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Mammoth steppe and Pleystocene parks

Canada Wolverine Offline
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( This post was last modified: 02-17-2019, 12:23 PM by Rishi )


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MAMMOTH STEPPE

During the Last Glacial Maximum, the mammoth steppe was the Earth’s most extensive biome. It spanned from Spain eastwards across Eurasia to Canada and from the arctic islands southwards to China. It had a cold, dry climate; the vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs, and the animal biomass was dominated by the bison, horse, and the woolly mammoth. This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, and then suddenly became all but extinct about 12,000 years ago.
During glacial periods, there is clear evidence for intense aridity due to water being held in glaciers and their associated effects on climate.The mammoth steppe was like a huge 'inner court' that was surrounded on all sides by moisture-blocking features: massive continental glaciers, high mountains, and frozen seas. These kept rainfall low and created more days with clear skies than are seen today, which increased evaporation in the summer leading to aridity, and radiation of warmth from the ground into the black night sky in the winter leading to cold. 
This is thought to have been caused by seven factors:
-The driving force for the core Asian steppe was an enormous and stable high-pressure system north of the Tibetan Plateau.
-Deflection of the larger portion of the Gulf Stream southward, past southern Spain onto the coast of Africa, reduced temperatures (hence moisture and cloud cover) that the North Atlantic Current brings to Western Europe.


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-Growth of the Scandinavian ice sheet created a barrier to North Atlantic moisture.
-Icing over of the North Atlantic sea surface with reduced flow of moisture from the east.
-The winter (January) storm track seems to have swept across Eurasia on this axis.
-Lowered sea levels exposed a large continental shelf to the north and east producing a vast northern plain which increased the size of the continent to the north.
-North American glaciers shielded interior Alaska and the Yukon Territory from moisture flow. These physical barriers to moisture flow created a vast arid basin or protected 'inner court' spanning parts of three continents.


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Animal biomass and plant productivity of the mammoth steppe were similar to today's African savannah. There is no comparison to it today.

The mammoth steppe was dominated in biomass by bison, horse, and the woolly mammoth, and was the center for the evolution of the Pleistocene woolly fauna. On Wrangel Island, the remains of woolly mammoth, woolly rhinoceros, horse, bison and musk ox have been found. Reindeer and small animal remains do not preserve, but reindeer excrement has been found in sediment. In the most arid regions of the mammoth steppe that were to the south of Central Siberia and Mongolia, woolly rhinoceros were common but woolly mammoths were rare.Reindeer live in the far north of Mongolia today and historically their southern boundary passed through Germany and along the steppes of eastern Europe, indicating they once covered much of the mammoth steppe. Mammoths survived on the Taimyr Peninsula until the Holocene. A small population of mammoth survived on St. Paul Island, Alaska, up until 3750 BC, and the small mammoths of Wrangel Island survived until 1650 BC. Bison in Alaska and the Yukon, and horses and muskox in northern Siberia, have survived the loss of the mammoth steppe.One study has proposed that a change of suitable climate caused a significant drop in the mammoth population size, which made them vulnerable to hunting from expanding human populations. The coincidence of both of these impacts in the Holocene most likely set the place and time for the extinction of the woolly mammoth
The mammoth steppe had a cold, dry climate. During the past interglacial warmings, forests of trees and shrubs expanded northwards into the mammoth steppe, when northern Siberia, Alaska and the Yukon (Beringia) would have formed a mammoth steppe refugium. When the planet grew colder again, the mammoth steppe expanded. This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, and then suddenly became extinct about 12,000 years ago.


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