Spheres of discharge of springs   总被引：3，自引：0，他引：3  

Abraham E. Springer  Lawrence E. Stevens 《Hydrogeology Journal》2009,17(1):83-93

Although springs have been recognized as important, rare, and globally threatened ecosystems, there is as yet no consistent and comprehensive classification system or common lexicon for springs. In this paper, 12 spheres of discharge of springs are defined, sketched, displayed with photographs, and described relative to their hydrogeology of occurrence, and the microhabitats and ecosystems they support. A few of the spheres of discharge have been previously recognized and used by hydrogeologists for over 80 years, but others have only recently been defined geomorphologically. A comparison of these spheres of discharge to classification systems for wetlands, groundwater dependent ecosystems, karst hydrogeology, running waters, and other systems is provided. With a common lexicon for springs, hydrogeologists can provide more consistent guidance for springs ecosystem conservation, management, and restoration. As additional comprehensive inventories of the physical, biological, and cultural characteristics are conducted and analyzed, it will eventually be possible to associate spheres of discharge with discrete vegetation and aquatic invertebrate assemblages, and better understand the habitat requirements of rare or unique springs species. Given the elevated productivity and biodiversity of springs, and their highly threatened status, identification of geomorphic similarities among spring types is essential for conservation of these important ecosystems.  相似文献   

Land use and disturbance effects on the dynamics of natural ecosystems of the Monte Desert: Implications for their management     

P.E. Villagra  G.E. Defossé  H.F. del Valle  S. Tabeni  M. Rostagno  E. Cesca  E. Abraham 《Journal of Arid Environments》2009,73(2):202-211

The complex interactions between human activity and natural processes determine non-linear dynamics in ecosystems that can difficult their management. Human settlements in arid lands contribute to the modification of disturbance regimes, including the introduction of new disturbances and the elimination of others. In consequence, they can alter the functional mechanisms that allow systems to overcome limiting factors, leading to desertification. In this revision, we evaluated the effects of the changes on disturbance regimes produced by the different forms of land transformation on the structure and function of ecosystems of the Monte Biogeographical Province, in Argentinean arid west. Two approaches were used: the analysis of land use history and the analysis of the effects of the main disturbances on the dynamics of different communities. We concluded that throughout the history of the Monte Desert, the joint action of natural and anthropic agents has resulted in complex dynamics that lead most area of the Monte to a moderate to severe status of desertification. The modification of the disturbance regime had strong consequences for several aspects of the dynamics of communities, such as species composition and diversity, water dynamics, soil conditions, trophic structure and productivity of Monte Desert ecosystems. However, disturbance regimes could be managed to promote favorable transitions in ecosystems and, therefore, could be a tool for optimizing productivity of agro-ecosystems, and recovering and conserving natural ecosystems.  相似文献   

The story of galaxy evolution in full colour     

Richard S Ellis  Roberto G Abraham  Jarle Brinchmann  Felipe Menanteau 《Astronomy& Geophysics》2000,41(2):2.10-2.16

A Holy Grail of modern astronomy is understanding the origin of Edwin Hubble's morphological sequence of galaxy types. What made some collapsing gas clouds turn into elegant spiral systems like our own Milky Way, whereas others became smooth, featureless ellipticals? More fundamentally, does the taxonomic scheme introduced by Hubble in the 1920s have any physical relevance? The Space Telescope that bears Hubble's name is providing answers to these and other questions in the context of modern theories of structure formation.
Richard S Ellis, Roberto G Abraham, Jarle Brinchmann and Felipe Menanteau show how modern telescopes producing colourful images are pointing the way to understanding galaxy evolution.  相似文献   

Precession and nutation in the η Carinae binary system: evidence from the X-ray light curve     

Z. Abraham  D. Falceta-Gonçalves 《Monthly notices of the Royal Astronomical Society》2010,401(1):687-694

It is believed that η Carinae is actually a massive binary system, with the wind–wind interaction responsible for the strong X-ray emission. Although the overall shape of the X-ray light curve can be explained by the high eccentricity of the binary orbit, other features like the asymmetry near periastron passage and the short quasi-periodic oscillations seen at those epochs have not yet been accounted for. In this paper we explain these features assuming that the rotation axis of η Carinae is not perpendicular to the orbital plane of the binary system. As a consequence, the companion star will face η Carinae on the orbital plane at different latitudes for different orbital phases and, since both the mass-loss rate and the wind velocity are latitude dependent, they would produce the observed asymmetries in the X-ray flux. We were able to reproduce the main features of the X-ray light curve assuming that the rotation axis of η Carinae forms an angle of  29°± 4°  with the axis of the binary orbit. We also explained the short quasi-periodic oscillations by assuming nutation of the rotation axis, with an amplitude of about  5°  and a period of about 22 days. The nutation parameters, as well as the precession of the apsis, with a period of about 274 years, are consistent with what is expected from the torques induced by the companion star.  相似文献   

Preface     

Elisabete M. de Gouveia Dal Pino  Anthony L. Peratt  Gustavo A. Medina Tanco  Abraham C. -L. Chian 《Astrophysics and Space Science》1996,242(1-2):1-2

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Crustal Structure of Israel: Constraints From Teleseismic and Gravity Data   总被引：1，自引：0，他引：1  

Abraham Hofstetter  Lea Feldman  Yair Rotstein 《Geophysical Journal International》1991,104(2):371-379

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Hydraulic and salinity regime of two affected sites in the Yizre'el valley,Israel     

Abraham Gafni  Yigal Salingar 《水文研究》1992,6(1):55-65

Causes of recent salinization of numerous plots in the Yizre'el Valley of Israel were examined through a detailed field study of two severely affected sites. in particular, the theory of artesian influence on salt build-up in the upper cultivated soil layer was investigated. Two piezometer nests and 12 wells were installed to study the subsurface hydraulic regime. Water samples and soil extracts were taken to characterize the chemical composition down to 10m. No significant head differences were measured at the lower site, while at the upper site 96 per cent of the head that existed at the deep (7.5 m) artesian layer was dissipated within the overlying thick clay layer. Slight head differences were noted in the shallow layers. the deep-lying, coarse-textured aquifer differs markedly from the upper confining layers and constitutes an independent water body that has little relevance to surface processes. Chemical and hydrological analyses indicate that applied low-quality irrigation waters May, be the primary cause of downward-moving salinity and alkalinity which, in turn, affect soil permeability and site productivity.  相似文献   

A warm-season comparison of WRF coupled to the CLM4.0, Noah-MP,and Bucket hydrology land surface schemes over the central USA     

Matthew?S.?Van Den BroekeEmail authorView author&#;s OrcID profile  Andrew?Kalin  Jose?Abraham?Torres?Alavez  Robert?Oglesby  Qi?Hu 《Theoretical and Applied Climatology》2018,134(3-4):801-816

In climate modeling studies, there is a need to choose a suitable land surface model (LSM) while adhering to available resources. In this study, the viability of three LSM options (Community Land Model version 4.0 [CLM4.0], Noah-MP, and the five-layer thermal diffusion [Bucket] scheme) in the Weather Research and Forecasting model version 3.6 (WRF3.6) was examined for the warm season in a domain centered on the central USA. Model output was compared to Parameter-elevation Relationships on Independent Slopes Model (PRISM) data, a gridded observational dataset including mean monthly temperature and total monthly precipitation. Model output temperature, precipitation, latent heat (LH) flux, sensible heat (SH) flux, and soil water content (SWC) were compared to observations from sites in the Central and Southern Great Plains region. An overall warm bias was found in CLM4.0 and Noah-MP, with a cool bias of larger magnitude in the Bucket model. These three LSMs produced similar patterns of wet and dry biases. Model output of SWC and LH/SH fluxes were compared to observations, and did not show a consistent bias. Both sophisticated LSMs appear to be viable options for simulating the effects of land use change in the central USA.  相似文献   

Ecological Risk Assessment for seabird interactions in Western and Central Pacific longline fisheries     

Susan M. Waugh  Dominique P. Filippi  David S. Kirby  Edward Abraham  Nathan Walker 《Marine Policy》2012,36(4):933-946

The risk of seabird–fishery interactions in the Western and Central Pacific Ocean (WCPO) was examined by analysing the overlap of seabird distributions with tuna and swordfish pelagic longline fisheries managed by the Western and Central Pacific Fisheries Commission (WCPFC) and its constituent members. The study used spatially-explicit Productivity–Susceptibility Analysis (PSA). Key data inputs were species productivity, fishing effort, likelihood of capture and species density by region. The outputs tailored results to the needs of fisheries- and wildlife-managers, indicating areas of greatest risk of species interactions, species of greatest concern for population impacts, and the flags or fisheries most likely to contribute to the risk. Large albatross species were found to be most likely to suffer population effects when exposed to longline fishing activity, followed by the larger petrels from the genuses Procellaria, Macronectes and Pterodroma. A mixture of coastal states with nesting seabird populations in their Exclusive Economic Zones (New Zealand, Australia and United States of America), distant water fishing nations (Japan, Taiwan) and flags of convenience (Vanuatu) contributed 90% of the risk to seabird populations. Recommendations include enhancing the level of fisheries observer monitoring in areas indicated as high to medium risk for seabird interactions, and consideration of spatial management tools, such as more intensive or more stringent seabird bycatch mitigation requirements in high- to medium-risk areas. The methods used, and similar studies conducted in the Atlantic Ocean could lead to improved targeting of monitoring resources, and greater specificity in the needs for seabird-mitigation measures. This will assist in reducing seabird mortality in longline fishing operations and with more effective use of resources for fishery managers in both domestic fisheries and RFMOs.  相似文献   

赞比亚伊索卡东部片麻岩锆石U-Pb年代学、地球化学特征及岩石成因     

左立波  任军平  邱亮  王杰  古阿雷  孙宏伟  许康康  Alphet Phaskani DOKOWE  Abraham MUKANGWA  Daniel MALUNGA  Chisamba MWANSA  Peter CHIPUMBU 《地质学报》2021,95(4):1144-1158

赞比亚伊索卡东部位于伊鲁米德带上,伊鲁米德带是一个北东走向的褶皱俯冲带,位于赞比亚中东部,南部以新元古代赞比西带为界,北东至赞比亚-坦桑尼亚-马拉维边境,并以北西向古元古代乌本迪带为界.锆石U-Pb测年结果表明,黑云母二长片麻岩、二云母石榴斜长片麻岩、含石榴黑云母钾长片麻岩和含石榴黑云母斜长片麻岩的岩浆侵位年龄为1949±18 Ma～2025±15 Ma,形成于古元古代.岩石地球化学分析结果表明,伊索卡东部片麻岩岩浆为过铝质高钾钙碱性—钾玄系列;稀土配分模式明显呈右倾型,富含轻稀土,贫重稀土,铕和铈表现为极微弱的负异常;微量元素原始地幔标准化蛛网图显示,富集Rb、K、La、Pb、Nd、Sm等元素,亏损Ba、Nb、Ta、Ce、Sr、P、Ti等元素.根据伊鲁米德带的构造演化阶段,可以判断伊索卡东部片麻岩形成于乌萨加兰期.  相似文献