Wednesday, 9 March 2016

ECOSYSTEMS OF INDIA


India is a vast country and possess many types of natural ecosystems.

(a) Terrestrial :
1. Forests
2. Grasslands
3. Deserts - Thar deserts & Rann of Kutch
4. Mountains - The Himalayas &Ghats
(b) Aquatic:
1. Fresh water ecosystem
2. Marine ecosystem
Terrestrial ecosystem in India :

Forests
·        Tropical rain forests
·        Tropical deciduous forests
·        Temperate broad leaf forests
·        Temperate needle – leaf or coniferous forests
·        Alpine and tundra forests
·        tidal forests,
·        Himalayan vegetation,
·        rain forests of southern India,
·        desert region, etc.

(i) Tropical rain forests:

·        These types of forests include the tropical evergreen forests and tropical semi-evergreen forests.
·        They are mostly found in places where there is plenty of rainfall and sunshine throughout the year.
·        Growth of the trees is usually at its best where rainfall is in surplus of 200 cm, with a short dry season.
·        Trees grow very briskly in these forests and attain heights of about 60 m and above.
·        Ebony, mahogany and rosewood are the main trees of these forests.


Distribution:

·        rainy slopes of the Western Ghats,
·        plains of West Bengal and Orissa and north-eastern India.

(ii) Tropical deciduous forests :


·        Tropical deciduous forests are also known as deciduous (whether it is moist or dry)forests because they cast leaves for about six to eight weeks in summer.
·        They are also called the monsoon forests with all their grandeur and beauty.
·        within regions having 200 and 75 cm of annual rainfall.
·        The tropical deciduous forests are pretty substantial, cost- effective and they demand a lot of maintenance, as they are less resistant to fire.

Distribution:

·        Most of the tropical deciduous forests are found in the state of Kerala in India.
·        eastern slopes of Western Ghats and
·        north eastern parts of the peninsular plateau and
·        valleys of the Himalayas.
Types :
 1. moist and deciduous forests.
 2.dry deciduous forests.

·        The moist deciduous forests are most commonly found on the eastern slopes of the Western Ghats.
·        They are also found in the region of Chhotanagpur plateau, covering east Madhya Pradesh, south Bihar, and west Orissa, Shiwaliks in the northern India.
Important trees : teak, sal, and sandalwood.


(iii) Temperate broad leaf forests :

·        It mainly occur between 1500-2400 m altitudes in western Himalayas.
·        Height of the trees may be 25-30 m.
·        Trees canopy is dense, herbaceaus layer is least developed and grasses are generally lacking. 
Species :
·        Oak (Quercus) are found in these forests.
·        Oak species are ever green in the Himalayan region.
·        These species show peak leaf fall during summer but never become leafless.
·        The Oak forests are often rich in epiphytic flora.

(iv) Temperate needle leaf or coniferous forests :


·        This type of forests are found in the Himalaya over 1700 to 3000 m altitude.
·        These forests contain economically valuable gymnospermous trees like pine , deodar , Cypress , Spruce  and siver fir.
·        Coniferous forests are taller 30-35 m and possess evergreen canopy of long needle like leaves.
·        Canopy of these trees always remains green. In many species, it is cone-shaped.

(v) Alpine and Tundra forests :


·        Vegetation growing at altitudes above 3600 m is usually known as alpine vegetation and
·        It can be noticed that with the increment of the altitude, the plants show stunted growth.
·        The trees like silver fir, pine, juniper and birch belong to this category.
·        The alpine grasslands are mainly found at higher altitudes in this region.
·        The people belonging to the tribal groups like Gujjar and Bakarwal make extensive use of this region.
·        The vegetations like lichen and mosses are also found in high altitudinal regions.

Tidal forests:
·        They found along the coasts and rivers and they are enshrouded by mangrove trees that can live in both fresh and salt water.
·        Sundari is a renowned mangrove tree, mainly found in the tidal
forests and it is after this tree that the name Sundarban has been entitled to the forested parts of the Ganga-Brahmaputra delta.

Himalayan vegetation :
·        The thick tropical forests in the eastern region of India have a sharp distinction with the pine and coniferous woodlands of the western Himalayas.
·        Chir pine grows throughout the northwest Himalayas, with the exception of Kashmir.
·        Chilgoza (pine nut), oak, maple, ash , etc also grow abundantly in the eastern Himalayas.

Rain forests of Southern India :

·        The most luxuriant rain forests lie on the southwestern coast, in the state of Kerala.

·        Here the lagoons are canopied by coconut trees and lead to the longest uninterrupted stretch of rain forests in the country.
·        The Andaman and Nicobar Islands and the state of Arunachal Pradesh are some of the other regions with well preserved rain forests in India.
·        Apart from that, dense sandal, teak and sisoo forests also flourish on the wet Karnataka plateau.

Thar Desert :
·        The trees in this desert are short and stout, and stunted by the scorching sun.
·        Cacti, reunjha (Acacia leucophloea), khejra , kanju , Oak  etc are common plants in this region.

(2) Grasslands :
·        Grasslands are one of the intermediate stage in ecological succession and cover a part of the land on all the altitudes and latitudes at which climatic and soil conditions do not allow the growth of trees.
·        In India, grasslands are found as village grazing grounds (Gauchar)
·        and extensive low pastures of dry regions of western part of the country an also in Alpine Himalayas .
·        Perennial grasses are the dominant plant community. In some regions grasslands also support a variety of other herbaceous plants like sedges, legumes and members of the sunflower family
·        Rats, mice, rodents, deer, elephant, dog, buffalo, tiger, lion, ferrets are some common mammals of grasslands.
·        In the north east India, one horned rhinoceros is amongst the
threatened animal of grassland is this region.
·        A large number of avian fauna makes the grassland colourful.

(3) Deserts :

·        The Thar desert in Rajasthan is an extension of the Sahara deserts through Arabian and Persian deserts.
·        They extend from Punjab, Haryana, Rajasthan to Gujarat state.
·        Indian deserts are divided into four main types:
hills, plains with hills, marshes and plains with sand dunes.
·        The distinct Rann of Kutchch–Bhuj in Gujarat forms a separate zone with in Thar deserts due to its different climatic conditions. It represents vast saline flats.
·        The region of sand dunes is most spectacular and covers an area of 100,000 sq. km nearly.  It extends into Pakistan.
·        The dunes are highly sandy and contain 0.12–0.18 mm size grain, 1.8 to 4.5 % of clay and 0.4–1.3% of silt.
·        There are only some thorn forests and dry open grasslands.
·        Indira Gandhi canal which carries water through Punjab and Haryana enters into Rajasthan supports some vegetation.
·        The main crops of desert are bajra, millet, wheat, barley, maize, jowar, guwar.
·        Medicinal plants found here are mehndi, hak, isabgole and gugal.
·        Indian deserts support many threatened species of birds and mammals, such as Asiatic lion, wild ass, bats, scaly ant eater, desert fox, Indian gazzel, four horned antelope , white browed Bushchat, Great Indian Bustard, Cranes and Sandgrouse.
·        Gulf of Kuchch is distinguished by the presence of living corals, pearl oyster, sea turtles and a large number of migratory birds like kingfisher, cranes ibis and herons.

(4) Mountains – The Himalayas




Distribution:
·        It spreads over a west northwest to east- southeast over a distance of about 2500 km covering Afganistan , Pakistan, India, Nepal, Bhutan and China.
·        In India, it extends from the Indus trench below Nangaparbat in the west to Yarlungtsangpo- Brahmputra George below Namchebarwa peak in east.
·        The Himalayas lying within India occupy nearly 5,31,250 sq. km area
·        They cover about 16.6% of India’s total geographical area.
·        spread partially or completely over 12 states namely: Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Sikkim, West Bengal, Arunachal Pradesh, Assam, Nagaland, Manipur, Tripura, Mizoram and Meghalaya.



Himalayas are geographically divided into:

(i) the Eastern Himalayas or the Assam Himalayas:
·        It has a greater diversity of ecosystems like, forests, grasslands, marshes, swamps, lakes streams and rivers Eastern Himalayas consists of nearly 8000 species of the flowering plants.
·        It has many primitive as well as many endemic plant species.
·        Eastern Himalayas is known as centre of origin of cultivated plants .
·        Many cereals, fruits and vegetables are cultivated here. E.g. Orchids, Aster, Accasia, Albizzia, Delbergia species (timber) and many legumes etc.
(ii) the Central Himalayas or the Nepal Himalayas
(iii) the Western Himalayas: On the western Himalayas cold deserts of Ladakh support drought and cold resistant varieties of plants and animals e.g. Yak.
(iv) the North-West Himalayas or the Punjab Himalayas.

(5) Ghats :

Western ghats:

·        It also known as Sahyadri extend from Tapti river in north to Kanyakumari
·        in south covering nearly 1,40,000 sq km parallel to the west coast of peninsular India.
·        They pass through the states of Gujarat, Maharashtra, Goa, Karnatka, Tamilnadu and Kerala.
·        Western ghats are one of 25 hot spots of the world.
·        June- September are rainy months.
·        The rainfall may vary from 100 to 500 cm.
·        Soil is mainly red or black in most of the regions and rich in nutrients.
·        3500 species of flowering plants have been recorded from western ghats of which nearly1500 are endemic species.

Eastern ghats :
·        extend in north south-west strike in Indian peninnsula covering an area of about 75000 sq. km.
·        They are spread through the states of Orissa, Andhra Pradesh telangana and Tamilnadu.
·        The eastern ghats do not form a continuous range because the great rivers Mahanadi,Godavari and Krishna cut across them.
·        They are an assemblage of discontinuous ranges of hills, plateaus and basins.
·        The climate of these ghats may be semiarid to semihumid with a rainfall ranging from 60 to 160 cm.
·        The vegetation ranges from evergreen trees to that of dry savannas.

Aquatic ecosystem in India :
Freshwater ecosystem :
·        Freshwater are terrestrial aquatic ecosystems. Lakes, flood ponds, reservoirs and rivers are its important components.
·        The total freshwater area of India is about 7.6 million hectare.
·        Lakes are naturally formed deep water bodies e.g. Sultanpur lake, Batkal lake (Haryana).
·        Flood points are the places that undergo periodic flooding as a river channel overflows with flood water i.e. natural areas constituting shallow and seasonal water bodies.
·        Bank of large rivers have flood points.
·        Reservoir is man made areas holding water irrigation and human use. e.g, reservoirs formed by dams used for irrigation.
·        Rivers are the flowing water bodies as you have studied in this lesson.

Marine ecosystem :
·        India has a long coastline of about 8000 km stretching along nine states and two island chains.
·        At the coast a number of rivers form estuaries at their confluence with the sea.
·        There are three gulfs - one on the east coast that is gulf of Mannar and two on the west coast i.e. gulf of Kutchch and gulf of Khambhat.

·        The tides are very important in determining the marine life.
·        Nearly 14 species of sea grasses and 120 species of sea weeds are found along the coast.
·        Corals are the most abundant and play a very important role.
·        199 Species of corals are known from Indian Ocean.


·        The biodiversity in a coral reef is comparable to that of a tropical rain forest. Sea shore provides feeding and breeding ground to a number of birds also. Sea crows, whales and dolphins are the mammals that have secondarily invaded the sea .
·        Marine fisheries constitute a highly productive sector in India It is a source of food and employment to the coastal population.

THE THREATENED ECOSYSTEMS
Some of the natural ecosystems are very sensitive to misuse by humans and to natural disasters or calamities.

Estuaries :


·        An estuary is a place where a river or a stream opens into the sea.
·        It is a partially enclosed coastal area at the mouth of the river where its fresh water carrying fertile silt and runoff from the land mixes with the salty sea water.
·        It represents an ecotone between fresh water and marine ecosystem and shows a variation of salinity due to mixing of sea water with fresh water.
·        Estuaries are very dynamic and productive ecosystems since the river flow, tidal range and sediment distribution is continuously changing in them.
·        Examples of estuaries are river mouths, coastal bays, tidal marshes, lagoons and deltas.
·        Deltas are triangular areas bordering the river valley towards the mouth.
·        They are associated with the land projecting into the sea in the form of protuberances.
·        Estuaries are richer in nutrients than fresh waters or marine waters therefore; they are highly productive and support abundant fauna.
·        In general the phytoplanktons of estuaries are diatoms, dinoflagellates, green algae, blue-green algae.
·        Towards the sea coast of the estuaries there are large algae and sea grasses.
·        Near the mouth of the rivers and deltas there are mangrove forests.
·        The vast mangrove forests act as barriers for the costal habitat to check the wind speed during cyclones and high velocity landward winds.
·        All the plants and animals in the estuaries are subjected to variations in salinity to which they are adapted (osmoregulation).
·        Estuaries have been damaged due to urbanization, industrialization and population growth.

Mangroves :


·        Mangroves represent a characteristic littoral (near the sea shore) forest ecosystem.
·        These forests grow in sheltered low lying coasts, estuaries, mudflats, tidal creeks backwaters (current less, coastal waters held back on land), marshes and lagoons of tropical and subtropical regions.
·        They are distributed over the east and west coast and island of Andaman and Nicobar.
·        Mangroves along the east coast are more luxuriant and considerably
diverse due to the presence of nutrient rich deltas formed by the rivers Ganga, Mahanadi, Godavari, Krishna and Cauvery.
·        Since mangroves are located between the land and sea they represent the best example of ecotone.
Characteristics of mangrove ecosystem:-
·        The mangrove forests include a diverse composition of trees and shrubs.
·        Plants are well adapted to high salinity(halophytic).
·        Resistant to tidal effect.
·        Tolerant to high temperature.
·        Roots bear pneumatophore ( or aerial roots ), which is an aerating system.
·        Mangroves are highly productive ecosystems and the trees may vary in height from 8 to 20 m.
·        They protect the shoreline from the effect of cyclones and tsunamies.
 The animal communities are of two types:
·        Permanent fauna mainly bentic are molluscs, crustaceans, polychaetes, insects and birds like kingfishers.
·        Visiting fauna includes mollusks, echinomerms, crustaceans and birds which come from adjacent terrestrial ecosystems and rivers .

·        Tree frogs, crocodiles, turtles and snakes are also found in these forests.

·        They are breeding and spawning ground for many commercially important fishes.
·        Sunderban mangroves are the only mangroves where tiger population is found.
·        Mangroves in India have been reduced to more than 50% during the last forty years.

Islands :
·        Islands are land masses surrounded by sea water from all sides They may be far away from the continent (oceanic island )or may be very close to it (continental island).
·        India has two main island groups:
(1)Andaman and Nicobar islands in Bay of Bengal and
(2)Lakshadweep in Arabian sea.
·        These ecosystems are threatened mainly due to habitat
destruction for resources and tourism.
·        Although industrial pollution is much less on these
·        islands, oil spills in oceans have greatly affected their fauna and flora.

ECOTONE :

·        Ecotone is a zone of junction between two or more diverse ecosystems e.g. the mangrove forests.
·        They represent an ecotone between marine and terrestrial ecosystem.
·        Some more examples of ecotone are – grassland, estuary and river bank.
Characteristics of ecotone:
·        It may be very narrow or quite wide.
·        It has the conditions intermediate to the adjacent ecosystems. Hence ecotone is a zone of tension.
·        It is linear as shows progressive increase in species composition of one in coming community and a simultaneous decrease in species of the other out going adjoining community.
·        A well developed ecotones contain some organisms which are entirely different from that of the adjoining communities.
·        Sometimes the number of species and the population density of some of the species is much greater in this zone than either community. This is called edge effect.

·        The organisms which occur primarily or most abundantly in this zone are known as edge species.
·        In the terrestrial ecosystems edge effect is especially applicable to birds.
·        For example the density of song birds is greater in the mixed habitat of the ecotone between the forest and the desert.




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