Environmental Engineering Reference
In-Depth Information
catastrophe, old age or human activity is colonized by species
different from those originally growing there.
COLONIZATION OF THE BRITISH ISLES BY VEGETATION IN
POSTGLACIAL TIMES
key concepts
Successions are changes in vegetation occurring over time periods of decades or at most a
few hundred years. Vegetation change can also be driven by environmental change over
much longer time scales. For example, significant climatic changes have been taking
place during the postglacial Holocene epoch, since the end of the last Ice Age at 10,000
years BP. At the beginning of the present interglacial period the climate changed quite
rapidly from the ice and tundra severity of the Pleistocene to a more temperate climate
which could support deciduous broad-leaved forests. The natural vegetation of the British
Isles is similar to the deciduous forests of the rest of north-west Europe, except for two
regions, namely the coniferous forest of Scots pine (
Pinus sylvestris
) in the Scottish
Highlands, the so-called Caledonian Forest, and the woodlands of south-west Ireland
which resemble the evergreen broad-leaved woods of south-west Europe. When the ice
cover was at its maximum at about 20,000 years BP, trees and other plants found
refugia
or safe havens in continental Europe far beyond the ice limits. With the postglacial
warming of climate, different tree species spread back into the British Isles at different
speeds and with different patterns. The speed and pattern of re-invasion shown by each
species depended on its biological ability to propagate and spread, and on its particular
climatic preferences.
Figure 1
Wildwood of the British Isles in 4000 BP.
Source: After Rackham (1990).
At the glacial maximum sea level was about 100 m lower than at present and a land
