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General Forestry for APPSC Forest Section Officer · Chapter 3

Forest Ecology and Biodiversity: Ecosystems, Succession, Hotspots, CBD, In-situ and Ex-situ Conservation

What to remember

  • An ecosystem has biotic and abiotic parts. Energy flows one way (sun to producers to consumers). Matter cycles. Only about 10 per cent of energy passes to the next trophic level.
  • Succession is the orderly change of plant communities. It starts with pioneers and ends in a stable climax. Primary succession begins on bare rock. Secondary succession begins where soil is already present.
  • India has hotspots in the Himalaya, the Western Ghats and Sri Lanka, and Indo-Burma (plus the Sundaland, which includes the Nicobar Islands). Conservation is in-situ (in natural habitat) or ex-situ (outside it).

1. Basic ideas of ecology

  • Ecology is the study of the relationship of living things with their environment.
  • Ecosystem: a community of living organisms and their non-living surroundings working as a unit.
  • Biotic factors: producers, consumers, decomposers. Abiotic factors: light, temperature, rainfall, soil, wind, humidity.
  • Habitat is the place where an organism lives. Niche is its role in the ecosystem.
  • Population is a group of individuals of one species in a place. Community is all populations living in an area.
  • Ecotone is a transition zone between two ecosystems. Edge effect is greater variety at the ecotone.
  • Biome is a large area with a similar climate and vegetation, such as tropical forest or desert.

2. Structure and function of the forest ecosystem

Trophic levels

LevelGroupExample in forest
1ProducersTrees, shrubs, grasses
2Primary consumers (herbivores)Deer, elephant, insects
3Secondary consumersFrogs, small carnivores
4Tertiary consumersTiger, eagle
–DecomposersFungi, bacteria, termites
  • Food chain: a single path of food transfer. Food web: many linked chains.
  • Ecological pyramids may be of numbers, biomass or energy. The energy pyramid is always upright. The number pyramid of a tree-insect-bird chain can be inverted.
  • Ten per cent law: about 10 per cent of energy is passed to the next level. If producers hold 10,000 kJ, herbivores get about 1,000 kJ and carnivores about 100 kJ.
  • Primary productivity: the rate at which producers store energy. Gross primary production (GPP) minus respiration (R) gives net primary production (NPP): NPP = GPP − R.

*Worked example:* GPP = 2,000 and R = 800 units. NPP = 2,000 − 800 = 1,200 units.

Nutrient cycles. Carbon, nitrogen, phosphorus and water cycles return matter. Decomposition of leaf litter returns nutrients to the soil. Tropical forests recycle nutrients fast, so most nutrients are in the plants and not in the soil.

3. Types of forests and climate (general)

Major Indian forest groups follow the standard classification into tropical wet evergreen, tropical moist deciduous, tropical dry deciduous, tropical thorn, montane and littoral or swamp forests. Rainfall and temperature decide the type. In Andhra Pradesh, the dry deciduous and thorn forests dominate, with mangroves on the coast and moist deciduous patches on the Eastern Ghats.

4. Ecological succession

Succession is the gradual and predictable replacement of one community by another until a stable community is reached.

TermMeaning
Pioneer speciesFirst colonisers (lichens on rocks)
SereSeries of stages in succession
Seral stageAn intermediate community
Climax communityStable final community in balance with climate
Primary successionStarts on a bare area with no soil, such as rock or new lava
Secondary successionStarts where soil and seeds exist, such as after fire or felling
HydrosereStarts in water
Xerosere (lithosere)Starts on dry rock

Typical lithosere: crustose lichen, foliose lichen, moss, herbs, shrubs, trees (climax). Secondary succession is faster than primary succession. Climax is decided by climate (climatic climax) or by soil or fire (edaphic or fire climax). Teak forest and many Indian dry deciduous forests are kept as stages by fire and grazing.

5. Biodiversity

Biodiversity is the variety of life at three levels: genetic, species and ecosystem diversity.

  • Alpha diversity: variety within one habitat. Beta diversity: change between habitats. Gamma diversity: variety over a large region.
  • Endemic species occur only in one region. Keystone species have a large effect on the ecosystem. Flagship species (tiger) attract public support. Indicator species show the condition of habitat. Umbrella species need a large habitat, so protecting them protects others.
  • Causes of loss: habitat loss and fragmentation, poaching, invasive species, pollution, climate change and over-use.

IUCN Red List categories (in order of decreasing risk): Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC). Data Deficient (DD) and Not Evaluated (NE) are the others.

Biodiversity hotspot: a region with at least 1,500 endemic plant species that has lost at least 70 per cent of its original habitat. The idea was proposed by Norman Myers. India's hotspots: Himalaya, Western Ghats and Sri Lanka, Indo-Burma, and Sundaland (Nicobar Islands part).

6. Convention on Biological Diversity (CBD)

  • Adopted at the Earth Summit, Rio de Janeiro, 1992 and in force from 1993. India is a party.
  • Three goals: conservation of biological diversity, sustainable use of its components, and fair and equitable sharing of benefits from genetic resources.
  • Protocols: Cartagena Protocol (biosafety, living modified organisms) and Nagoya Protocol (access and benefit sharing).
  • India's law is the Biological Diversity Act, 2002. It created the National Biodiversity Authority (headquarters at Chennai), State Biodiversity Boards and Biodiversity Management Committees at local level.
  • Other treaties: CITES (trade in endangered species), Ramsar Convention (wetlands), World Heritage Convention.

7. Conservation: in-situ and ex-situ

In-situ (inside natural habitat)Ex-situ (outside natural habitat)
National parksZoological gardens
Wildlife sanctuariesBotanical gardens
Biosphere reservesSeed banks and gene banks
Conservation and community reservesCryopreservation, tissue culture
Sacred grovesArboreta, herbaria
  • A national park has strict protection. Sanctuary allows some activities with permission.
  • Biosphere reserve has a core zone, buffer zone and transition zone. Under the UNESCO Man and Biosphere programme. Biosphere reserves in Andhra Pradesh include the Seshachalam Hills.
  • Project Tiger (launched 1973) and Project Elephant (1992) are species programmes.
  • AP has Nagarjunasagar-Srisailam Tiger Reserve, one of the largest in India, plus Sri Venkateswara National Park and Coringa and other sanctuaries. Coringa is a mangrove sanctuary.
  • Wildlife (Protection) Act, 1972 protects wild animals and plants and creates protected areas. Forest (Conservation) Act, 1980, renamed the Van (Sanrakshan Evam Samvardhan) Adhiniyam, 1980 by the 2023 amendment, controls diversion of forest land for non-forest use.

8. Measuring vegetation and population (formulas)

  • Density = total number of individuals ÷ total area sampled.
  • Frequency (per cent) = (number of quadrats in which the species occurs ÷ total quadrats studied) × 100.
  • Abundance = total number of individuals ÷ number of quadrats in which the species occurs.
  • Relative density (per cent) = (density of one species ÷ density of all species) × 100.
  • Basal area of a tree = π d² ÷ 4, where d is the diameter at breast height.
  • Population growth: birth rate + immigration − death rate − emigration.

*Worked example:* 60 trees are counted in 2 hectares. Density = 60 ÷ 2 = 30 per hectare.

*Worked example:* a species occurs in 12 of 40 quadrats. Frequency = 12 ÷ 40 × 100 = 30 per cent.

Invasive alien species such as *Lantana camara* and *Prosopis juliflora* spread fast, reduce native plants and are a major threat to forest biodiversity. Forest litter and humus feed the soil, and decomposition is faster in warm, moist forests than in cold or dry ones. Mangroves protect coasts from storms and are nurseries for fish.

Exam traps

  • 1. Primary succession starts without soil. Secondary succession starts with soil.
  • 2. Climax is stable. Seral stages are temporary.
  • 3. The energy pyramid is never inverted. Number or biomass pyramids can be.
  • 4. In-situ means within habitat. A zoo is ex-situ.
  • 5. Nagoya Protocol deals with access and benefit sharing. Cartagena Protocol deals with biosafety.
  • 6. CITES is about trade. Ramsar is about wetlands.
  • 7. Endemic means found only in that place. Exotic means introduced.
  • 8. A hotspot needs both high endemism and high habitat loss.

One-liners

  • 1. The CBD was opened at the Rio Earth Summit in 1992.
  • 2. Only about 10 per cent of energy goes to the next trophic level.
  • 3. NPP = GPP − respiration.
  • 4. Pioneer species begin a primary succession.
  • 5. A climax community is the stable end of succession.
  • 6. Biodiversity has genetic, species and ecosystem levels.
  • 7. The Biological Diversity Act was passed in 2002.
  • 8. The National Biodiversity Authority is at Chennai.
  • 9. Biosphere reserves have core, buffer and transition zones.
  • 10. Gene banks and botanical gardens are ex-situ methods.
  • 11. The Wildlife (Protection) Act was passed in 1972.
  • 12. The Forest (Conservation) Act was passed in 1980.

Practice questions

  1. Which term describes the role of an organism in an ecosystem?

    1. Biome
    2. Habitat
    3. Ecotone
    4. Niche
    Answer

    D. Niche

    Niche is the functional role. Habitat is the place.

  2. In a forest ecosystem the producers are:

    1. Fungi
    2. Tigers
    3. Green plants
    4. Deer
    Answer

    C. Green plants

    Green plants make food by photosynthesis.

  3. Decomposers in a forest include:

    1. Eagles
    2. Fungi and bacteria
    3. Tigers
    4. Herbivores
    Answer

    B. Fungi and bacteria

    Fungi and bacteria break down dead matter.

  4. The ecological pyramid that is always upright is that of:

    1. Energy
    2. Numbers
    3. Size
    4. Biomass
    Answer

    A. Energy

    Energy always decreases at each level, so the pyramid cannot be inverted.

  5. If GPP = 3,500 units and respiration = 1,500 units, NPP is:

    1. 3,500
    2. 1,500
    3. 5,000
    4. 2,000
    Answer

    D. 2,000

    NPP = GPP - R = 3,500 - 1,500 = 2,000.

  6. In a sample of 5 hectares, 150 trees are counted. Density is:

    1. 25 per ha
    2. 75 per ha
    3. 30 per ha
    4. 10 per ha
    Answer

    C. 30 per ha

    150 / 5 = 30 trees per hectare.

  7. A species appears in 9 of 30 quadrats. Its frequency is:

    1. 45 per cent
    2. 20 per cent
    3. 9 per cent
    4. 30 per cent
    Answer

    D. 30 per cent

    9/30 x 100 = 30 per cent.

  8. A species has 48 individuals found in 12 quadrats where it occurs. Its abundance is:

    1. 2
    2. 6
    3. 4
    4. 12
    Answer

    C. 4

    Abundance = 48 / 12 = 4 per occupied quadrat.

  9. A tree has a diameter at breast height of 20 cm. Using basal area = pi d2/4 with pi = 3.14, basal area is:

    1. 314 cm2
    2. 628 cm2
    3. 157 cm2
    4. 1,256 cm2
    Answer

    A. 314 cm2

    3.14 x 20 x 20 / 4 = 314 cm2.

  10. A forest area of 400 ha holds 12,000 trees of a species. Density per hectare is:

    1. 40
    2. 30
    3. 20
    4. 120
    Answer

    B. 30

    12,000 / 400 = 30 per ha.

  11. Relative density of species A is (density of A 20, total density of all species 80) per cent:

    1. 40
    2. 20
    3. 10
    4. 25
    Answer

    D. 25

    20/80 x 100 = 25 per cent.

  12. Secondary succession begins:

    1. On bare rock
    2. Only on lava
    3. In deep ocean
    4. Where soil and seeds are present
    Answer

    D. Where soil and seeds are present

    Secondary succession starts in areas that already have soil, as after fire or felling.

  13. Pioneer species on bare rock are generally:

    1. Grasses
    2. Tall trees
    3. Lichens
    4. Shrubs
    Answer

    C. Lichens

    Crustose lichens begin the lithosere.

  14. The stable final community in succession is the:

    1. Ecotone
    2. Climax community
    3. Pioneer community
    4. Seral community
    Answer

    B. Climax community

    The climax community is in balance with the climate.

  15. A series of stages in succession is called a:

    1. Sere
    2. Population
    3. Niche
    4. Biome
    Answer

    A. Sere

    A sere is the sequence of communities.

  16. Succession that starts in water is:

    1. Hydrosere
    2. Xerosere
    3. Lithosere
    4. Psammosere only
    Answer

    A. Hydrosere

    Hydrosere is a water-based succession. Xerosere starts on dry sites.

  17. Which level is NOT part of biodiversity?

    1. Genetic diversity
    2. Ecosystem diversity
    3. Atmospheric diversity
    4. Species diversity
    Answer

    C. Atmospheric diversity

    The three levels are genetic, species and ecosystem diversity.

  18. A species found only in a particular region is:

    1. Extinct
    2. Endemic
    3. Keystone
    4. Exotic
    Answer

    B. Endemic

    Endemic species are restricted to a region.

  19. A species whose protection also protects many others because it needs a wide habitat is a(n):

    1. Weed
    2. Pest
    3. Exotic species
    4. Umbrella species
    Answer

    D. Umbrella species

    Umbrella species need large habitats, so their protection covers other species.

  20. A biodiversity hotspot must have lost at least what share of original habitat?

    1. 90 per cent
    2. 30 per cent
    3. 70 per cent
    4. 50 per cent
    Answer

    C. 70 per cent

    Hotspots have at least 1,500 endemic plants and have lost at least 70 per cent of habitat.

  21. Which of these is a hotspot found in India?

    1. Western Ghats and Sri Lanka
    2. Cape Floristic
    3. Madagascar
    4. Amazon
    Answer

    A. Western Ghats and Sri Lanka

    India has parts of the Himalaya, Indo-Burma, Western Ghats and Sri Lanka and Sundaland hotspots.

  22. The Convention on Biological Diversity was adopted at:

    1. Kyoto
    2. Rio de Janeiro Earth Summit
    3. Paris
    4. Stockholm Conference
    Answer

    B. Rio de Janeiro Earth Summit

    The CBD was opened for signature at the Rio Earth Summit in 1992.

  23. The Nagoya Protocol deals with:

    1. Access and benefit sharing
    2. Trade in species
    3. Biosafety
    4. Wetlands
    Answer

    A. Access and benefit sharing

    Cartagena Protocol covers biosafety. Nagoya covers access and benefit sharing.

  24. The agreement that regulates international trade in endangered species is:

    1. Kyoto Protocol
    2. CBD
    3. CITES
    4. Ramsar
    Answer

    C. CITES

    CITES controls trade in endangered wild fauna and flora.

  25. The National Biodiversity Authority was set up under the:

    1. Wildlife Act, 1972
    2. Biological Diversity Act, 2002
    3. Forest Act, 1927
    4. Environment Act, 1986
    Answer

    B. Biological Diversity Act, 2002

    The Biological Diversity Act, 2002 created NBA, State Boards and BMCs.

  26. Which of the following is an ex-situ conservation method?

    1. Sacred grove
    2. National park
    3. Biosphere reserve
    4. Botanical garden
    Answer

    D. Botanical garden

    Botanical gardens and gene banks conserve outside natural habitat.

  27. Which is an in-situ conservation area?

    1. Cryobank
    2. Wildlife sanctuary
    3. Zoo
    4. Seed bank
    Answer

    B. Wildlife sanctuary

    Sanctuaries conserve species in their natural habitat.

  28. The three zones of a biosphere reserve are:

    1. Core, edge and peak
    2. Wet, dry and cold
    3. Core, buffer and transition
    4. Urban, rural and forest
    Answer

    C. Core, buffer and transition

    Core zone is strictly protected, with buffer and transition zones outside.

  29. Project Tiger was launched in:

    1. 1973
    2. 1983
    3. 1953
    4. 1963
    Answer

    A. 1973

    Project Tiger started in 1973.

  30. Consider these statements. 1. Primary succession begins on bare rock. 2. Secondary succession is faster than primary succession. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Soil and seeds already exist, so secondary succession is faster.

  31. Consider these statements. 1. The energy pyramid can be inverted. 2. The number pyramid can be inverted in some chains. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Energy pyramids are always upright. Number pyramids can be inverted.

  32. Consider these statements. 1. A zoo is an in-situ conservation site. 2. A national park is an in-situ site. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Zoos are ex-situ. National parks are in-situ.

  33. Consider these statements. 1. The CBD has the goal of fair sharing of benefits from genetic resources. 2. The CBD is a treaty on wetlands. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Ramsar is the wetland treaty.

  34. Consider these statements. 1. Decomposers return nutrients to soil. 2. Decomposition is faster in warm, moist forests. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both are correct.

  35. Consider these statements. 1. Keystone species have a large effect on their ecosystem. 2. Flagship species are those that attract public support. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    These are the standard definitions.

  36. Consider these statements. 1. Lantana camara is an invasive alien species. 2. Invasive species help increase native plants. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Invasive species reduce native plant growth.

  37. Consider these statements. 1. A hotspot needs high endemism. 2. A hotspot needs high habitat loss. Which is correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both criteria apply.

  38. Match the IUCN category with the right meaning: Critically Endangered is:

    1. Safe species
    2. Already extinct
    3. Not yet evaluated
    4. Extremely high risk of extinction in the wild
    Answer

    D. Extremely high risk of extinction in the wild

    CR means extremely high risk of extinction in the wild.

  39. Which IUCN category shows the highest risk among these?

    1. Endangered
    2. Near Threatened
    3. Vulnerable
    4. Critically Endangered
    Answer

    D. Critically Endangered

    The order is VU, EN, CR with CR the highest risk.

  40. The Wildlife (Protection) Act was passed in:

    1. 1962
    2. 1992
    3. 1982
    4. 1972
    Answer

    D. 1972

    The Wildlife (Protection) Act is of 1972.

  41. Which Act controls diversion of forest land for non-forest use?

    1. Forest (Conservation) Act, 1980
    2. Biological Diversity Act, 2002
    3. Water Act, 1974
    4. Wildlife Act, 1972
    Answer

    A. Forest (Conservation) Act, 1980

    The Forest (Conservation) Act, 1980 restricts de-reservation and diversion.

  42. Coringa Wildlife Sanctuary is notable for:

    1. Alpine meadow
    2. Coral reef
    3. Desert vegetation
    4. Mangrove forest
    Answer

    D. Mangrove forest

    Coringa has mangroves on the Godavari delta coast.

  43. A transition zone between two ecosystems is called:

    1. Niche
    2. Ecotone
    3. Sere
    4. Biome
    Answer

    B. Ecotone

    An ecotone is the zone between two communities.

  44. Producers fix 8,000 kJ. If each level passes 10 per cent, how much reaches tertiary consumers (level 4)?

    1. 8,000 kJ
    2. 8 kJ
    3. 800 kJ
    4. 80 kJ
    Answer

    B. 8 kJ

    Level 2 gets 800, level 3 gets 80, level 4 gets 8 kJ.

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