Desert ecology

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Sand dunes in the Sahara Desert Algeria Sahara Desert Photo From Drone 5.jpg
Sand dunes in the Sahara Desert

Desert ecology is the study of interactions between both biotic and abiotic components of desert environments. A desert ecosystem is defined by interactions between organisms, the climate in which they live, and any other non-living influences on the habitat. Deserts are arid regions that are generally associated with warm temperatures; however, cold deserts also exist. Deserts can be found in every continent, with the largest deserts located in Antarctica, the Arctic, Northern Africa, and the Middle East.

Contents

Climate

Temperatures were 115degF, enough to melt the street signs Melting signs.jpg
Temperatures were 115°F, enough to melt the street signs

Deserts experience a wide range of temperatures and weather conditions, and can be classified into four types: hot, semiarid, coastal, and cold. Hot deserts experience warm temperatures year round, and low annual precipitation. Low levels of humidity in hot deserts contribute to high daytime temperatures, and extensive night time heat loss. The average annual temperature in hot deserts is approximately 20 to 25 °C, however, extreme weather conditions can lead to temperatures ranging from -18 to 49 °C.

Rainfall generally occurs, followed by long periods of dryness. Semiarid deserts experience similar conditions to hot deserts, however, the maximum and minimum temperatures tend to be less extreme, and generally range from 10 to 38 °C. Coastal deserts are cooler than hot and semiarid deserts, with average summer temperatures ranging between 13 and 24 °C. They also feature higher total rainfall values. Cold deserts are similar in temperature to coastal deserts, however, they receive more annual precipitation in the form of snowfall. [1] Deserts are most notable for their dry climates; usually a result from their surrounding geography. For example, rain-blocking mountain ranges, and distance from oceans are two geographic features that contribute to desert aridity. Rain-blocking mountain ranges create Rain Shadows. As air rises and cools, its relative humidity increases and some or most moisture rains out, leaving little to no water vapor to form precipitation on the other side of the mountain range.

Deserts occupy one-fifth of the Earth's land surface and occur in two belts: between 15° and 35° latitude in both the southern and northern hemispheres. [2] These bands are associated with the high solar intensities that all areas in the tropics receive, and with the dry air brought down by the descending arms of both the Hadley and Ferell atmospheric circulation cells. Dry winds hold little moisture for these areas, and also tend to evaporate any water present.

Many desert ecosystems are limited by available water levels, rather than rates of radiation or temperature. Water flow in these ecosystems can be thought of as similar to energy flow; in fact, it is often useful to look at water and energy flow together when studying desert ecosystems and ecology. [3]

Water availability in deserts may also be hindered by loose sediments. Dust clouds commonly form in windy, arid climates. Scientists have previously theorised that desert dust clouds would enhance rainfall, however, some more recent studies have shown that precipitation is actually inhibited by this phenomenon by absorbing moisture from the atmosphere. This absorption of atmospheric moisture can result in a positive feedback loop, which leads to further desertification. [4]

Landscape

Erosion over time due to wind and rains have created beautiful canyons in the landscape. Antelope Canyon, AZ Antelope Canyon Heart.jpg
Erosion over time due to wind and rains have created beautiful canyons in the landscape. Antelope Canyon, AZ

Desert landscapes can contain a wide variety of geological features, such as oases, rock outcrops, dunes, and mountains. [5] Dunes are structures formed by wind moving sediments into mounds. Desert dunes are generally classified based on their orientation relative to wind directly. Possibly the most recognizable dune type are transverse dunes, characterized by crests transverse to the wind direction. Many dunes are considered to be active, meaning that they can travel and change over time due to the influence of the wind. However, some dunes can be anchored in place by vegetation or topography, preventing their movement. [6] Some dunes may also be referred to as sticky. These types of dunes occur when individual grains of sand become cemented together. Sticky dunes tend to be more stable, and resistant to wind reworking than loose dunes. [7] Barchan, and Seif dunes are among the most common of desert dunes. Barchan dunes are formed as winds continuously blow in the same direction, and are characterized by a crescent-shape atop the dune. Seif dunes are long and narrow, featuring a sharp crest, and are more common in the Sahara Desert. [8]

Analysis of geological features in desert environments can reveal a lot about the geologic history of the area. Through observation and identification of rock deposits, geologists are able to interpret the order of events that occurred during desert formation. For example, research conducted on the surface geology of the Namib Desert allowed geologists to interpret ancient movements of the Kuiseb River based on rock ages and features identified in the area. [9]

Organism adaptation

The high body temperatures of bactrian camels allow them to preserve water. Chameau de bactriane.JPG
The high body temperatures of bactrian camels allow them to preserve water.

Animals

Deserts support diverse communities of plant and animals that have evolved resistance, and circumventing methods of extreme temperatures and arid conditions. For example, desert grasslands are more humid and slightly cooler than its surrounding ecosystems. Many animals obtain energy by eating the surrounding vegetation, however, desert plants are much more difficult for organisms to consume. [10] To avoid intense temperatures, the majority of small desert mammals are nocturnal, living in burrows to avoid the intense desert sun during the daytime. These burrows prevent overheating and dehydration as they maintain an optimal temperature for the mammal. [11] Desert ecology is characterized by dry, alkaline soils, low net production and opportunistic feeding patterns by herbivores and carnivores. Other organisms' survival tactics are physiologically based. Such tactics include the completion of life cycles ahead of anticipated drought seasons, and storing water with the help of specialized organs. [12]

Desert climates are particularly demanding on endothermic organisms. However, endothermic organisms have adapted mechanisms to aid in water retention in habitats such as desert ecosystems which are commonly affected by drought. [13] In environments where the external temperature is less than their body temperature, most endotherms are able to balance heat production and heat loss to maintain a comfortable temperature. However, in deserts where air and ground temperatures exceed body temperature, endotherms must be able to dissipate the large amounts of heat being absorbed in these environments. In order to cope with extreme conditions, desert endotherms have adapted through the means of avoidance, relaxation of homeostasis, and specializations. Nocturnal desert rodents, like the kangaroo rat, will spend the daytime in cool burrows deep underground, and emerge at night to seek food. Birds are much more mobile than ground-dwelling endotherms, and can therefore avoid heat-induced dehydration by flying between water sources. To prevent overheating, the body temperatures of many desert mammals have adapted to be much higher than non-desert mammals. Camels, for example, can maintain body temperatures that are about equal to typical desert air temperatures. This adaptations allows camels to retain large amounts of water for extended periods of time. Other examples of higher body temperature in desert mammals include the diurnal antelope ground squirrel, and the oryx. Certain desert endotherms have evolved very specific and unique characteristics to combat dehydration. Male sandgrouse have specialized belly feathers that are able to trap and carry water. This allows the sandgrouse to provide a source of hydration for their chicks, who do not yet have the ability to fly to water sources themselves. [14]

The hairy, white bristles of the old man cactus help deflect strong desert sunlight. Jardin de Cactus - Lanzarote - J06.jpg
The hairy, white bristles of the old man cactus help deflect strong desert sunlight.

Plants

Although deserts have severe climates, some plants still manage to grow. Plants that can survive in arid deserts are called xerophytes, meaning they are able to survive long dry periods. Such plants may close their stomata during the daytime and open them again at night. During the night, temperatures are much cooler, and plants will experience less water loss, and intake larger amounts of carbon dioxide for photosynthesis.

Adaptations in xerophytes include resistance to heat and water loss, increased water storage capabilities, and reduced surface area of leaves. One of the most common families of desert plants are the cacti, which are covered in sharp spines or bristles for defence against herbivory. The bristles on certain cacti also have the ability to reflect sunlight, such as those of the old man cactus. Certain xerophytes, like oleander, feature stomata that are recessed as a form of protection against hot, dry desert winds, which allows the leaves to retain water more effectively. Another unique adaptation can be found in xerophytes like ocotillo, which are "leafless during most of the year, thereby avoiding excessive water loss". [15]

There are also plants called phreatophytes which have adapted to the harsh desert conditions by developing extremely long root systems, some of which are 80 ft. long; to reach the water table which ensures a water supply to the plant. [16]

Exploration and research

The harsh climate of most desert regions is a major obstacle in conducting research into these ecosystems. In the environments requiring special adaptations to survive, it is often difficult or even impossible for researchers to spend extended periods of time investigating the ecology of such regions. To overcome the limitations imposed by desert climates, some scientists have used technological advancements in the area of remote sensing and robotics. One such experiment, conducted in 1997, had a specialized robot named Nomad travel through a portion of the Atacama Desert. During this expedition, Nomad travelled over 200 kilometers and provided the researchers with many photographs of sites visited along its path. [17] In another experiment in 2004, named the United Arab Emirates Unified Aerosol Experiment, researchers used satellites and computer models to study emissions and their effect on the climate in the Arabian Desert. [18]

See also

Related Research Articles

<span class="mw-page-title-main">Biome</span> Biogeographical unit with a particular biological community

A biome is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. Biomes may span more than one continent. A biome encompasses multiple ecosystems within its boundaries. It can also comprise a variety of habitats.

<span class="mw-page-title-main">Kalahari Desert</span> Semi-arid sandy savanna in Southern Africa

The Kalahari Desert is a large semi-arid sandy savanna in Southern Africa extending for 900,000 square kilometres (350,000 sq mi), covering much of Botswana, as well as parts of Namibia and South Africa.

<span class="mw-page-title-main">Desert climate</span> Arid climate subtype in the Köppen climate classification system with very little precipitation

The desert climate or arid climate is a dry climate sub-type in which there is a severe excess of evaporation over precipitation. The typically bald, rocky, or sandy surfaces in desert climates are dry and hold little moisture, quickly evaporating the already little rainfall they receive. Covering 14.2% of Earth's land area, hot deserts are the second most common type of climate on Earth after the polar climate.

<span class="mw-page-title-main">Deserts and xeric shrublands</span> Habitat type defined by the World Wide Fund for Nature

Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this habitat type vary greatly in the amount of annual rainfall they receive, usually less than 250 millimetres (10 in) annually except in the margins. Generally evaporation exceeds rainfall in these ecoregions. Temperature variability is also diverse in these lands. Many deserts, such as the Sahara, are hot year-round, but others, such as East Asia's Gobi, become quite cold during the winter.

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<span class="mw-page-title-main">Great Basin Desert</span> Desert in the western United States

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<span class="mw-page-title-main">Aeolian processes</span> 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.

<span class="mw-page-title-main">Dryland farming</span> Non-irrigated farming in areas with little rainfall during the growing season.

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<span class="mw-page-title-main">Biological soil crust</span> Communities of living organisms on the soil surface in arid and semi-arid ecosystems

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<span class="mw-page-title-main">Fog desert</span> Type of desert

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A xerophyte is a species of plant that has adaptations to survive in an environment with little liquid water. Examples of xerophytes include cacti, pineapple and some gymnosperm plants. The morphology and physiology of xerophytes are adapted to conserve water during dry periods. Some species called resurrection plants can survive long periods of extreme dryness or desiccation of their tissues, during which their metabolic activity may effectively shut down. Plants with such morphological and physiological adaptations are said to be xeromorphic. Xerophytes such as cacti are capable of withstanding extended periods of dry conditions as they have deep-spreading roots and capacity to store water. Their waxy, thorny leaves prevent loss of moisture.

<span class="mw-page-title-main">Desert</span> Area of land where little precipitation occurs

A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to 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.

<span class="mw-page-title-main">Desert greening</span> Process of man-made reclamation of deserts

Desert greening is the process of afforestation or revegetation of deserts for ecological restoration (biodiversity), sustainable farming and forestry, but also for reclamation of natural water systems and other ecological systems that support life. The term "desert greening" is intended to apply to both cold and hot arid and semi-arid deserts. It does not apply to ice capped or permafrost regions. It pertains to roughly 32 million square kilometres of land. Deserts span all seven continents of the Earth and make up nearly a fifth of the Earth's landmass, areas that recently have been increasing in size.

<span class="mw-page-title-main">Marsupial lawn</span>

Marsupial lawns are portions of land where the soil moisture is much higher than in the vegetation surrounding it. These high moisture levels create lawns that attract a large amount of grazing by marsupials. Commonly found in Tasmania, the lawns function as habitats for local animals.

<span class="mw-page-title-main">Drylands</span> Ecozones where precipitation is balanced by evaporation from surfaces and by transpiration by plants

Drylands are defined by a scarcity of water. Drylands are zones where precipitation is balanced by evaporation from surfaces and by transpiration by plants (evapotranspiration). The United Nations Environment Program defines drylands as tropical and temperate areas with an aridity index of less than 0.65. One can classify drylands into four sub-types:

The fungal loop hypothesis suggests that soil fungi in arid ecosystems connect the metabolic activity of plants and biological soil crusts which respond to different soil moisture levels. Compiling diverse evidence such as limited accumulation of soil organic matter, high phenol oxidative and proteolytic enzyme potentials due to microbial activity, and symbioses between plants and fungi, the fungal loop hypothesis suggests that carbon and nutrients are cycled in biotic pools rather than leached or effluxed to the atmosphere during and between pulses of precipitation.

<span class="mw-page-title-main">Tropical desert</span> Type of desert

Tropical deserts are located in regions between 15 and 30 degrees latitude. The environment is very extreme, and they have the highest average monthly temperature on Earth. Rainfall is sporadic; precipitation may not be observed at all in a few years. In addition to these extreme environmental and climate conditions, most tropical deserts are covered with sand and rocks, and thus too flat and lacking in vegetation to block out the wind. Wind may erode and transport sand, rocks and other materials; these are known as eolian processes. Landforms caused by wind erosion vary greatly in characteristics and size. Representative landforms include depressions and pans, Yardangs, inverted topography and ventifacts. No significant populations can survive in tropical deserts due to extreme aridity, heat and the paucity of vegetation; only specific flora and fauna with special behavioral and physical mechanisms are supported. Although tropical deserts are considered to be harsh and barren, they are in fact important sources of natural resources and play a significant role in economic development. Besides the equatorial deserts, there are many hot deserts situated in the tropical zone.

<span class="mw-page-title-main">Central Persian desert basins</span> Ecoregion in Iran and Afghanistan

The Central Persian desert basins ecoregion covers the arid steppe and desert basins of central Iran, stretching into northwestern Afghanistan. The ecoregion extends over the Central Iranian Plateau, which is surrounded by mountain ranges and has no outlets to the sea. Much of the terrain is hot sand-and-gravel desert and large salt flats. The vegetation includes many specialized species of halophytes (salt-tolerant), xerophytes (drought-tolerant), and psammophile (sand-loving) plants.

References

  1. ↑ Pullen, Stephanie. "The Desert Biome". University of California Museum of Paleontology. Retrieved 7 November 2017.
  2. ↑ "World Deserts". Mojave National Preserve: Desert Ecology. National Park Service . Retrieved 2008-02-22.
  3. ↑ Noy-Meir, Imanuel (1973-11-01). "Desert Ecosystems: Environment and Producers". Annual Review of Ecology and Systematics. 4 (1): 25–51. doi:10.1146/annurev.es.04.110173.000325. ISSN   0066-4162.
  4. ↑ Rosenfeld, Daniel; Rudich, Yinon; Lahav, Ronen (22 May 2001). "Desert dust suppressing precipitation: A possible desertification feedback loop". Proceedings of the National Academy of Sciences of the United States of America. 98 (11): 5975–5980. Bibcode:2001PNAS...98.5975R. doi: 10.1073/pnas.101122798 . PMC   33408 . PMID   11353821.
  5. ↑ "Desert Features". U.S. Geological Survey. Retrieved 7 November 2017.
  6. ↑ Edgell, H. Stewart (2006). Arabian Deserts. Springer. pp. 201–238. ISBN   978-1-4020-3970-6.
  7. ↑ Hesse, Paul (15 November 2011). "Sticky dunes in a wet desert: Formation, stabilisation and modification of the Australian desert dunefields". Geomorphology. 134 (3–4): 309–325. Bibcode:2011Geomo.134..309H. doi:10.1016/j.geomorph.2011.07.008.
  8. ↑ "What is a Desert Landform: Features and Main Landforms in a Desert". Earth Eclipse. 2017-05-31. Retrieved 2019-02-17.
  9. ↑ Eckardt, Frank D.; Livingstone, Ian; Seely, Mary; Von Holdt, Johanna (17 October 2013). "The Surface Geology and Geomorphology Around Gobabeb, Namib Desert, Namibia". Geografiska Annaler. 95 (4): 271–284. doi:10.1111/geoa.12028. S2CID   128387707.
  10. ↑ "Desert Ecosystem". digital-desert.com. Retrieved 2017-05-03.
  11. ↑ Whitford, Walter G. (2002). Ecology of Desert Systems. San Diego, California: Elsevier Science Ltd. pp. 128, 132. ISBN   978-0127472614.
  12. ↑ Cloudsley-Thompson, J.L. (1996). "Current trends in desert ecology". Science Progress. 79 (3): 215–232. JSTOR   43423916.
  13. ↑ Buckley, Lauren (January 23, 2012). "Broad‐scale ecological implications of ectothermy and endothermy in changing environments". Global Ecology and Biogeography. 21 (9): 873–885. doi: 10.1111/j.1466-8238.2011.00737.x .
  14. ↑ Pough, F. Harvey; Janis, Christine M.; Heiser, John B. (2013). Vertebrate Life (9th ed.). Pearson. pp. 549–556. ISBN   978-0-321-77336-4.
  15. ↑ Reece, Jane B.; Urry, Lisa A.; Cain, Michael L.; Wasserman, Steven A. (2012). Campbell Biology Canadian Edition. Pearson. p. 835. ISBN   978-0-321-77830-7.
  16. ↑ "Desert Plant Survival - DesertUSA". www.desertusa.com. Retrieved 2019-05-01.
  17. ↑ Wettergreen, David; Bapna, Deepak; Maimone, Mark; Thomas, Geb (28 February 1999). "Developing Nomad for robotic exploration of the Atacama Desert". Robotics and Autonomous Systems. 26 (2–3): 127–148. CiteSeerX   10.1.1.92.7152 . doi:10.1016/S0921-8890(99)80002-5.
  18. ↑ "Scientists Study Desert Air to Understand Weather and Climate". NASA Jet Propulsion Laboratory (JPL). Retrieved 2024-03-09.
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