EXECUTIVE SUMMARY - UNESCO World Heritage

During the glacials, the snow line in Scandinavia
dropped to the zone of maximum
precipitation, giving rise to a vast continental
ice sheet of up to 3,000 metres in thickness.
With the water bound, sea levels fell by up
to 120 metres. Th e Baltic Sea region was
covered by huge glaciers but the southern
North Sea, and the greatest part of the
Adriatic turned into dry land (SCHROE-
DER 1998). Th e Alps were also glaciated,
leaving only a single ice-free strip in Central
Europe between the Nordic continental
ice sheet and the Alpine glaciers that were
reaching far into the foreland. Consequently,
the climate was extreme here, and tundra
was spreading.
With the inland ice approaching from the
north and due to the chill, plant species of
the temperate zones became extinct. In
Europe, the “retreating” fl ora would, beside
the Alps, encounter the Mediterranean,
so that it sought out regions of the Mediterranean
coast with a favourable climate
as refuges. Trees could still grow in some
mountain ranges – places which also allowed
the beech to survive.
Like Europe, North America and parts of
north eastern Asia were also ice-covered.
Th e tundra had expanded here also. However,
while only relatively small refuge areas
with limited climates were available in
southern Europe for the species to survive,
the entire spectrum of species would persevere
in North America due to the availability
of large-area refuges. In East Asia, the
glacial epochs had only a mild impact resulting
from the much less extensive continental
ice sheet. Th e original arctotertiary
fl ora was not forced out of the region and
has consequently survived to the present day
almost unchanged (WALTER & STRAKA
1970, SCHROEDER 1998). Th e diff erent
consequences of the Quarternary climate
oscillations on the fl ora, which had still been
distributed all over the northern hemisphere
during the Tertiary, resulted in largescale
disjunction for many species.
During the interglacials, the climate would
keep fl uctuating from arctic through subarctic
to temperate or warm Atlantic and
back. In this manner, the climate oscillations
forced the plant species to migrate back
and forth, with many genuses of the Arctotertiary
becoming extinct in the process
(fl oristic impoverishment). Th e less pronounced
their capacity to expand and mutate,
the more threatened were the species.
FRENZEL (1967), for instance, describes
a forest composed of beeches, hornbeams,
tsuga, and elm trees for the Tegelen interglacial
(early Quarternary) of northwestern
Central Europe. In contrast, the beech
was rarely found during the interglacials of
the Middle Quaternary. Fagus was almost
completely absent during the last interglacial.
However, migrations during the
climate oscillations also resulted in new
species evolving. Only in this way could
what little of the Tertiary genuses was left
survive the ice age. While most of our
forest trees therefore belong to Tertiary
genuses, the species did not evolve before
the glacial climate change.
Postglacial development of Europe
With the end of the last ice age, the largearea
reforestation of Central and Western
Europe set in – the Central European
basic succession, which has found a typical
expression in Germany. With the climate
gradually warming and soil development
taking place, the territories were at fi rst
colonised by birches and pines. Th eir qualities
as anemochoric, rapidly migrating pioneers
proved benefi cial (POTT 1992), while the
zoochoric oaks and beeches with their
heavy fruits were not gaining much ground.
It was only in the further course of the
2. DESCRIPTION
Extreme climate fl uctuations
during the Glacial
period prompted the evolution
of new plant species
in Europe. It is safe to
assume that the beech is
also a result of this unique
process.
Nationale
Naturlandschaften
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