Geoscience Reference
In-Depth Information
higher elevations by sheep and the continued fragmentation of habitat, which is
accelerated by road construction, are also of concern because so few natural areas
remain.
Caspian hircanian mixed forest:
Hircanian forests extend for 800 km in length
and covers an area with 1,925,125 ha in the mid elevation of the middle altitudes
of the Alborz mountain. The Caspian Hircanian Mixed Forests experience abundant
rainfall and snowmelt that runs off the north slope of the Alborz mountain. It has
high production capacity due to humid temperate climate and suitable soil.
The key trees of this area are:
Fagus orientalis
,
Carpinus betulus
,
Tilia rubra
,
Taxus baccata
,
Ulmus glabra
,
Quercus castanefolia
,
Parrotia persica
,
Alnus gluti-
nosa
,
Punica granatum
,
Paliurus spira
-
ehristi
These forests sweep down to the coastal plain south of the Caspian Sea, where
they eventually yield to coastal lagoons, swamps, and salt marshes. Extensive
logging and clearing of forests for agriculture have nearly eliminated the forests
in this ecoregion. The invasion of non-native plant species has also posed a serious
threat to native plant communities.
Caspian lowland desert:
This ecoregion encompasses on the southern and eastern
shores of the Caspian Sea at elevations between
28 and 100 m above sea level.
To the south of the Caspian Lowland in Turkmenistan and Iran lies the delta of the
Atrek River - the only river to enter the Caspian Sea from the east (Babaev
1994
);
Most of its flow is used for irrigation so only flood waters actually reach the sea.
Average annual temperature is 17.1
ı
C. Annual precipitation is 187 mm (Heshmati
1998
). A long frostless period (271 days) encourages cultivation of crops such as
olive, fig, pomegranate, and cotton.
This ecoregion are covered by shrubs and grasses which are used by livestock.
The vegetation of the coastal Caspian desert within Iran is impoverished, it
consists of highly specialized halophytes (salt-resistant plants) represented by
shrubs and semishrubs such as various sagebrushes (
Artemisia
), tetyr (
Salsola
gemmascens
), kevreik (
S
.
orientalis
),boyalych (
S
.
arbuscula
), biyurgun (
Anabasis
salsa
,
A
.
ramosissimum
), sarsazan (
Halocnemum strobilaceum
),
Halostachys
,
Cer-
atocarpus
,
Nitraria
,
Kalidium
. Herbaceous vegetation is represented by species of
Aristida
,
Peganum
,
Agropyron
,
Anisantha
,
Eremopyrum
. One of the most typical
halophyte plant formations is dominated by tetyr (
Salsola gemmascens
), a 30-
50 cm shrub, associated with low species diversity and sparse coverage. Solonchaks
are sometimes occupied exclusively by sarsazan (
Halocnemum strobilaceum
). This
ecoregion encompasses the Caspian depression of Kazakhstan, the Karabogaz Kol
in Turkmenistan and includes the Volga Delta and surrounding semi-desert. Within
Central Asia, it is defined by deserts and halophytic regions of the syrt regions
according to Pereladova et al. (
1997
) map of Central Asian ecosystems. Adjacent
Iranian littoral salt land vegetation from Zohary's (
1973
) geobotanical map of the
Middle East is also included since it represents a similar halophytic environment.
The European portions of the ecoregion consist of northern lowland dwarf semi-
shrub deserts and small areas of floodplain vegetation and coastal and inland
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