Wednesday, August 6, 2014

Southern Deserts of Central Asia

The Southern Deserts of Central Asia make up the richest desert complex in Eurasia and encompass the majority of Turkmenistan and central Uzbekistan. The southern deserts stretch from the eastern Caspian coast (to the west) to the middle current of Syr Darya (to the east) and to the foothills of the Central Asian mountains. The southern deserts include the Caspian coastal plains, the southern part of Ustyurt Plateau, Krasnovodsk Plateau, Kara Kum sandy deserts, and the southern part of Kyzyl Kum sandy desert.

They are distinguished from the northern deserts in that they are warmer with more seasonal rainfall which encourages the growth of ephemerals. Also the plant species have a much stronger Irano-Turanian character than the deserts to the north. Sand acacia communities with their accompanying biological richness are much more abundant in the southern deserts.

Precipitation is greatest during the winter and spring while the average temperature and degree of aridity are higher than in the northern deserts. Consequently plants and animals in the region have developed certain physiological mechanisms to help them survive the combination of extremely cold winter temperatures and blistering hot summers.

Photo: Sand Cat (Feliz Margarita)

Reptile and rodent diversity are particularly high. Along with several endemic jerboa species, this ecoregion is home to rare and endangered cats such as Pallas’ cat and the small, secretive sand cat.

General Description

The characteristic feature of the climate of the Southern deserts is the considerable heat supply generated by the average annual temperature (day/night~+16º C) which is considerably higher than in the northern deserts. The pattern of precipitation is typical of the Mediterranean region at 125-170 mm with most falling during winter, spring and partly autum. Rains almost never occur in the middle of summer, causing a prolonged summer pause in almost all biotic activity. Winters are mild with the average temperature in January being –1 to 5º C. In the southern deserts a prolonged snow cover rarely occurs. Shorter duration snows are possible from the middle of December to the end of February.

Sands occupy large areas in the Southern Deserts. Two great Central Asian deserts, the Kara Kum and Kyzyl Kum, are both located here. In addition to the denuded, arid plateau (Ustyurt) and low alluvial and delta-alluvial plains of Amu Darya, the Tedzhen, Murghab, and Zeravshan rivers are also found in the eco region. There are some low mountains (760-920 m) on Paleozoic rocks in the Kysyl Kum. The elevated, inclined foothill plains are typically in the south while low solonchak plains occupy the Caspian coast and depressions.

The southern deserts are distinguished from the northern deserts by changes in the structure of dominant plant species and an increase in the diversity of ephemeroids and ephemers. This difference is connected to a mild winter and early spring in the Southern Deserts. The green aspect of ephemers (Bromus spp., Malcolmia spp., Koelpinia spp., Amberboa spp.) and ephemeroids (Eremurus spp., Rheum spp., Tulipa spp., Gagea spp.) dominates in March and April. By the end of May these plants finish their annual growth as the summer there is no precipitation.

The community structure of desert vegetation is closely associated with edaphic conditions. White saxaul (Haloxylon persicum) and black saxaul (Haloxylon aphyllum) occupy large areas on the sands. Saxaul is a high shrub (3-10 m). There are many endemic species found in sand the regions typical of the Southern Deserts (e.g., Salsola richteri, S. subaphylla, Ephedra strobilacea Ferula foetida). Sandy acacia (Ammodendron conollyi) grows on barkhans (sand-hills). In this region a diversity of shrub species such as Calligonum leucocladum, C. eriopodum, and C. setosum is great.

White salsola (Salsola arbuscula) and sagebrushe communities with a number of endemic species (Artemisia kemrudica, A. diffusa, A. dimoana, A. arenicola, Mausolea eriocarpa) are widespread on thin sandy soils and loamy sands. Endemic Astragalus vilosissimus and shrub bindweed (Convolvulus hammada) are characteristic for the east part of region. The perennial saltworts (Salsola gemmascens, S. orientalis) dominate on clay soils. Halophytic, succulent semishrubs such as Halostachys caspica, Halocnemum strobilaceum, Suaeda microphylla, and Salsola dendroides, grow on solonchaks.

Biodiversity Features

The fauna of deserts is characterized by a high degree of endemism. Especially rich is the fauna of sandy deserts. Among insects, the characteristic groups include grasshoppers, darkling beetles, scarabaeid beetles, butterflies, termites, and ants. The majority of Reptile species being autochthonous and belong to the core of the Central Asian herpetofauna.
The most common desert mammals are the long-eared hedgehog (Erinaceus auritus), long-quilled hedgehog (Piracohinus hypomelas), and tolai hare (Lepus tolai). A variety of rodents such as gerbils (Rhombomys spp., Meriones spp.), and more than ten species of jerboas (Allactaga, Dipus, Paradipus, Eremodipus, Stylodipus) also live here. The characteristic components of desert ecosystems are such rare and disappearing mammal species as the honey badger (Mellivora capensis), sand lynx (Felis caracal), sand cat (Felis margarita), onager (Equus hemionus), goitered gazelle (Gazella subgutturosa), and marbled polecat (Vormela peregusna).

Photo: Comb-toed Jeroba  

Endemics include the desert dormouse (Selevinia betpakdalensis), comb-toed jerboa (Paradipus ctenodactylus), three-toed and five-toed dwarf jerboas (Salpingotus heptneri, S. pallidus). Also endemic are several mammalian genera, such as Diplomesodon, Spermophilopsis, Pyderethmus, Allactodipus, Eremodipus and many others. Rare cats include Pallas’ cat (Otocolobus manul), cheetah (Acinonyx jubatus) which is extinct from the ecoregion, and the small sand cat which is restricted to dune areas with saxaul tree.

Photo: Houbara Buzzard

The common birds are larks (Calandrella spp., Galerida spp.), wheatears (Oenanthe isabellina, O. deserti), desert warbler (Sylvia nana), desert lark (Ammomanes deserti), desert raven (Corvus ruficollis), saksaul jay (Podoces panderi), desert shrike (Lanius excubitor), and desert sparrow (Paser simplex). Larger birds include the houbara bustard (Chlamydotis undulata), black-bellied and pin-tailed sandgrouse (Pterocles alcata, P. orientalis), cream-colored courser (Cursorius cursor), golden eagle (Aquila chrysaetus), short-toed eagle (Circaetus gallicus), steppe eagle (Aquila rapax), Egyptian vulture Neophron percnopterus), and saker falcon (Falco cherrug). Pander’s ground jay or saxaul jay (Podoces panderi) is a rare and unusual member of the crow family. The Asian desert sparrow (Passer zarudnyi) is also rare.

Reptiles and amphibians include: Khentau toad agama (Phrynocephalus rossikowi), Molchanov's toad agama (P. moltschanovi), Strauch's toad agama (P. strauchi), spotted toad agama (P. maculatus), Sogdian toad agama (P. sogdianus), Said-Aliev's toad agama (P. helioscopus saidalievi); gekkos (Alsophylax pipiens, A. laevis), Rustamov's skink gekko (Teratoscincus scincus rustamovi), Chernov's snake-lizard (Ophiomorus chernovi), Ferghana sand lizard (Eremias scripta pherganensis), black-eyed lizard (Eremias nigrocellata), gray monitor (Varanus griseus), Afghan lytorhynch (Lytorhynchus ridgewayi), and the cobra (Naja naja oxiana).

Types and Severity of Threats

The main anthropogenic threats are agriculture-related, especially irrigated cotton production. Other significant threats include hunting and poaching, and the overuse of woody plants for firewood and silk production. Overgrazing of livestock occurs in non-irrigated areas. Unregulated roads across the desert scape also threaten these especially fragile desert ecosystems.

Fauna and fauna of the sand deserts are particularly vulnerable to human disturbance. Saksaul and other trees and shrubs are cut extensively for fuel wood. It is believed that in recent decades the area covered by saksaul in Central Asia has decreased by half, leaving the topsoil prone to erosion. Species associated with saksaul are disappearing rapidly, as saksaul forests are illegally cut for heating and cooking needs. The reduction of native species has encouraged the spread of desert moss (Tortula desertorum), which provides no nutritional value for wildlife and prevents the re-seeding of higher forms of native plants.


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