Gene flow and demographic history of the mangrove crab Neosarmatium meinerti: A case study from the western Indian Ocean     

Lapo Ragionieri  Stefano Cannicci  Christoph D. Schubart  Sara Fratini 《Estuarine, Coastal and Shelf Science》2010

Most marine organisms are characterized by at least one planktonic phase during their life history, potentially allowing interconnection of populations separated by several hundred kilometers. For many years, the idea that marine species are genetically homogenous throughout their range of distribution, due to passive larval transport, has been a paradigm. Nowadays, a growing number of studies underline the existence of boundaries in the marine realm and highlight how larval dispersal is a complex process depending on biotic as well as abiotic factors. Marine fragmented habitats, such as atolls, mangroves and estuaries, are optimal systems for investigating the marine dispersion process under a metapopulation approach, since populations can be geographically defined a priori as opposed to those occupying open marine environments. Within this frame, the present paper investigates the population genetic structure and the demographic history of the mangrove crab Neosarmatium meinerti within the western Indian Ocean by partial sequences of the mitochondrial DNA cytochrome oxidase subunit I. A total of 167 specimens were sampled from six mangrove sites distributed along the East African coast, from Kenya to South Africa, also including a mangrove forest located on Mahé Island, Seychelles. A sharp genetic break between the mainland and the Seychelles is recorded, revealing the existence of two historically distinct groups that can be defined as independent evolutionary units. Gene flow along the East African coast appears to be high enough to form a single metapopulation, probably by means of stepping stone populations. Otherwise, this mainland metapopulation is currently under expansion through a gradual moving front from the subtropical toward the equatorial populations.  相似文献   

Transpiration and plant water relations of evergreen woody vegetation on a recently constructed artificial ecosystem under seasonally dry conditions in Western Australia     

Willis Gwenzi  Erik J. Veneklaas  Timothy M. Bleby  Isa A.M. Yunusa  Christoph Hinz 《水文研究》2012,26(21):3281-3292

Understanding transpiration and plant physiological responses to environmental conditions is crucial for the design and management of vegetated engineered covers. Engineered covers rely on sustained transpiration to reduce the risk of deep drainage into potentially hazardous wastes, thereby minimizing contamination of water resources. This study quantified temporal trends of plant water potential (ψ_p), stomatal conductance (g_s), and transpiration in a 4‐year‐old evergreen woody vegetation growing on an artificial sandy substrate at a mine waste disposal facility. Transpiration averaged 0.7 mm day^?1 in winter, when rainfall was frequent, but declined to 0.2 mm day^?1 in the dry summer, when the plants were quite stressed. In winter, the mean ψ_p was ?0.6 MPa at predawn and ?1.5 MPa at midday, which were much higher than the corresponding summer values of ?2.0 MPa and ?4.8 MPa, respectively. The g_s was also higher in winter (72.1–95.0 mmol m^?2 s^?1) than in summer (<30 mmol m^?2 s^?1), and negatively correlated with ψ_p (p < 0.05, r² = 0.71–0.75), indicating strong stomatal control of transpiration in response to moisture stress. Total annual transpiration (147.2 mm) accounted for only 22% of the annual rainfall (673 mm), compared with 77% to 99% for woody vegetation in Western Australia. The low annual transpiration was attributed to the collective effects of a sparse and young vegetation, low moisture retention of the sandy substrate, and a superficial root system constrained by high subsoil pH. Amending the substrate with fine‐textured materials should improve water storage of the substrate and enhance canopy growth and deep rooting, while further reducing the risk of deep drainage during the early stages of vegetation establishment and in the long term. Overall, this study highlights the need to understand substrate properties, vegetation characteristics, and rainfall patterns when designing artificial ecosystems to achieve specific hydrological functions. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Continuous measurements of hydrographic and hydrochemical parameters in surface waters of the Baltic Sea and the North Sea in march and april 1991     

Dr. Christoph Osterroht 《Ocean Dynamics》1994,46(2):115-130

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Palaeozoic flysch series in the Coastal Cordillera of Northern Chile     

Dr. Christoph Breitkreuz  Heinrich Bahlburg Dipl.-Geol. 《International Journal of Earth Sciences》1985,74(3):565-572

A discontinuous outcrop of Palaeozoic rhythmic clastites appears in the North Chilean Coastal Cordillera. The Formación El Toco (21°15–22°15S) whose scarce flora points to a presumably Upper Devonian age forms the northernmost part of the outcrop. It is discordantly overlain by Lower Jurassic volcanics (Fm. La Negra), its base, however, is not exposed. Hercynian heteromorphous deformation led to predominantly NW trending folds strongly inclined mostly to the SW. Chevron-like folds of 0.1 to 30 m occur locally and seem to display properties transitional between synsedimentary-gravitational and early tectonic deformation.The series which is at least 2300 m thick consists of proximal, in parts pebbly turbidites with non-turbiditic finegrained intercalations. Incomplete BOUMA-sequences frequently begin with A-beds of grey to green immature, badly sorted coarse sandstones of up to 6 m thickness containing isolated quartz- and pelite-clasts.Measurements of flute casts and f oresets show palaeocurrents which came from NW and NNE. Along with petrographic observations they indicate southward directed transport of detritus from low metamorphic sedimentary and magmatic source areas into an Upper Devonian nonvolcanic basin.

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Zusammenfassung Die Formación El Toco ist der nördlichste Aufschluß einer Kette von Vorkommen paläozoischer rhythmischer Klastite in der nordchilenischen Küstenkordillere. Diese Formation (21°15–22°15S), deren spärliche Flora vorbehaltlich dem Oberdevon zuzuordnen ist, wird diskordant von unterjurassischen Vulkaniten (Fm. La Negra) überlagert —das Liegende ist nicht aufgeschlossen. Variszische heteromorphe Deformation führte zu vorherrschend NW-streichender Faltung, die meist starke SW-Vergenz zeigt. Lokal tritt eine scharfe Verfaltung im 0,1 bis 30 m-Bereich hinzu, die sowohl synsedimentär-gravitative als auch frühtektonische Deformationsmerkmale zeigt.Die mindestens 2300 m mächtige Serie ist ein proximaler Flysch mit z. T. kiesführenden Turbiditen, in die nichtturbiditische feinkörnige Partien eingeschaltet sind. Die unvollständigen BOUMA-Sequenzen beginnen häufig mit einer aus grauen bis grünen unreifen und schlechtsortierten Grobsandsteinen bestehenden A-Division von bis zu 6 m Mächtigkeit, die isolierte Quarz- und Pelitklasten enthalten kann.Flute cast- und Foreset-Messungen weisen auf Paläoströmungsrichtungen aus NW und NNO hin. Zusammen mit petrographischen Analysen läßt sich daraus ein südwärts gerichteter Transport von schwachmetamorphsedimentärem und magmatischem Detritus in ein oberdevonisches nicht-vulkanisches Becken ableiten.

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Résumén Ritmitas clásticas de edad paleozoica forman afloramientos discontinuos en la Cordillera de la Costa del Norte de Chile. La Formación El Toco (21°15–22°15S), que contiene una flora escasa de probable edad Devónico Superior, constituye la parte más septentrional de estos afloramientos. La base no se conoce, mientras que el techo infrayace discordantemente a volcanitas jurásicas inferiores (Fm. La Negra). Deformaciones hercínicas heteromórficas llevan a la formación de pliegues orientados predominantemente al NW inclinados fuertemente al SW. Localmente aparecen pliegues en forma de chevron de un tamano de 0.1 a 30 m que muestran caracteristicas de deformación transicional entre sinsedimentana-gravitativa y tectónica temprana.La serie que tiene una potencia de por lo menos 2300 m consiste en turbiditas proximales parcialmente con gravas e intercalaciones finas no-turbidíticas. Secuencias incompletas de BOUMA empiezan frecuentemente con capas de la division A (espesor maximo 6 m) los cuales se componen con frecuencia de areniscas gruesas gris-verdes, composicionalmente inmaduras y mal seleccionadas, con clastos aislados de cuarzo y pelita.Medidas de flute casts y foresets muestran paleocorrientes provenientes de NW y NNE. Junto con observaciones petrográficas, las paleocorrientes indican un transporte de material detrítico, originado de áreas con rocas sedimentarias, metamórficas de bajo grado e ígneas, dirigido al sur hacia una cuenca no volcánica de edad Devónico Superior.

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- , - . (21°15 - 22°15 ) , ; - ( -). . , . . NW , SW. 0,1 30 , , - , - . 2300 , . , . , NW a NNE. , , .

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Atmospheric effects from post-nuclear fires     

Paul J. Crutzen  Ian E. Galbally  Christoph Brühl 《Climatic change》1984,6(4):323-364

During a large nuclear war, the atmosphere would be loaded with huge quantities of pollutants, which are produced by fires in urban and industrial centers, cultivated lands, forests and grasslands. Especially detrimental are the effects of light absorbing airborne particles. An analysis of the amounts of the various types of fuels which could burn in a nuclear war indicates that more than 10¹⁴ g of black smoke could be produced by fires started by the nuclear explosions. Due to this, the penetration of sunlight to the earth's surface would be reduced greatly over extended areas of the northern hemisphere, maybe even globally. This could temporarily cause extreme darkness in large areas in midlatitudes and reduce crop growth and biospheric productivity.This situation would last for several weeks and cause very anomalous meteorological conditions. Much solar radiation would be absorbed in the atmosphere instead of at the earth's surface. The land areas and lower atmosphere would, therefore, cool and the overlying atmosphere warm, creating strong vertical thermal stability in a highly polluted atmosphere. For extended periods and in large parts of the world, weather conditions would be abnormal. The resulting cold, probably freezing, temperatures at the ground would interfere severely with crop production during the growing season and cause extreme conditions for large sections of the biosphere. The combination of lack of sunlight, frost and other adverse meteorological conditions would add enormously to the already huge problems of the survivors.  相似文献   

Further Studies Of Atmospheric Turbulence In Layers Near The Surface: Scaling The Tke Budget Above The Roughness Sublayer   总被引：2，自引：0，他引：2  

Paul Frenzen  Christoph A. Vogel 《Boundary-Layer Meteorology》2001,99(2):173-206

The second of two experimental studies of the TKE budget conducted on sites of different roughness is described, and results are compared. The first took place within a shallow layer above a small field of mostly bare, cultivated soil; the second was carried out above a roughness sublayer of significant depth on an extensive plain of tall dry grass. Budget terms observed in the second study were scaled with a modified u which compensated for effects of an unusually large stress gradient and ensured that the _m functions would be collinear. By showing that the modification becomes negligible in smaller gradients, it is demonstrated that in normal conditions, budgets observed above significant roughness sublayers should be normalized by scaling in terms of the unreduced Reynolds stress at the sublayer's upper surface. This procedure is shown to be consistent with the expectation that TKE budgets in layers near the surface all scale in fundamentally the same way.Other findings include: (1) the fact that most _m functions previously reported are not quite collinear is attributed to a type of overspeeding known to affect three-cup anemometers; (2) revised _m functions, collinear and largely free of the effects of overspeeding, are determined from a well-established characteristic of the linear _m relation for the stable case; (3) data that define collinear _m functions can also be represented with single hyperbolic curves; (4) dissipation is found to be 10 to 15% too small to balance total TKE production in unstable and neutral conditions and to decrease with increasing z/L in thestable regime; and (5) new relations for based on the observed behaviour of the dissipation deficit provide an improved closure for the set of equations that express the budget terms as functions of _m and z/L.  相似文献   

Detection and analysis of coherent structures in urban turbulence   总被引：3，自引：0，他引：3  

C. Feigenwinter  R. Vogt 《Theoretical and Applied Climatology》2005,81(3-4):219-230

Summary The continuous wavelet transform provides a suitable tool to visualize the vertical structure of turbulence and to detect coherent structures in turbulent time series. This is demonstrated with a simple example of an artificially ramp structured time series. In this study turbulence data, i.e. the fluctuations of the horizontal wind components u′ and v′, the vertical component w′ and temperature T′, sampled with 20.83 Hz and measured simultaneously at three levels (z/h=1.5, 2.1 and 3.2, with z as the sensor height and h the height of the roughness elements) over an urban canopy in the inner city of Basel, Switzerland, are analyzed. The detection of the coherent structures was performed using the Mexican hat wavelet and the zero-crossing method. The analysis for unstable conditions shows that organized structures (ejection-sweep cycles) cover about 45% of the total run time. A conditional average from a total of 116 detected ejection-sweep sequences during 7 hours was calculated over a time window of 100 seconds. This dominating time scale was derived from peak frequencies of the wavelet spectra as well as from the Fourier spectra. It is shown that the normalized amplitudes of fluctuations of temperature and longitudinal wind speed during the events are largest at the lowest measurement level just above the canopy and decrease with increasing distance from the roughness elements. A comparison of related studies over different non-urban surfaces (mainly forests) shows that the shape of conditionally averaged ejection-sweep sequences is very similar for all canopies, however, the dominating time scale in general increases the rougher the surface is and the higher the roughness elements are.  相似文献   

Morphotectonic evolution of two depressions at the southern border of the Baikal rift system     

Henri Vogt  Thea Vogt 《Geomorphology》2007,86(3-4):480-495

Detailed study of two dry depressions in the Baikal rift system: the E–W Khoito Ghol-Tunka-Bistraya depression and the SW–NE Gusinoje–Ivolga depression, aims to provide a better understanding of tectonic control on the intershoulder relief evolution after the rift opened. Both depressions are grabens and both feature a suite of 10–20 km-wide basins alternating with more or less massive highs. Field and laboratory analysis shows that this pattern is of recent tectonic origin and that local breaking-up and subsidence followed the general sinking which originally formed the grabens. The subsidence belts seem to have gradually shifted north and northeastwards. Geomorphological analysis reveals that in both depressions the highs are remnants of a former pediment which was broken up. The young basins display numerous relevant hydrographic anomalies of the secondary channels and a general water-logging. They also suggest that the subsidence belts have gradually shifted north-and northeastwards. In the Gusinoje–Ivolga depression evidence was found of a Plio-Pleistocene river course, parallel to the Selenga river, which was later dismantled by the breaking-up. This depression, parallel to the Baikal rift and belonging to the Mesozoic system of grabens in the Caledonian fold belt, seems to have been included into the general system of rifts during the Pliocene tectonic phase. As for the main hydrographic axes, the Selenga river was set on a Palaeogene-age planation surface before the first tectonic phase and kept its original course. The Irkut river flowed in the Khoito Gol–Tunka–Bistraya depression after the first tectonic phase and was not affected by the later breaking-up. In contrast, the secondary drainage network is largely discordant. Despite their different geotectonic contexts, the two depressions show a similar development of relief pattern,which poses the question of the style of rift dynamics after the main Pliocene tectonic phase.  相似文献   

Parameterisation of the vertical transport in a small thermally stratified lake     

Christoph von Rohden  Karl Wunderle  Johann Ilmberger 《Aquatic Sciences - Research Across Boundaries》2007,69(1):129-137

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Conceptual examination of climate–soil controls upon rainfall partitioning in an open-fractured soil II: Response to a population of storms     

Iain Struthers  Christoph Hinz  Murugesu Sivapalan 《Advances in water resources》2007

A simple two-domain bucket model of fractured soil was coupled with a stochastic model of rainfall variability, in order to investigate the climate and soil controls upon the stochastic properties of the triggering of fracture flow and surface runoff, and the partitioning of rainfall between the matrix and fracture domains and surface runoff. Conventionally, soils are regarded as time domain filters between rainfall and hydrological response. This investigation highlights an additional type of threshold filtering especially important in understanding the infiltration behaviour of fractured soils, for which an event-based characterisation of rainfall in modelling is crucial. A priori-definable indices were derived which are capable of describing elements of this threshold filtering, by allowing the statistical properties of fracture flow- and surface runoff-triggering storms (i.e., mean and variance of storm duration, intensity and effective inter-storm period, as well as cumulative partitioning of rainfall), to be inferred directly from average storm and soil properties. Using these indices, the long-term response of fractured soils, including the long-term hydrological importance of fractures, can be estimated without simulation.  相似文献