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Prímula Viana Campos Pedro Manuel Villa Jaquelina Alves Nunes Carlos E.G.R. Schaefer Stefan Porembski Andreza Viana Neri 《山地科学学报》2018,15(6):1186-1198
In Eastern South America, high altitude grasslands represent a mountain system that has a high number of endemic species. However, studies on the ecology of plant communities in these environments remain scarce. We aimed to evaluate the patterns of biodiversity and structure of plant communities from rocky outcrops in high altitude grasslands of three areas at the Caparaó National Park, southeastern Brazil, by sampling 300 randomly distributed plots. Then, we compared the floristic composition, relative abundance, and biological and vegetation spectra among areas. We classified species as endemic and non-endemic and verified the occurrence of endangered species. Species richness was evaluated by rarefaction analysis on the sampling units. The importance value and species abundance distribution (SAD) models were assessed. We also performed an indicator species analysis. We sampled 58 species belonging to 49 genera and 32 families. The number of species decreased with increasing altitude, with significant differences being observed among areas regarding richness, abundance, and cover. Of the total number of species, 10 are endemic to the Caparaó National Park and 17 are listed on the Brazilian Red List of endangered species. The dominant families on all peaks were Asteraceae and Poaceae. The SAD models showed lognormal and geometric distributions, corroborating the fact that 10 species that were common to all three areas were also the most dominant ones in the communities and showed the highest importance values, which ranged between 35% and 60%. Indicator species analysis revealed that 28 species (48.27%) were indicators. Of these, 42.85% had maximum specificity, meaning that they occurred only in one area. Thus, the number of species per life form ratio was similar among areas, yet vegetation spectra differed, especially for hemicryptophytes. The altimetric difference among the areas showed to be a very important driver in the community assembly, influencing the evaluated variables, however, other drivers as soil depth, slope and water could also influence the community structure on a smaller and local spatial scale. 相似文献
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Characterization of beryl (aquamarine variety) from pegmatites of Minas Gerais,Brazil 总被引：2，自引：0，他引：2
R. R. Viana H. Jordt-Evangelista G. Magela da Costa W. B. Stern 《Physics and Chemistry of Minerals》2002,29(10):668-679
Eight samples of the beryl variety aquamarine were selected from four pegmatites in the Governador Valadares and Araçuaí regions in northeastern Minas Gerais State, Brazil. These samples were fully characterized by chemical analysis, infrared and UV-visible spectroscopy, thermal analyses, and high-temperature X-ray diffraction (from room temperature up to 800 °C). Several physical and chemical properties of beryl were found to depend on the amount of water and ions residing in the structural channels. The thermal expansion coefficients from room temperature to about 800 °C are temperature-independent, with αa ? ?3.2 × 10?6 ° C?1 and αc ? ?8.7 × 10?6 ° C?1. The contraction of both a and c unit-cell parameters with increasing temperature and the shift of the infrared band centered at about 1200 cm?1 were tentatively ascribed to interactions between channel water and the silicate rings.The color of beryl seems to be dictated by the relative proportions of Fe3+ in the octahedralsites and of fe2+ in the channels. Thus, deep-blue samples have little Fe3+, whereas greener samples have more Fe3+ or less channel Fe2+. 相似文献
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Geotechnical Characterization by In situ and Lab Tests to the Back-Analysis of a Supported Excavation in Metro do Porto 总被引：1，自引：1，他引：0
António Viana da Fonseca Sara Rios Silva Nuno Cruz 《Geotechnical and Geological Engineering》2010,28(3):251-264
This paper summarizes the geotechnical characterization conducted for the design and subsequent analysis of a strutted excavation in “Metro do Porto”. This region is geologically dominated by heterogeneous weathered granite masses with deep residual soil profiles. Local saprolitic soils exhibit, by their nature, a particular behavior characterized by very sensitive and weak relic micro-structures, due to their specific genesis. This study has included the interpretation of a significant volume of in situ test results, triaxial tests over undisturbed samples and monitoring data, giving rise to specific correlations between testing and design parameters. Real time monitoring enabled a back-analysis by FEM of a well instrumented section of the strutted excavation, which was calibrated taking into account the derived correlations and the deformability behavior of this specific geotechnical ambient. This geomaterial, although revealing very high initial stiffness values (for very small strain ranges) has shown low stiffness values for “medium to high” strain levels, reflecting a singular strong non-linearity in the stress-strain behavior. 相似文献
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Letícia de Barros Viana Hissa Britaldo Silveira Soares Filho 《Transactions in GIS》2014,18(3):449-463
Recently, the increasing demand for biofuels triggered a new phase for the sugar‐alcohol sector. In Brazil, as well as in other tropical countries, this process raised worries regarding the possible direct and indirect effects of the crop's expansion on the conversion of native vegetation coverings. Therefore, the modeling of spatial‐economic surfaces, representing the potential rent variation in its spatial component, for economic activities, may be a useful tool in the decision‐making process. Hence, here we propose and present the results of a combined framework composed of two modules using the modeling platform Dinamica EGO. The first module simulates sugarcane's growth, calculating the daily response of the crop to environmental conditions during the stages of the plant's development. The second module estimates rents for sugarcane cultivation in Brazil, identifying areas where this activity would bring higher economic return, looking at simulated productivity, production costs and selling prices in a way that is spatially explicit for Brazil. Two different scenarios for production costs were tested, and results ranged from negative values to maxima of R$/ha 929 and R$/ha 1176 for standard and efficient costs of production, respectively. The model successfully indicated non‐profitable and profitable areas, and regions where high expected economic return overlaps endangered ecosystems. 相似文献
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Andrew R. Liddle Pedro T. P. Viana A. Kathy Romer Robert G. Mann 《Monthly notices of the Royal Astronomical Society》2001,325(2):875-880
The redshift evolution of the galaxy cluster temperature function is a powerful probe of cosmology. However, its determination requires the measurement of redshifts for all clusters in a catalogue, which is likely to prove challenging for large catalogues expected from XMM-Newton , which may contain of the order of 2000 clusters with measurable temperatures, distributed around the sky. In this paper we study the apparent cluster temperature, which can be obtained without cluster redshifts. We show that the apparent temperature function itself is of limited use in constraining cosmology, and so concentrate our focus on studying how apparent temperatures can be combined with other X-ray information to constrain the cluster redshift. We also briefly study the circumstances under which the non-thermal spectral features can provide redshift information. 相似文献
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Large-eddy simulations of the neutrally-stratified flow over an extended homogeneous forest were used to calibrate a canopy model for the Reynolds-averaged Navier–Stokes (RaNS) method with the $k-\varepsilon $ k - ε turbulence model. It was found that, when modelling the forest as a porous medium, the canopy drag dissipates the turbulent kinetic energy (acts as a sink term). The proposed model was then tested in more complex flows: a finite length forest and a forested hill. In the finite length forest, the destruction of the turbulent kinetic energy by the canopy was overestimated near the edge, for a length approximately twice the tree height. In the forested hill, the model was less accurate inside the recirculation zone and overestimated the turbulent kinetic energy, due to an incorrect prediction of the production term. Nevertheless, the canopy model presented here provided consistent results in both a priori and a posteriori tests and improved the accuracy of RaNS simulations with the $k-\varepsilon $ k - ε model. 相似文献
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The Neogene-to-Quaternary sediment section along the south-eastern Brazilian margin was deeply influenced by bottom currents acting from the upper slope down to the continental rise in water depths ranging from 100 m to >3,500 m. Different depositional styles are observed as a resultant of the interaction between bottom currents, seafloor topography, available grain size and time span involved in the process. Their importance in the sedimentary record varies in accordance with the intensity of that interaction. Deposits associated to bottom currents are both coarse-grained and fine-grained and are distributed along all margins. The identification of coarse-grained deposits in deep-water is critical for the petroleum industry, thus characterising sandy contourites as relevant for the understanding of reservoir analogues. Slope plastered sand sheets occur in the upper slope setting. They are strike-fed, along slope-elongated and internally characterised by high amplitude seismic reflections usually developing reflection free blankets above erosional terraces due to their small thickness (in average less than 30 m thick). Middle and lower slope contourites are mostly constituted of fine-grained plastered and separated drifts, where a general upslope migration trend and an erosional basal surface are observed. The seafloor topography from the foot of the slope towards the continental rise is controlled by salt walls and diapirs which influence the acceleration of the currents and the development of contourite drifts. Paleoceanographic reconstructions supported by seismic evidence indicate that the major currents sculpting the seafloor are southerly originated and their action can overcome the importance of gravity currents where continental supply is reduced.E&P/UN-RIO/ATEX/ABIG-PL 相似文献
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