Included here are the deserts and semi-deserts of eastern Transcaucasia, the precaspian lowlands including the lower reaches of the Volga and Ural rivers, the eastern shores of the Caspian Sea to the basin of Lake Ala Kul, the Ust Urt Plateau, the Turan lowland around the Aral Sea, the Karakum and Kyzyl Kum deserts, the Muyunkum Sands, Bet-Pak-Dola and the Sary-Ishikotrau sands, the footshills of the Piedmont Plains along the Kopet Dagh and extending along the Pamiro-Alai and along the western Tien Shan, the intermontane valleys of the Mirzachcul, the Karshingsky Steppe and other plains of southern Uzbekistan.
Turanian Psammophilic Scrub
In total the area supports some 350 psammophilic (sand loving) species, 56% of which are endemic. The shrub communities are particularly interesting being represented by species of Calligonum including the endemic C. arborescens and C. eriopodum (Polygonaceae), which have their centre of distribution in Kazakhstan. Deserts within this zone, such as the Karakum Desert, also support a number of tree species, and some of these such as the endemic Ammodendron conolly and Eremospermum flaccidum (Fabaceae) can grow up to heights of 5 m or more. Spring geophytes are also well represented. Some of the more notable are Eminium lehmannii, Eremurus inderiensis, Iris songarica and the endemic Rhinopetalum arianum (Liliaceae) and Schummania karelinii (family?). The most extensive formation of the Karakum Desert is characterized by Haloxylon persicum (white sakaul formation). It has a complex structure and can be broadly divided into three layers. The upper layer, 1.5-2 m high, consists of Haloxylon persicum together with various other shrubs such as Ephedra strobolacea, Salsola richteri and various species of Calligonum such as the endemic C. eriopodum and C. setosum (Polygonaceae). Below this is another shrub layer up to 1 m high with species like Artemisia kelleri and the endemic Convolvulus divaricatus (Convolvulaceae). The third layer is largely herbaceous with perennials and biennials such as Astragalus chivensis, Cousinia oxiana, Stipagrostis pennata, Tournefortia sibirica and the endemic or near endemic Heliotropium argusioides (Boraginaceae) and Rheum turkestanicum (Polygonaceae). However, most species of the lower layer are annuals such as Anisantha tectorum, Cutandia memphitica, Erodium oxyrrhynchum, Roemeria hybrida, Strigosella circinnata and the endemic Streptoloma desertorum (Brassicaceae).
Other taxa that dominate sand dune formations include Ephedra strobilacea, Salsola richteri (cherkez) species of Calligonum and the endemic Ammodendron conollyi (Fabaceae). Ephedra strobilacea (bordzhok formations) represent the characteristic vegetation of barkhan dunes in the northern part of central Karakum. It can also be found at Chilmamedkum, Khanbaagykum and on the Dardzha Peninsula. Ephedra is unusual in being a gymnosperm shrub. It can grow to a height of 2 m and is one of the longest living of desert shrubs and can reach an age of up to 100 years. The formation in general is floristically poor with just a few associated shrubs such as Artemisia santoline and Convolvulus erinaceus and the grasses Hordeum leporinum and Stipagrostis karelinii. Formations dominated by Calligonum species (dzhuzgun formations) occur on both mobile and stabilized sand. Over ten species of Calligonum may be involved including Calligonum caput-medusae, C rubens, and the endemic C. arborescens, C. eriopodum, C. leucocladum, C. microcarpum and C. setosum (Polygonaceae). Some of these develop into tree-like forms reaching heights of up to 6 m, but most are shrubs up to 3 m high, and some species can acquire different growth forms depending on conditions. Other shrubs include Halothamnus subaphyllus, Salsola richteri and the endemic Smirnovia turkestana (Fabaceae), while common herbaceous species are Heliotropium dasycarpum, Senecio subdentatus and the endemic Ferula litwinowiana (Apiaceae). Also widespread on all types of sand, such as along the Amudarya and in the Karakum, are formations dominated by Salsola richteri (cherkez formation). The species can grow to a height of 2 m and live for up to 30 years. Most of the associated shrubs are mobile sand specialist such as the Acanthophyllum elatus, Artemisia dimcana and the endemic Eremosparton flaccidum (Fabaceae).
Only a few herbaceous elements are present. Perennials include Cistanche flava, Stipagrostis pennata and the endemic Heliotropium argusioides (Boraginaceae), while common ephemeroides are Carex physodes and Prangos diduma. Also of considerable interest are formation dominated by the endemic tree Ammodendron conolly (Fabaceae). These ‘desert forests’ (syuzen formation) are restricted to unstable sands in the Karakum Desert. Ammodendron trees can grow to heights of 10 m and live for 60 years or more. Floristically, however, the formation is generally poor but scattered shrubs such as the endemic species Calligonum microcarpum (Polygonaceae), Convolvulus divaricatus (Convolvulaceae) and Smirnovia turkestana (Fabaceae) may be present, while common annual or ephemeral species include Chrozophora gracilis, Cithareloma vernum, Horaninovia ulcina and the endemic Agriophyllum latifolium (Chenopodiaceae), Chartoloma platycarpum (Brassicaceae) and Corispermum papillosum (Chenopodiaceae). Finally on rare occasions grasses such as Peganum harmala, Stipagrostis karelinii, S. pennata or the endemic Agropyron fragilis (Poaceae) may dominate communities. Stipagrostis karelinii is a perennial that can reach 1 m in height and is often a pioneer of barkan dunes in the Karakum Desert. Stipagrostis pennata forms denser communities in more stable areas. Associated taxa usually include small shrubs such as Artemisia santolina and the endemic or near endemic Astragalus ammodendron and A. transcaspica (Fabaceae), while the herbaceous species may include Ceratocarpus utriculosus, Ferula assafoetida and Kochia odontoptera.
References
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Fet, V. & Atamuradov, K. I. 1994. Biogeography and Ecology of Turkmenistan. Kluwer Academic Publishers.
Paulsen, O. 1913. Transcaspian Vegetation. Journal of Ecology, 1: 133-134.
Walter, H. & Box, E. O. 1983. Central Kazakhstan. In: Ecosystems of the World 5 - Temperate Deserts and Semi-Deserts. Ed. N. E. West. Elsevier Scientific Publishing Company.
Walter, H. & Box, E. O. 1983. Middle Asian Deserts. In: Ecosystems of the World 5 - Temperate Deserts and Semi-Deserts. Ed. N. E. West. Elsevier Scientific Publishing Company.
Walter, H. & Box, E. O. 1983. The Karakum Desert. In: Ecosystems of the World 5 - Temperate Deserts and Semi-Deserts. Ed. N. E. West. Elsevier Scientific Publishing Company.
Walter, H. & Box, E. O. 1983. Caspian Lowland Biome. In: Ecosystems of the World 5 - Temperate Deserts and Semi-Deserts. Ed. N. E. West. Elsevier Scientific Publishing Company.
Wendelbo, P. 1971. Some distributional patterns within the flora Iranica area. In: Plant Life of South-West Asia. Eds. P. H. Davies, P. C. Harper & I. C. Hedge. The Botanical Society of Edinburgh.