Pelagic trophic transfer efficiency in an oligotrophic, dimictic deep lake (Lake Stechlin, Germany) and its relation to fisheries yield     

Michael Schulz  Rainer Koschel  Claudia Reese  Thomas Mehner 《Limnologica》2004,34(3):264-273

We investigated trophic transfer efficiency in the pelagic food chain of deep, oligotrophic Lake Stechlin (Germany) by analyses of the primary, secondary, and fish production. Primary production between April and November 2000 was estimated at 78 g C m⁻², pelagic secondary production at 14 g C m⁻², and production of the main planktivorous fish species [European cisco, Coregonus albula (L.)] at 0.77 g C m⁻². Thus, trophic transfer efficiency between primary and pelagic secondary production was around 18%, whereas between pelagic and fish production around 6%. The high efficiency at the first step of the chain is discussed to be due to the high food quality in oligotrophic lakes due to the dominance of Bacillariophyceae and Chlorophyceae rich in essential fatty acids. In turn, the relatively low trophic transfer efficiency between the secondary and the fish production is mainly explained by the avoidance of calanoid copepods as food source by the ciscoes. Concerning the trophic transfer efficiency, results from this study support the general assumption of a 10% transfer between neighbouring trophic levels within ecosystems.  相似文献   

Conditional statistical inverse modeling in groundwater flow by multigrid methods     

Volker Schulz  Andras Bardossy  Rainer Helmig 《Computational Geosciences》1999,3(1):49-68

Due to the notorious lack of data, stochastic simulation and conditioning of distributed parameter fields is generally acknowledged as a major task in order to produce realistic prognoses for groundwater flow phenomena, thus honouring the maximum of information available. In this paper, a new conditioning approach is presented which treats the distributed parameters directly without projection onto lower dimensional spaces and preserves certain desired statistical properties by explicitly stating them as constraints for the conditioning optimization problem. Typically, the conditioning task must be performed very often and the conditioning optimization problems are highly dimensional. Therefore, a second main focus of the paper is on the presentation of efficient multigrid methods for the solution of the conditioning problems. Numerical results are given for a practical application problem. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The development of forest damage — control and prognosis on the basis of remote sensing data     

Heiner Barsch  Uta Steinhardt  Rainer Söllner 《GeoJournal》1994,32(1):39-46

Forest damage can be caused by three types of stress which exercise their influence by predisposing, causative and contributory factors. Predisposing factors, above all permanent immision stress, cause the general diminishing of the trees' vitality. Causative fators such as long and extreme periods of dryness cause a fast and evident deterioration of the forest stand, contributory factors as eg pest attacks cause their mortification. When using remote sensing data to monitor the development of forest damage it is necessary therefore not only to pay attention to spectral signatures characterizing the degree of green space and thus the information of the canopy but also to spectral signs showing the water supply of the stands. This has not been done so far though nowadays the necessary multispectral satellite data are on regular offer. For this reason it may be suggested that the existing possibilities to predict the development of forest damage on the basis of remote sensing data have not yet been fully used.In order to examine these possibilities, in the environs of Berlin, ie in the east and south of the Land of Brandenburg both the vegetation index which has been known from literature for a long time and an index for the difference in remission identifying the water bands in the short-wave infrared have been calculated on the basis of Landsat-TM data. A multi-temporal comparison shows that despite the bad conditions of the forest in 1991 on the test site located north-east of Berlin due to a relatively good water supply in that year the pine forest damage had not progressed in 1992. This allows to draw the conclusion that at least in the pine forests of the East German interior lowland the development of forest damage is essentially determined by dryness stress. In this way on the basis of 1992 Landsat-TM data there was not only an inventory made of the actual condition of the forest on the east and south-east of the Land of Brandenburg but also trends of damage progress shown. The damage classification of pine stands be completed by a prognosis as to the development of damage.  相似文献   

Upper mantle and lithospheric heterogeneities in central and eastern Europe as observed by teleseismic receiver functions     

Wolfram H. Geissler  Rainer Kind  Xiaohui Yuan 《Geophysical Journal International》2008,174(1):351-376

Data from 90 permanent broad-band stations spread over central and eastern Europe were analysed using Ps receiver functions to study the crustal and upper-mantle structure down to the mantle transition zone. Receiver functions provide valuable information on structural features, which are important for the resolution of European lithospheric dynamics. Moho depths vary from less than 25 km in extensional areas in central Europe to more than 50 km at stations in eastern Europe (Craton) and beneath the Alpine–Carpathian belt. A very shallow Moho depth can be observed at stations in the Upper Rhine Graben area ( ca. 25 km), whereas, for example, stations in the SW Bohemian Massif show a significantly deeper Moho interface at a depth of 38 km. V_p / V_s ratios vary between 1.60 and 1.96, and show no clear correlation to the major tectonic units, thus probably representing local variations in crustal composition. Delayed arrivals of converted phases from the mantle transition zone are observed at many stations in central Europe, whereas stations in the cratonic area show earlier arrivals compared with those calculated from the IASP91 Earth reference model. Differential delay times between the P₄₁₀s and P₆₆₀s phases indicate a thickened mantle transition zone beneath the eastern Alps, the Carpathians and the northern Balkan peninsula, whereas the transition zone thickness in eastern and central Europe agrees with the IASP91 value. The thickening of the mantle transition zone beneath the eastern Alps and the Carpathians could be caused by cold, deeply subducted oceanic slabs.  相似文献   

Shaw meteorite: water-poor and water-rich melt inclusions in olivine and enstatite     

Thomas  Rainer  Davidson  Paul 《Mineralogy and Petrology》2019,113(1):1-5

Mineralogy and Petrology - During the petrological examination of a double polished thick section of the light-colored lithology of the Shaw meteorite, small melt inclusions, typically with...  相似文献   

Could surface roughness be a poor proxy for landslide age? Results from the Swabian Alb,Germany          下载免费PDF全文

Jason N. Goetz  Rainer Bell  Alexander Brenning 《地球表面变化过程与地形》2014,39(12):1697-1704

The potential of surface roughness to quantify geomorphological landforms and processes has been enhanced with the availability of high‐resolution digital terrain models (DTM). Recent studies that attempt to identify landslide features with surface roughness have suggested that this measure of topographic heterogeneity may also be applied to estimate the relative age of landslides. This is a provisional study that explores the potential of this relationship by assessing the ability of surface roughness to act as a proxy for relative landslide age. The surface roughness for a set of 12 dated landslides in the Swabian Alb that occurred between 1789 and 1985 was calculated from a 1 m² spatial resolution LiDAR DTM with three algorithms: root‐mean‐square‐height (RMSH), standard deviation of slope (SDS), and direction cosine eigenvalue ratios (DCE). Scale‐dependence was analysed by calculating surface roughness for a range of moving window sizes (3 × 3, 5 × 5, 9 × 9 and 15 × 15), and surface roughness for each landslide was summarized by the median and upper quartile. Only weak correlations (best Spearman's rho 0.58) were present between landslide age and surface roughness. This correlation becomes weaker with increasing moving window size. Given weak observed associations and discussed challenges pertaining to the complexities of landslide morphology change over time, we currently find that surface roughness alone may not be justifiable to act as a proxy for landslide age for our study region. Furthermore, we recommend future studies should focus on addressing possible natural and anthropogenic factors such as land use change that may alter surface roughness. These studies may focus on one of the three roughness measures used here as they are strongly correlated. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Sustainability of deep-sea fisheries   总被引：1，自引：0，他引：1  

Elliott A. Norse  Sandra BrookeWilliam W.L. Cheung  Malcolm R. ClarkIvar Ekeland  Rainer FroeseKristina M. Gjerde  Richard L. HaedrichSelina S. Heppell  Telmo Morato  Lance E. MorganDaniel Pauly  Rashid SumailaReg Watson 《Marine Policy》2012,36(2):307-320

As coastal fisheries around the world have collapsed, industrial fishing has spread seaward and deeper in pursuit of the last economically attractive concentrations of fishable biomass. For a seafood-hungry world depending on the oceans' ecosystem services, it is crucial to know whether deep-sea fisheries can be sustainable.The deep sea is by far the largest but least productive part of the oceans, although in very limited places fish biomass can be very high. Most deep-sea fishes have life histories giving them far less population resilience/productivity than shallow-water fishes, and could be fished sustainably only at very low catch rates if population resilience were the sole consideration. But like old-growth trees and great whales, their biomass makes them tempting targets while their low productivity creates strong economic incentive to liquidate their populations rather than exploiting them sustainably (Clark's Law). Many deep-sea fisheries use bottom trawls, which often have high impacts on nontarget fishes (e.g., sharks) and invertebrates (e.g., corals), and can often proceed only because they receive massive government subsidies. The combination of very low target population productivity, nonselective fishing gear, economics that favor population liquidation and a very weak regulatory regime makes deep-sea fisheries unsustainable with very few exceptions. Rather, deep-sea fisheries more closely resemble mining operations that serially eliminate fishable populations and move on.Instead of mining fish from the least-suitable places on Earth, an ecologically and economically preferable strategy would be rebuilding and sustainably fishing resilient populations in the most suitable places, namely shallower and more productive marine ecosystems that are closer to markets.  相似文献   

The current performance of the in situ 14C extraction line at ETH     

Kristina Hippe  Florian Kober  Heinrich Baur  Matthias Ruff  Lukas Wacker  Rainer Wieler 《Quaternary Geochronology》2009,4(6):493-500

We present the new ¹⁴C extraction line at ETH Zürich. This system is designed to extract in situ-produced cosmogenic ¹⁴C from terrestrial quartz samples, and to obtain pure CO₂ gas for analysis with a gas ion source Accelerator Mass Spectrometry (AMS) system. Samples are degassed at 1550–1600 °C without the use of a fluxing agent. Gas purification is achieved by a series of cryogenic traps and passage through hot Ag and Cu wool/mesh. Graphitization and, thus, sample dilution is not required. Tests to determine the CO₂ recovery after gas extraction and cleaning yielded consistently good recovery rates of >99.8% (n = 7). The ¹⁴C blank contribution from the all-metal tubing system is negligible. Our preliminary procedural blank estimate – deriving mostly from the hot extraction furnace – is <5 × 10^{5 14}C atoms. Extraction tests on two quartz samples by stepped-heating show a quantitative separation of atmospheric ¹⁴C at ≤500 °C from the in situ component above 1200 °C. Based on these data, we estimate to achieve a complete ¹⁴C extraction from a quartz sample.  相似文献   

The DATA program for the calculation of ESR age estimates on tooth enamel     

Rainer Grün 《Quaternary Geochronology》2009,4(3):231-232

The supplementary ZIP file of this paper contains the DATA program, which can be used for ESR age calculations of tooth enamel. This paper outlines the use and limitations of this program.  相似文献   

Book Review: Turbulence and Magnetic Fields in Astrophysics. By Edith Falgarone and Thierry Passot     

Rainer Arlt 《Astronomische Nachrichten》2004,325(9):762-762

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