Introduction, types, characteristics features structure and function of an forest ecosystem, grassland ecosystem and desert ecosystem

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Introduction, types, characteristics features structure and function of an forest ecosystem,  grassland ecosystem and desert ecosystem

 

The biosphere forms a thin crust of living beings over the surface of our planet and consists an immense variety of organisms out of which only about 1.5 million species have been identified and described. The existence and well being of living organisms depend on a system of complex interactions within and in between the components of environment – the lithosphere, hydrosphere, atmosphere and the biosphere and the biosphere itself. These interactions, which satisfy all needs of all living organism such as shelter, oxygen to respire, mates to reproduce etc. – essential for sustained life and continuation of species.

TERRESTRIAL HABITAT – BIOMES Terrestrial habitat refers to the land where the organisms live. Land constitutes only 30% of the earth‘s surface. However, it is characterized by a variety of climates diversity of abiotic factors and heterogeneity of biotic communities.

1. Characteristics of Terrestrial Habitat:

1. Water is very much limited, and there is the scarcity of water. Dryness prevails.

2. Dehydration predominates

3. Temperature fluctuations are great

4. The intensity of light is high

5. Atmospheric air is the source of O₂ 6. O₂ and CO₂ are provided at a constant rate

7. The land is not continuous, but is provided with a number of geographical barriers in the form of mountains, valleys, lakes, rivers, seas, etc.

8. Soil contains all the necessary nutrients for the production of energy.

9. On land the buoyancy is lesser when compared to water.

2. Geographical Classification of Land: Based on the distribution of animals and plants, the earth‘s surface is divided into six realms, namely,

 1. Palaeractic realm 4. Ethiopian realm 2. Nearctic realm 5. Oriental realm 3. Neotropical realm 6. Australian realm Each realm includes wide land masses and is separated from adjacent realms by oceans, mountains or deserts.

3. Ecological Classification of Land : Ecologically, the terrestrial habitat is subdivided into a number of subunits called biomes. A biome is defined as a major terrestrial community characterised by distinctive plants and animals.

Examples : 1. Forest biome, 2. Grassland biome, 3. Tundra biome, 4. Coniferous biome, 5. Cave biome and 6. Desert biome.

4. Characteristics of Biomes

1. A biome is a major terrestrial community. 2. It is formed of distinctive animals and plants 3. Many biomes are present in a geographical realm. 4. Each biome has a climax community which is dominant. The climax community forms the matrix of the biome. The biome is named after the climax community. For example, in a grassland biome, grasses form the climax community ; in a forest biome trees form the climax community. 5. In addition to climax community, each biome has many intermediate communities. Thus a biome consists of a special combination of a complex of communities. 6. The communities of a biome are maintained under the climatic conditions the region. 7. There is no clear-cut demarcation between adjacent communities. 8. The adjacent communities blend in the meeting place to form an ecotone. 9. A biome is different from an ecosystem in that the ecosystem consists of both biotic factors and abiotic factors. But a biome includes only plants and animals.

5. Tundra Biomes

Tundra refers to the treeless plain of the arctic region which remains marshy during summer and frozen hard in winter. About 5 million acres of Tundra stretch across North America, Northern Europe and Siberia. Tundra is characterised by the following salient features :

1. It lies between the Arctic ocean and the polar ice caps on the north and the coniferous forest in the south.

2. Rainfall is low.

3. Climate is cold

4. Winter is characterised by the continuous darkness and summer is characterised by continuous light. Even in summer the intensity of light is low.

5. The ground except the surface remains frozen. (10 or 20 cm), the frozen deeper soil is called permafrost.

6. The frozen soil starts thawing during summer.

7. The vegetation grows only for a brief period of 60 days in summer.

8. Flora : Trees are absent. All plants are low and ground –hugging forms. Eg. Lichen (reindeer moss), mosses, grasses, sedges and shrubs.

 9. Fauna : Arctic fox, hare, reindeer, lemmings, oxen, polar bear, caribou, walruses, seals, penguins, migratory birds and insects appear during summer.

6. Grassland Biomes

This biome is a plain land occupied by grasses. Grasses form the climax community in this biome. Grassland biome is also called prairies, steppes, pampas, etc. It is found in north America, Asia, Siberia, Russia and Africa. Grassland has the following characteristics.

1. Grasses form the climax community.

2. Trees are also present. They grow along the streams.

3. Grasses are of three types, namely tall grasses (above 1 meter), mid grasses (between 0.5 and 1 meter) and short grasses (less than 0.5 meter).

4. Grassland biome is intermediate between desert and forest in the amount of precipitations (rainfall). It ranges from 20 to 40 inches.

5. It is distributed in the interiors of continents.

6. Grassland soil is rich in humus.

7. It is an ideal home for grazing animals. Fauna : Bison, Wildhorses, ass, antelopes, zebra, rabbits, ground squirrels, prairie dogs, kangaroos, wallabies, prairie chicken, lark, sparrow, rattle snake Bufo (amphibian) etc.

 7. Forest Biomes

A forest biome is a land of thick growth of trees. Trees constitute the climax community. Precipitation is high. The moisture of the soil is high and constant. It exhibits a clear vertical stratification. It consists of an upper layer formed of leaves and braches of trees, a middle layer formed of herbs and shrubs and the forest floor. Based on the types of plants and the geographical location, forest biomes are classified into three types, namely,

1. Coniferous forests

2. Tropical rain forests and

3. Deciduous forests  

 

 1. Coniferous Forests (Taiga)

1. This biome is thickly populated with pine trees characterized by needle-like leaves. These trees belong to the class of Gymnosperms.

2. The leaves of the trees are evergreen.

3. It is confined to the northern hemisphere at high altitudes.

4. It stretches as a belt south of Tundra in North America and Eurasia

5. It is also called taiga because it gives thick shade and prevents the growth of herbs and shrubs.

6. The annual rate of production is great because of the ever-green leaves and continuous photo-synthesis throughout the year.

7. It forms the major supplier of timber.

8. The seeds of pine trees form the major source of food for certain animals.

9. Fauna : Hyla, Rana, Woodpeckers, Cross-bills, squirrels, hares, beavers, deers, Canadian porcupine, wolves, bears, foxes, caribou, lynx, wolf, bears, red fox, elk, insects like bark beetles, saw flies, geometrid moths etc. 2. Tropical Rain Forests :

1. This forest is characterized by thick growth of tall trees. The leaves of these trees are broad and evergreen.

2. Rain forests are found in tropical countries like India, Western ghats, Malaya, East Indias, Africa, Northern Australia, etc.

3. In these forests precipitation is high. It is more than 200 cm per year.

4. In these forests humidity is high.

5. In these forests illumination is reduced because of thick vegetation. 6. From these forests air-currents are absent.

7. Here vertical stratification is distinct. It is formed of three layers, namely an upper of leaves and branches, a middle layer of shrubs and small trees and a lower of forest floor.

 8. Fauna : Worms, snails, millipeds, centipeds, scorpions, isopods, spiders, insects, planarians, leeches, tree frogs, chamaeleon, geckoes, snakes, parakeets, birds of paradise, insectivores, leopards, jungle cats, ant eaters, flying squirrels, monkeys , sloths, arboreal kangaroos, tiger, elephant, samphar deer, spotted deer, gaur, etc.

3. Deciduous Forests

1. This forest is characterized by tall trees with broad and thin leaves, which fall during water.

2. Deciduous forests are found in Australia, Europe, Japan and Eastern United States.

3. The climate is warm during summer and cold during winter.

4. Precipitation is moderate and it ranges from 60 cm to 150 cm per year.

5. The winter is characterized by short days and summer by long days.

6. During autumn the trees shed their leaves and in winter the trees are without leaves and in a dormant condition.

7. Fauna : Deer, fox, bear, beaver, squirrel, flying squirrel, raccoon, wild boar, rattle snake, song birds, birds of prey, horned owl, hawks, crested fly catcher, thrushes, woodpecker, amphibians insects, etc.

4. Forest Adaptations :

1. Most of the forest animals are arboreal inhabit and they have adaptations for arboreal life (life on trees). The arboreal adaptations are as follows :

a. Small and slender body

b. Opposable toes Eg. Chamaeleon.

c. Digits are fused in groups – Syndactyly

d. Presence of claws.

e. Presence of adhesive discs on the digits. Eg. tree frogs

f. The tail is prehensile and it acts as the fifth limb.

g. Development of parachuting mechanism

h. The pectoral girdles are strong.

i. Limb are elongated.

j. Protective colouration

k. Reproduction is specially adapted for tree life. For example, the amphibian Phyllomedusa lays its eggs on rolled up leaves hanging above water, the tadpoles directly fall into the water on hatching.

2. The sense of hearing is well developed. The vision is poor.

3. Forest animals living on land are heavily built.

4. The antlers and horns are short or reduced.

8. Desert Biomes : A desert is a waterless, treeless, large waste-land often covered with sand. It is characterized by low or no rainfall, scarcity of water, extremes of temperature and dust – storms. The important deserts in the world are Rajasthan (India), Gobi (China), Sahara and Kalahari (Africa). Deserts are broadly classified into two groups, namely hot-deserts and cold deserts. In hot deserts the temperature is very high. Eg. Sahara, gobi, Rajasthan etc. In cold deserts the temperature is very low. They are situated at high altitudes. Eg. Tadakh, Tibet, Alps, Scandinavian mountains etc.

 1. Desert Fauna Uromastix, Moloch horridus, Heloderma, Mabuia, rattle snakes, Phrynosoma, Phrynocephalus, birds like quails, Indian bustard, grey partidge, and mammals like bats, hedgehog, hare, ant eater, porcupine, mouse, wild boar, samphar deer, spotted deer, wolf, red foxes, jungle cats, Panther etc. are some of the desert animals.

2. Desert Adaptations

Desert animals develop adaptations for four purposes.

They are : 1. Water conservation

2. Water getting

3. Tolerance of heat and

4. Protection.

1. Water conservation

Desert is characterised by dry atmosphere. Hence desert animals tend to lose water from their body through evaporation. So the desert animals have plenty of adaptations for conserving water.

1. Imprevious Skin : In desert animals evaporation through body-surface is prevented by the development of impervious skin. The skin may be covered by scales, spines, scutes, shields etc. eg. Moloch horridus.

2. Nocturnal Habit : To prevent evaporation, certain desert animals are active during night only.

3. Shady Places : Diurnal animals rest in shady places to prevent the loss of water.

4. Burrowing Habit : Evaporation is prevented by living inside burrows during hot days.

5. Aestivation : Certain desert animals like pocket mice, Kangaroo rat, etc. aestivate to prevent desiccation.

6. Excretion : Desert insects, reptiles and birds produce uric acid as their nitrogenous waste product, since the disposal of uric acid does not require water. Again water from faeces and urine is reabsorbed in these animals. Hence the faeces and urine are in the form of paste.

7. Absence of Sweat Glands : The desert rodents and ruminants have no sweat glands.

8. Reduced Metabolic Rate : The African antelope Oryx reduces its metabolic rate and conserves water.

4. Water Getting

Water scarcity is prevalent in deserts. Hence desert animals face problems of getting water. Water problem in deserts is solved in the following ways:

1. Water Holes : Desert animals get water from water holes.

2. Migration : Desert animals migrate short or long distances to get water.

3. Water From Food : Certain desert animals depend on the small amount of water present in the food taken in. The water present in succulent plants forms the source of water for rabbits and turtles.

4. Water From Seed : The rodent Jerboas can live without water except that obtained from dry seeds.

5. Water From Blood : Carnivorous animals get water from the blood of their prey.

6. Metabolic Water : Animals like ants and kangaroo rats depend on the small amount of water arising as a byproduct in metabolism. 

7. Hygroscopic Skin : The skin of spiny lizard Moloch horridus is hygroscopic. It absorbs water from the atmosphere like a blotting paper.

8. Intestinal storage : The lizard Uromastix stores water in the intestine.

9. Water Cells : Camel can take in large quantities of water when available. For example, it drinks 40 litres of water in 10 minutes. The water is stored in the water cells present in the rumen of stomach.

10. No Drinks : Desert birds like black – throated sparrow, zebra finch, grey-backed finch, lark etc., can survive indefinitely without drinking water. Similarly kangaroo rat can seal its burrow by day and thus keeps its chamber moist and can live throughout the year without drinking water.

3. Tolerance of Heat : Heat is very high in deserts. To escape from heat, desert animals possess the following adaptations.

1. Heat Resistance: Camel is resistant to heat. The body- temperature of camel is labile. During day it can allow its body-temperature to rise to 40.6 ⁰C without sweating. Similarly, at night it allows its body-temperature to drop to 33.8 ⁰C. Hence camel is resistant to heat. Similarly, the African antelope Oryx can store heat in its body during day. It causes a substantial rise in body-temperature (hyperthermia).

2. Aestivation: Certain desert animals like pocket mice, Kangaroo rat etc., aestivate to tide over extreme heat.

3. Tolerance of Dehydration: Most mammals die, when they lose as much as 20% of the water from their bodies. But camel can lose over 40% without serious danger.

4. Absence of Fatty Insulation: Camel accumulates its fat in the hump rather than over the body. This speeds up the flow of heat away from the body. 4. Protection

Desert Animals protect themselves in the following ways : 1. Nocturnal habit protects them form the scorching sun.

2. They live in burrows.

3. They have adaptations for swift running.

4. They are provided with long legs to keep their body above the burning sand. In Mabuya the lower eyelid is much enlarged and transparent ; it can be used to close the eye without affecting vision.

5. Their nostrils, eyes and ears are protected from dust-storms. In camel the nostril can be closed like eyes.

6. They are provided with spines for protection.

7. The presence of poison is another desert adaptation Eg. Rattle snake, Helodermapunctatum (lizard) , etc.

9. Cave Biome

Caves are natural hollows on the earth . They may be present on the surface of the earth or in the sides of hills, mountains, and rocks or underground or under bodies of water.

1. Origin of Caves Caves are formed in the following ways :

1. Flowing Rivers : Most of the caves are abandoned channels through which underground rivers must have flowed in the past.

2. Dissolution of Limestone : Limestone is readily soluble in water. When limestone is present somewhere on the earth, it gradually dissolves and the surface water gradually sinks to form crevices. These crevices deepen to form caves.

3. Wind Erosion : Caves in sand is formed by the erosion caused by winds.

 4. Sea Erosion : Caves in the sea are formed by the dashing of waves.

2. Zonation of Caves

Based on the penetration of light, a cave is divided into three zones, namely the dysphotic (twilight) region, the middle region and the inner region.

1. Dysphotic or Twilight Region : This is the mouth region of the cave. It extends upto the region where light can penetrate.

2. Middle Region : In this region, the penetration of light is lesser.

3. Inner Region : This region has no light at all. Total darkness prevails here.

3. Characteristics of Cave

1. Darkness : Light is absent from caves; hence total darkness prevails in caves.

2. Uniform Temperature : The temperature in caves remains uniform throughout the year.

3. High Humidity : The humidity in caves is high.

4. Absence of Air Currents : The air in caves remains stagnant.

4. Cave Flora The cave flora includes only the non-green plants like fungus, mold, mushrooms, etc.

5. Cave Fauna Caves are inhabited by the following animals : Platyhelminthes : Turbellarian worms Annelida : Chaetopod worms, leeches, etc. Annelida : Decapods,Isopods, Amphipods, Springtails, Mites, spiders, silverfish, cockroaches, cricket, etc. Mollusca : Snails Fishes : Amblyopsis, Typhlichthyes, Gronias nigrilabris, etc Amphibia : Proteus anguinus, Typhlotriton Spelerpes, Typhlomolge Birds : Owls Mammals : White-footed mouse, Peromyscus teucopus, bats, etc.

5. Cave Adaptations

The animals living in caves are called cavernicolous animals and their adaptations are called Cavernicolous adaptations. 

·         Loss of Pigmentations: Development of pigments on the skin requires light. As there is· no light in the cave, pigments are absent from cave animals. Hence they are pale or light in colour. When cave animals are brought to light, they develop pigments and become dark in colour. Hence the ability to develop pigments is not permanently lost in cave animals.

·         Absence of Eyes : Eyes are photoreceptors. They require light for their function. As there is no light in the cave, the eyes in cave animals are either nonfunctional or rudimentary or completely lost. 

·         Weak Exoskeleton: The exoskeleton of cave arthropods is weak and fragile. The shell of cave snails i thin; scales are completely lost from cave fishes. 

·         Slender Body: Cave animals are provided with a slender long body. 

·         Tactile organs: As photoreceptors are inefficient, cave animals are provided with powerful tactile organs in the form of long antennae, taste buds on head, snout, lips, etc.

·         Scarcity of Food: Caves are characterised by scarcity of food. This scarcity of food is due to lack of green vegetation. Hence cave animals have adaptations to live without food for many days. 

·         Neoteny : Cave urodeles exhibit neoteny. By neoteny the larval urodeles can produce young ones.

·         Carnivorous Habit: As there is no vegetation, most of the cave animals are carnivorous in habit. 

·         Degeneration: There is no struggle for existence and no competition in caves. Hence there is no specialization in cave animals; instead, they have undergone degeneration in many respects. 

·         Primitiveness: Caves provide a constant unchanging environment. Hence cave animals possess primitive characters and many archaic forms persist in caves.

MANGROVES

Mangroves refer to groups of small land trees that inhabit inertida flats and estuarine deltas along the tropical and subtropical sea-coasts. Several plant species dominate in mangroves. Hence mangroves are commonly called mangrove forests. The common representatives of mangroves are Rhizophora, Avicennia and Bruguiera. Mangroves can tolerate salinities from full strength sea water to fresh water. Hence the mangroves are polyhaline.

Salient Features of Mangroves

Mangroves are characterized by the following salient features :

1. Mangrove is an intertidal ecosystem found along the sea coasts of tropical and subtropical countries.

2. It is commonly found in estuarine deltas.

3. The mangrove ecosystem is dominated by trees and hence the mangroves are called mangrove forests.

4. The mangroves have the ability to tolerate wide ranges of salinity from sea water to fresh water. Hence they are called polyhaline.

5. They can tolerate dissolved oxygen levels low as zero.

6. The mangroves develop between the level of sea and the level of high tide.

7. Mangrove plants are recognized by the presence of pneumatophores, prop roots and viviparous seeds.

8. Mangroves grow in sheltered shores, penetrating into the estuaries of rivers, tidal creeks, backwaters, salt marshes, and coastal mudflats where salt water penetrates.

9. Mangroves are protected from continuous wave action.

10. Mangroves receive terrestrial freshwater runoff.

11. Mangrove is a good habitat for a variety of organisms. It is an excellent rearing area for juvenile fish, shellfish and reptiles. Crabs are abundant in the mangrove ecosystem.

12. Mangrove is a human resource potential. It helps in building up an maintaining the coastline from erosion damage. It is a source of building material, as a source of tanning material in the leather industry and for productive fisheries.

13. Mangroves are open systems since they are constantly subject to tidal flow and seasonal flooding.

14. The mangrove soil is mainly formed of silt. The silt brought by the high tides from the sea contains shells of foraminifera and molluses.

The Mangroves of India

About 80% of mangroves in India are located in West Bengal. The common mangroves are as follows:

1. Pitchavaram mangrove at Cauvery delta.

 2. Muthupet Chatram mangrove.

3. Orda mangrove in Goa.

4. Ribandar mangrove in Goa.

5. Andaman and Nicobar mangroves.

6. Sunderbans in West Bengal.

The Ecological Conditions of Mangrove

The development of mangrove vegetation requires the following ecological conditions:

1. Shallow water.

2. Thick mud

3. High rainfall

4. High humidity and cloudy weather

5. Water-logged saline soil or loose soil with a large amount of organic matter.

Mangrove plants

Mangrove vegetation is formed of the following plant types : Rhizophora, Sonneratia, Avicennia, Excoecaria, Acanthus, Ceriops, Casula, Xylocarpus, Oryza, Bruguiera, etc.

Adaptations of Mangrove Plants

The mangrove vegetation possesses the following adaptations:

1. Pneumatophores : These are respiratory roots produced by mangroves for efficient aeration of root system in the water-logged conditions.

2. Prop Roots and Stilt Roots : These are produced from the main trunk of the tree for the efficient anchorage of the plants.

3. Habit : Most of the mangrove plants are shrubs. Herbs are rare.

4. Succulent Stem : Mangrove plants are provided with succulent stem.

5. Germination : Mangrove plants exhibit vivparous germination.

6. Salt-Coping Strategy : Though mangroves exist in saline environment, they depend to a great extent on freshwater to maintain an optimum salinity balance and to get nutrient salts. Rhizophore has a salt excluding device in the root system allowing passage of water and essential nutrients into the tree and not the slat. Avicennia freely allows salt to enter and pass through the leaf stomata in the transpiration stream of water, the salt –ex-cluding mechanism being between the xylem and phloem.

Fauna of Mangroves

The roots, the stems and the branches of the mangroves provide a good habitat for tropical animals. The pockets of organic mud held between the roots and stems of mangrove vegetation form a good dwelling place for or-ganisms. Mangrove is a unique ecosystem where animals of the terrestrial, fresh water and marine animals inhabit. The following are the organisms of the mangroves:

1. Phytoplankton : The following are the common phytoplankton of mangroves : Asterionella, Thalassiothrix, Hemidiscus, Bellerochea, Melosira, Chaetoceros, Stephanopyxis, Eucampia, Biddulphioa, Navivula, Pleurosigma.

2. Zooplankton : Zooplanktonic components of mangroves are the following : Ceratium, peridinium, oithona, Acrocalanus, Lucifer, Sagitta, Pleurobrachia, Oikopleura (Urochordate),etc.

3. Annelids : Burrowing polychaetes are abundant in the sediments of mangroves. The following annelids are represented in the mangroves : Arenicola, Dendronereis, Cossura delta, Laonome indica, Ldopatra neapolitina, Harmathoe, Nerine cirratulus, Ammotrypane aulogaster, Clymene annandalei, Sternaspis, Stylaroides, Ochetostomia septemyotum, (echiuroid worm),etc.

4. Crustacea : Crustaceans are abundant in the mangroves. Crabs are dominant among crustaceans. The following are the crustaceans of the mangroves : Uca (fiddler crab), Metaplex crenulatus (mud crab), crabs such as Birgus tro, Sesarma, Coenobtia, Scylla serrata, Macrophthalmus, etc., Thalassina anomala (mud lobster), etc. Large number of barnacles are found attached to the roots and stems of mangroves. The hermit crab Clibanarius longitarsus is abundant in mangroves. It can climb to trees reaching heights well above those reached by high tides.

5. Molluses : Molluscs are also abundant in the mangroves, large number of oysters are found attached to the roots and stems of mangroves. Eg. Cras-sostrea calcullate. Littorinids in habit the twigs and trunks of mangroves. Eg : Littorinids melanostoma, L., scabra, I undulata,etc. Other molluscs are Martesis striata, Bankia edmondsoni, Teredo juttingae, Onchidium, verruculatum, Telescopium telescopium, Cerithidea fluviatilis, Trebralia palustris,etc.

6. Fishes : Mudskippers are abundant in the mangroves. Eg. Periophtalmus and Boleophthalmus. They are small fish having large heads with protruding stalked eyes. When the tide goes out, the mudskippers breathe in air and use their fins like legs to crawl and hop over the mud. They have special sucker-like fins to climb up mangrove roots and stems. If danger threatens the fish quickly jumps or skips away.

7. Reptiles : Boiga dendrophila is a mangrove snake. It lives on birds Laticauda colubrina is a sea snake of mangroves. The monitor lizard Varanus slavator and the sea crocodile Crocodylus porosus are other reptiles.

 8. Birds : The birds of mangroves are the graceful fish eagles, Haliaeetus leucogaster, and the tall adjutant storks Leptoptilos Javanicus.

 9. Mammals : Mammals of mangroves include Macacacrus (long-tailed monkey) and Nasalis larvatus (proboscis monkey)

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The forest ecosystem has two parts: The non-living or abiotic aspects of the forest: The type of forest depends upon the abiotic conditions at the site. Forests on mountains and hills differ from those along river valleys. Vegetation is specific to the amount of rainfall and the local temperature which varies according to latitude and altitude. Forests also vary in their plant communities in response to the type of soil.

The living or the biotic aspects of the forest:   The plants and animals form communities that are specific to each forest type. For instance coniferous trees occur in the Himalayas. Mangrove trees occur in river deltas. Thorn trees grow in arid areas. The snow leopard lives in the Himalayas while the leopard and tiger live in the forests of the rest of India. Wild sheep and goats live high up in the Himalayas. Many of the birds of the Himalayan forests are different from the rest of India. Evergreen forests of the Western Ghats and North East India are most rich in plant and animal species.The biotic component includes both the large (macrophytes) and the microscopic plants and animals.

Plants include the trees, shrubs, climbers, grasses, and herbs in the forest. These include species that flower (angiosperms), and non-flowering species (gymnosperms) such as ferns, bryophytes, fungi and algae.The animals include species of mammals, birds, reptiles, amphibians, fish, insects and other invertebrates and a variety of microscopic animals.As the plant and animal species are closely dependent on each other, together they form different types of forest communities.

Forest types in India: The forest type depends upon the abiotic factors such as climate and soil characteristics of a region. Forests in India can be broadly divided into Coniferous forests and Broadleaved forests.

They can also be classified according to the nature of their tree species – evergreen, deciduous, xerophytic or thorn trees, mangroves, etc. They can also be classified according to the most abundant species of trees such as Sal or Teak forests. In many cases a forest is named after the first three or four most abundant tree species.

Coniferous forests grow in the Himalayan mountain region, where the temperatures are low. These forests have tall stately trees with needlelike leaves and downward sloping branches so that the snow can slip off the branches. They have cones instead of seeds and are called gymnosperms.

Broadleaved forests have several types, such as evergreen forests, deciduous forests, thorn forests, and mangrove forests. Broadleaved forests have large leaves of various shapes.

Evergreen forests grow in the high rainfall areas of the Western Ghats, North Eastern India and the Andaman and Nicobar Islands. These forests grow in areas where the monsoon lasts for several months. Some even get two monsoons, such as in Southern India. Evergreen plants shed a few of their leaves throughout the year. There is no dry leafless phase as in a deciduous forest. An evergreen forest thus looks green throughout the year. The trees overlap with each other to form a continuous canopy. Thus very little light penetrates down to the forest floor. Only a few shade loving plants can grow in the ground layer in areas where some light filters down from the closed canopy. The forest is rich in orchids and ferns. The barks of the trees are covered in moss. The forest abounds in animal life and is most rich in insect life

Deciduous forests are found in regions with a moderate amount of seasonal rainfall that lasts for only a few months. Most of the forests in which Teak trees grow are of this type. The deciduous trees shed their leaves during the winter and hot summer months. In March or April they regain their fresh leaves just before the monsoon, when they grow vigorously in response to the rains. Thus there are periods of leaf fall and canopy regrowth. The forest frequently has a thick undergrowth as light can penetrate easily onto the forest floor.

Thorn forests are found in the semi- arid regions of India. The trees, which are sparsely distributed, are surrounded by open grassy areas. Thorny plants are called xerophytic species and are able to conserve water. Some of these trees have small leaves, while other species have thick, waxy leaves to reduce water losses during transpiration. Thorn forest trees have long or fibrous roots to reach water at great depths. Many of these plants have thorns, which reduce water loss and protect them from herbivores.Mangrove forests grow along the coast especially in the river deltas.

Grassland ecosystems

What is a grassland ecosystem?

Grasslands cover areas where rainfall is usually low and/or the soil depth and quality is poor. The low rainfall prevents the growth of a large number of trees and shrubs, but is sufficient to support the growth of grass cover during the monsoon. Many of the grasses and other small herbs become dry and the part above the ground dies during the summer months. In the next monsoon the grass cover grows back from the root stock and the seeds of the previous year. This change gives grasslands a highly seasonal appearance with periods of increased growth followed by a dormant phase.

A variety of grasses, herbs, and several species of insects, birds and mammals have evolved so that they are adapted to these wide-open grass covered areas. These animals are able to live in conditions where food is plentiful after the rains, so that they can store this as fat that they use during the dry period when there is very little to eat. Man began to use these grasslands as pastures to feed his livestock when he began to domesticate animals and became a pastoralist in ancient times.

  Grassland Types in India: Grasslands form a variety of ecosystems that are located in different climatic conditions ranging from near desert conditions, to patches of shola grasslands that occur on hillslopes alongside the extremely moist evergreen forests in South India. In the Himalayan mountains there are the high cold Himalayan pastures. There are tracts of tall elephant grass in the low-lying Terai belt south of the Himalayan foothills. There are semi-arid grasslands in Western India, parts of Central India, and in the Deccan Plateau.

The Himalayan pasture belt extends upto the snowline. The grasslands at a lower level form patches along with coniferous or broadleaved forests. Himalayan wildlife require both the forest and the grassland ecosystem as important parts of their habitat. The animals migrate upinto the high altitude grasslands in summer and move down into the forest in winter when the snow covers the grassland. These Himalayan pastures have a large variety of grasses and herbs. Himalayan hill slopes are covered with thousands of colourful flowering plants. There are also a large number of medicinal plants.

The Terai consists of patches of tall grasslands interspersed with a Sal forest ecosystem. The patches of tall elephant grass, which grows to a height of about five meters, are located in the low-lying waterlogged areas. The Sal forest patches cover the elevated regions and the Himalayan foothills. The Terai also includes marshes in low-lying depressions. This ecosystem extends as a belt south of the Himalayan foothills.

The Semi-arid plains of Western India, Central India, Deccan trai India and the Deccan are covered by grassland tracts with patches of thorn forest. Several mammals such as the wolf, the blackbuck, the chinkara, and birds such as the bustards and floricans are adapted to these arid conditions. The Scrublands of the Deccan Plateau are covered with seasonal grasses and herbs on which its fauna is dependent. It is teaming with insect life on which the insectivorous birds feed.

Shola grasslands consist of patches on hillslopes along with the Shola forests on the Western Ghats, Nilgiri and Annamalai ranges. This forms a patchwork of grassland on the slopes and forest habitats along the streams and lowlying areas.

Grasslands are not restricted only to low rainfall areas. Certain grassland types form when clearings are made in different forest types. Some are located on the higher steep hill slopes with patches of forest that occur along the streams and in depressions. The grasslands are related to repeated fires that do not permit the forest to grow.

The grasses are the major producers of biomass in these regions. Each grassland ecosystem has a wide variety of species of grasses and herbs. Some grass and herb species are more sensitive to excessive grazing and are suppressed if the area is over grazed. Others are destroyed by repeated fires and cannot regenerate. Thus overused or frequently burnt grasslands are degraded and are poor in plant species diversity.

Grasslands are the grazing areas of many rural communities. Farmers who keep cattle or goats, as well as shepherds who keep sheep, are highly dependent on grasslands. Domestic animals are grazed in the ‘common’ land of the village. Fodder is collected and stored to feed cattle when there is no grass left for them to graze in summer. Grass is also used to thatch houses and farm sheds. The thorny bushes and branches of the few trees that are seen in grasslands are used as a major source of fuelwood.

Overgrazing by huge herds of domestic livestock has degraded many grasslands. Grasslands have diverse species of insects that pollinate crops. There are also predators of these insects such as the small mammals like shrews, reptiles like lizards, birds of prey, and amphibia such as frogs and toads. All these carnivorous animals help to control insect pests in adjoining agricultural lands.

What are the threats to grassland ecosystems?

 In many areas grasslands have been used for centuries by pastoral communities. Overutilization and changes in landuse of the ‘common grazing lands’ of rural communities has lead to their degradation. The grassland cover in the country in terms of permanent pastures now covers only 3.7 percent of land. A major threat to natural grasslands is the conversion of grasslands into irrigated farmlands. In the Deccan, grasslands have been altered to irrigated farms and are now mainly used to grow sugarcane. After continuous irrigation such land becomes saline and useless in a few years. More recently many of these residual grassland tracts have been converted into industrial areas. This provides short-term economic gains but result in long-term economic and ecological losses.

Grasslands have a limited ability to support domestic animals and wildlife. Increasing this pressure by increasing the number of domestic animals reduces the ‘naturalness’ of the grassland ecosystem leading to its degradation.

Most grassland ecosystems are highly modified by human activities. Cattle, sheep and goat grazing, and lighting repeated fires affects grasslands adversely. Changing the grasslands to other forms of landuse such as agriculture, tree plantations and industrialization forms a serious threat to this highly productive ecosystem. Thus some of the grassland patches which are in a less disturbed state and have retained their special plants and animals need to be urgently protected.

Degradation of grasslands due to over grazing by cattle, sheep and goats occurs if more than a critical number of domestic animals are present in the grasslands. When animals overgraze the area, the grasses are converted into flat stubs with very little green matter. Degraded grasslands have fewer grass species as the nutritious species are entirely used up by the large number of domestic animals. They are thus unable to regenerate.

When fires are lit in the grasslands in summer, the burnt grass gets a fresh flush of small greenshoots which the domestic animals graze on. If this is done too frequently the grasslands begin to deteriorate. Finally grasslands become bare, the soil is solidly compacted by trampling, or is washed away during the monsoon by rain and whipped into dust storms during the hot dry summer. The land is degraded, as there is no grass to hold the soil in place. It becomes a wasteland.

Why are our grassland species vanishing?

Most people feel that it is only our forests and its wildlife that is disappearing. However, other natural ecosystems such as grasslands are disappearing even more rapidly.

Many of the grassland species have disappeared from several parts of India in which they were found 50 or 60 years ago. The Cheetah is extinct in India. The Wolf is now highly threatened. Blackbuck and chinkara are poached for meat. Birds such as the beautiful Great Indian Bustards are vanishing. Unless grassland species are protected they will vanish from their shrinking habitat, as natural and undisturbed grasslands are left in very few locations. If these animals and birds are killed or their habitat is reduced further, their extinction will rapidly follow.

What if our grasslands disappear? If our grasslands are lost we will lose a highly specialized ecosystem in which plants and animals have been adapted to these habitat conditions over millions of years. Local people will not be able to support their livestock herds.

The extinction of species is a great loss to Mankind. The genes of wild grasses are extremely useful for developing new crop varieties. New medicines could well be discovered from wild grassland plants. It is possible that genes from wild herbivores such as wild sheep, goats and antelopes may be used for developing new strains of domestic animals

How can grassland ecosystems be conserved?

Grasslands should not be overgrazed and areas of the grasslands should be closed for grazing. It is better to collect grass for stall feeding cattle. A part of the grassland in an area must be closed every year so that a rotational grazing pattern is established. Fires must be prevented and rapidly controlled. In hilly areas soil and water management in each micro-catchment helps grasslands to return to a natural highly productive ecosystem.

To protect the most natural undisturbed grassland ecosystems, Sanctuaries and National Parks must be created. Their management should focus on preserving all their unique species of plants and animals. Thus they should not be converted into plantations of trees. The open grassland is the habitat of its specialised fauna. Planting trees in these areas reduces the natural features of this ecosystem resulting in the destruction of this unique habitat for wildlife.

What should we do?

There is a need to preserve the few natural grassland areas that still survive by creating National Parks and Wildlife Sanctuaries in all the different types of grasslands.

Animals such as the wolf, blackbuck, chinkara and birds such as bustards and floricans have now become rare all over the country. They must be carefully protected in the few National Parks and Wildlife Sanctuaries that have natural grassland habitats as well as outside these Protected Areas.

We need to create awareness among people that grasslands are of great value. If we are all concerned about our disappearing grasslands and their wonderful wildlife, the Government will be motivated to protect them.

Desert ecosystem

Desert and semi arid lands are highly specialised and sensitive ecosystems that are easily destroyed by human activities. The species of these dry areas can live only in this specialised habitat.

What is a desert or a semi-arid ecosystem?

 Deserts and semi arid areas are located in Western India and the Deccan Plateau. The climate in these vast tracts is extremely dry. There are also cold deserts such as in Ladakh, which are located in the high plateaus of the Himalayas. The most typical desert landscape that is seen in Rajasthan is in the Thar Desert. This has sand dunes. There are also areas covered with sparse grasses and a few shrubs, which grow if it rains. In most areas of the Thar the rainfall is scanty and sporadic. In an area it may rain only once every few years. In the adjoining semi arid tract the vegetation consists of a few shrubs and thorny trees such as kher and babul.

The Great and Little Rann of Kutch are highly specialized arid ecosystems. In the summers they are similar to a desert landscape. However as these are low-lying areas near the sea, they get converted to salt marshes during the monsoons. During this period they attract an enormous number of aquatic birds such as ducks, geese, cranes, storks, etc. The Great Rann is famous, as it is the only known breeding colony of the Greater and Lesser Flamingos in our country. The Little Rann of Kutch is the only home of the wild ass in India.

Desert and semi arid regions have a number of highly specialized insects and reptiles. The rare animals include the Indian wolf, desert cat, desert fox and birds such as the Great Indian Bustard and the Florican. Some of the commoner birds include partridges, quails and sandgrouse.

How are desert and semi-arid ecosystems used?

Areas of scanty vegetation with semi-arid scrubland have been used for camel, cattle and goat grazing in Rajasthan and Gujarat, and for sheep grazing in the Deccan Plateau.

Areas that have a little moisture, such as along the watercourses, have been used for growing crops such as jowar, and bajra. The natural grasses and local varieties of crops have adapted to growing at very low moisture levels. These can be used for genetic engineering and developing arid land crops for the future.

What are the threats to desert ecosystems?

Several types of development strategies as well as human population growth have begun to affect the natural ecosystem of the desert and semi arid land. Conversion of these lands through extensive irrigation systems has changed several of the natural characteristics of this region. The canal water evaporates rapidly bringing the salts to the surface. The region becomes highly unproductive as it becomes saline. Pulling excessive groudwater from tubewells lowers the water table creating an even drier environment. Thus human activities destroy the naturalness of this unique ecosystem. The special species that evolved here over millions of years may soon become extinct.

How can desert ecosystems be conserved?

Desert ecosystems are extremely sensitive. Their ecological balance that forms a habitat for their plants and animals is easily disturbed. Desert people have traditionally protected their meagre water resources. The Bishnois in Rajasthan are known to have protected their Khejdi trees and the blackbuck antelope for several generations. The tradition began when the ruler of their region ordered his army to cut down trees for his own use. Several Bishnois were said to have been killed while trying to protect their trees.

There is an urgent need to protect residual patches of this ecosystem within National Parks and Wildlife Sanctuaries in desert and semi arid areas. The Indira Gandhi Canal in Rajasthan is destroying this important natural arid ecosystem, as it will convert the region into intensive agriculture. In Kutch, areas of the little Rann, which is the only home of the Wild Ass, will be destroyed by the spread of salt works.

Development Projects alter the desert and arid landscape. There is a sharp reduction in the habitat available for its specialized species bringing them to the verge of extinction. We need a sustainable form of development that takes the special needs of the desert into account.

Q&A

1. What is the ecosystem?

The ecosystem is the community of living organisms in conjunction with non-living components of their environment, interacting as a system.

2. What are the different types of ecosystems?

The different types of the ecosystem include:

• Terrestrial ecosystem
• Forest ecosystem
• Grassland ecosystem
• Desert ecosystem
• Tundra ecosystem
• Freshwater ecosystem
• Marine ecosystem

3. Which ecosystem do we live in?

We live in a terrestrial ecosystem. This is the ecosystem where organisms interact on landforms. Examples of terrestrial ecosystems include tundra, taigas, and tropical rainforests. Deserts, grasslands and temperate deciduous forests also constitute terrestrial ecosystems.

4. What is the structure of the ecosystem?

The structure of the ecosystem includes the organisms and physical features of the environment, including the amount and distribution of nutrients in a particular habitat. It also provides information regarding the climatic conditions of that area.

5. Which is the largest ecosystem in the world?

The largest ecosystem in the world is the aquatic ecosystem. It comprises freshwater and marine ecosystem. It constitutes 70% of the surface of the earth.

6. What is the major function of an ecosystem?

The ecosystem is the functional unit of the environment system. The abiotic components provide the matrix for the synthesis of organic components. This process involves the exchange of energy.

7. What makes a good ecosystem?

A good ecosystem consists of native plants and animal species interacting with each other and the environment. A healthy ecosystem has an energy source and the decomposers that break down dead plants and animal matter, returning essential nutrients to the soil.

8. What all include the non-living things in an ecosystem?

The non-living things in an ecosystem include air, wind, water, rocks, soil, temperature and sunlight. These are known as the abiotic factors of an ecosystem.