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11.
The current study provides long-term catch-rate, biological and feeding data for smooth hammerhead sharks, Sphyrna zygaena, caught in South Africa’s KwaZulu-Natal bather protection programme. In total, 2 512 S. zygaena were caught in net installations between 1978 and 2014, and 72 S. zygaena were caught on drumlines between 2007 and 2014. There was no significant log-linear year trend in the net catch rate over time (slope = 0.0054, t = 1.808, p = 0.07). However, there was a significant temporal increase in mean size of the captured sharks (slope = 0.0012, t = 3.502, p < 0.001). A quasi-Poisson generalised additive mixed model showed that increasing latitude, winter months, colder sea temperatures and the deployment of drumlines all had a significant positive effect on the catch rate of sharks in nets. The size frequency of the catch was unimodal, with significantly more females caught in the nets and more males on the drumlines. The majority (93.1%) of all sharks caught were immature and measured between 80 and 120 cm precaudal length. Teleosts and cephalopods dominated the sharks’ diet in terms of all dietary indices. The prey species consumed indicate that immature S. zygaena are feeding primarily within the pelagic zone of shallow coastal habitats. 相似文献
12.
Giulia Zuecco Chiara Marchina Ylenia Gelmini Anam Amin H. J. van Meerveld Daniele Penna Marco Borga 《水文研究》2021,35(3):e14095
Ressi is a small (2.4 ha) forested catchment located in the Italian pre-Alps. The site became an experimental catchment to investigate the water fluxes in the soil–plant–atmosphere continuum and the impact of vegetation on runoff generation in 2012. The elevation of the catchment ranges from 598 to 721 m a.s.l. and the climate is humid temperate. The bedrock consists of rhyolites and dacites; the soil is a Cambisol. The catchment is covered by a dense forest, dominated by beech, chestnut, maple, and hazel trees. The field set up includes measurements of the rainfall in an open area, streamflow at the outlet, soil moisture at various depths and locations, and depth to water table in six piezometers at a 5- or 10-min interval. Samples of precipitation, stream water, shallow groundwater and soil water are collected monthly for tracer analysis (stable isotopes (2H and 18O), electrical conductivity and major ions), and during selected rainfall–runoff events to determine the contribution of the various sources to runoff. Since 2017, soil and plant water samples have been collected to determine the sources of tree transpiration. Data collected in the period 2012–2016 are publicly available. Data collection is ongoing, and the data set is expected to be updated on an annual basis to include the most recent measurements. 相似文献
13.
Acta Geotechnica - Root depth and leaf area ratio are two important features of a plant and exhibit a coupled relation. Assessing their coupled effects on induced soil suction is essential for... 相似文献
14.
Predicting groundwater level of wells in the Diyala River Basin in eastern Iraq using artificial neural network 下载免费PDF全文
Al-Mansourieh zone is a part of Al-Khalis City within the province of Diyala and located in the Diyala River Basin in eastern Iraq with a total area about 830 km2.Groundwater is the main water source for agriculture in this zone.Random well drilling without geological and hydraulic information has led the most of these wells to dry up quickly.Therefore,it is necessary to estimate the levels of groundwater in wells through observed data.In this study,Alyuda NeroIntelligance 2.1 software was applied to predict the groundwater levels in 244 wells using sets of measured data.These data included the coordinates of wells(x,y),elevations,well depth,discharge and groundwater levels.Three ANN structures(5-3-3-1,5-10-10-1 and 5-11-11-1)were used to predict the groundwater levels and to acquire the best matching between the measured and ANN predicted values.The coefficient of correlation,coefficient determination(R2)and sum-square error(SSE)were used to evaluate the performance of the ANN models.According to the ANN results,the model with the three structures has a good predictability and proves more effective for determining groundwater level in wells.The best predictor was achieved in the structure 5-3-3-1,with R2 about 0.92,0.89,0.84 and 0.91 in training,validation,testing and all processes respectively.The minimum average error in the best predictor is achieved in validation and testing processes at about 0.130 and 0.171 respectively.On the other hand,the results indicated that the model has the potential to determine the appropriate places for drilling the wells to obtain the highest level of groundwater. 相似文献
15.
Valderrama-Landeros Luis H. Martell-Dubois Raúl Ressl Rainer Silva-Casarín Rodolfo Cruz-Ramírez Cesia J. Muñoz-Pérez Juan J. 《地理学报(英文版)》2019,29(10):1637-1654
Journal of Geographical Sciences - The goal of our work was to locate and quantify changes that occurred in 66% of the Mexican coastline, based on four land cover maps generated by the Mexican... 相似文献
16.
Kryštof Materna Jiří Hasman David Hána 《Norsk geografisk tidsskrift. Norwegian journal of geography》2019,73(4):197-214
ABSTRACTThe development of globalisation has ushered in fundamental changes that have led to a break in the relationship between places of production and places of consumption, and sometimes a rejection of global products and corporations at the local level in accordance with neolocalism. The objective of the article is to examine the effect of regional identity on the local impacts of global processes by applying a multilevel analysis of the brewing industry, in which consumers are very sensitive to changes in the beer offered and can influence it, for example by putting pressure on representatives of restaurants. Beginning with extensive research on the international level, the authors point out the various impacts of brewery acquisitions in three Central European countries – Czechia, Poland and Slovakia – that differ regarding the role of beer in the identity of their inhabitants. Thereafter, they focus on two Czech beer brands, the production of which was relocated to other regions after acquisitions. Based on field studies in the regions of the brands’ original production, the authors find that both brands lost popularity among their original customers. They conclude that for Czech customers, the place of production may be an important factor when choosing a beer brand. 相似文献
17.
Harry Y. McSween Jr. Joshua P. Emery Andrew S. Rivkin Michael J. Toplis Julie C. Castillo‐Rogez Thomas H. Prettyman M. Cristina De Sanctis Carle M. Pieters Carol A. Raymond Christopher T. Russell 《Meteoritics & planetary science》2018,53(9):1793-1804
The mineralogy and geochemistry of Ceres, as constrained by Dawn's instruments, are broadly consistent with a carbonaceous chondrite (CM/CI) bulk composition. Differences explainable by Ceres’s more advanced alteration include the formation of Mg‐rich serpentine and ammoniated clay; a greater proportion of carbonate and lesser organic matter; amounts of magnetite, sulfide, and carbon that could act as spectral darkening agents; and partial fractionation of water ice and silicates in the interior and regolith. Ceres is not spectrally unique, but is similar to a few other C‐class asteroids, which may also have suffered extensive alteration. All these bodies are among the largest carbonaceous chondrite asteroids, and they orbit in the same part of the Main Belt. Thus, the degree of alteration is apparently related to the size of the body. Although the ammonia now incorporated into clay likely condensed in the outer nebula, we cannot presently determine whether Ceres itself formed in the outer solar system and migrated inward or was assembled within the Main Belt, along with other carbonaceous chondrite bodies. 相似文献
18.
Factors influencing biodeposit production by the New Zealand freshwater mussel Echyridella menziesii
Kevin J. Collier Susan J. Clearwater Paula H. M. W. Neijenhuis Susanna A. Wood 《新西兰海洋与淡水研究杂志》2018,52(1):1-15
Laboratory experiments on the New Zealand freshwater mussel Echyridella menziesii were used to investigate the short-term effects (7–8 days) of food type on rates of biodeposition and benthic substrate respiration. Post-feeding biodeposition rates ranged from 0.34 to 1.52?mg?g?1?h?1 (mean?=?0.50?mg g?1?h?1) and were unaffected by the addition of toxin-producing Microcystis. Addition of suspended sediment (30?mg?L?1) visibly altered substrate composition, and increased total and inorganic biodeposit production rates by 24–33% compared to mussels fed commercial phytoplankton stock. Biodeposition rates of mussels in lake bed substrates were 38% higher than those in silica sand for identical feeding regimes, suggesting that a significant proportion of material produced in this experiment could have been derived from feeding on organic matter in the lake bed sediments. Respiration rates were higher in treatments with Microcystis but were unaffected by the presence of mussels. This laboratory study suggests that biodeposition by E. menziesii is resilient to short-term exposure to Microcystis, and highlights the ability of mussels to alter benthic substrate composition by incorporating suspended sediment into substrates. 相似文献
19.
K. Belov A. Branch S. Broschart J. Castillo-Rogez S. Chien L. Clare R. Dengler J. Gao D. Garza A. Hegedus S. Hernandez S. Herzig T. Imken H. Kim S. Mandutianu A. Romero-Wolf S. Schaffer M. Troesch E. J. Wyatt J. Lazio 《Experimental Astronomy》2018,46(2):241-284
This paper reports a design study for a space-based decametric wavelength telescope. While not a new concept, this design study focused on many of the operational aspects that would be required for an actual mission. This design optimized the number of spacecraft to insure good visibility of approx. 80% of the radio galaxies– the primary science target for the mission. A 5,000 km lunar orbit was selected to guarantee minimal gravitational perturbations from Earth and lower radio interference. Optimal schemes for data downlink, spacecraft ranging, and power consumption were identified. An optimal mission duration of 1 year was chosen based on science goals, payload complexity, and other factors. Finally, preliminary simulations showing image reconstruction were conducted to confirm viability of the mission. This work is intended to show the viability and science benefits of conducting multi-spacecraft networked radio astronomy missions in the next few years. 相似文献
20.
Zeno F. Levy Donald I. Siegel Soumitri S. Dasgupta Paul H. Glaser Jeffrey M. Welker 《水文研究》2014,28(18):4938-4952
Ground water recharge is assumed to occur primarily at raised bog crests in northern peatlands, which are globally significant terrestrial carbon reservoirs. We synoptically surveyed vertical profiles of peat pore water δ18O and δ2H from a range of bog and fen landforms across the Glacial Lake Agassiz Peatlands, northern Minnesota. Contrary to our expectations, we find that local‐scale recharge penetrates to not only the basal peat at topographically high bog crests but also transitional Sphagnum lawns and low‐lying fen water tracks. Surface landscape characteristics appear to control the isotopic composition of the deeper pore waters (depths ≥0.5 m), which are partitioned into discrete ranges of δ18O on the basis of landform type (mean ± standard deviation for bog crests = ?11.9 ± 0.4‰, lawns = ?10.6 ± 0.1‰, fen water tracks = ?8.8 ± 1.0‰). Fen water tracks have a shallow free‐water surface that is seasonally enriched by isotope fractionating evaporation, fingerprinting recharge to underlying pore waters at depths ≥3 m. Isotope mass balance calculations indicate on average 12% of the waters we sampled from the basal peat of the fen water tracks was lost to surface evaporation, which occurred prior to advection and dispersion into the underlying formation. These new data provide direct support for the hypothesis that methane production in deeper peat strata is fuelled by the downward transport of labile carbon substrates from the surface of northern peat basins. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献