Nebkha or nabkha with prosopis glandulosa

A nabkha, nebkha or nebka is a type of sand dune. Other terms used include coppice dune and dune hummock or hummocky dune, but these more accurately refer to similar, but different, sand dune types.Langford, R. P. (2000)
Nabkha (coppice dune) fields of south-central New Mexico, USA.
''Journal of Arid Environments'' 46(1) 25-41. Authors have also used the terms phytogenic hillock,El-Sheikh, M. A., et al. (2010)
Vegetation ecology of phytogenic hillocks (nabkhas) in coastal habitats of Jal Az-Zor National Park, Kuwait: Role of patches and edaphic factors.
''Flora'' 205(12) 832-40. bush-mound, shrub-coppice dune, knob dune, dune tumulus, rebdou, nebbe, and takouit.Khalaf, F. I., et al. (1995)
Sedimentological and morphological characteristics of some nabkha deposits in the northern coastal plain of Kuwait, Arabia.
''Journal of Arid Environments'' 29(3) 267-92. In simplest terms, a nabkha is a sand dune that forms around vegetation. It is an aeolian landform, a structure built and shaped by the action of

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...

. Nabkhas are common and occur in many regions. Well known nabkha fields occur in the

Lut Desert The Lut Desert, widely referred to as Dasht-e Lut ( fa, دشت لوت, "Emptiness Plain"), is a large salt desert located in the provinces of Kerman and Sistan and Baluchestan, Iran. It is the world's 33rd-largest desert, and was included on U ...

Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...

, Arabian Desert of

Kuwait Kuwait (; ar, الكويت ', or ), officially the State of Kuwait ( ar, دولة الكويت '), is a country in Western Asia. It is situated in the northern edge of Eastern Arabia at the tip of the Persian Gulf, bordering Iraq to the nort ...

, the Hotan River Basin in

Xinjiang Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest ...

, China,Wu, S., et al. (2008)
The morphological characteristics and growth mode of nabkha in the basin of Hotan River, Xinjiang.
''Geographical Research'' 27(2) 314-22. and

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ke ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

and adjacent Chihuahua in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

Structure

Many species of sand-dwelling plants form nabkhas. In the

Chihuahuan Desert The Chihuahuan Desert ( es, Desierto de Chihuahua, ) is a desert ecoregion designation covering parts of northern Mexico and the southwestern United States. It occupies much of far West Texas, the middle to lower Rio Grande Valley and the lo ...

they include soaptree (''Yucca elata''),

creosote Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics. Some creosote types were ...

(''Larrea tridentata''), and atriplex (''Atriplex'' spp.). In China nabkhas form quite often around ''

Caragana microphylla ''Caragana'' is a genus of about 80–100 species of flowering plants in the family Fabaceae, native to Asia and eastern Europe. They are shrubs or small trees growing tall. They have even-pinnate leaves with small leaflets, and solitary or clu ...

'', as well as '' Cleistogenes squarrosa'', ''

Leymus chinensis ''Leymus chinensis'', commonly known as false wheatgrass or Chinese rye grass, is a species of wild rye Wild rye is a common name used for several grasses. Wild ryes belong to any of three genera: * '' Elymus'' (wheatgrasses) * ''Leymus ''Le ...

'', '' Caragana stenophylla'', '' Stipa grandis'', and '' S. glareosa'',Wang, X., et al. (2006)
Nebkha development and its significance to wind erosion and land degradation in semi-arid northern China.
''Journal of Arid Environments'' 65 129-41. plus tamarisks, reeds, and

alhagi ''Alhagi'' is a genus of Old World plants in the family Fabaceae. They are commonly called camelthorns or manna trees. There are three to five species. ''Alhagi'' species have proportionally the deepest root system of any plants - a 1 m h ...

.Li, Z., et al. (2010
Bio-geomorphologic features and growth process of ''Tamarix'' nabkhas in Hotan River Basin, Xinjiang.
''Journal of Geographical Sciences'' 20(2) 205-18. In Jal Az-Zor National Park in Kuwait, they occur around ''

Nitraria retusa ''Nitraria retusa'', commonly known as Nitre bush, is a salt-tolerant and drought-resistant shrub in the family Nitrariaceae. It can grow to heights of , although it seldom exceeds more than 1 m in height. It produces small white/green colo ...

'', '' Zygophyllum qatarense'', '' Haloxylon salicornicum'', and ''

Panicum turgidum ''Panicum turgidum'' is an old world clumping desert bunchgrass of the genus '' Panicum''. It is a plant of arid regions across Africa and Asia, and has been introduced to other parts of the world. Description ''Panicum turgidum'' is a perennia ...

''.

Halophyte A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. Th ...

s such as '' Tamarix aucheriana'', ''

Halocnemum strobilaceum ''Halocnemum strobilaceum'' is a species of flowering plant in the subfamily Salicornioideae of the family Amaranthaceae. It is native to coastal areas of the Mediterranean Sea and the Red Sea and parts of the Middle East and central Asia, wher ...

'' and ''

Salicornia europaea ''Salicornia europaea'', known as common glasswort or just glasswort, is a halophytic annual dicot flowering plant in the family Amaranthaceae. Glasswort is a succulent herb also known as ‘Pickle weed’ or ‘ Marsh samphire’. As a succule ...

'' have nabkhas in saline soils, while '' Cyperus conglomeratus'', ''

Rhanterium epapposum ''Rhanterium epapposum'' is a plant of the family Asteraceae. Native to the deserts of the Arabian Peninsula including Saudi Arabia, Kuwait and Qatar where it is known locally as ''arfaj'' (). The ''arfaj'' consists of a complicated network of b ...

'', '' Astragalus spinosus'', '' Lycium shawii'', and '' Citrulus colocynthis'' are seen in non-saline zones.Al-Dousari, A. M., et al. (2008)
Characteristics of nabkhas in relation to dominant perennial plant species in Kuwait.
''Kuwait Journal of Science'' 35(1). On the

Sinai Peninsula The Sinai Peninsula, or simply Sinai (now usually ) (, , cop, Ⲥⲓⲛⲁ), is a peninsula in Egypt, and the only part of the country located in Asia. It is between the Mediterranean Sea to the north and the Red Sea to the south, and is ...

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...

they are recorded on ''

Artemisia monosperma ''Artemisia monosperma'' is a species of flowering plant in the wormwood genus '' Artemisia'', family Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera ...

'', '' Moltkiopsis ciliata'', '' Calligonum polygonoides'', '' Stipagrostis scoparia'', and ''

Retama raetam ''Retama raetam'' is a species of flowering plant in the family Fabaceae, native to northern Africa from the Western Sahara to Sudan, Sicily, Israel, Sinai Peninsula, the Palestine region and Saudi Arabia, and widely naturalized elsewhere. F ...

''.El‐Bana, M. I., et al. (2007)
Role of host identity in effects of phytogenic mounds on plant assemblages and species richness on coastal arid dunes.
''Journal of Vegetation Science'' 18(5) 635-44. In central Asia and surrounding areas they occur on '' Calotropis'', ''

Ziziphus ''Ziziphus'' is a genus of about 40 species of spiny shrubs and small trees in the buckthorn family, Rhamnaceae, distributed in the warm-temperate, subtropical and tropical regions of the world. The leaves are alternate, entire, with three promi ...

'', '' Salvadora'', and ''

Heliotropium ''Heliotropium'' is a genus of flowering plants in the heliotrope family, Heliotropiaceae. There are around 325 species in this almost cosmopolitan genus, which are commonly known as heliotropes (sg. ). It is highly toxic for dogs and cats. ...

'' species.Cooke, R. U., et al. ''Desert Geomorphology''. Taylor & Francis. 1993. pg. 357. A nabkha is variable in size and shape. The typical example is a steep mound with a flat top. The larger nabkhas of the Chihuahuan Desert reach about 4.3 meters tall by 40 meters wide. The largest known were 10 meters tallMilich, L
Dunes.
Arid Lands Resource Sciences. The University of Arizona. Tucson. 1998. and a kilometer long; these large dunes have been called mega-nabkhas. Mega-nabkhas in various places have also been called precipitation ridges, bordering dune ridges, and in

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

, ''randwallen''. Sometimes only the tips of the branches of the plant within protrude from the sand, and sometimes the plant is completely engulfed.Saqqa, W. and M. Atallah. (2004)
Characterization of the aeolian terrain facies in Wadi Araba Desert, southwestern Jordan.
''Geomorphology'' 62(1) 63-87. Nabkhas may join together and form broad, hilly dune fields, or more often, chains and scattered dune patches. The sand composition is also variable.

Silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel ...

and

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

pellets can be part of the dune. Nabkhas in the

Namib Desert The Namib ( ; pt, Namibe) is a coastal desert in Southern Africa. The name is of Khoekhoegowab origin and means "vast place". According to the broadest definition, the Namib stretches for more than along the Atlantic coasts of Angola, Nami ...

are rich in

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

. On the Kuwaiti coastline nabkhas form around ''Nitraria retusa'' growing on

sabkha A sabkha ( ar, سبخة) is a coastal, supratidal mudflat or sandflat in which evaporite-saline minerals accumulate as the result of semiarid to arid climate. Sabkhas are gradational between land and intertidal zone within restricted coastal p ...

s, a form of salt pan. These dunes are composed of

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywal ...

, and

feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) felds ...

sands mixed with bits of

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...

and calcite grains. Fragments of mollusc shell and oolites can be found. Traces of

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...

, topaz, and

tourmaline Tourmaline ( ) is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors. The te ...

occur.

Dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

is common. Coastal nabkhas can be eroded by saltwater, and even washed away completely, leaving the plant behind. The type of plant influences the shape of the nabkha; for example, treasure flower (''Gazania rigens'') forms tall, conical or elongated dunes, while beach daisy (''Arctotheca populifolia'') forms shorter, semi-circular dunes.Hesp, P. and A. McLachlan. (2000)
Morphology, dynamics, ecology and fauna of ''Arctotheca populifolia'' and ''Gazania rigens'' nabkha dunes.
''Journal of Arid Environments'' 44(2) 155-72. ''Retama raetam'' is a salinity-tolerant woody shrub that can extend roots up to 20 meters deep in the soil, persisting through harsh conditions and eventually building nabkhas up to 8 meters wide. A plant generally cannot hold enough sand to start a nabkha until it is at least 10 centimeters tall.Mares, M. A. ''Encyclopedia of Deserts''. University of Oklahoma Press. 1999. pg. 189.Ahmed, M. M., et al. (2009)
Chemical and morphological characteristics of phytogenic mounds (nabkhas) in Kuwait.
''Arab Gulf Journal of Scientific Research'' 27(3) 114-26. Some sources describe nabkhas as

ephemeral Ephemerality (from the Greek word , meaning 'lasting only one day') is the concept of things being transitory, existing only briefly. Academically, the term ephemeral constitutionally describes a diverse assortment of things and experiences, fr ...

features of the landscape, but other research shows that they may last longer than previously thought. Some last over 100 years. Still, a nabkha on an annual plant generally only lasts one season. A nabkha can also be self-limiting if the sand accumulation lifts the plant far enough out of the

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

that it dies.

Ecology

Nabkhas are common features in landscapes that are undergoing desertification. In North America, a characteristic sign of desertification is the spread of mesquites (''Prosopis'' spp.) into the habitat. Mesquites rapidly accumulate windblown sand, forming nabkhas. In northern China, nabkhas were present on

grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...

s before they were converted to agriculture, but this conversion accelerated their development and they are a common feature of abandoned farm fields in the region. They are indicators of soil

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

there. Nabkhas develop their own

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s. They are home to a variety of animals, including many invertebrates such as nematodes and the sand flea '' Talochestria capensis''. The dune tends to have more organic material than the surrounding sand, as windblown plant matter accumulates in it and the roots of the plant penetrate it. In degraded and

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

polluted Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

desert areas in Kuwait, plants with nabkhas act as ecosystem engineers, hosting a sheltered site with layers of relatively rich soil in which other plants can grow. Nabkhas on

nitrogen-fixing Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. Atm ...

plants like legumes can have elevated nitrogen levels and other nutrients that other plants can use. The dunes can become islands of plant diversity in otherwise poor habitat.

Etymology

''Nabkha'' is an

Arabic Arabic (, ' ; , ' or ) is a Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C. E.Watson; Walter ...

word that has been in use for at least 14 centuries. It translates roughly to "small, sandy hillock".

References

{{reflist Dunes Arabic words and phrases