Distribution and growth of snapper Chrysophrys auratus in the North Taranaki Bight,and management implications of these data     

Peter L. Horn 《新西兰海洋与淡水研究杂志》2013,47(3):419-430

A bottom trawl survey was used to determine the position of a nursery ground for snapper, Chrysophrys auratus, in the North Taranaki Bight, New Zealand, and so indicate what area should be protected from potentially harmful fishing techniques. A nursery ground for trevally, Caranx georgianus, was also identified. The growth rate of snapper from the North Taranaki Bight is shown to be much faster than Hauraki Gulf and East Cape stocks, but quite similar to Tasman Bay fish. The onset of sexual maturity appears to be related to fish size rather than age, with about 80% of snapper being mature at a fork length of 25 cm. Recruitment success varies greatly between years, and successful recruitment may be related to warm spring temperatures.  相似文献   

The surface dilational viscosity of polypropylene glycol solutions and its influence on water flow and foam behavior     

S.N. Tan  A. Jiang  J.J. Liau  S.R. Grano  R.G. Horn   《International Journal of Mineral Processing》2009,93(2):194-203

The non-equilibrium interfacial properties of a homologous series of aqueous polypropylene glycol solutions (400–2000 g/mol) were investigated as a function of concentration to understand their role in determining foam behavior. The overflowing cylinder technique was used to generate a continually expanding surface. Static and dynamic surface tensions, as well as the surface velocity of the expanding surface, were characterized. The surface dilational viscosity was compared to water flow rate and foam retention time of the polypropylene glycol solutions reported in the literature. This study suggests that the surface dilational viscosity is a key parameter in the Marangoni effect which retards water drainage, resulting in wetter foam and increased water recovery across flowing foams.  相似文献   

Controls of surface soil moisture spatial patterns and their temporal stability in a semi‐arid steppe     

Y. Zhao  S. Peth  X. Y. Wang  H. Lin  R. Horn 《水文研究》2010,24(18):2507-2519

Temporal stability of soil moisture spatial patterns has important implications for optimal soil and water management and effective field monitoring. The aim of this study was to investigate the temporal stability of soil moisture spatial patterns over four plots of 105 m × 135 m in grid size with different grazing intensities in a semi‐arid steppe in China. We also examined whether a time‐stable location can be identified from causative factors (i.e. soil, vegetation, and topography). At each plot, surface soil moisture (0–6 cm) was measured about biweekly from 2004 to 2006 using 100 points in each grid. Possible controls of soil moisture, including soil texture, organic carbon, bulk density, vegetation coverage, and topographic indices, were determined at the same grid points. The results showed that the spatial patterns of soil moisture were considerably stable over the 3‐y monitoring period. Soil moisture under wet conditions (averaged volumetric moisture contents > 20%) was more stable than that under dry ( ) or moist ( ) conditions. The best representative point for the whole field identified in each plot was accurate in representing the field mean moisture over time (R² ≥ 0·97; p < 0·0001). The degree of temporal persistence varied with grazing intensity, which was partly related to grazing‐induced differences in soil and vegetation properties. The correlation analysis showed that soil properties, and to a lesser extent vegetation and topographic properties, were important in controlling the temporal stability of soil moisture spatial patterns in this relatively flat grassland. Response surface regression analysis was used to quantitatively identify representative monitoring locations a priori from available soil‐plant parameters. This allows appropriate selection of monitoring locations and enhances efficiency in managing soil and water resources in semi‐arid environments. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

The pre-Colombian footprint on terrestrial nutrient cycling in Costa Rica: insights from phosphorus in a lake sediment record     

Gabriel M. Filippelli  Catherine Souch  Sally P. Horn  Derrick Newkirk 《Journal of Paleolimnology》2010,43(4):843-856

The impact of pre-Columbian subsistence agriculture on soil nutrient cycling in the American tropics is poorly quantified. Paleolimnological research can address this deficit by documenting the temporal evolution of nutrient cycling in lake watersheds over different time scales. Here we describe our use of a chemical sequential extraction technique adapted from soil fertility research to discern geochemical fractions of phosphorus (P) in lake sediments that serve as proxies for landscape-scale soil nutrient status. These P fractions are mineral P (the original lithic source of bioavailable P), occluded P (mainly bound to soil oxides), and organic P (remains of organic matter production by plants). We applied the P fractionation technique to a lake sediment core from a small lake in southern Costa Rica, Laguna Zoncho. Prior analyses of microfossils and stable carbon isotopes in this core documented an approximately 3,000 year history of human occupation and agricultural activity in the Zoncho watershed, and shifts in diatom communities in the lake associated both with human impacts and with climate-driven changes in lake level. Our P analyses revealed relatively constant P geochemistry during the first approximately 2,500 years of the record, when other sedimentary proxies reveal forest clearance and maize agriculture of varying intensity. However, the period from approximately 500 to 100 years BP is marked by a drastic shift toward a P geochemistry dominated by occluded forms, with a concomitant decrease in the relative content of both the organic and mineral P forms. This interval coincides with post-Conquest depopulation and forest regeneration at the site, and with an apparent deepening of the lake caused by a shift toward a wetter climate. The dominance of the occluded P fraction during this interval is the opposite of the trend expected with such a climate shift, implicating human dynamics as the principal driver of the changes in soil nutrient status indicated by the P fractions in the Zoncho core. We propose that the entire P geochemical record is dominated by human-induced alteration of the soil nutrient cycles via agriculture and occupation, and that the only interval that reveals the “natural” nutrient status in the region is the short interval when the site is abandoned and surrounding forests regrow. These results for Laguna Zoncho reveal the close connection between even relatively low-technology human activities and soil nutrient status.  相似文献   

Fire and the Environment: Ecological and Cultural Perspectives     

Sally P. Horn 《The Professional geographer》1990,42(4):493-494

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Diatom paleoecology of Laguna Zoncho,Costa Rica     

Kurt?A.?HaberyanEmail author  Sally?P.?Horn 《Journal of Paleolimnology》2005,33(3):361-369

We analyzed diatoms in a sediment profile from Laguna Zoncho in southern Pacific Costa Rica (lake elevation 1190 m asl, depth 2.6 m, area 0.75 ha) spanning some 3240 cal yr. Diatoms are common in the profile, which we subdivide into three zones. Zone C (3240–1020 cal yr B.P.) is dominated by Staurosira construens var. venter and Aulacoseira spp.; during this time, the lake was dilute and circumneutral. Benthic and acidophilous taxa increase gradually in the upper section of this zone. Zone B (1020–460 cal yr B.P.) almost totally lacks Aulacoseira, and instead is dominated by combinations of Eunotia minor, Encyonema lunatum, Gomphonema gracile, and Pinnularia braunii. Previous pollen and charcoal analysis indicates that this zone falls within the peak of prehistoric agricultural activity at the lake, but diatoms may also reflect climate change. During this period, the lake was likely shallower and more acidic, but not eutrophic. Finally, Zone A (460 cal yr B.P. to AD 1997) begins near a 1.5-cm tephra layer from nearby Volcán Barú; diatom assemblages are dominated by Aulacoseira spp., and suggest deepening of the lake and return to conditions similar to Zone C. This was a time of indigenous population decline and forest recovery in the Zoncho region, probably reflecting the impact of European diseases on the native population, although climate change and impacts of the tephra deposition cannot be wholly discounted.  相似文献   

Upper Proterozoic and Phanerozoic Pole Positions and Potassiumargon (K-Ar) Ages From the East Sahara Craton     

S. Saradeth  H. C. Soffel  P. Horn  D. Müller-Sohnius  A. Schult 《Geophysical Journal International》1989,97(2):209-221

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Swash zone sediment transport modes     

Diane P Horn  Travis Mason 《Marine Geology》1994,120(3-4):309-325

The result of field experiments, designed to investigate the relative proportions of bedload and suspended load, are described. The ratio of bedload to suspended sediment load in the swash zone is examined in both swash and backwash on four beaches by measuring the amounts collected in a sediment trap. Bedload transport is found to dominate the backwash. The relative proportions of bedload and suspended load change over the tidal cycle, with increasing bedload dominance at low tide. The total amount of sediment transported as swash and backwash is noticeably greater at high tide than at low tide. More sediment is transported on the flood tide than on the ebb.  相似文献   

Evaluating sedimentary DNA for tracing changes in cyanobacteria dynamics from sediments spanning the last 350 years of Lake Tiefer See,NE Germany     

Nwosu  Ebuka C.  Brauer  Achim  Kaiser  Jérôme  Horn  Fabian  Wagner  Dirk  Liebner  Susanne 《Journal of Paleolimnology》2021,66(3):279-296

Journal of Paleolimnology - Since the beginning of the Anthropocene, lacustrine biodiversity has been influenced by climate change and human activities. These factors advance the spread of harmful...  相似文献   

Performance of the veto detector incorporated into the ZEPLIN-III experiment     

C. Ghag  D.Yu. AkimovH.M. Araújo  E.J. BarnesV.A. Belov  A.A. BurenkovV. Chepel  A. CurrieL. DeViveiros  B. EdwardsV. Francis  A. HollingsworthM. Horn  G.E. KalmusA.S. Kobyakin  A.G. KovalenkoV.N. Lebedenko  A. Lindote  M.I. LopesR. Lüscher  K. LyonsP. Majewski  A.St J. MurphyF. Neves  S.M. PalingJ. Pinto da Cunha  R. PreeceJ.J. Quenby  L. ReichhartP.R. Scovell  C. SilvaV.N. Solovov  N.J.T. SmithP.F. Smith  V.N. StekhanovT.J. Sumner  C. ThorneR.J. Walker 《Astroparticle Physics》2011,35(2):76-86

The ZEPLIN-III experiment is operating in its second phase at the Boulby Underground Laboratory in search of dark matter WIMPs. The major upgrades to the instrument over its first science run include lower background photomultiplier tubes and installation of a plastic scintillator veto system. Performance results from the veto detector using calibration and science data in its first six months of operation in coincidence with ZEPLIN-III are presented. With fully automated operation and calibration, the veto system has maintained high stability and achieves near unity live time relative to ZEPLIN-III. Calibrations with a neutron source demonstrate a rejection of 60% of neutron-induced nuclear recoils in ZEPLIN-III that might otherwise be misidentified as WIMPs. This tagging efficiency reduces the expected untagged nuclear recoil background from neutrons during science data taking to a very low rate of ?0.2 events per year in the WIMP acceptance region. Additionally, the veto detector provides rejection of 28% of γ-ray induced background events, allowing the sampling of the dominant source of background in ZEPLIN-III - multiple scatter γ-rays with rare topologies. Since WIMPs will not be tagged by the veto detector, and tags due to γ-rays and neutrons are separable, this population of multiple scatter events may be characterised without biasing the analysis of candidate WIMP signals in the data.  相似文献