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Oleg Polunin & Martin Walters
A guide to the vegetation of Britain and Europe
Oxford University Press 1985
0-19-217713-3
Parts of chapter 4:
*Recent history of the development of vegetation in Europe*
This was intended as part of my reply to PRD's
"Transforestation at the NW. European Neolith/
Mesolithic boundary" post, but I thought it was
too long for that.
I included the whole post-last glacial period, but
the period under discussion starts in the Atlantic
period.
Since the emphasis of the discussion is on trees,
I removed many references to scrubs and herbs.
"... Further south in Europe, mountain masses
such as the Pyrenees, Alps, and Carpathians
acted as partial barriers to the migration of
species northwards, but there were in some
places lowland corridors through which
migration took place, as for example south of
the Pyrenees and through France, and in the
east through the Danube valley and Poland.
During the pre-Boreal period (10000 - 95000 bp),
pollen analysis shows a rapid increase of
Juniper followed by Birch and later an influx of
Pine from the warmer south. Light woods
developed in the northern parts of Europe.
In the Boreal period (95000 - 75000 bp) warmer-
loving deciduous trees and bushes, such as
oaks and elms, and in particular Hazel,
/Corylus avellana/, became abundant in north-
western Europe. Forests of Pine and Birch and
thickets of Hazel became widespread in the
early-Boreal period.
The Atlantic period (75000 - 5000 bp) was the
warmest and most humid of the post-glacial
periods. Oaks and Wych elm, /Ulmus glabra/,
became abundant and formed forests, and at
the same time there was a marked increase in
Alder, /Alnus glutinosa/. Limes, /Tilia/ species,
had their widest distribution in England at this
time, indicating the warmer climate, while in
Scandinavia there was a marked increase of
pollen of Ivy, /Hedera helix/; and the great Fen-
sedge, /Cladium mariscus/, in Sweden. The
distinctive increase of peat deposits and raised
bogs also indicated heavier rainfall and greater
humidity.
Mixed oak forests, with elms and limes became
the climax forests and covered large areas of
Europe. They were well established in Britain for
example, to altitudes of at least 750 m, while
species of open habitats became much less
evident. Coastal plants... continue to survive in
'refuges' to this present day, far south of their
present main distribution. Also ... open-habitat
species ... showed much reduced pollen counts
at this period, only to return abundantly later
when man-made habitats began to develop.
The sub-Boreal period (5000-2500 bp)
commenced with a steep fall in the percentage
of Elm pollen in northwestern Europe. At the
same time pollen counts indicate a notable
increase of many herbaceous species ...
[including many indicating human influence.
PA] Also there was an increase of such
pioneering trees as Ash /Fraxinus excelsior/;
and Birch /Betula/ species, which were usually
among the first trees to recolonize areas
cleared of forest.
All these changes were probably due to the
activities of Neolithic and early Bronze Age
man, who by this time was keeping livestock
and carrying out shifting cultivation. Forests
were cleared locally, and for several years crops
were grown in these clearings. At the same
time invasion of weed species occurred.
However after a few years the soil fertility
became much reduced and these cleared areas
were abandoned. They were quickly recolonized
by such trees as Ash and Birch, to develop in
time into the mixed climax forest. This
clearance occurred particularly on lighter soils,
and there was a marked increase of such spiny
bushes as Hawthorn, /Crataegus/; and Gorse,
/Ulex/. The expansion of grasslands and heaths
also occurred at this time.
The [start of the] sub-Atlantic period (2500-0 bp)
more or less coincided with the Iron Age in
northwestern Europe, when for the first time
permanent fields were established. There was
at this time a marked (real or apparent) decline
in Ash, /Fraxinus excelsior/; and limes, /Tilia/
species, and this is thought at least in part, to
be due to the process of pollarding, when
branches of these trees were regularly cut for
fodder for man's domestic animals. Beech and
Hornbeam, by contrast, increased at this time,
but there is no clear indication as to why this
occurred.
In general the climate was cooler and wetter in
this sub-Atlantic period than in the preceding
period. There was a considerable increase in
peat-covered areas, and forest was replaced by
bogs and fens, particularly in the more northerly
parts of Europe. "
--
p.a.
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