Geochemistry of salt marsh sediments deposited during simulated sea-level rise and consequences for recent and Holocene coastal development of NW Germany   总被引：2，自引：2，他引：0  

Kerstin Kolditz  Olaf Dellwig  Jan Barkowski  Thomas H. Badewien  Holger Freund  Hans-Jürgen Brumsack 《Geo-Marine Letters》2012,32(1):49-60

De-embankment in the salt marshes of the island of Langeoog was carried out in 2004, thereby inducing an artificial transgression within an area of 2.2 km². Material from three suspended matter traps (SMTs) located along a N–S transect was collected monthly between January 2006 and February 2007. Besides geochemical (major and trace elements) and grain-size analyses, the duration and height of water cover were continuously measured by pressure gauges during the sampling period at two sites, thus revealing inundation frequency (max. 280 year⁻¹) and level (max. 2.4 m). Generally, the silt-dominated SMT material exhibits a geochemical composition similar to that of suspended particulate matter from the adjacent Wadden Sea. However, distinctly increasing enrichments of TOC, P, Mn and Mo from the shoreline towards the higher salt marsh clearly indicate fractionation processes during material transport. Geochemical comparison with older Holocene coastal deposits reveals a mixture of brackish and tidal flat sediments, thus reflecting an early stage of sea-level rise and the development from a terrestrial towards a marine-dominated system. Sedimentation rates are higher than the local sea-level rise, as revealed by vertical salt marsh growth. Storm surges deliver the highest amounts of sediment and play an important role in salt marsh accumulation within the study area. Average accumulation rates of TOC (780 t year⁻¹), P (54 t year⁻¹) and Mn (5.2 t year⁻¹) in the de-embanked area suggest that the former sand-dominated sediments currently receive significant amounts of reactive organic-rich material, thus fostering biogeochemical cycling.  相似文献   

Paleolimnology of three Jackman Sound Lakes,Southern Baffin Island,based on down-core diatom analyses     

Kerstin M. Williams 《Journal of Paleolimnology》1990,4(3):203-217

Three lakes, informally named Lakes Inqua, Instaar and Mercer, from the Jackman Sound area in Southern Baffin Island were cored. The elevation of the three lakes are 36 m above high tide (aht), 10 m aht and 1 m aht. The cores from Lakes Inqua and Mercer penetrated the marine/lacustrine boundary; the core from Lake Instaar is estimated to have come within ca. 5 cm of this boundary. In addition, grab samples and water samples were retrieved from the lakes. The cores have been ¹⁴C dated (AMS). Emergence of the three lake basins from the sea occurred approximately 8650 BP (Lake Inqua), 8630 BP (Lake Instaar) and 7900 BP (Lake Mercer, averaged date). This suggests a very rapid rate (>5 m/100 yrs) of glacio-isostatic rebound for this area. Down-core analyses of diatom assemblages indicate that the paleolimnology in the three lakes was similar. The diatom analyses suggest a change in climate between approximately 8000 and 6000 BP, which is also reflected in the marine record from the same area, and the onset of the neoglacial period around 4500 to 3800 BP. A decrease in diatom-inferred pH is evident in the lakes' development and can probably be related to the general change of the watershed vegetation with time.  相似文献   

Historical ecology of a central California estuary: 150 years of habitat change   总被引：1，自引：0，他引：1  

Eric Van Dyke  Kerstin Wasson 《Estuaries and Coasts》2005,28(2):173-189

We investigated the historical ecology of Elkhorn Slough, a 1,200 ha tidal wetland system in central California. The goal of this study was to identify patterns of change in the extent and distribution of wetland habitats during a 150-yr period and to investigate the causes of these changes. Using a geographic information system (GIS), we interpreted historic maps, charts, and aerial photographs. We created a series of summary maps to illustrate and quantify changes in tidal flow and habitat types at six representative historical periods. With the aid of custom software tools, we performed semi-automated spatial analysis of historic aerial photographs to quantify changes in marsh cover at fixed quadrats and tidal creek width at fixed cross sections. Our multiscale analysis documents dramatic shifts in the distribution of habitat types resulting from anthropogenic modifications to the hydrology of the slough. More than half of the marshlands were diked, and more than two thirds have either degraded or been converted to other habitat types. The construction of an artificial mouth abruptly transformed the wetland system from depositional to highly erosional, enlarging channels, widening creeks, and converting marsh to intertidal mudflat or open water. Increased tidal amplitude and velocity are the likely causes. In recent decades, levee failure and intentional breaching have restored the acreage under tidal influence to nearly historic levels, but recolonization of former wetlands by salt marsh vegetation has been minimal. Degraded former marshland and unvegetated mudflat are now the dominant habitat types at Elkhorn Slough. The rate of habitat change remains high, suggesting that a new equilibrium may not be reached for many decades. This study can help tidal wetland managers identify patterns and mechanisms of habitat change and set appropriate conservation and restoration goals.  相似文献   

The contributions of zooarchaeology to historical ecology in the neotropics     

Peter W. Stahl   《Quaternary International》2008,180(1):5

Zooarchaeology can contribute to issues that lie beyond the traditional boundaries of archaeology and paleobiology. The techniques and methods of zooarchaeology are essential to an historical ecology that has emerged as a powerful perspective for understanding indigenous peoples and landscapes of the neotropics, both in the present and the past. In order to realize fully its potential contributions to historical ecology, zooarchaeology must reject the arbitrary dichotomization of culture and nature and a viewpoint that considers indigenous peoples as passive reactors to environments rather than as active creators of human landscapes. Zooarchaeology must avoid the seduction of neo-Malthusian assumptions that underlie many cherished models, and should do more than simply list extinctions at the hands of prehistoric humans. Instead, zooarchaeologists should focus on the study of past human landscapes, explore dynamic disturbances and the human maintenance of habitat mosaics, record the infrastructure of intensive agriculture, and understand the indigenous logic of past biodiversity management. When archaeologists study the landscapes of previous human populations, they are engaged in the practice of historical ecology.  相似文献   

Vegetation-based bioindication of humus forms in coniferous mountain forests     

Kerstin Anschlag  Dylan Tatti  Niels Hellwig  Giacomo Sartori  Jean-Michel Gobat  Gabriele Broll 《山地科学学报》2017,14(4):662-673

Humus forms, especially the occurrence and the thickness of the horizon of humified residues(OH), provide valuable information on site conditions.In mountain forest soils, humus forms show a high spatial variability and data on their spatial patterns is often scarce. Our aim was to test the applicability of various vegetation features as proxy for OH thickness.Subalpine coniferous forests dominated by Picea abies(L.) H. Karst. and Larix decidua Mill. were studied in the Province of Trento, Italian Alps,between ca. 900 and 2200 m a.s.l. Braun-Blanquet vegetation relevés and OH thickness were recorded at152 plots. The vegetation parameters, tested for their suitability as indicators of OH thickness,encompassed mean Landolt indicator values of the herb layer(both unweighted and cover-weighted means) as well as parameters of vegetation structure(cover values of plant species groups) calculated from the relevés. To our knowledge, the predictive power of Landolt indicator values(LIVs) for humus forms had not been tested before. Correlations between OH thickness and mean LIVs were strongest for the soil reaction value, but indicator values for humus,nutrients, temperature and light were also significantly correlated with OH thickness. Generally,weighting with species cover reduced the indicator quality of mean LIVs for OH thickness. The strongest relationships between OH thickness and vegetation structure existed in the following indicators: the cover of forbs(excluding graminoids and ferns) and the cover of Ericaceae in the herb layer. Regression models predicting OH thickness based on vegetation structure had almost as much predictive power as models based on LIVs. We conclude that LIVs analysis can produce fairly reliable information regarding the thickness of the OH horizon and, thus,the humus form. If no relevé data are readily available,a field estimation of the cover values of certain easily distinguishable herb layer species groups is much faster than a vegetation survey with consecutive indicator value analysis, and might be a feasible way of quickly indicating the humus form.  相似文献