Arid landscape development in contrasting settings

What is aridity?

When speaking about the arid landscape, aridity results from the existence of dry, descending air. In this way, aridity is found generally in places where anticyclonic conditions are steady, similar to the case in the locales lying under the anticyclones of the subtropics. 

The impact of subtropical anticyclones on precipitation increases with the proximity of cold surfaces. Arid conditions likewise happen in the lee of significant mountain ranges that disrupt tornados, disregarding them, making “precipitation shadow” impacts. Precipitation is likewise prevented by the nearness of incredibly hot land surfaces; as a result, large regions of dry atmosphere exist a long way from the ocean. 

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Arid zone atmosphere 

The arid zone is described as having excessive heat and insufficient, variable precipitation; in any case, differences in the atmosphere happen. As a rule, these climatic changes result from contrasts in temperature, the season where rain falls, and the level of aridity. Three significant sorts of the climate are recognised when portraying the arid zone: the Mediterranean, tropical and continental. 

In a Mediterranean climate, the rainy season occurs in autumn and winter. Summers are sweltering without any downpours; winter temperatures are clement. The figure below outlines the Mediterranean atmosphere, with a wet season beginning in October and ending in April or May, followed by five months of the dry season. 

In the tropical climate, rainfall happens throughout the summer—the further away from the Equator, the shorter the rainy season. Winters are long and dry. A typical example of a tropical climate is Sennar, Sudan, where the rainy season lasts from the middle of June until the finish of September, with an ensuing dry period of about nine months.

In the continental climate, the rainfall occurs consistently throughout the year with an increase in precipitation in summer. In Alice Springs, Australia, every month to month, precipitation is not as much as double the comparing mean month to month temperature; henceforth, the dry season stretches out over the entire year.

Figure 1.1 Annual precipitation and temperature in Rabat, Morocco. 

The arid landscape is characterised by high temperatures and low rainfall. Like this annual precipitation and temperature in Rabat, Morocco, demonstrates.
Figure 1.2 Annual precipitation and temperature in Sennar, Sudan. 
Sennar, Sudan
Alice Springs, Australia

The Arid Landscape: Precipitation 

The precipitation that tumbles from the air in a specific area is either captured by trees, bushes, and other vegetation, or it strikes the ground surface and becomes an overland stream, subsurface stream, and groundwater stream. Notwithstanding its deposition, a significant part of the precipitation returns to the atmosphere by evapotranspiration from the vegetation or by evaporation from streams and different waterways into which overland, subsurface, and groundwater flow, as outlined by the hydrologic cycle in Figure 1,4. The general elements of the hydrologic cycle in a zone are resolved, in enormous part, by the spatial and temporal nature of the precipitation patterns, temperature and barometrical humidity systems, soil and topographic features, and vegetative attributes of the territory. 

In contrast to conditions in mild locales, the precipitation dispersion in arid zones changes in summer and winter. For instance, Rabat, Morocco, gets downpours during the winter period, while the warm summer months are practical without precipitation. Then again, Sennar, Sudan, has a long dry season throughout the winter, while the downpours fall throughout the mid-year months. Although Rabat and Sennar get a similar measure of precipitation, the variety in precipitation is wide. Winter rains in Rabat can enter the ground to underground stockpiling, while the mid-year rains in Sennar fall on the scorching surface and are lost to evaporation, especially when downpours are light. In this way, the precipitation accessible to plants is higher in Rabat than in Sennar. 

This model shows that increasing yearly precipitation is required in summer rainfall regions than in colder winter regions to get a similar measure of water accessible to plants. In any case, where plants are dormant throughout the winter, they cannot utilize the accessible water during that period. 

Precipitation additionally differs from one year to the next in arid zones; this can without much of a stretch be affirmed by taking a look at precipitation measurements over some time for a specific spot. The difference between the least and most elevated precipitation recorded in different years can be generous, even though it is, for the most part, inside the scope of ± 50% of the mean yearly precipitation. The variation in the month to month precipitation is considerably more apparent. 

In many cases, the average precipitation in a given spot is not equivalent to the mean yearly precipitation recorded over many years. Variation in precipitation is imperative to forestry, since when downpours fail, recently settled woodland areas suffer. The determination of a planting date to concur with precipitation is of fundamental significance to the achievement of a successful forest. 

Precipitation
Figure 1.4 The hydrological cycle. 

Precipitation intensity is another parameter that must be considered. Since the soil will most likely be unable to absorb all the water during substantial precipitation, water might be lost by spillover. In like manner, the water from a downpour of low force can be lost because of evaporation, especially on the off chance that it falls on a dry surface. Precipitation intensity can be estimated as the number of stormy days or ideally, as the measure of downpour every hour or every day. 

Precipitation intensity likewise identifies with the danger of soil erosion. It is realized that single raindrops convey energy fit for displacing soil, especially topsoil. The erosion brought about by falling drops of water called sprinkle erosion additionally can corrupt or devastate the soil structure. It has been discovered that, as the precipitation force approaches 35 millimetres for each hour, there is a large rise in the erosive intensity of the downpour. An enormous level of precipitation in the tropics happens over this value (the supposed “erosion limit”).

Temperature 

The climatic example in the arid zones is as often distinguished by a general “cool” dry season, followed by a generally “hot” dry season, and at last by a “moderate” stormy season. All in all, there are noteworthy diurnal temperature vacillations during these seasons. Regularly, during the “cool” dry season, daytime temperatures top somewhere in the range of 35°C and 45°C and tumble to 10°C to 15°C around evening time. Daytime temperatures can move toward 45°C during the “hot” dry season and drop to 15°C during the night. During the blustery season, temperatures can go from 35°C in the daytime to 20°C around evening time. Much of the time, these diurnal temperature changes limit the development of plant species. 

The development of plants can happen just between specific, most significant and least temperatures. Amazingly high or low temperatures can be harmful to plants. Plants may endure high temperatures, as long as they can make up for these high temperatures by transpiration, yet development will be influenced contrarily. High temperatures in the outer layer of the soil result in quick loss of soil moisture because of the elevated levels of evaporation and transpiration. Even though issues of low temperatures, as a rule, are less regular in arid zones, when they do happen for moderately significant periods, plant development can be limited; at temperatures below 0°C, the plants can die. 

Air moistness 

Although precipitation and temperature are the essential elements on which aridity is based, different elements have an impact. The dampness noticeable all around has significance for the water balance in the soil. At the point when the moisture content in the soil is higher than noticeable all around, there is a propensity for water to dissipate into the air. At the point when the inverse is the situation, water will consolidate in the soil. Mugginess is commonly low in arid zones. 

In numerous zones, the event of dew and mist is vital for the survival of plants. Dew is the aftereffect of the buildup of water vapour from the air on surfaces during the night, while the fog is a suspension of tiny water beads noticeable all around. Water that is gathered on the leaves of plants as dew or fog can, on occasion, be soaked up through the open stomata, or on the other hand, fall onto the ground and add to soil moisture. Dew and fog prompt higher moistness in the air and, in this manner, decreased evapotranspiration and the preservation of soil moisture. 

Wind 

Due to the shortage of vegetation that can decrease the development of wind, arid districts regularly are windy. Winds evacuate the moist air around the plants and soil and, subsequently, increase evapotranspiration. 

Soil erosion by wind will happen in any place, soil, vegetative, and climate when conditions are helpful for this sort of erosion. These conditions (free, dry, or fine soil, smooth ground surface, sparse vegetation, and wind strong enough to start soil movement) are more prevalent in arid zones. Diminishing vegetative cover on the land is the fundamental reason for soil erosion by wind. The most damage from wind-blown soil particles is the arranging of soil material; gradual wind erosion expels sediment, earth, and fundamental issue from the surface soil. The rest of the materials might be sandy and barren. Frequently, sand accumulates in dunes and exhibits a genuine danger to the surrounding terrain. 

Precipitation is the first exchange of moisture from the water vapour in the air to the ground. The fulfilment of this hydrologic cycle is through evaporation. Loss of water from the soil because of evaporation is significant while considering “compelling” precipitation—evaporation increases with steady breezes, high temperatures, and low moisture. 

As referenced above, plants must transpire to make up for high temperatures. Transpiration results in a large amount of water loss from the soil. The force of transpiration relies upon the wind, temperature, moistness, and the plant itself. A few plants are increasingly adjusted to dry conditions and transpire less than others. In this manner, the arrangement of vegetation affects the pace of transpiration. The mix of evaporation and transpiration, called evapotranspiration, is the foremost part of the water cycle that can be impacted via land management to build water yield. 

Arid zone soils and the significance of soil properties 

Soils are shaped after some time as atmosphere and vegetation follow up on parent rock material. Significant parts of soil formation in an arid atmosphere are:

  1. Significant diurnal changes in temperature, cause mechanical or physical breaking down of rocks. 
  2. Wind-blown sands that score and wear away uncovered stone surfaces. 

The physical deterioration of rocks generally leaves large parts; only chemical weathering can separate these surfaces. The procedure of weathering in arid zones is moderate on account of the typical water shortfall. Likewise, long times of water inadequacies are significant in the disposal or draining of dissolvable salts, for which the high evaporation upgrades the aggregation. Short times of water spillover do not allow profound infiltration of salts (just short-separation transport), frequently bringing about the aggregation of salts in closed depressions. 

Vegetation assumes an essential role during the formation of soil by separating the stone particles and improving the soil with organic matter from aerial and underground parts. In any case, this job of the vegetation is decreased in arid zones on account of the small vegetation cover and the reduced improvement of aerial parts. By and by, the root systems frequently show excellent development and have the best effect on the soil. 

A forester is generally more worried about the soil properties that are imperative for the development of trees and shrubs than with the improvement of the soil profile or with the systems of local soil order. Of essential significance for arid zone soils are the water-holding limit and the capacity to supply supplements. 

The water-retaining limit of soil relies upon its physical qualities, including surface, structure, and soil depth. Surface alludes to the overall appropriation of the particles (earth, sand, and sediment). When all is said in done, the better the surface, the more prominent the water maintenance. Structure, the inside arrangement of the soil particles, is impacted by the measure of the fundamental issue that ties the soil particles. Sandy soils have no structure; clay soils have various types of structure, and the spaces between particles enable the course of air and water. The bigger these spaces, the more noteworthy is their penetrability. 

The depth of the soil oversees the measure of soil dampness and the sort of root constitution of the trees. All in all, colluvial and alluvial soils are deep; however, residual soils are variable, contingent upon the level of slant, the length and force of weathering, and the biotic impacts (development, domesticated animals brushing, and so forth.). Soils on the edges and upper inclines are regularly shallow, while those on the midslopes and valleys are respectably deep to very deep. A “hardpan” layer regularly constrains the depth of soils in arid areas. Such hardpans, which comprise of ironstone or laterite rock in the tropical zone and consolidated calcite in the Mediterranean zone, can be pretty much uninterrupted from 5 to 60 centimetres underneath the surface. 

As there are little deposition and collection of natural litter in arid zones, the fundamental issue substance of the soil is low. At the point when this soil is developed, the limited natural content that exists is soon lost. 

The chemical properties of soil control the accessibility of nutrients. Arid soils are distinguished by critical leaching of supplements and concentrated weathering of minerals, even though these two exercises are reduced by diminishing precipitation. Natural richness (which, to a great extent, relies on the fundamental issue substance of the topsoil) is frequently low. 

As a result of the aridity of the atmosphere, edaphic qualities which limit water constraints will be ideal for the planting of trees and shrubs. A portion of these edaphic qualities are: 

  1. The nearness of a water table at a depth achievable by the roots. 
  2. A soil that is sufficiently thick to retain water. 
  3. A soil surface that holds the largest amount of water. 

It ought not to be ignored that the geography of the territory can likewise assume a significant job. For example, the shallows and the lower portions of dunes can gather a significant amount of water, which can be utilized by adjusted vegetation. 

Lastly, because arid zone soils are vulnerable to both wind and water erosion, conservation and soil fixation are significant.

Frequently Asked Questions

How do arid landscapes develop in desert regions?

Arid landscapes in deserts develop through the cumulative effects of weathering, erosion, and sediment transport shaped by limited water availability.

How do arid landscapes differ in coastal desert settings compared to inland deserts?

Coastal deserts may have more diverse ecosystems due to marine influences, while inland deserts often showcase distinct landforms like sand dunes, mesas, and canyons.

What are some similarities between arid landscapes in different settings?

Despite location differences, arid landscapes often share common features like rocky terrain, sparse vegetation, and unique adaptations of plants and animals.

How does arid landscape development relate to climate and geological factors?

Arid landscapes are strongly influenced by climate patterns, including low precipitation and high evaporation rates, as well as geological processes shaping landforms.

What are the challenges and opportunities of sustainable development in arid landscapes?

Challenges include water scarcity and fragile ecosystems, but opportunities arise from innovative water management, eco-tourism, and renewable energy initiatives.

References

  • Arid and Semi-arid Region Landforms. (n.d.). Retrieved from NPS: https://www.nps.gov/subjects/geology/arid-landforms.htm
  • Arid Land. (n.d.). Retrieved from Science Direct: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/arid-land
  • Arid landscape development in contrasting settings. (n.d.). Retrieved from AQA: https://www.aqa.org.uk/subjects/geography/as-and-a-level/geography-7037/subject-content/physical-geography/hot-desert-systems-and-landscapes/arid-landscape-development-in-contrasting-settings
  • Arid Region Landforms and Eolian Processes. (n.d.). Retrieved from cengage: http://www.cengage.com/resource_uploads/downloads/0495555061_137188.pdfChapter I. The arid environments. (n.d.). Retrieved from FAO: http://www.fao.org/3/t0122e/t0122e03.htm

Cite/Link to This Article

  • "Arid landscape development in contrasting settings". Geography Revision. Accessed on March 28, 2024. https://geography-revision.co.uk/a-level/physical/arid-landscape-development-in-contrasting-settings/.

  • "Arid landscape development in contrasting settings". Geography Revision, https://geography-revision.co.uk/a-level/physical/arid-landscape-development-in-contrasting-settings/. Accessed 28 March, 2024.

  • Arid landscape development in contrasting settings. Geography Revision. Retrieved from https://geography-revision.co.uk/a-level/physical/arid-landscape-development-in-contrasting-settings/.