Environmental Engineering Reference
In-Depth Information
Evidence for regional climatic change that would have affected Mediterranean
mountains is indirect, deriving from marine sediment cores from the Mediterranean
Sea. Based on pollen assemblages, Suc (1984), Suc et al. (1995) and Popescu et al.
(2010) have confirmed the tripartite division of the Pliocene suggested by Zagwijn
(1960), though the third subdivision is now designated as the Quaternary, as dis-
cussed above.
5.2 to 3.37 × 10 6 years ago
The evidence for this time period derives from a variety of sites and as might be
expected it reveals considerable variation throughout the Mediterranean region. Suc
et al. (1995) describe six spatial units of which those numbered 2, 3 and 4 below
are particularly relevant to mountain environments:
1. In the Atlantic region warm, humid conditions prevailed and subtropical and
warm-temperate tree species dominated with ericaceous shrubs.
2. South of latitude 42 N ecosystems were dominated by xerophytic species in-
cluding species characteristic of desert margins, which suited the seasonally
dry climates.
3. In the northwest, i.e. the Pyrenees to Central Italy including the Apennines,
three forest belts developed. Spruce ( Picea ) and fir ( Abies ) dominated
high altitudes; middle altitudes were characterized by cedar ( Cedrus ) with
Sequoia -type species and with Cathaya dominant at low latitudes. Such
assemblages indicate an altitudinal gradient towards cooler and humid con-
ditions. In this region, lowlands were characterized by a Mediterranean-like
vegetation mosaic.
4. In the northeast, temperate forest species alternated with grassland species.
5. Savanna with a few desert species and sparse riparian tropical gallery-forests
occupied the Nile delta area.
6. Wetlands in Portugal, Catalonia and Romania were dominated by Taxodium-
type, Nyssa, Myrica and Cyrillaceae-Clethraceae.
Recent work by Popescu et al. (2006, 2010) provides further evidence for early
Pliocene environmental change. Pollen analysis of a core from the Lupoaia section,
a delta system of lignites near the Carpathians in southwest Romania, shows that
thermophilous elements and trees reacted to orbital forcing parameters. In particular
the former increased during eccentricity minima while the tree line descended alti-
tudinally during maxima when overall temperatures were lower. Precession also
had an impact in relation to humidity, which encouraged the spread of cypress
swamps and marshes during precession maxima. Although the Carpathians are
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