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21.
22.
Submerged vegetation complexity modifies benthic infauna communities: the hidden role of the belowground system 下载免费PDF全文
Vanessa González‐Ortiz Luis Gonzalo Egea Rocio Jiménez‐Ramos Francisco Moreno‐Marín José Lucas Pérez‐Lloréns Tjeerd Bouma Fernando Brun 《Marine Ecology》2016,37(3):543-552
Marine plants provide a variety of functions with high economic and ecological values in ecosystems. The above‐ (AG) and below‐ground (BG) systems increase the structural complexity of plants, which also enhance faunal abundance and diversity. The ecological role of the AG compartment in structuring inter‐tidal macrobenthic communities has been widely studied; however, this is not the case for the BG compartment. This study addressed the effects of variation in vegetation complexity (in both AG and BG systems) on associated macrobenthic infauna with respect to abundance, species richness, composition, weight and body type. To achieve this aim, a field experiment using artificial vegetation mimics was carried out using replicated treatments with different AG‐BG complexity ratios. We found a significant increase in the density and the number of taxa of macrobenthic infaunal species in plots with vegetation mimics compared with unvegetated areas, regardless of either AG or BG complexity. This effect was found even when AG parts were not present (i.e. when only BG parts were used). Furthermore, a positive relationship between structural complexity and diversity was recorded. Variation in one or both plant compartments was strongly related to diversity changes in the associated macrobenthic infauna. In conclusion, our experimental set‐up provides the first evidence that the BG compartment is at least as important as the AG compartment in controlling diversity in inter‐tidal vegetated areas because it was able to strongly affect community structure even when the AG system was totally absent. 相似文献
23.
Eline Tolstoy Kim Venn Matt Shetrone Francesca Primas Vanessa Hill Andreas Kaufer Thomas Szeifert 《Astrophysics and Space Science》2002,281(1-2):217-218
It is a truth universally acknowledged, that a galaxy in possession of a good quantity of gas must want to form stars. It is the details of how and why that baffle us all. The simplest theories either would have this process a carefully self-regulated affair, or one that goes completely out of control and is capable of wrecking the galaxy which hosts it. Of course the majority of galaxies seem to amble along somewhere between these two extremes, and the mean properties tend to favour a quiescent self-regulated evolutionary scenario. But there area variety of observations which require us to invoke transitory ‘bursts’ of star-formation at one time or another in most galaxy types. Several nearby dwarf spheroidal galaxies have clearly determined star-formation histories with apparent periods of zero star formation followed by periods of fairly active star formation. If we are able to understand what separated these bursts we would understand several important phenomena in galaxy evolution. Were these galaxies able to clear out their gas reservoir in a burst of star formation? How did this gas return? or did it? Have these galaxies receieved gas from the IGM instead? Could stars from these types of galaxy contribute significantly to the halo population in our Galaxy? To answer these questions we need to combine accurate stellar photometry and Colour-Magnitude Diagram interpretation with detailed metal abundances to combine a star-formation rate versus time with a range of element abundances with time. Different elements trace different evolutionary process (e.g., relative contributions of type I and II supernovae). We often aren't even sure of the abundance spread in these galaxies. We have collected detailed high resolution UVES spectra of four nearby dwarf spheroidal galaxies (Sculptor, Fornax, Leo I &; Carina) to begin to answer these questions. This is a precursor study to a more complete study with FLAMES. We presented at this meeting the initial results for the Sculptor and Fornax dwarf spheroidal galaxies which have been previously had single element (low resolution) calcium abundance studies (Tolstoy et al., 2001). See Figures 1 and 2. 相似文献
24.
Andrew Steele David t. Goddard Dave Stapleton Jan k. w. Toporski Vanessa Peters Virginia Bassinger George Sharples David d. Wynn‐Williams David s. Mckay 《Meteoritics & planetary science》2000,35(2):237-241
Abstract— Examination of fracture surfaces near the fusion crust of the martian meteorite Allan Hills (ALH) 84001 have been conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM) and has revealed structures strongly resembling mycelium. These structures were compared with similar structures found in Antarctic cryptoendolithic communities. On morphology alone, we conclude that these features are not only terrestrial in origin but probably belong to a member of the Actinomycetales, which we consider was introduced during the Antarctic residency of this meteorite. If true, this is the first documented account of terrestrial microbial activity within a meteorite from the Antarctic blue ice fields. These structures, however, do not bear any resemblance to those postulated to be martian biota, although they are a probable source of the organic contaminants previously reported in this meteorite. 相似文献
25.
Vanessa Haverd Ray Leuning David Griffith Eva van Gorsel Matthias Cuntz 《Boundary-Layer Meteorology》2009,130(2):209-228
One-dimensional Lagrangian dispersion models, frequently used to relate in-canopy source/sink distributions of energy, water
and trace gases to vertical concentration profiles, require estimates of the standard deviation of the vertical wind speed,
which can be measured, and the Lagrangian time scale, T
L
, which cannot. In this work we use non-linear parameter estimation to determine the vertical profile of the Lagrangian time
scale that simultaneously optimises agreement between modelled and measured vertical profiles of temperature, water vapour
and carbon dioxide concentrations within a 40-m tall temperate Eucalyptus forest in south-eastern Australia. Modelled temperature
and concentration profiles are generated using Lagrangian dispersion theory combined with source/sink distributions of sensible
heat, water vapour and CO2. These distributions are derived from a multilayer Soil-Vegetation-Atmospheric-Transfer model subject to multiple constraints:
(1) daytime eddy flux measurements of sensible heat, latent heat, and CO2 above the canopy, (2) in-canopy lidar measurements of leaf area density distribution, and (3) chamber measurements of CO2 ground fluxes. The resulting estimate of Lagrangian time scale within the canopy under near-neutral conditions is about 1.7
times higher than previous estimates and decreases towards zero at the ground. It represents an advance over previous estimates
of T
L
, which are largely unconstrained by measurements. 相似文献
26.
The Todagin Creek landslide is located at 57.61° N 129.98° W in Northwest British Columbia. A seismic station 90 km north
of the landslide recorded the event at 1643 hours coordinated universal time (UTC; 0943 hours Pacific daylight time (PDT))
on October 3, 2006. The signal verifies the discovery and relative time bounds provided by a hunting party in the valley.
The landslide initiated as a translational rock slide on sedimentary rock dipping down slope at 34° and striking parallel
to the valley. The landslide transformed into a debris avalanche and had a total volume estimated at 4 Mm3. An elevation drop of 771 m along a planar length of 1,885 m resulted in a travel angle (fahrb?schung) of 21.3°. The narrowest
part of the landslide through the transport zone is 345 m. The widest part of the divergent toe of the landslide reaches a
width of 1,010 m. Landslide debris impounded a lake of approximately 32 ha and destroyed an additional 67 ha of forest. The
impoundment took 7 to 10 days to fill, with muddied waters observed downstream on October 13. No clear linkage exists with
precipitation and temperature records preceding the landslide, but strong diurnal temperature cycles occurred in the days
prior to the event. The Todagin Creek area appears to have an affinity for large landslides with the deposits of three other
landslides >5 Mm3 observed in the valley. 相似文献
27.
Vanessa Cerqueira Koppe João Felipe Coimbra Leite Costa Jair Carlos Koppe Fernando Gambin Gary Fallon Nick Davies 《Natural Resources Research》2007,16(4):293-303
Seismic reflection methods measure the time a seismic wave takes to travel through the ground, from the user defined source
to a series of signal monitoring sensors known as geophones. The measured times need to be depth converted to allow for integration
with other geological data. In order to convert from time to depth, an estimate of the rock volume velocity field must be
made. The velocity field estimate can be made by assignment of velocity estimates to a geological model independent of the
seismic processing. This article presents the results of using the acoustic geophysical log data extrapolated via sequential
Gaussian simulation to derive the velocity field. The uncertainties associated with the velocity estimates were significant
and provided the means to assess confidence limits for the actual depth determination. The technique is assessed by application
to a major coal deposit, approximately 2.1 m thick and 210 m deep. Considering only the uncertainty associated with estimating
the velocity field, half of the confidence interval values showed approximately 1 m of uncertainty in depth. The application
of sequential Gaussian simulation to model the 3D distribution of acoustic velocity can be extended to other geophysical log
parameters or derived estimates. 相似文献
28.
de Abreu Corrêa A Albarnaz JD Moresco V Poli CR Teixeira AL Oliveira Simões CM Monte Barardi CR 《Marine environmental research》2007,63(5):479-489
The State of Santa Catarina produces the greatest quantity of edible mollusks in Brazil. To guarantee sanitary qualify, mollusk cultures should be monitored for contamination by pathogenic microorganisms. A self-purification or "depuration" system that eliminates Salmonella enterica serovar Typhimurium contamination from oysters has been developed and evaluated. The depuration process occurred within a closed system, in which 1000 L of water was recirculated for 24 h. The water was sterilized with ultraviolet (UV) light, chlorine, or both together. Oysters (Crassostrea gigas) artificially contaminated with S. typhimurium were harvested every 6 h. Samples of oyster tissue were excised and both the presence and numbers of bacteria were determined. Combined UV light and chlorine treatments resulted in total elimination of bacteria within 12 h. Polymerase chain reaction detected bacteria in water exposed to the three treatments. This pioneering study is the first of its kind in Brazil and represents a major contribution to commercial mollusk culture in this country. 相似文献
29.
30.
Mechanisms controlling soil carbon turnover and their potential application for enhancing carbon sequestration 总被引:6,自引:0,他引:6
In addition to increasing plant C inputs, strategies for enhancing soil C sequestration include reducing C turnover and increasing
its residence time in soils. Two major mechanisms, (bio)chemical alteration and physicochemical protection, stabilize soil organic C (SOC) and thereby control its turnover. With (bio)chemical alteration, SOC is transformed by biotic
and abiotic processes to chemical forms that are more resistant to decomposition and, in some cases, more easily retained
by sorption to soil solids. With physicochemical protection, biochemical attack of SOC is inhibited by organomineral interactions
at molecular to millimeter scales. Stabilization of otherwise decomposable SOC can occur via sorption to mineral and organic
soil surfaces, occlusion within aggregates, and deposition in pores or other locations inaccessible to decomposers and extracellular
enzymes. Soil structure is a master integrating variable that both controls and indicates the SOC stabilization status of
a soil. One potential option for reducing SOC turnover and enhancing sequestration, is to modify the soil physicochemical
environment to favor the activities of fungi. Specific practices that could accomplish this include manipulating the quality
of plant C inputs, planting perennial species, minimizing tillage and other disturbances, maintaining a near-neutral soil
pH and adequate amounts of exchangeable base cations (particularly calcium), ensuring adequate drainage, and minimizing erosion.
In some soils, amendment with micro- and mesoporous sorbents that have a high specific surface – such as fly ash or charcoal
– can be beneficial.
All authors contributed equally to this article. 相似文献