Plant diversity and community structure of Brazilian <Emphasis Type="Italic">Páramos</Emphasis>     

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   

Experimental impact cratering: A summary of the major results of the MEMIN research unit     

Thomas Kenkmann  Alex Deutsch  Klaus Thoma  Matthias Ebert  Michael H. Poelchau  Elmar Buhl  Eva-Regine Carl  Andreas N. Danilewsky  Georg Dresen  Anja Dufresne  Nathanaël Durr  Lars Ehm  Christian Grosse  Max Gulde  Nicole Güldemeister  Christopher Hamann  Lutz Hecht  Stefan Hiermaier  Tobias Hoerth  Astrid Kowitz  Falko Langenhorst  Bernd Lexow  Hanns-Peter Liermann  Robert Luther  Ulrich Mansfeld  Dorothee Moser  Manuel Raith  Wolf Uwe Reimold  Martin Sauer  Frank Schäfer  Ralf Thomas Schmitt  Frank Sommer  Jakob Wilk  Rebecca Winkler  Kai Wünnemann 《Meteoritics & planetary science》2018,53(8):1543-1568

This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two-stage light-gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane-driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high-temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.  相似文献   

Diel and seasonal variability in the fish community structure of a mud‐bottom estuarine habitat in the Gulf of Mexico     

Manuel Castillo‐Rivera  Rocío Zárate‐Hernández  Selene Ortiz‐Burgos  José Zavala‐Hurtado 《Marine Ecology》2010,31(4):633-642

We hypothesized that temporal variation in fish species composition and community structure in a low complexity habitat in the Pueblo Viejo Lagoon, Mexico, is influenced by diel light/dark cycles and tidal stage, and by seasonal changes in salinity and temperature. We collected a total of 17,661 individuals during 2‐h interval sampling over six bi‐monthly 24‐h sampling cycles representing 53 species, of which 11 (～20%) were previously unknown in the system. Diel variation indicated that significantly higher numbers of individuals and species were caught at night, whereas diversity and evenness were higher during the day. Species richness was significantly higher in July and January, whereas diversity and evenness peaked around May; both were correlated with temperature. Diel variation in species composition was influenced primarily by the light/dark cycle. Cluster analyses of each diel cycle separated fish assemblages from midday samples from those of nocturnal samples, separated by an extended wide transition period as fish moved at dawn and during the late afternoon/dusk. Significant shifts (as determined by MANOVA) in assemblage structure occurred between months. Canonical correspondence analysis showed that temperature and day/night effects were the most important environmental variables structuring the fish community. This constrained ordination also defined species with specific habitat preferences as follows: (i) diurnal, warm temperature species (mainly planktivores) (Brevoortia gunteri, Cetengraulis edentulus, Diapterus auratus, and Membras martinica); (ii) nocturnal, warm temperature species (mainly predators) (Citharichthys spilopterus, Cathorops melanopus, and Bairdiella spp.); and (iii) low temperature, diurnal species (Brevoortia patronus and Mugil curema) or those with twilight and nocturnal distributions (Anchoa mitchilli, the most numerically abundant species). Our results indicate that diel and seasonal changes in fish community structure were mainly related to day/night cycles and temperature regimes.  相似文献   

Observations of a Radio-Quiet Solar Preflare     

Arnold O. Benz  Marina Battaglia  Manuel Güdel 《Solar physics》2017,292(10):151

The preflare phase of the flare SOL2011-08-09T03:52 is unique in its long duration, in that it was covered by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and the Nobeyama Radioheliograph, and because it showed three well-developed soft X-ray (SXR) peaks. No hard X-rays (HXR) are observed in the preflare phase. Here we report that no associated radio emission at 17 GHz was found either, despite the higher sensitivity of the radio instrument. The ratio between the SXR peaks and the upper limit of the radio peaks is higher by more than one order of magnitude than the ratio in regular flares. The result suggests that the ratio between acceleration and heating in the preflare phase was different than in regular flares. Acceleration to relativistic energies, if any, occurred with lower efficiency.  相似文献   

Sampling the vertical particle flux in the upper water column using a large diameter free-drifting NetTrap adapted to an Indented Rotating Sphere sediment trap     

Michael L. Peterson  Joan Fabres  Stuart G. Wakeham  Cindy Lee  Ivn J. Alonso  Juan Carlos Miquel 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1547-1557

Further development of the large, surface-tethered sediment trap (NetTrap) employed as part of the MedFlux program is described whereby the large collection capacity of the NetTrap is combined with an Indented Rotating Sphere/Sample Carousel (IRSC) sediment trap (IRSC–NT). This trap is capable of collecting particle flux either in a time series or settling velocity mode; settling velocity mode allows the collection of particles that fall within discrete settling velocity intervals. During short field deployments in the Mediterranean Sea the IRSC–NT configured in the settling velocity mode successfully collected unpoisoned samples for chemical and microbiological experiments. In addition to the development of the IRSC–NT, particle-settling behavior above and below the swimmer-excluding IRS valve was tested during on-deck experiments using a specially constructed water-tight trap. Chemical analyses of settling materials (published elsewhere) suggested that separation of particles by settling velocity was achieved. However, due to the motion of the ship, it was not possible to directly measure particle-settling velocities within the trap. Particle release from the IRS did not bias the apparent settling velocity spectrum. Rotation of the IRS did not engender turbulence at the surface of the sphere or within the skewed funnel below. Tests of different ball designs over the course of the MedFlux program showed that a “ridge and saddle” pattern was optimal for efficiently transferring particles under the IRS seal while still reducing swimmer entrance to the collection funnel. The large size of the IRSC–NT did not prevent it from drifting effectively with the current. Several modifications of the present design are proposed that should improve the accuracy of the settling velocity measurements.  相似文献   

Can marine fisheries and aquaculture meet fish demand from a growing human population in a changing climate?     

Gorka Merino  Manuel Barange  Julia L. Blanchard  James Harle  Robert Holmes  Icarus Allen  Edward H. Allison  Marie Caroline Badjeck  Nicholas K. Dulvy  Jason Holt  Simon Jennings  Christian Mullon  Lynda D. Rodwell 《Global Environmental Change》2012,22(4):795-806

Expansion in the world's human population and economic development will increase future demand for fish products. As global fisheries yield is constrained by ecosystems productivity and management effectiveness, per capita fish consumption can only be maintained or increased if aquaculture makes an increasing contribution to the volume and stability of global fish supplies. Here, we use predictions of changes in global and regional climate (according to IPCC emissions scenario A1B), marine ecosystem and fisheries production estimates from high resolution regional models, human population size estimates from United Nations prospects, fishmeal and oil price estimations, and projections of the technological development in aquaculture feed technology, to investigate the feasibility of sustaining current and increased per capita fish consumption rates in 2050. We conclude that meeting current and larger consumption rates is feasible, despite a growing population and the impacts of climate change on potential fisheries production, but only if fish resources are managed sustainably and the animal feeds industry reduces its reliance on wild fish. Ineffective fisheries management and rising fishmeal prices driven by greater demand could, however, compromise future aquaculture production and the availability of fish products.  相似文献   

Process length variation of the cyst of the dinoflagellate Protoceratium reticulatum in the North Pacific and Baltic‐Skagerrak region: calibration as an annual density proxy and first evidence of pseudo‐cryptic speciation     

Kenneth Neil Mertens  Manuel Bringué  Nicolas Van Nieuwenhove  Yoshihito Takano  Vera Pospelova  Andre Rochon  Anne De Vernal  Taoufik Radi  Barrie Dale  R. Timothy Patterson  Kaarina Weckström  Elinor Andrén  Stephen Louwye  Kazumi Matsuoka 《第四纪科学杂志》2012,27(7):734-744

Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparède et Lachmann) Bütschli in surface sediments from the North Pacific was investigated. The average process length showed a significant inverse relation to annual seawater density: σ_{t annual} = ?0.8674 × average process length + 1029.3 (R² = 0.84), with a standard error of 0.78 kg m^?3. A sediment trap study from Effingham Inlet in British Columbia revealed the same relationship between average process length and local seawater density variations. In the Baltic–Skagerrak region, the average process length variation was related significantly to annual seawater density: σ_{t annual} = 3.5457 × average process length ? 993.28 (R² = 0.86), with a standard error of 3.09 kg m^?3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), which show the presence of several genotypes and the occurrence of pseudo‐cryptic speciation within this species. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Strato-mesospheric ozone and IMF sector boundary     

Manuel Gil  Jan Laštovička  Reviever L. Křivský 《Studia Geophysica et Geodaetica》1989,33(1):101-103

Summary We find no effect of the interplanetary magnetic field(IMF) sector boundary crossing in ozone at altitudes ranging from the middle stratosphere(10 hPa) to the lower mesosphere(0.4 hPa) at middle latitudes(40°–60° N), based on winter data over the period of December 1979–December 1982.

---

Резюме Мы не нaшлu нuкaко о эффекma nересеченuя секmорноŭ рaнuцы межnлaнеmно о мa нumно о nоля в озоне в облaсmu высоm меж?rt;у сре?rt;неŭ сmрamосфероŭ(10 Пa) u нuжнеŭ мезосфероŭ(0,4 Пa) нa сре?rt;нuх шuроmaх(40°–60° с.ш.), nрuменяя зuмнuе ?rt;aнные зa nерuо?rt; ?rt;екaбрь 1979 – ?rt;екaбрь 1982 .

  相似文献   

Discussion of ‘The Azuara impact structure (Spain): new insights from geophysical and geological investigations’ by K. Ernston and J. Fiebag     

Marc Aurell  Ángle González  A. Pérez  Joan Guimerà  Albert Casas  Ramon Salas 《International Journal of Earth Sciences》1993,82(4):750-755

  相似文献   

Formic and acetic acids in atmospheric condensate in Wilmington,North Carolina     

Joan D. Willey  Carol A. Wilson 《Journal of Atmospheric Chemistry》1993,16(2):123-133

Formic and acetic acids occurred in atmospheric condensate with concentrations similar to rainwater collected in Wilmington, North Carolina, during the sampling period from June to October of 1990. Atmospheric concentrations of these acids (calculated from the condensate concentrations) were higher in continental versus maritime air masses. Concentrations of formic and acetic acids were correlated with each other in both condensate and air. Traffic was a source of acetic acid and of bisulfite to atmospheric condensate in this study.  相似文献