Indigenous Plant Species from the Drylands of Iran, Distribution and Potential for Habitat Maintenance and Repair - Combating Desertification in Asia, Africa and the Middle East - page 348

spp., or others while higher up (700-800 m) forests or forest remnants of Quercus
brantii and/or Q . boissieri occur up to an altitude of about 1,700 m. Above the
timber line (1,900-2,000 m) a relatively wide zone of sub-alpine vegetation grows
(Zohary 1973 ).
Further south along the range, the forest becomes more impoverished and a richer
steppe flora develops among the trees. Forest remnants consist primarily of Quercus
persica and, up to an elevation of 2,400 m, xerophilous forest of Quercus spp.,
hawthorn ( Crataegus ), almond ( Prunus amygdalus ), nettle tree ( Celtis ) and pear
( Pyrus spp.) predominates. Below 1,400 m, the vegetation is steppic, with shrubs
predominating.

2.3 Iran-O-Touranian Zone

The region covers an area of about 3,452,775 ha with dry and mainly cold climate in
winter. They are situated in Khorasan, Azarbaijan, Markazi and western Provinces.
Based on topographical conditions and diversity of species, the region is divided
into plain and mountainous sub - regions.

2.3.1 Iran-O-Touranian, Plain Area

This ecoregion is dominated by the central Iranian plateau, an immense area
covering 1,648,000 km 2 in the center of Iran and encompassing a great variety of
climates, soils and topography. It is almost completely surrounded on all sides by
mountain ranges. According to Zohary ( 1973 ), the area can be divided into two
major units: the Dasht-e-Kavir in the north, a vast saline desert, and the Dasht-e-
Lut in the south, largely a sand and gravel desert and one of the hottest deserts in
the world. The plateau is also partly covered with sand dunes. Adjacent regions,
such as the Kavir-e-Namak ('salt desert') and a series of marshes and lakes east
of Qom, are also included in this ecoregion (Zohary 1973 ). In the northwestern
corner of the central plateau, where the Kavir National Park is situated, habitat
types range from desert and semi-desert to dry steppe. In the northeastern reaches
of the plateau, in the area of the Touran Biosphere Reserve, the variety of landforms
includes extensive plains, a saline river system, alluvial fans, limestone outcrops,
salt desert, and 200,000 ha of the northern most sand dunes in Iran (UNEP-WCMC
1989 ; Boulos et al. 1994 ). The peaks and ranges of the Kuhrud Kohbanan Mountains
forest steppe ecoregion encroach upon the higher altitudes of this region, extending
long fingers in a northwest-southeast direction along the western and central part of
the plateau and also rising along its eastern margins.
The central plateau and the mountain slopes facing it have a temperate, continen-
tal desert climate with extreme temperatures (Zohary 1973 ). While the mean annual
temperature ranges from 15 to 18 ı C, the extreme maximum temperature can reach
42 ı C. and the extreme minimum temperature can fall to

20 ı C. In most of the