Postglacial vegetation and climatic change in the upper Peace River district, Alberta

1986 ◽  
Vol 64 (10) ◽  
pp. 2305-2318 ◽  
Author(s):  
James M. White ◽  
Rolf W. Mathewes
Keyword(s):  
Climatic Change ◽  
Pollen Analysis ◽  
Sediment Cores ◽  
Growing Season ◽  
Radiometric Dating ◽  
Glacial Meltwater ◽  
Peace River ◽  
Spruce Decline ◽  
Paper Birch ◽  
Relict Vegetation

Pollen analysis and radiometric dating of sediment cores from two lakes in the Saddle Hills, Peace River district, Alberta, were used to investigate postglacial vegetation and climatic change. A poplar – willow – sage – grass – sedge zone began about 11 700 ± 260 years BP. A distinct pine and spruce rise indicates the local presence of conifers. Peace River spruce could have served as a source for spruce in the Yukon, transported by glacial meltwater conceivably as early as about 11 100 years BP. A paper birch rise and spruce decline between about 8700 and 8200 years BP is likely due to fires during a period of enhanced seasonality. It is suggested that subsequent weakening of the anticyclone associated with the Laurentide ice lengthened the growing season, permitting pine to be the major fire successor to spruce. During the pine peak ca. 7400 years BP there was no grassland over the Saddle Hills, so the Peace River grasslands cannot be explained as Hypsithermal relict vegetation. Conditions similar to the present were apparently reached by about 5000 years BP.

Holocene vegetation and climatic change in the Peace River district, Canada

1982 ◽  
Vol 19 (3) ◽  
pp. 555-570 ◽  
Author(s):  
James M. White ◽  
Rolf W. Mathewes
Keyword(s):  
Climatic Change ◽  
Pollen Analysis ◽  
Radiocarbon Dating ◽  
Vegetation Change ◽  
Human Populations ◽  
Pollen Record ◽  
Radiocarbon Dates ◽  
Black And White ◽  
Peace River ◽  
Permanent Pond

A sediment core from a pond on the Alberta Plateau in the Peace River district of British Columbia was studied using pollen analysis and radiocarbon dating. Percentage and influx diagrams were produced, and radiocarbon dates were corrected to calendar years to calculate the sedimentation rate. The 231 cm core terminated in clay, and a basal date of 7250 ± 120 years BP was obtained, several thousand years after the recession of Glacial Lake Peace. The formation of the pond is interpreted as resulting from a climatic change, probably a transition from the peak of the Hypsithermal. Zone 1, from 7250 to 5500 years BP, is interpreted as representing a seasonal slough, with upland vegetation percentages consistent with a boreal forest. At about 5500 years BP a permanent pond with surrounding sedge wetlands was formed. Vegetation has been essentially modern during the last 3100 years. Measurements of spruce grains suggest the presence of black and white spruce throughout the pollen record. The formation of permanent ponds and wetlands on the Alberta Plateau at about 5500 years BP is thought to have been the most important vegetation change of the last 7000 years, which may have affected faunal and human populations.

scholarly journals Contrasting the ecological effects of decreasing ice cover versus accelerated glacial melt on the High Arctic's largest lake

2020 ◽  
Vol 287 (1929) ◽  
pp. 20201185
Author(s):  
Neal Michelutti ◽  
Marianne S. V. Douglas ◽  
Dermot Antoniades ◽  
Igor Lehnherr ◽  
Vincent L. St. Louis ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Fold Increase ◽  
Mass Gain ◽  
Ecological Change ◽  
Diatom Assemblages ◽  
Lake Ice ◽  
Glacial Meltwater ◽  
Glacial Runoff ◽  
Common Era ◽  
Ecological Functioning

Lake Hazen, the High Arctic's largest lake, has received an approximately 10-fold increase in glacial meltwater since its catchment glaciers shifted from net mass gain to net mass loss in 2007 common era (CE), concurrent with recent warming. Increased glacial meltwater can alter the ecological functioning of recipient aquatic ecosystems via changes to nutrient budgets, turbidity and thermal regimes. Here, we examine a rare set of five high-resolution sediment cores collected in Lake Hazen between 1990 and 2017 CE to investigate the influence of increased glacial meltwater versus alterations to lake ice phenology on ecological change. Subfossil diatom assemblages in all cores show two major shifts over the past approximately 200 years including: (i) a proliferation of pioneering, benthic taxa at approximately 1900 CE from previously depauperate populations; and (ii) a rise in planktonic taxa beginning at approximately 1980 CE to present-day dominance. The topmost intervals from each sequentially collected core provide exact dates and demonstrate that diatom regime shifts occurred decades prior to accelerated glacial inputs. These data show that diatom assemblages in Lake Hazen are responding primarily to intrinsic lake factors linked to decreasing duration of lake ice and snow cover rather than to limnological impacts associated with increased glacial runoff.

scholarly journals Pollen analysis: state of the art

2010 ◽  
Vol 31 (1-2) ◽  
pp. 151-159 ◽  
Author(s):  
Gordon J. Ogden
Keyword(s):  
North America ◽  
Pollen Analysis ◽  
Sediment Cores ◽  
Data Bank ◽  
Sedimentation Rates ◽  
Data Set ◽  
Radiocarbon Dates ◽  
Surface Pollen ◽  
Pollen Stratigraphy ◽  
Better Than

Although nearly 50 years have passed since P.B. Sears introduced pollen analysis to North America, it remains an occult art. Dramatic improvements in sampling and analytic techniques continue to be limited by intractable problems of differential production, dispersal, ballistics, sedimentation, and preservation. It is a basic tenet of pollen stratigraphy that the data set, consisting primarily of microfossils preserved in sediments, is better than anything we have yet been able to do with it. Basic agreement between late- and postglacial pollen records has been confirmed wherever the method has been applied. Quantitative sampling techniques, sample preparation, and analytic procedures, together with multiple radiocarbon dates, permits calculation of sedimentation rates and absolute pollen influx. Of approximately 300 sediment cores from northeastern North America, fewer than 30 have more than 3 radiocarbon determinations from which least squares power curve regressions can be reliably calculated in the determination of sedimentation rates. Analogy with modern environments represented by surface pollen spectra is limited by an insufficient number of samples of uniform quality to characterize a vegetational mosaic covering 40 degrees of latitude (40-80°N) and longitude (60-100°W). The present surface pollen data bank includes about 700 samples, unevenly spaced and of uneven quality, permitting a grid resolution of no better than 10,000 km2.

Home sapiensorCastor fiber?

Antiquity ◽  
1983 ◽  
Vol 57 (220) ◽  
pp. 95-102 ◽  
Author(s):  
J. M. Coles ◽  
B. J. Orme
Keyword(s):  
Climatic Change ◽  
Pollen Analysis ◽  
Ice Sheets ◽  
Change Rate ◽  
Species Migration ◽  
Atlantic Period ◽  
Vegetational Change ◽  
Vegetational Succession ◽  
Glacial Refuges

Following the development of pollen analysis in the earlier part of this century, much effort was devoted to unravelling the sequence of vegetational change during and after the retreat of the last European ice-sheets. The outlines established, questions of causation came to the fore, and the debate focused on factors such as climatic change, rate of species migration from glacial refuges, and natural vegetational succession. In more recent decades, a further factor has been widely investigated, namely the possible influence of humans on the landscape, principally as farmers and smiths. The development and modification of hypotheses is well illustrated by the Elm Decline of the Atlantic period, where climate (Iversen, 1941) or man (Troels-Smith, 1960) and occasionally disease (see refs in Simmons & Tooley, 1981, 134) have been held responsible for a widespread but by no means straightforward decline in elm pollen.

Radiometric dating of the United Kingdom SWAP sites

1990 ◽  
Vol 327 (1240) ◽  
pp. 233-238 ◽  
Keyword(s):  
Sediment Cores ◽  
Radiometric Dating ◽  
Recent Sediment ◽  
Accumulation Rates ◽  
Water Acidification ◽  
Sediment Record ◽  
The United Kingdom ◽  
Surface Water Acidification ◽  
Study Sites ◽  
Gamma Assay

Measurements of 210 Pb by direct gamma assay have been used to date sediment cores from Surface Water Acidification Project (SWAP) study sites in the U.K. The results were checked against additional dating evidence from the artificial fallout isotopes 137 Cs and 241 Am. At one of the sites, Devoke Water in Cumbria, the 137 Cs and 241 Am data were crucial in identifying a recent sediment hiatus. At sites with recently afforested catchments the sediment record indicated substantial increases in accumulation rates.

Climatic change and foresight in agriculture: the possibilities of long-term weather advice

1973 ◽  
Vol 7 (5) ◽  
pp. 203-210 ◽  
Author(s):  
H H Lamb
Keyword(s):  
Twentieth Century ◽  
Seventeenth Century ◽  
Climatic Change ◽  
Middle Ages ◽  
Growing Season ◽  
Early Middle Ages ◽  
Dry Areas ◽  
Westerly Winds ◽  
Nw Europe

Long-term weather analysis indicates a shortening of the average growing season in NW Europe from the early Middle Ages to the seventeenth century, followed by a lengthening to the mid-twentieth century, but this trend now appears to have reversed. On a world scale, wet areas exposed to prevailing westerly winds became wetter, and dry areas became drier in the first half of the twentieth century. The implications of these changes for agriculture are considerable.

scholarly journals Sediment geochronology and spatio-temporal and vertical distributions of radionuclides in the Upper Bonny Estuary (South Nigeria)

2014 ◽  
Vol 41 (4) ◽  
pp. 369-376 ◽  
Author(s):  
Omorotionmwan Omokheyeke ◽  
Francis Sikoki ◽  
Abdelmourhit Laissaoui ◽  
David Akpuluma ◽  
Peter Onyagbodor ◽  
...  
Keyword(s):  
Sediment Cores ◽  
Sediment Accumulation ◽  
Dry Weight ◽  
Radiometric Dating ◽  
Layer By Layer ◽  
Excess 210Pb ◽  
Radio Nuclide ◽  
Vertical Distributions ◽  
Southwest Nigeria ◽  
Spatio Temporal

Abstract Surface deposits and sediment cores were collected from the Upper Bonny Estuary, located in Southwest Nigeria, and analyzed to determine spatio-temporal and vertical distributions of radio-nuclide activities expressed in Bq·kg−1 dry weight. The results of activities of naturally occurring radionuclides of 226Ra (15 ± 2–34 ± 3 Bq·kg−1), 228Ra (32 ± 5–48 ± 6 Bq·kg−1), 40K (264 ± 29–462 ± 36 Bq·kg−1) were found to be all within the range of typical values reported for coastal regions. Ratios of 226Ra to 228Ra suggested accretion for all samples with low sediment accumulation registered during rainy months. In addition, vertical distributions at the three sampling sites were also studied with the initial aim of establishing chronologies from the decay of excess 210Pb. In two cores, excess 210Pb, estimated by subtracting 226Ra from total 210Pb on a layer-by-layer basis, exhibit relatively constant activity with discrete minima and maxima. Therefore, these cores were excluded from radiometric dating. Only the third core could be dated by the constant rate of supply model, and 137Cs was utilized to validate the 210Pb chronology.

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