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in principle and as far as palaeoenvironmental reconstructions allow given their
limitations (for a discussion see Mannion, 1999; Wilson
et al.
, 2000), a means of
investigating natural interglacial development against the concentrations of atmo-
spheric carbon dioxide and methane, which were considerably below those of the
present as indicated by concentration data from ice core records (see Luthi
et al
.,
2008, and Loulergue
et al.,
2008, for records of changes in atmospheric concen-
trations of carbon dioxide and methane during the last 800 000 years). Tzedakis
(2009) and Tzedakis
et al.
(2004, 2009) have commented on the nature of inter-
glacial stages in terms of duration and forest development, and draw attention to
diversity rather than uniformity. In general, interglacials involved a vegetation suc-
cession that began with an increase in birch (
Betula
), juniper (
Juniperus
) and pine
(
Pinus
). Oak (
Quercus
), elm (
Ulmus
), lime
(Tilia
) and hazel (
Corylus
) then ex-
panded followed by hornbeam (
Carpinus
), beech (
Fagus
) and fir (
Abies
) as late
invaders. However, regional variations in relation to timing and forest composition
occurred as Tzedakis (2009) has reviewed in detail. Tzedakis
et al.
(2009) conclude
that 'Examination of the palaeoclimate record of the past 800 000 years reveals a
large diversity among interglacials in terms of their intensity, duration and inter-
nal variability, but a general theory accounting for this diversity remains elusive.'
It is highly likely that such comments are just as relevant to the interglacial envi-
ronments of Mediterranean mountains as they are to the mid-altitude and lowland
areas in which the lake basins containing the sediments are located.
30
×
10
3
to 10
×
10
3
years ago
The Last Glacial Maximum (LGM), that is the maximum extent of ice sheets and
glaciers during the last glacial stage, occurred c. 20
10
3
years ago in northern Eu-
rope and North America. The highest parts of mountains in the Mediterranean zone
were ice-covered, as discussed by Hughes and Woodward (2009) and Hughes (see
Chapter 3), though they point out that in the Mediterranean mountains there is ev-
idence for maximum ice extent c. 10
×
10
3
years earlier with subsequent phases of
glacial advance and retreat. There are a number of sites that contain pollen records
of the period around and after the LGM; the synthesis by Tzedakis (2009) gives
a list, described as partial, of 17 sites from Spain, France, Italy, Slovenia, Greece,
Syria and Tunisia, which provide evidence for the existence of tree populations
during the LGM. In general, pine (
Pinus
) and birch (
Betula
) dominate the pollen
spectra of sites from the northern part of the Mediterranean Basin, while deciduous
oak (
Quercus
spp.) and other deciduous species dominate the eastern and southern
basin. These data could and probably do reflect climatic control of vegetation com-
munities on the basis of latitude and possibly longitude (see also comments by Suc
and Popescu, 2005) though there is the possibility that some species, such as pine
(
Pinus
), are over-represented in the pollen spectra. Some of these records are from
mountain regions and reinforce the idea that at least in some mountain areas there
were indeed tree-covered refugia (see above) during glacial stages. Recent research,
×
