Small-scale spatial variation of benthic algal assemblages in a peat bog   总被引：1，自引：0，他引：1  

Kate?ina ?erná 《Limnologica》2010,40(4):315-321

Spatial patterns on a very small scale (10 cm), and the effect of artificial barriers on the composition of phytobenthic algal assemblages along two transects within different microhabitat types were investigated. Samples were taken in a peat bog along linear transects on a scale of 10 cm, and water chemistry was examined. The distribution of algae along both transects was influenced by both spatial distance and environmental conditions in similar proportions. Differences in species composition in various parts of the transects were observed, but this pattern was primarily related to the abundance of species, rather than to their presence/absence in samples. Similarity in species composition correlated with spatial distance and environmental parameters in both microhabitat types. I concluded that, given a homogenous environment on a small scale, spatial distribution of algae is affected by both the environmental conditions of the microhabitats and their dispersal limitations. Moreover, an artificial barrier constituted an obstruction for water and nutrient flow, as well as algal migration, and had an impact on species composition.  相似文献   

A critical review of the glaciomarine model for Irish sea deglaciation: evidence from southern Britain,the Celtic shelf and adjacent continental slope     

J. D. Scourse  M. F. A. Furze 《第四纪科学杂志》2001,16(5):419-434

In support of their ‘glaciomarine’ model for the deglaciation of the Irish Sea basin, Eyles and McCabe cited the occurrence of distal glaciomarine mud drapes onshore in the Isles of Scilly and North Devon, and of arctic beach‐face gravels and sands around the shores of the Celtic Sea. Glacial and sea‐level data from the southern part of the Irish Sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model. The suggestion that the glacial sequences of both the Isles of Scilly and Fremington in North Devon are glaciomarine mud drapes is rejected. An actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south‐central Celtic Sea. Relative sea‐levels were lower, and therefore glacio‐isostatic depression less, than envisaged in the glaciomarine model. Geochronological, sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the Celtic Sea and English Channel were deposited at, or during regression soon after, interglacial eustatic highstands. Evidence for ice‐rafting at a time of high relative sea‐levels is restricted to a phase(s) earlier than the Late Devensian. These data indicate that the raised beach sequences have no bearing on the style of Irish Sea deglaciation. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

BOOK REVIEWS     

《The Professional geographer》1986,38(4):430-457

Book Reviewed in this article: Latin America: Case Studies . Richard G. Boehm and Sent Visser Locality and Rurality: Economy and Society in Rural Regions . Tony Bradley And Philip Lowe The City and the Grassroots . Manuel Castells Geopolitics and Conflict in South America. Quarrels among Neighbors . Jack Child Post-Industrial America: A Geographical Perspective . David Clark Coastal Research: UK Perspectives . Malcolm W. Clark A Rural Policy for the EEC? Hugh Clout Peasant Agriculture in Assam: A Structural Analysis . M. M. Das . Environmental Change and Tropical Geomorphology . I. Douglas and T. Spencer Advances in Abandoned Settlement Analysis: Application to Prehistoric Anthrosols in Colombia, South America . Robert C. Eidt Measuring Culture . Jonathan L. Gross and Steve Rayner North America: A Human Geography . Paul Guinness and Michael Bradshaw A Geographical Bibliography for American Libraries . Chauncy D. Harris et al. Geography and the Urban Environment: Progress in Research and Applications, Vol. VI . D. T. Herbert and R. J. Johnston Changes in Global Climate: A Study of the Effect of Radiation and Other Factors During the Present Century . K. Ya . Kondrat'ev . Rural Development and the State: Contradictions and Dilemmas in Developing Countries . David A. M. Lea and D. P. Chaudhri The Martial Metropolis: U.S. Cities in War and Peace . Roger W. Lotchin The Climate of the Earth . Paul E. Lydolph . Weather and Climate . Paul E. Lydolph . Spatial Divisions of Labor: Social Structures and the Geography of Production . Doreen Massey . Panorama of the Soviet Union . N. Mikhailov . Soviet Armenia . K. S. Demirchian . USSR: Geography of the Eleventh Five-Year Plan Period . K. Spidchenko . Planung und Verwirklichung der Wiener Ringstrassenzone (Planning and Materialization of the Ringstrasse-Zone of Vienna). Kurt Mollik , Hermann Reining , Rudolf Wurzer . The American West Transformed: The Impact of the Second World War Gerald D. Nash . An Overview of the Survey of Income and Program Participation . Dawn Nelson , David Mc Millen, and Daniel Kasprzyk . Phenomenology, Science and Geography: Spatiality and the Human Sciences . John Pickles . Biological Diversification in the Tropics . Ghillean T. Prance Die Wanderviehwirtschaft im gebirgigen Westen der U.S.A. und ihre Auswirkungen im Naturraum . Gisbert Rinschede . Social and Economic Aspects of Radioactive Waste Disposal: Considerations for Institutional Management . World-Wide Weather . K. Takahashi Coastal Geomorphology in Australia . B. G. Thom Settlement System in Rural India: A Case Study of the Lower Ganga-Yamuna Doab . Ram Chandra Tiwari . Computer Programming for Geographers . David J. Unwin and John A. Dawson . Late Quaternary Environments of the Soviet Union . A. A. Velichko, ed . H. E. Wright , Jr. and C. W. Barnosky Ethics in Planning . Martin Wachs  相似文献   

From peat bog to lignite seam: a new method to calculate the consolidation coefficient of lignite seams,Wielkopolska region in central Poland     

M. Widera  G. Jachna-Filipczuk  R. Kozula  S. Mazurek 《International Journal of Earth Sciences》2007,96(5):947-955

Only one quantitative method is described in the literature to estimate the consolidation coefficient of lignite seams. More studies concentrate on the compaction of plant tissues, which explains why the obtained results are overestimated. Moreover, most studies do commonly not determine the consolidation of the whole peat bog but usually those of some of its elements only. We propose a new approach, which conceptually is fairly close to the Hager et al. (Fortschr Geol Rheinld Westf 29:319–352, 1981) method. Our method has been tested on an example of the first Middle-Polish Lignite Seam and the second Lusatian Lignite Seam from some Wielkopolska lignite deposits in central Poland. The consolidation coefficients, C _c, range between 2.34 and 2.56 for the second Lusatian Lignite Seam and between 1.80 and 2.14 for the first Middle-Polish Lignite Seam.  相似文献   

Dynamics of attached bacteria at the water-sediment interface in a mesotrophic swampy bog of Japan     

Motoo Utsumi  Yukihiro Nojiri  Nozomi Ytow  Humitake Seki 《Journal of Oceanography》1998,54(2):179-184

The population dynamics of attached bacteria at the water-sediment interface were studied in a mesotrophic swampy bog, Matsumi-ike, near Tsukuba, Japan. The density of attached bacteria was higher at the sediment boundary layer than in the water column, and low inside the sediment (deeper, than 10 mm below the sediment surface) throughout the year. The density of bacteria attached on the glass slide was highest during spring when the source of organic matter in the water column was mainly withered cattail, and gradually decreased toward summer, while the phytoplankton became the dominant source of organic matter in the water column. The epibacterial populations in the water column and at the boundary showed almost the same seasonal fluctuation in attachment and detachment rates. However, bacterial growth rates did not show the same seasonal fluctuation, and annual average growth rates on the glass slides were all lower than that of bacterioplankton (free-living bacteria in water) in the water column.  相似文献   

A proxy record of late Holocene climate change from May Moss,northeast England     

R. C. Chiverrell 《第四纪科学杂志》2001,16(1):9-29

Quantitative reconstruction of changes in mire surface wetness has been used to reconstruct proxy climate from an upland ombrotrophic blanket mire on the North York Moors in northeast England (May Moss). Testate amoebae, plant macrofossil and humification analyses were carried out for six peat profiles. Transfer functions are used to generate estimates of water table levels from the testate amoebae stratigraphy, which complement the semi‐quantitative indications of changing surface wetness provided by plant macrofossil and humification analysis. ¹⁴C dates provide the chronology for the stratigraphy. Differences were encountered between AMS ¹⁴C dates on pure Sphagnum remains and radiometric dates on bulk peat from the same horizon, which perhaps arise from the heterogeneity of peat. Replicate palaeoecological analysis of adjacent cores identifies consistency within testate amoebae and plant macrofossil stratigraphies, and reveals a strong agreement between the water table level proxies. The record of hydrological changes at sites across May Moss are in synchrony, and so climate change is the most likely cause of the moisture fluctuations. Changes to a wetter or cooler climate were identified cal. ad 260–540, ca. ad 550–650, cal. ad 670–980, ca. ad 1350–1450, cal. ad 1400–1620 and ca. ad 1700–1800. Periods with a drier or warmer climate precede all of these wet shifts, with particularly dry periods between cal. ad 650–860 and 690–980 and between cal. ad 1290–1410 and 1400–1620. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

New relative sea-level curves for the southern Scott Coast,Antarctica: evidence for Holocene deglaciation of the western Ross Sea     

Brenda L. Hall  George H. Denton 《第四纪科学杂志》1999,14(7):641-650

Here we present new relative sea-level (RSL) curves developed from Holocene-aged raised beaches along the southern Scott Coast of the western Ross Sea, Antarctica. Fifty-four dates of marine shells, seal skin and elephant seal remains incorporated within raised beaches during storms afford a chronology for these curves. All of the curves show the same pattern and timing of RSL change within a small range of error. The best-dated curve suggests that final unloading of grounded Ross Sea ice from the southern Scott Coast and McMurdo Sound region occurred shortly before 6500 ¹⁴C yr BP. This age is consistent with glacial geological evidence that places deglaciation between 5730 and 8340 ¹⁴C yr BP. Our data strongly suggest that grounding-line retreat of the Ross Sea ice sheet southward through the McMurdo Sound region occurred in mid- and late Holocene time. If this is correct, then rising sea level could not have driven ice recession to the present-day grounding line on the Siple Coast, because global deglacial sea-level rise was essentially accomplished by mid-Holocene time. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献