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Sand Deposition (sand + deposition)

Distribution by Scientific Domains

Earth and Environmental Science	50%

Selected Abstracts

Disturbance and recovery of microbial community structure and function following Hurricane Frances

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2007
Anthony C. Yannarell
Summary Disturbance and recovery influence microbial community structure and ecosystem functions in most natural environments. This study from a hypersaline Bahamian lagoon details the response of a benthic cyanobacterial mat to disturbance by Hurricane Frances, a category-4 storm. Clone libraries of cyanobacterial small subunit r-RNA genes and nitrogenase genes revealed significant shifts in cyanobacterial and diazotroph community composition following the hurricane. Post-hurricane clone libraries were dominated by sequences that had been rare in pre-hurricane communities. In spite of this dominance shift, re-colonizing mat communities performed nitrogen fixation and photosynthesis at rates within the normal range of variation measured in the mat at similar salinities. There was a tendency for nitrogen fixation rates from mats re-colonizing sites with hurricane-related sand deposition to be higher than those from mats re-colonizing sites without significant sand deposition. This suggests that the altered communities responded to a carbon : nitrogen imbalance that was particularly pronounced in areas subjected to disturbance by sand burial. The post-hurricane dominance of organisms that had been previously rare suggests that pre-hurricane diversity and functional redundancy contributed to the rapid recovery of ecosystem function in the post-disturbance environment. [source]

Preliminary soil micromorphology studies of landscape and occupation history at Tabon Cave, Palawan, Philippines

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 7 2007
Helen Lewis
Preliminary soil micromorphology study of cultural sediments at Tabon Cave, Philippines, supports interpretations of sporadic occupation in the Paleolithic. The presence in some deposits of authigenic minerals potentially related to altered cultural materials, such as ash, needs further investigation. Later in the sequence there is a marked change in local depositional processes, with the onset of significant quartz sand deposition in layers dating from the Middle to Late Holocene. This could relate to beach development in the area. Future sedimentological study and dating would confirm this interpretation, which suggests that in appropriate settings, stratified cave sediments could be useful for the study of regional sea level rise. © 2007 Wiley Periodicals, Inc. [source]

The Devensian periglacial record on Thanet, Kent, UK

PERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2003
J. B. Murton
Abstract The Devensian periglacial record on Thanet, Kent, is traced from c. 88 to 74,ka and from c. 24 to 12,ka by optical luminescence dating of aeolian sand and silt in the periglacial stratigraphy. The record commences before 88,ka with valley cutting at Pegwell Bay. Valley filling had begun by c. 88,ka and continued to at least 74,ka, coinciding with a major episode of loess deposition in Europe. Permafrost aggradation commenced before c. 21,ka, brecciating near-surface chalk by ice segregation in permafrost and the overlying active layer. Deposition of aeolian sand (coversand) occurred at c. 24,21,ka, correlating with the Older Coversand I in mainland Europe. Permafrost degradation commenced at c. 21,ka, probably due to climate warming during Greenland Interstadial 2. The resulting active-layer deepening through ice-rich permafrost initiated soft-sediment deformation and formation of large-scale patterned ground in an active layer c. 2,m deep. Renewed permafrost aggradation between c. 21.25 and 18,ka coincided with climate cooling during Greenland Stadial 2c and led to cryoturbation in a thinner active layer. Final permafrost degradation commenced no later than c. 14.7,ka, that is, the start of Greenland Interstadial 1e, and may have occurred to some extent during the climate warming associated with Greenland Stadial 2b (c. 19.5,16.9,ka). Renewed deposition of aeolian sand took place at c. 15.5,ka, coincident with loess deposition on Thanet. A final episode of aeolian sand deposition occurred at 12,ka, correlating with the Younger Coversand deposits that are widespread in northwest Europe and formed during Greenland Stadial 1. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Recruitment limitation along disturbance gradients in river flood plains

JOURNAL OF VEGETATION SCIENCE, Issue 1 2005
W.H.J.M. van Eck
Abstract. Question: Along river floodplains lower distribution limits of plant species seem largely determined by their tolerance to rarely occurring floods in the growing season. Such distribution patterns remain fixed for many years suggesting additional effects of winter floods at lower positions. Our objective was to investigate the direct and indirect effects of winter floods on colonization of floodplains in a series of field experiments. Location: River Rhine, The Netherlands. Methods: We measured the direct effects of winter floods on seedling survival and seed removal and survival at low and high floodplain elevation. Indirect effects of winter flooding through changes in the soil were investigated by measuring seedling emergence on soil transplants that were exchanged between high and low floodplain elevation. To investigate indirect effects of floods on the germination environment through changes in the vegetation structure, we measured the effects of vegetation removal on recruitment of sown species. Results: Recruitment was seed limited at both floodplain elevations. An additional effect of vegetation removal on seedling emergence was also observed. Soil types from both zones did not differently affect seedling emergence. Seeds were not removed from the soil surface by a single winter flood. Moreover, seeds remained viable in the soil for at least two years, while the experimental plots were flooded several times during the experimental period. During one of those floods a thick sand layer was deposited at the low zone and subsequently no seedlings were observed anymore. Conclusions: Colonization of low floodplain zones in years between subsequent summer floods is prevented by seed limitation while the direct effects of winter floods are limited except for irregularly occurring sand depositions. [source]