of Hydrology》2003,280(1-4):272-284

Discharge areas of hydrothermal springs are known to be inhabited by diverse types of microorganisms including archaea, prokaryotes and eukaryotes. A total of 11 hydrothermal samples from the Rio Grande rift and the Valles caldera in New Mexico were analyzed to investigate the correlation between chemical and microbiological parameters of hydrothermal waters. The sampled fluids are categorized into three chemical groups: (I) steam-condensing acid sulfate waters, (II) deep geothermal and derivative waters and (III) thermal meteoric waters. Analyses of the microbial phospholipid fatty acids and denaturing gradient gel electrophoresis of DNA show that acid sulfate waters were populated by thermoacidophilic organisms and had high biomass content. Mineralized deep geothermal and derivative waters exhibited a high degree of microbial diversity, but had low biomass content. Thermal meteoric waters are low in total dissolved solids, and exhibit very low biomass content and microbial diversity. DNA sequences from several previously unknown microbial species were detected. The results of this study support the hypothesis that microbes can be used as tracers for specific types of subsurface environments.  相似文献   

Experimental measurements and modeling of sorption competition on montmorillonite     

Michael H. Bradbury  Bart Baeyens 《Geochimica et cosmochimica acta》2005,69(17):4187-4197

The source terms arising from radioactive/toxic metal waste repositories will contain a multitude of dissolved metal species, as do natural systems. The influence of sorption competition on the uptake of safety-relevant metals, and the effects this may have on transport rates to the biosphere, is an important repository performance assessment issue which has not, as yet, been resolved. The main aim of this work was to quantify the influence of competition between metals in different valence states on their individual sorption characteristics under conditions dominated by pH-dependent sorption. The sorption experiments were carried out on Na- and Ca-montmorillonites using various combinations and concentrations of Co(II), Ni(II), Zn(II), Eu(III), Nd(III), Am(III), Th(IV), and U(VI). For metals sorbing at trace concentrations in a background electrolyte containing a competing metal up to mmolar concentrations, and pH values generally greater than 6, all of the experimental results were consistent with the observation that metals with similar chemistries (valence state, hydrolysis behavior) compete with one another, but metals with dissimilar chemistries do not compete, i.e., competition is selective. For example Eu, Nd, and Am exhibit unambiguous sorption competition effects, as do Ni, Co, and Zn. On the basis of the above preliminary criteria, competition between divalent transition metals and trivalent lanthanides, Th(IV), and U(VI) and between Th (IV) and U(VI) would not be expected, and this is found experimentally. In general, neither single-fixed-site capacity models nor two-site (strong/weak) models with fixed capacities, whether with or without electrostatic terms, are capable of modeling the spectrum of experimental results presented here. To explain the competitive effects observed it is proposed that multiple sets of strong sites exist as subsets of the 40 mmol kg⁻¹ of weak sites present in the montmorillonite conceptual model. It is shown that if the 2SPNE SC/CE sorption model is extended to include multiple strong sites, and the average site capacity and protolysis constant values defined in previous publications are assigned to each of the sets of strong sites, then the model can be used to reproduce all of the experimental data, provided it can be specified which groups of metals are competitive and which are not.  相似文献   

Post‐wildfire changes in suspended sediment rating curves: Sabino Canyon,Arizona     

Sharon L. E. Desilets  Bart Nijssen  Brenda Ekwurzel  Ty P. A. Ferré 《水文研究》2007,21(11):1413-1423

Wildfire has been shown to increase erosion by several orders of magnitude, but knowledge regarding short‐term variations in post‐fire sediment transport processes has been lacking. We present a detailed analysis of the immediate post‐fire sediment dynamics in a semi‐arid basin in the southwestern USA based on suspended sediment rating curves. During June and July 2003, the Aspen Fire in the Coronado National Forest of southern Arizona burned an area of 343 km². Surface water samples were collected in an affected watershed using an event‐based sampling strategy. Sediment rating parameters were determined for individual storm events during the first 18 months after the fire. The highest sediment concentrations were observed immediately after the fire. Through the two subsequent monsoon seasons there was a progressive change in rating parameters related to the preferential removal of fine to coarse sediment. During the corresponding winter seasons, there was a lower supply of sediment from the hillslopes, resulting in a time‐invariant set of sediment rating parameters. A sediment mass‐balance model corroborated the physical interpretations. The temporal variability in the sediment rating parameters demonstrates the importance of storm‐based sampling in areas with intense monsoon activity to characterize post‐fire sediment transport accurately. In particular, recovery of rating parameters depends on the number of high‐intensity rainstorms. These findings can be used to constrain rapid assessment fire‐response models for planning mitigation activities. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

西格陵兰全新世古环境研究进展     

任健  蒋辉  Kuijpers A 《极地研究》2007,19(4):285-294

西格陵兰地区由于其特殊的地理位置(北极地区-北大西洋地区),使之在全球变化研究中占有重要地位。回顾了近年来西格陵兰地区陆地、海洋全新世古环境研究的现状,并探讨了该地区不同全新世气候记录之间的差异及其成因。最后,根据当前全新世古气候研究的重点和热点,探讨了西格陵兰全新世古环境研究的不足,并展望了其动向。  相似文献