ENVIRONMENT STUDIES

1. Ecological succession
■ Succession is the natural process of replacement of one
community by other community is a same location over a
period of time.
■ If forest get cleared by any mean like fire forest or any
calamities, it is initially colonized by certain group of plants
and animals which gradually changes the process of
community development.
■ The cleared area is gradually changes into grassland, shrub
land and finally into a woodland and a forest, if it permitted
to do so without human interference.

2. ■ An ecosystem is not static rather it is dynamic in nature.
■ Its structure as well as function with time and quite interestingly, these
changes are very orderly and can be predicted.
■ It is observed that one type of a community is totally replaced by another
type of community over a period of time and simultaneously several
changes also occur. This process is known as ecological succession.
■ Ecological succession is defined as an orderly process of
changes in the community structure and function with time
mediated through modifications in the physical environment
and ultimately culminating in a stabilized ecosystem known as
climax.

3. Process of Succession
■ (i) Nudation: It is the development of a bare area without any life form. The bare
area may be caused due to landslides, volcanic eruption etc. (topographic
factor), or due to drought, glaciers, frost etc. (Climatic factor), or due to
overgrazing, disease outbreak, agricultural/ industrial activities (biotic factors).
■ (ii) Invasion: It is the successful establishment of one or more species on a bare
area through dispersal or migration, followed by establishment. Dispersal of the
seeds, spores etc. is brought about by wind, water, insects or birds. Then the
seeds germinate and grow on the land. As growth and reproduction start, these
pioneer species increase in number and form groups or aggregations.
■ (iii) Competition and coaction: As the number of individuals grows there is
competition, both inter-specific (between different species) and intra-specific
(within the same species), for space, water and nutrition. They influence each
other in a number of ways, known as coaction.

4. ■ (iv) Reaction: The living organisms grow, use water and nutrients from the
substratum, and in turn, they have a strong influence on the environment
which is modified to a large extent and this is known as reaction. The
modifications are very often such that they become unsuitable for the
existing species and favour some new species, which replace them. Thus,
reaction leads to several seral communities.
■ (v) Stabilization: The succession ultimately culminates in a more or less
stable community called climax which is in equilibrium with the
environment.
The climax community is characterized by maximum biomass and symbiotic
(mutually beneficial) linkages between organisms and are maintained quite
efficiently per unit of available energy.

6. Ecological successions starting on different types of areas or
substrata are named differently as follows:
■ (i) Hydrarch or Hydrosere: Starting in watery area like pond, swamp.
■ (ii) Mesarch: starting in an area of adequate moisture.
■ (iii) Xerarch or Xerosere: Starting in a dry area with little moisture.
They can be of the following types:
a) Lithosere : starting on a bare rock
b) Psammosere : starting on sand
c) Halosere : starting on saline soil

7. Hydrosere (Hydrarch):
■ This type of succession starts in a water body like pond.
■ A number of intermediate stages come and ultimately it culminates in a climax
community which is a forest.
■ The pioneer community consists of phytoplanktons, which are free floating
algae, diatoms etc.
■ Gradually these are replaced by rooted submerged plants followed by rooted-
floating plants.
■ Growth of these plants keep on adding organic matter to the substratum by
death and decay and thus a layer of soil builds up and shallowing of water
takes place.
■ Then Reed swamp (marshy) stage follows in which the plants are partly in water
and partly on land.
■ This is followed by a sedge meadow stage of grasses then by a woodland
consisting of shrubs and trees and finally by a forest acting as climax.

8. Ecological succession: A hydrach—from lake to woodland community.
Open water body (lake), sediment brought in by river.
Sediment accumulation continues, organic debris from plants
too add to soil formation and shrinking of water body occurs.
A mat of vegetation covers the water which is mostly a marshy
habitat now, with a small part as aquatic system
Eventually the former lake is covered by climax woodland
community, representating a terrestrial ecosystem.

9. Xerosere (Xerarch):
■ This type of succession originates on a bare rock, which lacks water and
organic matter.
■ Here also the climax community is a forest, although the intermediate stages
are very different.
■ The pioneer community here consists of crustose and foliose lichens. These
lichens produce some weak acids and help in disintegrating the rock, a
process known as weathering.
■ Their growth helps in building up gradually some organic matter, humus and
soil. Then comes the community of mosses, followed by herbs, shrubs and
finally the forest trees. Throughout this gradual process there is a slow build
up of organic matter and water in the substratum.
■ Thus, succession tends to move towards mesic conditions (moderate
condition), irrespective of the fact, whether it started from a dry (Xeric)
condition or a moist (hydric) condition and it culminates in a stable climax
community, which is usually a forest

10. ECOSYSTEM SERVICES
■ The term "environmental services" was introduced in a 1970
report of the Study of Critical Environmental Problems
which listed services including insect
pollination, fisheries, climate regulation and flood control.
■ As per the 2006 Millennium Ecosystem Assessment (MA),
ecosystem services are "the benefits people obtain from
ecosystems". The MA also delineated the four categories of
ecosystem services—supporting, provisioning, regulating
and cultural.

11. Payment for ecosystem services
■ 10 Himalayan states in India voiced a unique demand — payment for the clean water that flows
down from the hills to the plains, and for the forests that remain standing. The demand, made in
the presence of Finance Minister Nirmala Sitharaman and Chairman of the 15th Finance
Commission N.K. Singh at a meeting in Mussoorie, would mean that the financial relations
between the federal and provincial governments must undergo a fundamental shift.
■ The total value of forest ecosystem services flowing from Uttarakhand is about $2.4 billion / year
(Rs 10,700 crore / year). At the Indian Himalayan-level, it is Rs 94,300 crore / year.
■ This is one of India’s major carbon sink. Besides it averts soil erosion from the world’s youngest
mountain range.
■ The 13th Finance Commission allocated Rs 5,000 crore, based on the area under forest cover
with an added parameter of Canopy density.
■ The 14th commission reformed the revenue-sharing formula between the Union and the states. It
brought the landmark change of including forest cover as a determining factor in a state’s share.
■ In the distribution of funds to states, the commission attached a 7.5 per cent weight to forest
cover.

15. Types of Ecosystem
Terrestrial ecosystem Aquatic ecosystem
Forest Pond
Grassland Wetland
Semi-arid River
Mountains Delta
islands Marine
• Nature, structure and function of the Ecosystem
• Benefits of the ecosystem
• Ecosystem degradation
• Ecosystem conservation

16. FOREST ECOSYSTEM
■ Forest includes the area dominant by tree species. It is used to refer to land with a tree
canopy cover of more than 10 percent and area of more than 0.5 ha (FAO, 2000).

17. ■ Forest is structurally defined by its trees, shrubs, climbers and ground
cover.
■ The most natural undisturbed forest are located mainly in national parks
and wildlife sanctuaries.
■ Each type of forest forms a habitat for a specific community of animals that
are adapted to live in it.
■ With their variation in the biotic and abiotic component, the forest
ecosystem are vary from each other.
Forest
ecosystem
The non-living or
abiotic aspect
Eg: mountain, hills, river
valley, soil types, rainfall
pattern
The living or biotic
aspect
Eg: Coniferous trees in the
Himalaya, mangrove trees in
river delta, Snow leopard in
Himalaya and rest of India

18. Forest types in India
■ Depend on abiotic factors, the climate and soil,
the Forest in India is broadly classified into
coniferous and broad-leaved forests.
■ Coniferous type of forest are found in Himalayan
region where the temperature is low. These
forest contain very tall trees with needle like leaf
to avoid the snow stability on it.
■ These type of forest produce cones instead of
seed and are called Gymnosperm.

19. The broad-leaved forest are of many types
such as Evergreen, Deciduous, thorn and
mangrove forest.
■ Evergreen forest found in high rainfall areas
such as Western Ghat, Northeastern India and
Andaman Nicobar islands. The forest is abundant
with animal and insect life.
■ Deciduous forest found in moderate amount of
rainfall where, the seasonal rainfall takes place.
■ Thorn forest are found in semi-arid region of
India where the thorny plants (xerophytic
species) are dominant.
■ Mangroove forest are found along the coast,
especially in the river deltas. These plants have
unique feature to adopt to grow in a mix of saline
and freshwater. The breathing roots
(pneumatophores) are the characteristic feature
of this forest.

21. Benefits of Forest Ecosystem
■ Services:
– Control flow of water in streams and rivers
– Ruduce surface run-off and allow groundwater recharge.
– Reduce soil erosion
– Regulate temperature of surrounding
– Absorb carbon dioxide and release oxygen
Direct use Indirect use
Fruits, food, fiber, fodder for grazing
animals, medicinal plants, timber
for building huts and houses
Furniture, medicinal products to
process into drugs, paper from
bamboo and softwoods etc.

22. Forest degradation
■ Over-utilization of forest resources
■ Illegal extraction of wood from forest
■ Rapid population growth, urbanization, industrialization and
expansion of agricultural field leads to degradation of forest.
■ With respect to total geographical area of India, it must has 33% of
forest cover which has reduced to 24.56 percent (FSI, 2019).
■ Degraded due to mining and dam construction.
■ Many forest species are seriously under threated condition and if it
extinct can not be brought back.

23. Forest conservation
■ By sustainable life style
■ Afforestation
■ In situ and ex situ conservation

24. Grassland Ecosystem
■ The landscape where the grasses is found abundantly with annual plants.
■ The area where the rainfall is usually poor and hence the seasonal species
become dominant.
■ The grassland getting utilized from ancient time when the cattle was being
used by human.

25. Types of grassland
The variability is due to climatic condition in India.
■ The Himalayan pasture belt found at high altitude
area with coniferous and broad-leaved forests. It
is dominant with thousands colorful flowering
plants with numerous medicinal plants.
■ The Tarai consist of tall grassland which grow to
height of about five meters and located in the
low-lying waterlogged areas. This ecosystem
located in a belt of South of the Himalayan
foothills.
■ The semi-arid plains of Western India, Central
India and the Deccan are coverd with patches of
thorn forest where the wolf, chinkara and birds
such as bustard and floricans are adopted in this
arid condition.
■ The shola grassland consist of patches on hill-
slopes that occur alongside of shola forest on the
Western Ghats, the Nilgiri and Anamalai ranges.

26. Benefits of Grassland Ecosystem
■ Use as fodder to feed cattle.
■ Maintain biodiversity and act as storehouse for carbon.
■ Used to make houses in tribal community and farm-sheds
■ The thorny bushes and branches use as main source of
fuelwood.

27. Degradation of grassland ecosystem
■ Threats due to common grazing land for rural community.
■ Very little capability to support domestic animals and wildlife.
■ India lost 31 per cent, or 5.65 million hectares (mha), of grassland area in a
decade, showed data the Union government presented to the United
Nations Convention to Combat Desertification (UNCCD) during the 14th
Conference of Parties (COP)
■ Conversion into irrigated farmlands
■ Conversion into industrial areas
■ The grazing of fresh shoot (from burnt area), leads to destruction of
grassland.
■ Conversion of grassland into bare land leads to soil degradation and finally it
becomes the wasteland.

28. Grassland conservation
■ The overgrazing should be stopped.
■ Rotational grazing pattern should be establish.
■ The grassland of an area must be closed every year.
■ Sanctuaries and national parks must be created.
■ Grassland should be conserve and the tree planation should
minimize in this type of ecosystem.

29. Desert Ecosystem
■ It is very sensitive ecosystem where the rainfall is
found below 25 mm.
■ The species of this ecosystem have very less chance to
survive other ecosystem.
■ The most typical example of desert ecosystem in Thar
desert of Rajasthan.
■ The Great and Little Rann of Kutch are extraordinally
specialized arid ecosystem. During monsoon season,
this area attract many aquatic birds such as ducks,
geese, cranes and storks. It is famous for breeding
colony of the greater and lesser flamingos in our
country.
■ The Runn of Kutch is the only habitat of wild ass in
India.
■ The desert ecosystem is the habitat of highly
specialized insects and reptiles. Eg: rattlesnakes, coral
snakes, beetles, grasshoppers, ants, bees and
butterflies etc

30. Benefits of desert ecosystem
■ The sparse and scanty vegetation use for the grazing of
cattle, camel, sheep and goat.
■ The crops like Jowar and Bajra used to grow during low
moisture condition.
■ The grasses of this ecosystem is capable of growing in very
less moisture condition, this can be use for research
purpose to grow vegetation in water scarcity areas.

31. Desert ecosystem degradation
■ Human population growth begun to affect the
natural ecosystem of desert.
■ Conversion of desert into agricultural land lead to
destruction of natural ecosystem.
■ Due to human intervention, the native species are
leads to extinct in this area.

32. Conservation of desert ecosystem
■ The Bishnoi tribe in Rajathan is very known for the
protection of their Khejri trees and blackbuck antelope for
several generations.
■ This ecosystem need to be protected by making national
parks and wildlife sanctuaries in Desert.
■ The Kutch area which is only habitat of wild ass, will be
destroyed by the spread of salt works.

33. Aquatic ecosystem
Aquatic
ecosystem
Fresh water
ecosystem
Flowing water
(Lotic system)
Example: streams,
springs, rivers
Still water
(Lentic system)
Example: ponds,
deltas, wetlands
Marine ecosystem
Brackish water
Example: coastal,
estuaries
Saline water
Example: deep
ocean, shallows
coral reefs
• The aquatic ecosystem is characterize by their specific biotic community and
abiotic features.
• The abiotic feature include the physical aspect such as quality of water, its
clarity, salinity, dissolved oxygen and the rate of flow.
• These abiotic aspect including beds, rocks and mud influence plant and
animal species composition in aquatic ecosystem.

34. Pond ecosystem
■ Pond ecosystem is a good example of fresh
water ecosystem.
■ It is the simplest aquatic ecosystem which
may be monsoonal or filled with water
throughout the year.
■ During rainy season, many food chain
develop and filled with many aquatic
animals, insects, snails and worms.
Whereas, many floating weeds and rooted
vegetation started emerges from the
surface of the water.
■ The waste material excreted from animal
and the dead or decaying plant and animal
matter act as nutrient for aquatic plant,
insect, worms and snails.

35. Lake ecosystem
■ Lake is like a giant permanent pond.
■ There is no clear scientific distinction
between pond and the lake ecosystem.
But most of the time, lakes are bigger
than ponds.
■ Most of the features of lakes are same as
pond ecosystem.
■ Lake is characterize by some specialized
fish such as catfish which depend on the
muddy bed of the lake and they are
called as bottom feeders or bottom
dwellers.
Eg: Chilka lake, Dal lake, Wular lake etc.

36. River and stream ecosystem
■ The biota of river and stream ecosystem are different from lakes and pond
ecosystem.
■ Stream get large amount of nutrient in the form of leaf litter, fallen wood
and dissolved organic matter from adjacent forest.
■ In this system, the water current is the major controlling factor and
responsible for the variation in the plant and animal species.
■ In the zone of fast current, only specialized species can survive that cling to
the hard bottom. Eg: snail
■ Some species of fish such as Mahseer exist because it can swim against
strong current.
■ The plankton found only where the water is deep and the current is gentle.

37. Marine ecosystem
■ The marine ecosystem of India govern by Arabian sea, Indian
ocean and Bay of Bengal.
■ The marine ecosystem is different from other ecosystem due to
salty water and variation the plant and animal species.
■ The producer in the marine ecosystem ranges from microscopic
algae to large seaweeds.
■ The coral reefs are found under the shallow sea where fish,
crustaceous, starfish, jellyfish and polyps deposits coral.
■ The marine ecosystem is facing threats due to the advancement
in the fishing technology.

38. Seashore ecosystem
■ The shoreline is found in the form of sandy, rocky, shell-
covered or muddy beaches.
■ It is characterized by various crustaceous such as crabs,
shore birds which depend on prey near to shorelines.

39. Benefits of aquatic ecosystem
■ Provide life support system in form of clean fresh water.
■ Dam help to provide water thought out the year and also use
for electricity generation.
■ The industries and agricultural sector are very much
dependent on the water.
■ Fisheries is a big sector for the food purpose as well as to earn
livelihood.
■ Marshes and wetlands have their great economic and
environmental importance.

40. Degradation of aquatic ecosystem
■ The discharging of untreated sewage
water pollute heavily to the riverine
system and other freshwater system.
■ Excessive fertilizer and nutrient input
into water leads to Eutrophication of
water.
■ Chemical and heavy metal pollution
from industries kills aquatic animals and
affect nearby people which depend on
this water.
■ The obstruction of river flow by Dam
construction change the aquatic
ecosystem, biological diversity, habitat
loss etc.
■ Artificial irrigation leads to salinization of
soil surface.

41. Conservation of aquatic ecosystem
■ Sustainable use of water
■ Prevent pollution at source
■ More and efficient Water treatment plant should be install.
■ Maintain flow of river system
■ Aquatic ecosystem like wetland, estuaries etc. must conserve by
sanctuaries or national parks. By this the conservation of rare
species that become endangered can be conserve. Eg. Mahseer
fish
■ The wetland and marshes are very fragile ecosystem, it must be
conserve.