Ecosystem Desert

by Sandra Irmisch

Deserts cover about one fifth of the Earth's surface and occur where rainfall is less than 50 cm/year.Disturbances are common in the form of occasional fires or cold weather, and sudden, infrequent, but intense rains that cause flooding.
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Climate Conditions in the Hot Desert

A hot desert is hot, sunny and dry all year-round. They are found under subtropical ridge where unbroken sunshine and stable descending air and high pressure is for the whole year.Temperatures exhibit daily extremes because the atmosphere contains little humidity to block the Sun’s rays. Desert surfaces receive a little more than twice the solar radiation received by humid regions and lose almost twice as much heat at night.Many mean annual temperatures range from 20-25° C. The extreme maximum ranges from 43.5-49° C. Minimum temperatures sometimes drop to -18° C.


Rainfall is lowest on the Atacama Desert of Chile, where it averages less than 1.5 cm. Some years are even rainless. Inland Sahara also receives less than 1.5 cm a year. Rainfall in American deserts is higher — almost 28 cm a year.


Summer


  • max temperatures 113 degrees F


Winter


  • temperatures can drop below freezing due to radiation loss under clear skies
  • average temp. 86 degrees F
  • very little rainfall

Fall


  • warm


Spring


  • warm

Climate Conditions in the cold desert

Cold deserts are typically found at higher altitudes than hot desert climates, and are usually drier than hot desert climates.


The mean winter temperature is between -2 to 4° C and the mean summer temperature is between 21-26° C.


The mean annual precipitation ranges from 15-26 cm. Annual precipitation has reached a maximum of 46 cm and a minimum of 9 cm.


Summer


  • hot and dry
  • average temperature each month:



Winter


  • cold, dry
  • temperatures far below freezing
  • a bit of snow

Fall


  • warmer than winter but still cold



Spring


  • warmer than winter but still cold

Average Temperatures each month in the desert

Summer

  • June 71 degrees
  • July 77 degrees
  • August 79 degrees


Winter


  • December 64 degrees
  • January 59 degrees
  • February 59 degrees



Fall


  • September 77 degrees
  • October 72 degrees
  • November 68 degrees


Spring



  • March 62 degrees
  • April 66 degrees
  • May 70 degrees


See self made bar chart below Average Precipitation

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Average Precipitation each month in the desert

Summer


  • June 60 mm
  • July 80 mm
  • August 90 mm


Winter


  • December 60 mm
  • January 50 mm
  • February 50 mm



Fall


  • September 80 mm
  • October 90 mm
  • November 70 mm



Spring


  • March 50 mm
  • April 70 mm
  • May 90 mm


For self made bar charts of Temperature and Precipitation, click on link below!

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Animals and their Adaptions in the desert

Animals that live in these harsh environments have developed mechanisms over time to survive in the desert.


Examples


African Addax


  • ability to obtain all its moisture from plants that make up its food supply
  • large spread up hooves
  • nomadic nature



Mouse- Tailed Bat


  • stores fat in summer for winter season
  • go to sleep during winter



Camel


  • stores fat in humps
  • metabolizes water as needed
  • large divided hooves to walk across sand without sinking



Fennec Fox


  • huge ears to scatter heat
  • active at night
  • stays in burrow during hot times of the day
  • fur that match color of desert soil



Birds


  • fly elsewhere to seek out water supplies
  • hover high above in cooler atmosphere
  • synchronize their breeding period



Reptiles


  • waterproof skin
  • lay hard-shelled eggs
  • regulate their internal body temperature
  • produce uric acid instead of urine




Some animals simply avoid the scorching daylight temperatures by sleeping in burrows, such as the Spadefoot toad (it stays underground for nine months – an extreme example). Many spiders, lizards and snakes take advantage of burrows.

Others remain relatively immobile during the hottest part of the day, seeking shelter in the shade of the plants or rocks. Examples include meerkats, jack rabbits, insects, lizards, and snakes.

Many adapt by coming out to feed only at night, and these are referred to as nocturnal animals.

Additional adaptations include the absence of sweat glands (to prevent loss of moisture), the presence of salt glands (allowing salt secretion without water loss) and the concentration of urine during hibernation (gerbils).

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Plants and their Adaptions in the desert

Desert plants are remarkable in their ability to capture moisture when it is available and to store it during droughts. The two main adaptations are their ability to collect and store water, and features to reduce water loss.Most desert plants are low shrubs, either evergreen or deciduous, short woody trees, with small leaves and very often with spines, thorns or aromatic oils.

Many have extensive root systems extending far away from the trunk in order to maximize the collection of any rainfall.

Examples

Saguaro Cactus


  • extensive root system
  • photosynthesis only in top layer of the stem


Prickly Pear Cactus


  • stores water in spongy tissues
  • thorns ward off animal predators



Leaves are reduced to spines and not only protect the plant from being eaten but also shade the plant’s surface from losing water vapour (transpiration).


Some plants such as yuccas, agaves, etc. open their pores (stomata) only at night when water evaporation is less. Other plants have silvery or glossy leaves in order to reflect more radiant energy; they often have a bad odour or taste to ward off potential predators.


Some plants have a very short life cycle occurring only during periods of rain. During droughts, the seed has a waterproof coating and can lay dormant for years, if necessary, until rainfall occurs again.

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Soil

Soils often have abundant nutrients because they need only water to become very productive and have little or no organic matter. That makes it hard for plants to grow, so they had to adapt.


Soils are course-textured, shallow, rocky or gravely with good drainage and have no subsurface water. They are coarse because there is less chemical weathering. The finer dust and sand particles are blown elsewhere, leaving heavier pieces behind.


Desert soils tend to be poorly developed, with a high content of mineral particles but little organic matter. This is caused by the low plant productivity, which restricts the soil-building properties of microorganisms that convert organic matter into the humus components of soils.All these factors are inter-related, because soils with a low organic matter content have a low water-holding capacity - they cannot retain all the water that falls onto them. In addition, the intense evaporation of water from desert soils tends to bring dissolved salts to the surface. The high surface content of sodium and calcium ions can lead to extensive saltpans, where little or nothing can grow.


Low desert soils usually have a high clay content, low organic material content (less than 1%) and a high pH, meaning the soil is very alkaline (salty). The high clay content helps the soil to retain water and nutrients. This may sound great, but that same clay also compacts easily, can be void of vital oxygen, and can make it difficult to dig planting holes. At the other end of the spectrum, you may have sandy soils, which like clay soils contain little organic matter and do not retain moisture. The clay, silt and sand content refer to the soil texture which is nearly impossible to change.


Compost – can be made at home from vegetable waste or leaves or purchased at a nursery and has a low nutrient content but improves water holding capacity.

Manure – use manure only from plant eating animals such as cows, sheep, horses, rabbits and chickens. It needs to be well aged (six months to a year) or it could damage your plants’ roots with its high salt content.

Leaves – best if composted first, but if you have leaf drop in your yard, consider leaving it under your plants rather than raking it up. Leaves contain nutrients that are important for a plant’s health.

Mulch - Many materials are used as mulches such as grass clippings, leaves, hay, straw, kitchen scraps, sawdust, woodchips, shredded newspaper, cardboard, etc.

Shredded bark– available from your local nursery or garden center. The small bark pieces eventually interlock and will not be disturbed by the wind. Bark could be used as a total landscape cover in place of crushed granite.

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