Karakum desert, Black Sands in Turkic languages (Earthen Sands – another interpretation)
It is stretching clockwise between the Caspian Sea, Sarakamysh lake, Aral Sea area, Amu Darya river, Karabil uphills, Murghab and Tejen rivers lower streams and Kopet Dag Mountain range. The sandy desert is a geographically well delineated biome of the temperate desert, zonobiome of the Arid- Temperate Climate, with a little rain, hot summers and cold winters, extensive droughts about 4- 6 months.
The large basin of Karakum desert is remain part of the ancient Paratethys Sea and Tethys Ocean. Then since the Tertiary has been in the process of being filled with loose alluvial rocks by paleo- Amu Darya river and later by Murghab and Tejen rivers. In the course of the long period the sand barchans had been formed. The dust particles have been deposited by wind, on the Kopetdag slopes in the south forming a dune region.
The paleo- Amu Darya originally crossed Karakum desert basin and into the Caspian Sea, often changing its course what can be clearly seen on the example of Erbent 1,000 km long wedge left by Amu Darya. Later, Amu Darya was displaced to the east by the delta deposits of the Murghab and Tedzhen rivers and redirected to the Aral Depression. It emptied into the Aral Sea.
Amu Darya river is still important for the basin, since its water infiltrates directly from Amu Darya, via Karakum canal and Turkmen lake in the desert, to feed a groundwater lake underlying the entire central Karakum. It is proved that groundwater lake moves slowly from east to west but probably none of this flows to Caspian Sea. The water is slightly brackish, although it is covered by a lens of fresh water beneath the bare dunes, owing to the rainwater seepage, even in the year with lowest precipitation recorded. Wells made in such places collect good drinking water.
Inflow to the subterranean groundwater lake:
- Groundwater infiltration from Amu Darya 150 cubic m per sec
- Rainwater seepage in the barchans region 30 cubic m per sec
- Infiltration from Murghab and Tejen rivers 21 cubic m per sec
- Subterranean inflow from Kopet Dag 20 cubic m per sec
- Seepage from elevations and takyrs 1 cubic m per sec
Totally: 222 cubic m per sec
- Evaporation from saltpans above high groundwater table (average) 165 cubic m per sec
- Groundwater loss due to phreatophytes (plants dependent on groundwater) 57 cubic m per sec
Totally: 222 cubic m per sec
Paleo-Amu Darya riverbed left the chain of depressions, some 10 - 15 km long and 1-4 km wide, known as Unguz line, stretching from the east to old Uzboy riverbed, for 470 km long. Unguz divide Karakum desert into Zaunguz (Northern 102,000 square km) part, Central or Low Karakum sands and Southeastern Karakum. Total area of Karakum desert 350,000 square km. Annual Precipitation: The northwest of the desert less 100 mm, the central and southeastern parts of the desert around 150 mm. Potential evaporation in the desert amounts 1500- 2000 mm, what 10-15 times exceeds the precipitation.
Flora of Karakum
The distinctive feature of the desert biome is the often highly heterogeneous origin of its flora. This is especially true for the Central Asia deserts, the species of which originated in the surrounding high mountain areas and on the littorals of the ancient Tetis. Its long evolutionary history under gradually increasing xeric conditions and its large gene pool may explain the high percentage of endemics and a considerable diversity with respect to adaptive characters, both morphological and physiological.
Two groups of plants can be distinguished with respect to photosynthetic behavior in the Karakum desert. Ephemeres and ephemeroids, which finish the life cycle before May, are characterized by high potential photosynthesis. In drought-enduring shrubs and trees (Haloxylon, Calligonum, Salsola, Ephedra) the photosynthesis is lower. At different times of the year, the maximum photosynthesis rates vary as per different life forms: Ephemeres and Ephemeroids coincide with the onset of fructification, end of March – end of April, in Ferula, Carex, Horaninovia. For plants completing the vegetative period at the beginning of the summer, they precede summer dormancy and partial leaf shedding – Smirnovia, Astragalus, Convolvulus. For drought enduring shrubs and trees they occur during the hottest and the driest period in the middle of June.
In the Karakum desert, the water content of the drought enduring species is low and remains almost constant during the day, with water saturation deficits not exceeding 6-15 % even on a midsummer day (sub-lethal saturation deficits are in the range 46-53 %). Photorespiration was found in few species Haloxylon, Aristida, Calligonum.
In sandy desert, three vegetation layers are usually identified:
- The first layer, formed by shrubs – Haloxylon species, Salsola richteri, Calligonum species, Ephedra strobilacea, 120 -250 cm in height
- The second layer, 60-90 cm in height, formed by semi-shrubs and high herbs – Artemisia kemrudica, Astragalus species, Aristiuda karelini
- The Third layer, 15- 25 cm in height, formed by Carex physodes and annuals.
Vegetation of clay deserts mainly formed by shrubs and semi shrubs. The main plants are Haloxylonaphyllum, Salsola orientalis, Salsola gemascens, Salsola arbuscula, Artemisia kemrudica, Artemisia badkhysi, Artemisia turcomanica, Ceratoides papposa. Annual halophytes – Gamacanthus gamocarpa, Halimocnemum longifolia, Halocharis hispida. Grasses and spring ephemeres are also met in these communities. Plant cover is very low.
Vegetation of gypsum desert – Haloxylon aphyyllum, Salsola gemascens, Salsola arbuscula, Anabasis salsa, Artemisia kemrudica, Artemisia badkhysi, Artemisiasublessiana, Artemisia terra alba, Artemisia arenaria, Stipa sareptana, Nanopnyton erinaceum, Atriplex cana. Only two plant layares are common in this formation: The upper layer formed by semi shrubs and second layer formed by small herbs (Eremopyrum buonapartis, Carex pachystylis etc).
Vegetation of salt deserts – Halocnemun srobilaceum, Nitraria schoebery, Kalidum capsicum. These communities are confined to soils rich in water soluble salts. Dense patches of halophytes sometimes can be seen on solonchak.
Vegetation of loess deserts – located in foothill of the country, highlands of Karabil and Badkhyz are typical habitats of this formation, know also as ADYR in Turkmen (Bair in Uzbek). Plant communities are formed here mainly by herbs – Carex pachystilis, Poa bulbosa, Eremopirum triticeum, Aegilops juvenali, Psammogeton canescens, Astragalus sp., etc. ferula badrakema and Dorema badkhysi, high ephemerals from Umbeliferae familyform the first layer. They give a specific aspect to this landscape. Artemisia turanica and Artemisia badkhysi (sagebrush) also form several communities in this area.
Tugai vegetation: Vegetation of river valleys is known in Central Asia as - tugai. The areas occupied by tugai jungle have been declining from year to year because of severe human pressure and agricultural reclamation. There are three main formation in tugai: forests, shrubs, herbaceous vegetation. The most common species are the following: Populus ., Salix (Willow)., Tamarix ., Lycium turcomanicum(Kyzgan, dereza turkenstanskaya), Halimodendron halodentron (salt tree)… More than 70 herbaceous plant species form here dense thickets.