Class 11 Geography Notes Chapter 5 (Natural vegetation) – India Physical Environment Book

Detailed Notes with MCQs of Chapter 5, 'Natural Vegetation,' from our 'India Physical Environment' textbook. This is a vital chapter, not just for understanding India's geography but also frequently tested in various government examinations. Pay close attention to the classifications, distributions, and characteristic species.

Chapter 5: Natural Vegetation - Detailed Notes for Exam Preparation

1. Introduction: What is Natural Vegetation?

• Definition: Refers to a plant community that has grown naturally without human aid and has been left undisturbed by humans for a long time. This is often termed virgin vegetation.
• Flora vs. Vegetation: Flora refers to plant species of a particular region or period, while vegetation refers to the assemblage of plant species living in association with each other in a given environmental frame (the plant cover).
• India's Biodiversity: India is one of the 12 mega bio-diversity countries of the world. It has about 47,000 plant species (about 15,000 flowering species which are endemic/indigenous to India).
• Forest Cover: According to the India State of Forest Report (ISFR) - [Note: Specific percentages change with reports, focus on trends and classifications. Check the latest ISFR for current data if needed for specific exams, but NCERT provides the foundational understanding]. Forest cover is crucial for ecological balance, resources, and climate regulation.

2. Factors Influencing Natural Vegetation

Two broad categories:

(A) Relief:

• Land: The nature of land influences the type of vegetation. Fertile, level land (like the Northern Plains) is generally devoted to agriculture, while undulating, rough terrains often support grasslands and woodlands. Mountains usually have conical trees and specific altitudinal vegetation zones.
• Soil: Different soil types support different vegetation. Sandy soils of the desert support cactus and thorny bushes, while wet, marshy, deltaic soils support mangroves and deltaic vegetation. Hill slopes with deep, fertile soil have conical trees.

(B) Climate:

• Temperature: Temperature, along with humidity, precipitation, and soil, determines the character and extent of vegetation. On slopes of the Himalayas and hills of the Peninsula above 915m, the fall in temperature affects vegetation types (tropical to subtropical, temperate, and alpine).
• Photoperiod (Sunlight): Variation in duration of sunlight at different places is due to differences in latitude, altitude, season, and duration of the day. Longer sunlight duration aids faster growth (e.g., trees grow faster in summer).
• Precipitation (Rainfall): This is the most crucial factor for vegetation distribution in India. Areas of heavy rainfall have denser vegetation compared to areas of less rainfall. The advancing Southwest Monsoon (June-September) and retreating Northeast Monsoon significantly impact vegetation types.

3. Types of Forests/Vegetation in India

Based primarily on climatic factors (especially rainfall) and relief, Indian forests are broadly classified into the following major types:

(i) Tropical Evergreen Forests (Tropical Rainforests)

• Rainfall: Heavy rainfall areas (> 200 cm) with a short dry season.
• Temperature: Warm and wet climate throughout the year (Mean annual temp > 22°C).
• Regions: Western slopes of the Western Ghats (Maharashtra, Karnataka, Kerala, Goa), hills of Northeastern states (Assam, Arunachal Pradesh, Nagaland, Meghalaya, Tripura, Manipur, Mizoram), and the Andaman and Nicobar Islands.
• Characteristics:
  • Luxuriant, dense, multi-layered structure (canopy, understorey, ground layer).
  • Trees reach great heights (up to 60 m or even above).
  • Appear green all year round as there is no definite time for trees to shed leaves (different species shed leaves at different times).
  • Rich in biodiversity.
• Important Species: Ebony, Mahogany, Rosewood, Rubber, Cinchona, Aini, Chaplas. [Remembering key species is important for MCQs]

(ii) Tropical Deciduous Forests (Monsoon Forests)

• Most Widespread: These are the most common type of forests in India.
• Rainfall: Between 70 cm and 200 cm.
• Characteristics: Trees shed their leaves for about six to eight weeks in the dry summer season to conserve water.
• Sub-types: Based on water availability:
  • a) Moist Deciduous Forests:
    • Rainfall: 100 cm to 200 cm.
    • Regions: Found mostly in the eastern part of the country – northeastern states along the foothills of Himalayas, Jharkhand, West Odisha, Chhattisgarh, and eastern slopes of the Western Ghats.
    • Important Species: Teak (most dominant), Sal, Shisham, Sandalwood, Khair, Kusum, Arjun, Mulberry.
  • b) Dry Deciduous Forests:
    • Rainfall: 70 cm to 100 cm.
    • Regions: Found in rainier parts of the Peninsular plateau and the plains of Bihar and Uttar Pradesh. Large parts of these forests have been cleared for cultivation or used for grazing.
    • Characteristics: Open stretches where trees are interspersed with patches of grass.
    • Important Species: Teak, Sal, Peepal, Neem, Tendu, Palas, Amaltas, Bel, Khair, Axlewood.

(iii) Tropical Thorn Forests and Scrubs

• Rainfall: Less than 70 cm.
• Regions: Semi-arid areas of North-Western India (Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Uttar Pradesh, Haryana) and leeward sides/rain-shadow areas of the Deccan Plateau.
• Characteristics:
  • Vegetation consists of thorny trees and bushes.
  • Plants remain leafless for most of the year or have small leaves to minimize transpiration.
  • Stems are often succulent to conserve water.
  • Roots penetrate deep into the soil in search of moisture.
• Important Species: Acacias (Kikar/Babool), Palms (Khajur), Euphorbias, Cacti, Khair, Ber.

(iv) Montane Forests (Mountain Forests)

• Characteristics: Vegetation changes according to altitude due to decreasing temperature. Exhibits altitudinal zonation, mimicking the transition from tropical to tundra regions.
• Altitudinal Zones (Himalayas):
  • Foothills (up to ~1000-1200 m): Tropical Deciduous forests (Sal dominant in east).
  • Wet Temperate Type (1000 - 2000 m): Evergreen broad-leaf trees like Oaks and Chestnuts dominate. Higher rainfall areas in NE India have denser forests.
  • Temperate Forests (1500 - 3000 m): Coniferous trees like Pine (Chir Pine), Deodar, Silver fir, Spruce, and Cedar. Found on southern slopes of Himalayas, and higher reaches of NE India. These forests cover most of the southern slopes and are commercially valuable. Temperate grasslands are also found at higher elevations.
  • Alpine Vegetation (Above 3000 - 3600 m): Temperate forests and grasslands give way to Alpine vegetation. Silver fir, Junipers, Pines, and Birches are common. They get progressively stunted as they approach the snow-line.
  • Alpine Grasslands/Tundra (Above 3600 m): Shrubs and scrubs merge into Alpine grasslands, used extensively for grazing by nomadic tribes (Gujjars, Bakarwals). Beyond this, vegetation is limited to mosses and lichens closer to the permanent snow line.
• Southern Mountain Forests: Found in Peninsular India, mainly in the Western Ghats, Vindhyas, and Nilgiris. As these are closer to the tropics and lower in altitude (avg. 1500m), they show:
  • Subtropical vegetation at lower levels.
  • Temperate vegetation (called 'Sholas' in Nilgiris, Anaimalai, Palani hills) at higher levels (>1500m). Species include Magnolia, Laurel, Cinchona, Wattle. These forests are often interspersed with grasslands.

(v) Mangrove Forests (Littoral and Swamp Forests)

• Regions: Found in coastal areas influenced by tides (deltas of major rivers, estuaries). Mud and silt get accumulated on such coasts.
• Characteristics:
  • Dense mangroves with roots submerged under water.
  • Trees adapted to survive in saline conditions and tidal variations. Many have pneumatophores (specialized roots) that grow upwards out of the water/mud to facilitate oxygen absorption.
• Major Areas: Deltas of the Ganga (Sundarbans - largest tract), Mahanadi, Krishna, Godavari, and Kaveri rivers. Sundarbans are named after the Sundari tree, which provides durable hard timber.
• Important Species: Sundari, Palm, Coconut, Keora, Agar. Royal Bengal Tiger is famous in the Sundarbans. Turtles, crocodiles, gharials, and snakes are also found.

4. Forest Conservation

• Importance: Forests are crucial for ecological balance, biodiversity, soil conservation, climate regulation, and providing resources.
• Threats: Deforestation due to agriculture expansion, urbanization, industrialization, overgrazing, logging, and infrastructure development.
• Conservation Measures:
  • Afforestation & Social Forestry: Planting trees on barren lands, community lands, etc.
  • Legal Framework: Wildlife Protection Act (1972), Forest Conservation Act (1980).
  • Protected Areas Network:
    • National Parks: Areas set aside to protect natural environment and wildlife, high degree of protection, no human activity allowed generally.
    • Wildlife Sanctuaries: Protection given mainly to fauna, certain human activities may be permitted.
    • Biosphere Reserves: Large, multi-purpose protected areas to preserve genetic diversity, ecosystems, and landscapes. They promote research, education, and sustainable use. India has 18 designated Biosphere Reserves (e.g., Nilgiri, Nanda Devi, Sundarbans, Gulf of Mannar, Pachmarhi, Achanakmar-Amarkantak). [Knowing key Biosphere Reserves is important]
  • Specific Projects: Project Tiger (1973), Project Elephant (1992).

Practice MCQs for Exam Preparation

Here are 10 Multiple Choice Questions based on this chapter:

1. Which of the following factors is MOST significant in determining the distribution of natural vegetation types across India?
   a) Soil Type
   b) Landform / Relief
   c) Rainfall
   d) Photoperiod

2. Ebony, Mahogany, and Rosewood are commercially important trees typically found in which type of forest in India?
   a) Tropical Deciduous Forests
   b) Montane Forests
   c) Tropical Thorn Forests
   d) Tropical Evergreen Forests

3. The 'Sholas' found in the Nilgiri, Anaimalai, and Palani hills are examples of:
   a) Alpine Grasslands
   b) Tropical Thorn Forests
   c) Temperate Forests in Peninsular India
   d) Mangrove Forests

4. Which type of forest is most widespread in India, also known as Monsoon Forests?
   a) Tropical Evergreen Forests
   b) Tropical Deciduous Forests
   c) Mangrove Forests
   d) Montane Forests

5. Sundari trees, known for their hard, durable timber, are characteristic species of which vegetation type?
   a) Tropical Thorn Forests
   b) Himalayan Montane Forests
   c) Mangrove Forests
   d) Tropical Dry Deciduous Forests

6. In the Himalayan ranges, coniferous trees like Pine, Deodar, Silver fir, and Spruce are typically found in which altitudinal zone?
   a) Below 1000 m
   b) 1000 - 2000 m
   c) 1500 - 3000 m
   d) Above 3600 m

7. Acacias, Palms, Euphorbias, and Cacti are characteristic plants of regions experiencing rainfall:
   a) Above 200 cm
   b) Between 100 cm and 200 cm
   c) Between 70 cm and 100 cm
   d) Below 70 cm

8. Which of the following Biosphere Reserves is located in the delta region of the Ganga and Brahmaputra rivers?
   a) Nilgiri
   b) Nanda Devi
   c) Sundarbans
   d) Gulf of Mannar

9. Pneumatophores, or specialized roots that help in respiration, are an adaptation found in plants of:
   a) Desert areas
   b) Alpine Tundra
   c) Mangrove forests
   d) Tropical Evergreen forests

10. Teak and Sal are dominant species in which type of Indian forests?
    a) Tropical Evergreen Forests
    b) Tropical Moist Deciduous Forests
    c) Alpine Forests
    d) Tropical Thorn Forests

Answer Key:

1. (c) Rainfall
2. (d) Tropical Evergreen Forests
3. (c) Temperate Forests in Peninsular India
4. (b) Tropical Deciduous Forests
5. (c) Mangrove Forests
6. (c) 1500 - 3000 m
7. (d) Below 70 cm
8. (c) Sundarbans
9. (c) Mangrove forests
10. (b) Tropical Moist Deciduous Forests

Revise these notes thoroughly. Focus on the distribution maps in your NCERT book, the rainfall data associated with each forest type, and the key species. Understanding the 'why' behind the distribution (climate and relief factors) will help you remember the details better. Good luck with your preparation!