Desert ecosystem

Desert ecosystem

Definition

• Desert an ecosystem found where there is very little rainfall

• Main characteristics dry, often sandy region of little rainfall, extreme temperatures, and sparse vegetation.

Definition

• The desert ecosystem is an arid type ecosystem that exists in the areas where the rainfall is very little and the climate in this ecosystem is generally extreme in harshness

Types

• 2 types

• Hot desert

• Cold desert

Types - Hot desert

• Hot desert --- It has high daytime temperature for the whole year, though rather cold at night as temperature may fall below 10oC (50oF) or even below the freezing point When the maximum daytime temperature is above 40oC (104oF).

Food web in Hot desert• The food web in the hot desert biome is a simple one. Life in this

hot, dry environment is challenging, requiring adaptations from both animals and plants.

• The soil is often dry, and desert winds carry fine dust particles away, leaving a stony landscape.

• Plants that live in the desert year round have evolved special adaptations for capturing and storing water.

• Adaptations include secreting a waxy substance to protect their leaves from drying out, thorns and spines to keep hungry animals at bay, and body shapes that can expand rapidly when water becomes available.

• Plants have large networks of roots that lie near the surface and can capture rain when it falls.

• One bush, the creosote bush, actually secretes a substance in its roots that keep other roots out of its feeding area.

Food web in Hot desert

• Many desert plants no longer have leaves, or grow only very small ones.

• They have chlorophyll in their stems. • Many cacti do not have leaves at all. • Their rounded bodies have a low surface to volume ratio,

and the spines that protect them also cast a little precious shade on their green bodies.

• Annual desert plants germinate, grow, and flower quickly when there is a rainy year.

• They make small, hard seeds that may not sprout for ten years or longer.

• Some perennial plants store moisture in underground tubers or bulbs.


• Primary producers:• 1 st trophic level• Plants• These are plants that make food through

photosynthesis. Limited by the availability of water, they produce fewer than 200 Kilocalories of food for the animals for each square meter each year.

• Including:• Trees, shrubs, cactus, wildflowers, grasses

Food web in Hot desertConsumers:2 nd trophic level:Primary consumers:*The plant-eating animals are the primary consumers.*These animals are small, and can get by on very little food.*Many are insects, or reptiles, who are cold blooded and who use less

energy to maintain their bodies than mammals and birds do. *As food for predators, they provide about 20Kilocalories per squaremeter per year for predators.*The warmth of the desert sun heats their bodies so that they can movequickly.*A few small warm-blooded animals, such as kangaroo also live here.They hide from the heat in burrows, and come out at night to feed.• Eg:Ants and other insects, rats and mice, some reptiles the largest of

which are the tortoise and chuckwalla.


• 3rd Trophic Level:• Secondary Consumers• Small Carnivores• The predators are the secondary consumers.

They occupy the third trophic level. Again we see cold-blooded animals, such as snakes, insect-eating lizards, and tarantualas. Only about 2 Kilocalories per square meter per year are stored in their bodies. In the harsher desert environments, they are the top predators.


• 4th Trophic Level:

• Tertiary Consumers

• Carnivores

• These are high level consumers, carnivores that will eat other carnivores.

Oasis

• An interesting desert "extra" is the oasis, a place where springs of water flow to the surface, providing an environment where palm trees and shrubs may grow.

• Though rare, oases gladden the hearts of travelers, and provide a refreshing micro-world with its own ecology. Not all land classified as desert is equally arid.

• The driest parts may look very stony, but where there is more moisture there will be more plants, such as sage brush, seasonal grasses, and small shrubs.

• There may tree sized cacti, palo verde, and Joshua trees.• These greener deserts may be home to quail, pygmy owls, and

even desert foxes and hawks. • A few tertiary consumers may be able to survive in these richer

environments.

Hot deserts

• Examples : Sahara, Namib/Kalahari, Arabian, Iranian, Atacama, Australian and in North America: Sonoran, Mojave and Colorado.

Sahara desert

Types – Cold desert

• Cold desert--- It has hot summers but extremely cold winters.

• Examples : the desert complex in Western North America (Great Basin), Patagonian, Turkestan & Gobi Deserts

Food web

• Food production in this system varies with the seasons.• In winter, when the south pole is in darkness, there is no

light for photosynthesis, and so no plant growth. • In spring, deep ocean currents bring up nutrients from

the ocean bottom, and the plankton grows rapidly with both light and food.

• The animals that live on it grow and reproduce. Later in the year there are fewer nutrients, and growth slows.

• Some of the animals swim away to areas with more food.

Food web in cold desert

• This biome is an ocean shore environment.• The animals that live here find their food in the ocean.• Some of the top predators go onto the land to rest or

reproduce, but the food that they eat is in the icy waters.• The cold desert is inhospitable to life. • The valleys in the interior of Antarctica and the snowy

tops of high mountains cannot support life.• Birds or insects may visit there, but the cold keeps plants

from growing.• Without plants, there can be no animals because there

is nothing for animals to eat.


• 1st trophic level:• Primary producers:• The waters of the antarctic support plankton,

which includes unicellular plants.• These tiny plants photosynthesize during the

antarctic spring and summer, and become the primary producers of a food chain that nourishes animals on land as well as in the sea. This is the first trophic level of this system.


• 2nd trophic level:• Primary consumers:• Tiny animals, such as krill (a kind of tiny shrimp) and

very small fishes, feed on the plankton. • They become the primary consumers, taking on the role

of herbivores and becoming the second trophic level of this system.

• Krill are a very important part of the food chain in the ocean.

• During the recent El Nino seasons their numbers were reduced by environmental changes in the water, and many larger animals starved.


• 3rd trophic level:• Secondary consumers: • The secondary consumers include the

huge blue and humpback whales, who feed on krill. Seals and many kinds of fishes also feed on krill and the smaller fish. Many kinds of sea birds utilize these resources, and, in the Antarctic, penguins also feed on them.


• 4th trophic level:• Tertiary consumers:• The top predators in this food chain are killer

whales. (Polar bears occupy this position in the arctic north) These are large, powerful animals, well adapted to their niche in a cold, demanding environment. They eat whatever they can catch, and prey mainly on penguins and seals.

Cold desert

Cold desert

Types based on landscapes

• Sand desert --- a wavy sand sea

• Stony desert --- gravel surfaces

• Rock desert --- bare rock surfaces with huge pavement that kept clear of sand or gravel by wind

Types based on landscape

• Plateau desert --- rocky plateaux , deeply eroded wadis, buttes or inselbergs

• Mountain desert --- bare and arid arrays of jagged rock peaks( The above landscapes can be found quite close to each other, like the desert complex in North America )

Characteristics

• A desert ecosystem may look like a barren land that is devoid of living organisms but, several animal and plants do exist in the desert ecosystem. But the number of animals and plants is usually not as large as that is present in other ecosystems.

Characteristics

• Other arid type ecosystems are semidesert ecosystem, subdesert ecosystem, steppe ecosystem, and semiarid or arid grassland ecosystem.

• Due to presence of low moisture content in deserts the biological activities in this ecosystem are regulated by the ephemeral water availability.

Plants• Plants present in the desert ecosystem are normally dwarfed in size

due to lack of rainfall. • The most common plant that is present in this ecosystem is the

cactus.• More than hundred different types of cactus plants are seen in

desert ecosystem and each one of these plants are evolved to sustain the desert ecosystem and are endemic.

• Other plants this ecosystem includes saltbush and gravillias.• Plants of the desert ecosystem are evolved with succulent bodies so

that they can retain the precious available moisture which is needed for the growth and are with narrow needle like leaves that minimizes or reduces the loss of moisture easily.

• Also some plants in desert ecosystem grow under the shades of larger plants or spread across the ground.

Animals

• Animals that are present in this ecosystem include very few numbers of large mammals of which camel is the prominent animal found in desert ecosystem.

• Other animals that are found in desert ecosystem are fox like creatures, rabbits, rats, small rodents, and moles, burrowing animals, ants, snakes, insects, few species of birds, beetles, and lizards.

• Animals and other living creatures present in the desert ecosystem have adapted to survive in these harsh climates, hot days, and freezing nights, by controlling their body heat.

Conclusion

• The fragile equilibrium of the desert ecosystem is been nowadays damaged due to the excess human activity. It is very important to recognize and understand the life forms involved in the food chain of the desert ecosystem and take necessary preventive measures to preserve the desert ecosystem.

End

Madhumitha.M

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Desert ecosystem