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排序方式: 共有329条查询结果,搜索用时 803 毫秒
91.
Eva Ramirez-Llodra Joan Baptista Company Francisco Sardà & Guiomar Rotllant 《Marine Ecology》2010,31(1):167-182
The composition and structure of megabenthic communities in the Blanes canyon and adjacent open margin (Northwestern Mediterranean) were studied. The aim was to assess the effect of the canyon and commercial fishing intensity on the community composition and structure of benthic megafauna by (i) describing the megabenthic community composition, (ii) quantifying faunal abundance and biomass and (iii) describing community structure with MDS analyses and biodiversity indices. The results are compared between three sites (canyon head, canyon wall and open margin) located between 435 m and 700 m. Samples were collected using a commercial bottom trawl between April 2003 and March 2004. These sites are exploited by the local fishing fleet that targets the rose shrimp Aristeus antennatus . A total of 131 megabenthic species were identified from the three sites, with fishes and decapod crustaceans being the most speciose, most abundant and of higher biomass. The species richness, abundance and biomass of non-crustacean invertebrates were low. There were no significant differences in total abundance and biomass between the three sites. However, community structure analysis suggests that the open margin community is significantly different from the canyon head and canyon wall, with a lower species richness, lower diversity and lower evenness. The open margin community also reflects a higher degree of disturbance compared to the two canyon habitats. The results indicate that there is a canyon effect on the community structure of benthic megafauna, but this may be modulated by differing fishing pressure, which adds an additional factor to margin heterogeneity. 相似文献
92.
X射线荧光光谱法测定土壤样品中碳氮硫氯等31种组分 总被引:3,自引:3,他引:3
利用新型的ZSX Primus Ⅱ型X射线荧光光谱仪采用粉末压片法直接测定土壤样品中的C、N、S、Cl等31种元素。各元素分析晶体为N采用RX45,C采用RX61,Na、Mg采用RX25,C1、S、P采用Ge,Si、Al采用PET,其余元素均采用LiF200。结果表明,方法的检出限、精密度和准确度对绝大多数元素而言,均可满足多目标地球化学调查样品分析的质量要求: 相似文献
93.
94.
Steven P. Oncley Thomas Foken Roland Vogt Wim Kohsiek H. A. R. DeBruin Christian Bernhofer Andreas Christen Eva van Gorsel David Grantz Christian Feigenwinter Irene Lehner Claudia Liebethal Heping Liu Matthias Mauder Andrea Pitacco Luis Ribeiro Tamas Weidinger 《Boundary-Layer Meteorology》2007,123(1):1-28
An overview of the Energy Balance Experiment (EBEX-2000) is given. This experiment studied the ability of state-of-the-art
measurements to close the surface energy balance over a surface (a vegetative canopy with large evapotranspiration) where
closure has been difficult to obtain. A flood-irrigated cotton field over uniform terrain was used, though aerial imagery
and direct flux measurements showed that the surface still was inhomogeneous. All major terms of the surface energy balance
were measured at nine sites to characterize the spatial variability across the field. Included in these observations was an
estimate of heat storage in the plant canopy. The resultant imbalance still was 10%, which exceeds the estimated measurement
error. We speculate that horizontal advection in the layer between the canopy top and our flux measurement height may cause
this imbalance, though our estimates of this term using our measurements resulted in values less than what would be required
to balance the budget.
The National Center for Atmospheric Research is supported by the National Science Foundation 相似文献
95.
An incentive mechanism for reducing emissions from conversion of intact and non-intact forests 总被引:1,自引:0,他引:1
Danilo Mollicone Frédéric Achard Sandro Federici Hugh D. Eva Giacomo Grassi Alan Belward Frank Raes Günther Seufert Hans-Jürgen Stibig Giorgio Matteucci Ernst-Detlef Schulze 《Climatic change》2007,83(4):477-493
This paper presents a new accounting mechanism in the context of the UNFCCC issue on reducing emissions from deforestation
in developing countries, including technical options for determining baselines of forest conversions. This proposal builds
on the recent scientific achievements related to the estimation of tropical deforestation rates and to the assessment of ‘intact’
forest areas. The distinction between ‘intact’ and ‘non intact’ forests used here arises from experience with satellite-based
deforestation measurements and allows accounting for carbon losses from forest degradation. The proposed accounting system
would use forest area conversion rates as input data. An optimal technical solution to set baselines would be to use historical
average figures during the time period from 1990 to 2005. The system introduces two different schemes to account for preserved
carbon: one for countries with high forest conversion rates where the desired outcome would be a reduction in their rates,
and another for countries with low rates. A ‘global’ baseline rate would be used to discriminate between these two country
categories (high and low rates). For the hypothetical accounting period 2013–2017 and considering 72% of the total tropical
forest domain for which data are available, the scenario of a 10% reduction of the high rates and of the preservation of low
rates would result in approximately 1.6 billion tCO2 of avoided emissions. The resulting benefits of this reduction would be shared between those high-rate countries which reduced
deforestation and those low-rate countries which did not increase their deforestation over an agreed threshold (e.g., half
of “global” baseline rate). 相似文献
96.
Eva Maria Walitzi 《Mineralogy and Petrology》1965,10(1-4):241-255
Zusammenfassung Denningit, (Mn, Ca, Zn) Te2O5 ist tetragonal mit der Raumgruppe P 42/n bc und den Gitterkonstanten a=8,82, c=13,04; Z=8. Die Struktur wurde mit Patterson-, Fourier- und (Fo-Fc)-Projektionen parallel [100], [110] und [001] bestimmt und verfeinert. Abschließend konnte eine least-squares-Verfeinerung durchgeführt werden. Je zwei trigonale TeO3-Pyramiden (Te–O=1,84–2,04 ) sind zu isolierten Te2O5-Gruppen verbunden. Mn, Ca und Zn in 8- und in [4+2]-Koordination bilden längs [001] Ketten, die durch Te2O5-Gruppen miteinander verknüpft sind.
Mit 3 Textabbildungen
Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet 相似文献
Summary Denningite, (Mn, Ca, Zn) Te2O5 is tetragonal with spacegroup P 42/n bc and unit-cell dimensions a=8,82, c=13,04; Z=8. The structure has been determined and refined by Patterson, Fourier and (Fo-Fc) projections along [100], [110] and [001]. Finally a least-squares refinement has been carried out. Pairs of trigonal TeO3 pyramids (Te–O=1,84–2,04) are connected to isolated Te2O5 groups. Mn, Ca and Zn in 8 coordination and in [4+2] coordination form chains along [001] connected by Te2O5 groups.
Mit 3 Textabbildungen
Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet 相似文献
97.
98.
The concept of climate impact response function is introduced and placed into the context of integrated assessment models to analyze policy options under climate change constraints. An example of developing such response functions is presented that entails a global model of potential natural vegetation driven by a climate change pattern derived from a general circulation model. A large array of strenuous issues are introduced that will be addressed by the set of papers included in this Special Issue. 相似文献
99.
Eva Kiss 《GeoJournal》2000,51(3):221-233
Rural settlements in Hungary account for 93% of all settlements and 37% of the country's population. Since 1989 they are scenes of spectacular changes. Based on some case studies of less developed villages this paper considers the most important characteristics of the post-socialist rural transformation by examining the local economy and living conditions. The main issues are how local actors (for example, economic corporations, households and individuals) have been affected by the interaction of supralocal and local factors and how they responded to them. Such responses can be considered to be manifestations of survival strategy. 相似文献
100.
Eva Thorborg Mørk Lise Lotte Sørensen Bjarne Jensen Mikael K. Sejr 《Boundary-Layer Meteorology》2014,151(1):119-138
The air–sea transfer velocity of $\mathrm{CO}_{2}\, (k_{\mathrm{CO}_{2}})$ was investigated in a shallow estuary in March to July 2012, using eddy-covariance measurements of $\mathrm{CO}_{2}$ fluxes and measured air–sea $\mathrm{CO}_{2}$ partial-pressure differences. A data evaluation method that eliminates data by nine rejection criteria in order to heighten parametrization certainty is proposed. We tested the data evaluation method by comparing two datasets: one derived using quality criteria related solely to the eddy-covariance method, and the other derived using quality criteria based on both eddy-covariance and cospectral peak methods. The best parametrization of transfer velocity normalized to a Schmidt number of 600 $(k_{600})$ was determined to be: $k_{600} = 0.3\,{U_{10}}^{2.5}$ where $U_{10}$ is the wind speed in m $\mathrm{s}^{-1}$ at 10 m; $k_{600}$ is based on $\mathrm{CO}_{2}$ fluxes calculated by the eddy-covariance method and including the cospectral peak method criteria. At low wind speeds, the transfer velocity in the shallow water estuary was lower than in other coastal waters, possibly a symptom of low tidal amplitude leading to low intensity water turbulence. High transfer velocities were recorded above wind speeds of 5 m $\mathrm{s}^{-1}$ , believed to be caused by early-breaking waves and the large fetch (6.5 km) of the estuary. These findings indicate that turbulence in both air and water influences the transfer velocity. 相似文献