3. CONTENTS
1. INTRODUCTION.
2.PHYSICAL CHARACTERISTICS.
3.ABIOTIC CHARACTERISTICS.
4.ADAPTATIONS IN SUB TROPICAL DESERTS.
5.WORLDWIDE LOCATIONS: CONTINENTS HAVING
SUB TROPICAL DESERTS.
6.PLANT LIFE IN SUB TROPICAL DESERTS.
7.ANIMAL LIFE IN SUB TROPICAL DESERTS.
8.FOOD WEB IN SUBTROPICAL DESERTS.
4. INTRODUCTION
TROPICAL DESERTS:
Tropical deserts are in regions between 5- and 30-degrees latitude.
Environment is very extreme. 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.
5. SUB – TROPICAL DESERTS:
A subtropical desert is a type of ecosystem, or biome that is characterized by
high temperatures, very low precipitation and warm soils. Examples of these
types of deserts are the Mojave, Sonoran, Chihuahua, Sahara and the Great
Victoria Deserts.
Subtropical deserts, which exist between 15° and 30° north and south latitude,
are centered on the Tropics of Cancer and Capricorn. In some years,
evaporation exceeds precipitation in this very dry biome. Subtropical hot
deserts may have daytime soil surface temperatures above 60°C (140°F) and
nighttime temperatures approaching 0°C (32°F). In cold deserts, temperatures
may be as high as 25°C (77°F) and may drop below -30°C (-22°F). Subtropical
deserts are characterized by low annual precipitation of fewer than 30 cm (12
in), with little monthly variation and lack of predictability in rainfall. In some
cases, the annual rainfall can be as low as 2 cm (0.8 in), such as in central
6. PHYSICAL CHARACTERISTICS
Subtropical desert’s warm, with average annual temperatures above 10 C and
precipitation up to 100 cm (about the length of a baseball bat)/year.
Most of the Subtropical Deserts are located at 30ONorthor South latitude; this is
where air that was warmed at the equator falls back to the ground as cool, dry air
(losing its water as it rises wet and steamy over the equator). These dry winds dry the
land except for areas which are wetted by onshore breezes from warm offshore waters,
such as the Gulf coast of the United States or the eastern coast of Indochina.
Due to high evaporation of water in deserts, clay soils form the driest habitats as
water is kept close to the surface by capillary action and thus prone to evaporation.
Sandy soils offer better water supplies, and rocky and fissured soils provide the
wettest habitat.
Some desert areas haven't received a single drop of rain in hundred of years!
7. The region is characterized by dry-desert vegetation, a class of
xerophytic plants that are widely dispersed and provide negligible
ground cover.
In dry periods, visible vegetation is limited to small hard-leaved or
spiny shrubs, cacti, or hard grasses.
Many species of small annuals may be present, but they appear only
after the rare but heavy rains have saturated the soil.
There are relatively few large mammals in deserts because most are
not capable of storing sufficient water and withstanding the heat.
Deserts often provide little shelter from the sun for large animals.
The dominant animals of warm deserts are nonmammalian
vertebrates, such as reptiles.
Mammals are usually small, like the kangaroo mice of North American
deserts.
8. ABIOTIC CHARACTERISTICS
Temperature
Tropical deserts have the highest average daily temperature on the planet, as both the
energy input during the day and the loss of heat at night are large. This phenomenon
causes an extremely large daily temperature range. Specifically, temperatures in a low
elevation inland desert can reach 40°C to 50°C during the day, and drop to
approximately 5°C at night; the daily range is around 30 to 40°c
There are some other reasons for significant changes in temperature in tropical
deserts. For instance, a lack of water and vegetation on the ground can enhance the
absorption of the heat due to insolation. Subsiding air from dominant high pressure
areas in a cloud-free sky can also lead to large amounts of insolation; a cloudless sky
enables day temperature to escape rapidly at night.
9. Precipitation
Precipitation is very irregular in tropical deserts. The average annual
precipitation in low latitude deserts is less than 250 mm. Relative humidity is
very low only 10% to 30% in interior locations. Some deserts do not have
rainfall all year round, because they are located far from the ocean. High-
pressure cells and high temperatures can also increase the level of aridity.
Wind
Wind greatly contributes to aridity in tropical deserts. If wind speed exceeds 80
km/h, it can generate dust storms and sandstorms and erode the rocky surface.
Therefore, wind plays an important role in shaping various landforms. This
phenomenon is known as the eolian process. There are two types of eolian
process: deflation and abrasion.
10. First, deflation may cause the light lowering of ground
surface, leading to deflation hollows, plains, basins, blowouts,
wind-eroded plains and parabolic dunes. Second, the eolian
process leads to abrasion, which forms special landforms
with a significant undercut.
Soil:
The soil in Subtropical Deserts is either sandy or
coarse and rocky. But either way it is very dry which
makes supporting plant life very difficult.
11. Plants and animals in subtropical
deserts must be able to withstand
the hot temperatures and lack of
moisture. Shrubs and small trees in
the subtropical desert usually have
leaves adapted to retain moisture.
Animals in subtropical deserts are
usually active at night, when it is
cooler.
ADAPTATIONS OF SUB TROPICAL DESERT
13. Locations of the five subtropical desert cities: Beer Sheva,
Israel; Hotan, China; Jodhpur, India; Kharga, Egypt; Las
Vegas, NV, USA.
14. PLANT LIFE IN SUB - TROPICAL
DESERTS
• The most common plants in sub
tropical deserts are cacti, spiny,
shrubs, hard grass species
• Plants in sub tropical deserts
must be equipped to withstand the
high temperatures and lack of
moisture. Many of the shrubs
usually have leaves which have
adapted to lock in moisture.
•
15. Desert environment is usually not best suited for subtropical plants
-Subtropical plants grow well in fertile, decomposed ,deep loam soil.
They will not survive in locations with poor drainage.
-Xerophytes (dry loving plants) are common
Creosote bush: Open scraggly shrub
-Elephant trees: Stores water in spongy wood in trunk
-Therophytes (annuals via seeds)
Geophytes (survive under ground)
-Cactus (commonly found in deserts)
Desert annuals(The soil contains a "seedbank. “Many annual shave
hard seed coats of variable thickness)
16. ANIMAL LIFE IN SUB –
TROPICAL DESERTS
• Most animals who live in
Subtropical Deserts are nocturnal.
It is very hard to survive due to the
arid conditions. Many of the
animals are cold blooded.
• Many animals, such
as camels, tortoises, birds, foxes, r
odents and lizards, also live-in
subtropical deserts. A prime
example of a subtropical desert is
the Grand Canyon region, the
Mojave Desert or Sonoran Desert.
17. FENNEC FOXES:
have thick fur on feet protecting them from the hot ground;
have large, bat-like ears radiate body heat and help keep them
cool;
have long, thick hair that insulates them during cold nights and
protects them from the hot sun during the day;
have light coloured fur to reflect sunlight and keep their bodies
cools.
SPOTTED HYENA :
• They are good swimmers and can walk under water!
• They can make over 10 different sounds, but the most sound is the
laughing noise they make – therefore they are also called laughing
hyenas.
• They eat animals like zebra and wild beasts.
• They can survive in various types of environment, including dry
climates.
18. KANGAROO RAT
getting moisture from their seed diet;
living in burrows during the day to avoid extreme
heat;
having large back legs that allow them to jump
almost 3m to avoid predators;
having large ears, which enables them to hear
approaching predators
OSTRICHES:
• They may not be able to fly, but they are the largest
and fastest running birds in the entire world!
• They will eat pretty much anything if they have to,
but mostly plants, grass and seeds.
• They don’t drink very much that helps them survive
in dry climates.
19. CAMELS
have humps to store fat which a camel can break down into water and
energy when food is not available;
rarely sweat, even in hot temperatures.
have large, tough lips enable them to pick at dry and thorny desert
vegetation;
have broad, flat, leathery feet to spread their weight and provide
protection from hot sand.
20. FOOD WEB IN SUB - TROPICAL DESERTS
• A food web is the natural interconnection of food chains and a graphical representation of
what-eats-what in an ecological community.
• In a food chain in our Sub tropical desert region – as in a food chain in any other
biologically distinctive region, or “biome,” on earth – it is the plants, or the “producers,” that
capture the energy from the sun and initiate the flow, becoming the first link in the chain.
• In an almost magical-seeming process called “photosynthesis,” which means “gathering of
light,” all plants – from one-celled diatoms to mesquite and creosote shrubs to the
towering saguaro cactus to riverside cottonwoods and willows – use the sun’s energy, with
water and carbon dioxide, to produce a carbohydrate, or sugar, called “glucose,” a basic
component in the food chain.
• The plants then use the glucose to produce the carbohydrates, proteins and fats required
for reproduction and growth, drawing nourishment from various soil nutrients, for instance,
nitrogen, phosphorus and potassium.
• As producers, the plants, in effect, create storehouses of solar energy, setting the dinner
table, often impoverished in the desert, for the animals, the consumers
