Vegetation Response to Climatic Change in Central Rift Valley, Kenya

1991 ◽  
Vol 35 (2) ◽  
pp. 234-245 ◽  
Author(s):  
Joseph Mworia Maitima
Keyword(s):  
Shallow Water ◽  
Climatic Change ◽  
Sediment Core ◽  
Pollen Analysis ◽  
Aquatic Plants ◽  
Rift Valley ◽  
Lake Naivasha ◽  
Vegetation Response ◽  
Lowland Forest ◽  
Arid Conditions

AbstractPollen analysis of a 15.5-m sediment core from Lake Naivasha, central Rift Valley of Kenya, reveals that the vegetation from before 20,290 to nearly 12,000 yr B.P. was dominated by open grassland, indicating arid conditions. Within this period a moderately wetter climate existed between 17,000 and 15,000 yr B.P., shown by relatively slight increase in both the montane and lowland forest vegetation. From approximately 12,000 to 6500 yr B.P., a change toward more trees and forests started at lower altitudes around the basin of Lake Naivasha, and later in the higher montane regions. After 6000 yr B.P. a decline in forest and lowland trees opened the vegetation into more grasslands and by 4000 yr B.P. a vegetation similar to the present was attained and has persisted to the present. During this period shallow-water aquatic plants became abundant in Lake Naivasha.

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.

Calcretes, Palycretes and Silcretes in the Paleogene Detrital Sediments of the Duero and Tajo Basins, Central Spain

Clay Minerals ◽  
1994 ◽  
Vol 29 (2) ◽  
pp. 273-285 ◽  
Author(s):  
M. Rodas ◽  
F.J. Luque ◽  
R. Mas ◽  
M.G. Garzon
Keyword(s):  
Climatic Change ◽  
Clay Mineral ◽  
Granitic Rocks ◽  
Central Spain ◽  
Vertical Transfer ◽  
Arid Conditions ◽  
Lower Paleogene

AbstractThree duricrust types (calcretes, palycretes and silcretes) have been distinguished in the Lower Paleogene arkosic materials from the margins of the Duero and Tajo basins (central Spain). In the calcretes the cements are composed of calcite plus palygorskite, whereas palygorskite is the only cement in the palycretes. In the silcretes, the cement consists chiefly of opal and chalcedony, with minor quartz. The important duricrust development in the Paleogene detrital materials can be correlated with a drastic climatic change towards colder and more arid conditions during this time, as inferred from the sedimentological features and the clay mineral evolution. The origin of calcretes and palycretes is related to the movement of alkaline phreatic waters generated from dolomitic rocks of Cretaceous age cropping out in the near surroundings. Silcretes originated from the vertical transfer of silica from supersaturated groundwaters, from the Hercynian granitic rocks, up to the surface. Silcretes are developed either on unconsolidated arkosic materials or replace previous calcrete or palycrete levels.

Assessment of random wave energy dissipation due to submerged aquatic plants in shallow water using deep water wave conditions

2021 ◽  
pp. 147509022110399
Author(s):  
Dag Myrhaug ◽  
Pierre-Yves Henry
Keyword(s):  
Energy Dissipation ◽  
Shallow Water ◽  
Deep Water ◽  
Aquatic Plants ◽  
Wave Energy ◽  
Water Wave ◽  
Random Wave ◽  
Wave Energy Dissipation ◽  
Submerged Aquatic Plants ◽  
Deep Water Wave

This article addresses the random wave energy dissipation due to submerged aquatic plants in shallow water based on deep water wave conditions including estimation of wave damping. The motivation is to provide a simple engineering tool suitable to use when assessing random wave damping due to small patches of plants in shallow water. Examples of application for typical field conditions are provided. The present method versus common practice is discussed. A possible application of the outcome of this study is that it can be used as a parameterization of wave energy dissipation due to vegetation patches of limited size in operational estuarine and coastal circulation models.

Dugongs in Australian Waters

Oryx ◽  
1966 ◽  
Vol 8 (4) ◽  
pp. 221-222 ◽  
Author(s):  
Colin Bertram ◽  
Kate Bertram
Keyword(s):  
Shallow Water ◽  
Aquatic Plants ◽  
Ecological Niche ◽  
Native People ◽  
North East ◽  
The North ◽  
Aquatic Mammals

In their 1965 survey of dugongs on the north-east Australian coast, Dr. Colin and Dr. Kate Bertram made the welcome discovery that these aquatic mammals, whose numbers were seriously reduced throughout their range in the last century and the early decades of this, are now holding their own here and may even in a few places be increasing. Dugong meat and oil are highly valued by some Australian native people, and the animals fill an important ecological niche as consumers of aquatic plants in shallow water.

Paleolimnology and Prehistory

1967 ◽  
Vol 32 (1) ◽  
pp. 31-35
Author(s):  
John DeCosta ◽  
Claude N. Warren
Keyword(s):  
Environmental Factors ◽  
Climatic Change ◽  
Pollen Analysis ◽  
Climatic Changes ◽  
Important Data ◽  
Paleoclimatic Reconstruction ◽  
Micro Organisms

AbstractArchaeologists have failed to use all available data relevant to climatic changes and other environmental factors necessary for the reconstruction of paleoclimates. This neglect has fostered the continuance of significant problems of reconstruction and interpretation in archaeology. Paleolimnology can be helpful in elucidating some of these problems. Research of this sort has already provided valuable evidence for the advent of agricultural man in Austria, as well as providing data for the reconstruction of paleoclimates in other areas. While pollen analysis has traditionally been used as an indication of climatic change, certain aquatic micro-organisms manifest a more rapid and subtle response to slight climatic changes. Paleolimnological evidence can provide important data for paleoclimatic reconstruction in archaeology.

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