Location and General Description
This ecoregion is dominated by the central Iranian plateau, an immense area covering 1,648,000 km2 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 northernmost sand dunes in Iran (UNEP 1989c; 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, continental desert climate with extreme temperatures (Zohary 1973). While the mean annual temperature ranges from 15 to 18 degrees C., the extreme maximum temperature can reach 42 degrees C. and the extreme minimum temperature can fall to –20 degrees C. In most of the region, annual rainfall does not exceed 200 mm and in much of it rainfall is less than 100 mm (Zohary, 1973). In the northwest corner of the region, precipitation is highly variable from year to year, ranging from less than 50mm to over 300mm and falling mostly as rain from November to May (UNEP 1989b). The driest parts of Iran are found in the central and eastern parts of the plateau, with the Dasht-e-Hut receiving only up to 50 mm per year. The low amount of rainfall is aggravated by high evaporation rates.
The rivers descending into the central plateau from the surrounding mountain ranges carry high levels of soluble salts, and the ground in the plateau tends to be highly saline (Zohary 1973). On the margins of the plateau, and in a few patches in the interior where the topography is such that the soil is less saline, areas of piedmont fans and alluvial soils exist and can be farmed. Zohary (1973) differentiates the central plateau into a series of habitats, including poorly drained flats inhabited by halophytic communities and better drained flats inhabited by a variety of sagebrush (Artemisia) steppes. The flats are interspersed with sand dunes and gravel deserts. True sand deserts, consisting of vast dune fields, exist in Iran only in the central plateau and cover a surface area of about 183,000 sq. km; they are found at altitudes of about 500m to 1,200m.
According to Zohary (1973), the central Iranian sector hosts the most typical vegetation of Iran’s steppe and desert regions. Dwarf scrub vegetation (Artemisietea herbae-albae iranica Zohary 1973) is common in large areas of the interior of Iran and is very diverse and rich in species; in non-saline areas, a variant with many thorn-cushions (Artemisietea herbae-albe astragaletosum glaucacanthi Zohary 1973) is formed. Under extremely arid conditions, a very open variant of the dwarf shrublands appears, also characteristic of large areas of the Iranian interior; the dominant species are sagebrush (Artemesia herba-alba), Astragalus gossypius, and others (Frey & Probst 1986). In areas receiving over 100 mm of rain, other genera such as Pteropyrum, Zygophyllum and Amygdalus can also be found.
With regard to vegetation of the sand deserts in the interior regions of Iran, among the more characteristic genera are Ephedra, Calligonum, Heliotropum, and others (Frey & Probst 1986). Endemic shrubs and perennials include Astragalus (Ammodendron) kavirensis Freitag, Heliotropum rudbaricum, and others. Many species here are highly specialized as psammophytes; these sand-adapted species are estimated to make up one third to one half of the total number of species in the sand deserts of Iran and Afghanistan (Freitag 1986). Iranian deserts also have a striking number of Tamarix speces; they have been reported to occur on the margins of the more sandy and gravelly parts of the Dasht-e-Lut (Breckle 1983).
Halophytic communities of varying composition are found on the margins of the undrained salt pans of the central Iranian region, such as the Dasht-e-Kevir. In such areas, clays and sand soils have a high surface salt content due to insufficient water and high summer evaporation. Characteristic genera and species include Aellenia spp., Halocnemum strobilaceum, Haloxylon spp., Salsola spp., and others (Frey & Probst 1986). The inner parts of the salt pans have almost no vegetation. Zohary (1973) points out that saline soils can harbor an impressive number of plant communities, and he characterizes Iran as "outstanding in its rich halophytic flora and vegetation due to the abundance of saline habitats". He notes that Turanian stock in the central plateau region, particularly that of the dunes and saline areas, has supplied numerous taxa and their derivatives, especially halophytes and psammophytes, to the Old World northern subtropical deserts.
The critically endangered Asiatic cheetah (Acinonyx jubatus ssp. venaticus), the endangered onager (Equus hemionus ssp. onager), and the Persian ibex (Capra aegagrus – classified as vulnerable on the IUCN Red List) were once more common in this region but now are found only in small numbers (IUCN 2001). Other once typical inhabitants of the central plateau region include striped hyaena (Hyaena hyaena), red fox (Vulpes vulpes), caracal (Lynx caracal), wild sheep (Ovis ammon), mountain gazelle (Gazella gazella), goitered gazelle (G. subgutturosa) and hare (Lepus capensis)(Boulos et al. 1994). Leopard (Panthera pardus) and wolf (Canis lupis) are sighted occasionally within protected areas, as are golden jackal (Canis aureus), marbled polecat (Vormela peregusna) and the cats Felis catus, F. margarita, and F. manul may (Boulos et al. 1994; UNEP 1989c; Humphreys & Kahrom 1995). One of the more interesting creatures is the desert or Ruppell’s fox (Vulpes Ruppelli), which inhabits the driest and hottest desert regions and has adapted to this habitat by becoming entirely nocturnal (Humphreys & Kahrom 1995). The four-toed or steppe tortoise (Testudo horsefeldii), listed as vulnerable on the IUCN Red List, inhabits areas of Artemisia steppe (Breckle 1983; IUCN 2001).
A number of rodents are known from the deserts and rocky areas, the most abundant being Calomyscus bailwardii and Meriones persicus )(Breckle 1983). In addition, over 150 species of birds have been recorded in some areas, including the houbara bustard (Chlamydotus undulataa, the coronated sandgrouse (Pterocles coronatus) and other notable species (Breckle 1983; UNEP 1989c). There are also several lizards that occur only in the basins or mountain ranges of the central plateau; these include several species of Cyrtopodion, Rhinogecko misonnei, and others (Anderson 1999).
Throughout the ecoregion in general, woodland and scrub areas have been severely pushed back, as evidenced by remnant groves and scattered trees and woody plants in otherwise treeless areas. The species composition of plant formations has also been altered; in many areas, plateau grasses have been driven out of the dwarf-scrub formations and replaced by thorn cushions (Frey & Probst 1986).
The Kavir National Park, Protected Area and Biosphere Reserve, covering approximately 700 km2 in the northwest corner of Iran's arid central plateau, reportedly hosts about 280 species of higher plants and is home to a number of rare fauna (UNEP 1989b). The reserve is managed primarily to conserve rare desert plains species such as Equus hemionus, Gazella gazella, G. subgutturosa and Chlamydotis undulata.
The Touran Wildlife Refuge and Protected Area, located in the northeastern area of the central plateau, was established in 1971 and designated a Man and Biosphere Reserve in 1976. Covering 18,604 km2, this protected area is home to an estimated 1000 indigenous vascular plant species including semi-desert, psammophytic and halophytic vegetation and most of the 150 endemic species of the central deserts (Boulos et al. 1994). The reserve is also considered to have the most complete range of semi-desert fauna in Iran. The site was reportedly selected for long-term research on the impact of grazing by domestic stock and competition between wild and domestic herbivores (UNEP 1989c).
Types and Severity of Threats
Over-harvesting of woody vegetation for fuel and overgrazing by sheep, goats and camels, resulting in gully erosion in foothill areas, probably pose the most significant threats to vegetation in this area (UNEP 1989c; Boulos et al. 1994).
Desert mammals must compete for pasture and water with increasing numbers of livestock (Boulos et al. 1994). In addition, species such as Acinonyx jubatus are threatened by a loss of their prey base, such as small-medium size ungulates and hare, due to human hunting. People may also kill these predators because they are perceived as a danger to livestock (IUCN 2001). Previously implemented protective measures such as controls on hunting, charcoal burning and the cutting of shrubs have been weakly enforced since the Islamic Revolution, and a reintroduction of conservation measures and research to identify optimum resource use levels have been recommended (Boulos et al. 1994).
Justification of Ecoregion Delineation
The Central Persian Desert Basins ecoregion largely corresponds with the Iranian steppes of Artemisietea herbae-albae iranica as designated by Zohary’s (1973) geobotanical map of the Middle East. It also includes areas of saltland vegetation enclosed within this zone (Zohary 1973), including: littoral saltland vegetation of Salicornietea europaeae, falling primarily in the northern part of this ecoregion; the Irano-Turanian saltland vegetation of Halocnemetea strobilacei; and the Saharo-Arabian saltland vegetation of Suadetea deserta. Smaller scattered areas of Irano-Turanian psammophilous vegetation, with Haloxylon persicum and Stipagrostis pennata (Zohary, 1973), are also included. Adjacent chernopodiaceous communities in Afghanistan (Freitag 1971) were incorporated.
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UNEP-WCMC. 1989. Islamic Republic of Iran: Kavir National Park, Protection Area and Biosphere Reserve. Protected Areas Database on UNEP-UNEP web site (http://www.unep-wcmc.org/protected_areas/data/sample/0367v.htm), visited October 23, 2001.
UNEP-WCMC. 1989. Islamic Republic of Iran: Touran Wildlife Refuge, Protected Area and Biosphere Reserve. Protected Areas Database on UNEP-WCMC web pages (http://www.unep-wcmc.org/protected_areas/data/sample/1689v.htm), visited October 23, 2001.
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Prepared by: Julie Bourns
Reviewed by: In process