Nabkha

Last updated
Nabkha around honey mesquite (Prosopis glandulosa) in California Nebkha or nabkha with prosopis glandulosa.jpg
Nabkha around honey mesquite (Prosopis glandulosa) in California

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. [1] Authors have also used the terms phytogenic hillock, [2] bush-mound, shrub-coppice dune, knob dune, dune tumulus, rebdou, nebbe, and takouit. [3]

Contents

In simplest terms, a nabkha is a sand dune that forms around vegetation. [1] [2] It is an aeolian landform, a structure built and shaped by the action of wind. [3]

Nabkhas are common and occur in many regions. Well known nabkha fields occur in the Lut Desert of Iran, Arabian Desert of Kuwait, [2] the Hotan River Basin in Xinjiang, China, [4] and New Mexico in the United States and adjacent Chihuahua in Mexico. [1]

Structure

Many species of sand-dwelling plants form nabkhas. In the Chihuahuan Desert they include soaptree (Yucca elata), creosote (Larrea tridentata), and atriplex (Atriplex spp.). [1] In China nabkhas form quite often around Caragana microphylla , as well as Cleistogenes squarrosa , Leymus chinensis , Caragana stenophylla , Stipa grandis , and S. glareosa , [5] plus tamarisks, reeds, and alhagi. [4] [6] In Jal Az-Zor National Park in Kuwait, they occur around Nitraria retusa , Zygophyllum qatarense , Haloxylon salicornicum , and Panicum turgidum . [2] Halophytes such as Tamarix aucheriana , Halocnemum strobilaceum and Salicornia europaea have nabkhas in saline soils, while Cyperus conglomeratus , Rhanterium epapposum , Astragalus spinosus , Lycium shawii , and Citrulus colocynthis are seen in non-saline zones. [7] On the Sinai Peninsula of Egypt they are recorded on Artemisia monosperma , Moltkiopsis ciliata , Calligonum polygonoides , Stipagrostis scoparia , and Retama raetam . [8] In central Asia and surrounding areas they occur on Calotropis , Ziziphus , Salvadora , and Heliotropium species. [9]

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. [1] The largest known were 10 meters tall [10] and a kilometer long; these large dunes have been called mega-nabkhas. [3] Mega-nabkhas in various places have also been called precipitation ridges, bordering dune ridges, and in Dutch, randwallen. [9] Sometimes only the tips of the branches of the plant within protrude from the sand, and sometimes the plant is completely engulfed. [11] 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 and clay pellets can be part of the dune. [10] Nabkhas in the Namib Desert are rich in sediment. [1] On the Kuwaiti coastline nabkhas form around Nitraria retusa growing on sabkhas, a form of salt pan. These dunes are composed of quartz, gypsum, and feldspar sands mixed with bits of volcanic rock and calcite grains. Fragments of mollusc shell and oolites can be found. Traces of garnet, zircon, topaz, and tourmaline occur. Dolomite is common. Coastal nabkhas can be eroded by saltwater, and even washed away completely, leaving the plant behind. [3]

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. [12] 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. [8] A plant generally cannot hold enough sand to start a nabkha until it is at least 10 centimeters tall. [13] [14]

Some sources describe nabkhas as ephemeral features of the landscape, but other research shows that they may last longer than previously thought. [1] Some last over 100 years. [5] 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 that it dies. [9]

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. [1] In northern China, nabkhas were present on grasslands 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 there. [5]

Nabkhas develop their own ecosystems. They are home to a variety of animals, including many invertebrates such as nematodes and the sand flea Talochestria capensis . [12] 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. [1] In degraded and oil-polluted 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. [2] Nabkhas on nitrogen-fixing plants like legumes can have elevated nitrogen levels and other nutrients that other plants can use. [8] The dunes can become islands of plant diversity in otherwise poor habitat. [2] [8]

Etymology

Nabkha is an Arabic word that has been in use for at least 14 centuries. It translates roughly to "small, sandy hillock". [3]

Related Research Articles

Dune Hill of loose sand built by aeolian processes or the flow of water

A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat regions covered with wind-swept sand or dunes with little or no vegetation are called ergs or sand seas. Dunes occur in different shapes and sizes, but most kinds of dunes are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter slip face in the lee side. The valley or trough between dunes is called a dune slack.

Namib Desert in southern Africa

The Namib is a coastal desert in southern Africa. The name Namib is of Khoekhoegowab origin and means "vast place". According to the broadest definition, the Namib stretches for more than 2,000 kilometres (1,200 mi) along the Atlantic coasts of Angola, Namibia, and South Africa, extending southward from the Carunjamba River in Angola, through Namibia and to the Olifants River in Western Cape, South Africa. The Namib's northernmost portion, which extends 450 kilometres (280 mi) from the Angola-Namibia border, is known as Moçâmedes Desert, while its southern portion approaches the neighboring Kalahari Desert. From the Atlantic coast eastward, the Namib gradually ascends in elevation, reaching up to 200 kilometres (120 mi) inland to the foot of the Great Escarpment. Annual precipitation ranges from 2 millimetres (0.079 in) in the most arid regions to 200 millimetres (7.9 in) at the escarpment, making the Namib the only true desert in southern Africa. Having endured arid or semi-arid conditions for roughly 55–80 million years, the Namib may be the oldest desert in the world and contains some of the world's driest regions, with only western South America's Atacama Desert to challenge it for age and aridity benchmarks.

Arabian Desert desert located in Western Asia

The Arabian Desert is a vast desert wilderness in Western Asia. It stretches from Yemen to the Persian Gulf and Oman to Jordan and Iraq. It occupies most of the Arabian Peninsula, with an area of 2,330,000 square kilometers (900,000 sq mi). It is the fifth largest desert in the world, and the largest in Asia. At its center is Ar-Rub'al-Khali, one of the largest continuous bodies of sand in the world.

Ordos Desert

The Ordos Desert is a desert/steppe region in Northwest China, administrated under the prefecture of Ordos City in the Inner Mongolian Autonomous Region. It extends over an area of approximately 90,650 km2 (35,000 sq mi), and comprises two sub-deserts: China's 7th-largest desert, the Kubuqi Desert, in the north; and China's 8th-largest desert, the Mu Us Desert, in the south. Wedged between the arable Hetao region to the north and the Loess Plateau to the south, the soil of the Ordos Desert is mostly a mixture of dry clay and sand, and as a result is poorly suited for agriculture.

Aeolian processes Processes due to wind activity

Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth. Winds may erode, transport, and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture and a large supply of unconsolidated sediments. Although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts.

Lop Desert desert in China

The Lop Desert, or the Lop Depression, is a desert extending from Korla eastwards along the foot of the Kuruk-tagh to the former terminal Tarim Basin in the Xinjiang Uyghur Autonomous Region of China. It is an almost perfectly flat expanse with no topographic relief. Lake Bosten in the northwest lies at an altitude of 1,030 to 1,040 m, while the Lop Nur in the southeast is only 250 m lower.

Badain Jaran Desert

The Badain Jaran Desert is a desert in China which spans the provinces of Gansu, Ningxia and Inner Mongolia. It covers an area of 49,000 square kilometers. By size it is the third largest desert in China.

<i>Haloxylon ammodendron</i> Species of tree

Haloxylon ammodendron, the saxaul, black saxaul, sometimes sacsaoul or saksaul, is a plant belonging to the family Amaranthaceae.

Kumtag Desert

The Kumtag Desert, is an arid landform in Northwestern China, which was proclaimed as a national park in the year 2002.

Ephedra alata is a species of Ephedra. These plants are perennial and xerophytic gymnosperm shrubs.

Ephedra cutleri, the Navajo ephedra or Cutler's jointfir, is a species of Ephedra that is native to the Southwestern United States.

Desert Area of land where little precipitation occurs

A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of denudation. About one-third of the land surface of the Earth is arid or semi-arid. This includes much of the polar regions, where little precipitation occurs, and which are sometimes called polar deserts or "cold deserts". Deserts can be classified by the amount of precipitation that falls, by the temperature that prevails, by the causes of desertification or by their geographical location.

Sharqiya Sands

The Sharqiya Sands is a region of desert in Oman, The region was named for the Bani Wahiba tribe. Divided between the northern and southern governorates in the Eastern Region. The area is defined by a boundary of 180 kilometers (110 mi) north to south and 80 kilometers (50 mi) east to west, with an area of 12,500 square kilometers (4,800 sq mi). The desert has been of scientific interest since a 1986 expedition by the Royal Geographical Society documented the diversity of the terrain, the flora and fauna, noting 16,000 invertebrates as well as 200 species of other wildlife, including avifauna. They also documented 150 species of native flora.

<i>Nitraria retusa</i> Species of plant in the family Nitrariaceae

Nitraria retusa is a salt-tolerant and drought-resistant shrub in the family Nitrariaceae. It can grow to heights of 2.5 metres, although it seldom exceeds more than 1 m in height. It produces small white/green coloured flowers and small edible red fruit. The plant is native to desert areas of northern Africa, where it grows in primary succession on barren sand dunes, and in areas with high salinities such as salt marshes.

A foredune is a dune ridge that runs parallel to the shore of an ocean, lake, bay, or estuary. Foredunes consist of sand deposited by wind on a vegetated part of the shore. Foredunes can be classified generally as incipient or established.

<i>Arctotheca populifolia</i> Species of plant

Arctotheca populifolia is a species of flowering plant in the aster family known by the common names beach daisy, Cape beach daisy, South African beach daisy, coast capeweed, dune arctotheca, beach pumpkin, sea pumpkin, dune cabbage, and in South Africa, seepampoen, tonteldoek, and strandgousblom. This species is native to South Africa. It was introduced to Australia and is now a common weed of coastal areas in New South Wales, South Australia, Tasmania, Victoria, and Western Australia.

<i>Tetraena alba</i> Species of flowering plant

Tetraena alba is a species of plant in the family Zygophyllaceae which is found in arid regions of Africa and the Arabian Peninsula. It is a salt tolerant plant and dominates many of the plant communities in which it grows.

<i>Tamarix nilotica</i> Species of plant

Tamarix nilotica, the Nile tamarisk is a species of shrub or small tree in the tamarisk family. It is found in arid parts of North Africa and the Middle East, particularly areas with high salinity. It forms part of the dune stabilisation process.

Bogeda Biosphere Reserve

The Bogeda Biosphere Reserve is located in the eastern region of the Tianshan Mountains in China's Xinjiang Province. Local residents named the area the Sangong River Valley after one of the largest rivers in this region, which originates from Bogeda Peak. Altogether, five major landscapes are distributed throughout the northern and southern areas of the biosphere reserve: ice-snow belts, alpine and sub-alpine meadow belts, forest belts, steppe belts and sand desert dunes. The topography consists of a middle mountain belt, low mountain erosion hills and alluvial areas. Tianchi Lake is the only natural lake in the region and lies adjacent to the Sangong River.

Wildlife of Kuwait Flora and fauna of Kuwait

The wildlife of Kuwait consists of the flora and fauna of Kuwait and their natural habitats. Kuwait is a country in the Middle East at the head of the Persian Gulf, located between Iraq and Saudi Arabia.

References

  1. 1 2 3 4 5 6 7 8 9 Langford, R. P. (2000). Nabkha (coppice dune) fields of south-central New Mexico, USA. Archived 2014-02-21 at the Wayback Machine Journal of Arid Environments 46(1) 25-41.
  2. 1 2 3 4 5 6 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.
  3. 1 2 3 4 5 Khalaf, F. I., et al. (1995). Sedimentological and morphological characteristics of some nabkha deposits in the northern coastal plain of Kuwait, Arabia. Archived 2014-02-21 at the Wayback Machine Journal of Arid Environments 29(3) 267-92.
  4. 1 2 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.
  5. 1 2 3 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.
  6. ↑ 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.
  7. ↑ 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).
  8. 1 2 3 4 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.
  9. 1 2 3 Cooke, R. U., et al. Desert Geomorphology. Taylor & Francis. 1993. pg. 357.
  10. 1 2 Milich, L. Dunes. Arid Lands Resource Sciences. The University of Arizona. Tucson. 1998.
  11. ↑ Saqqa, W. and M. Atallah. (2004). Characterization of the aeolian terrain facies in Wadi Araba Desert, southwestern Jordan. Geomorphology 62(1) 63-87.
  12. 1 2 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.
  13. ↑ Mares, M. A. Encyclopedia of Deserts. University of Oklahoma Press. 1999. pg. 189.
  14. ↑ 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.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.