NCERT Solutions for Class 11 Geography Chapter 5: Natural Vegetation

Natural vegetation refers to the plant community that grows naturally without human interference and is left undisturbed for a long time. It is also known as 'virgin vegetation'.

Climatic conditions for Tropical Evergreen Forests:

• Annual precipitation >200 cm
• Very short or no dry season
• Mean annual temperature above 22°C
• High humidity throughout the year

Two main factors:

1. Climate (particularly temperature and rainfall, and photoperiod).
2. Soil (soil type, texture, moisture-holding capacity).

Vegetation in hot and dry regions: Tropical Thorn Forests and Scrubs — thorny plants and shrubs adapted to survive with very little rainfall (below 75 cm/year). Examples: Acacia, Euphorbias, Cactus.

Location: Tropical Deciduous Forests are found across a large part of India — foothills of Himalayas, Jharkhand, West Odisha, Chhattisgarh, and the eastern slopes of the Western Ghats. They are the most widespread forests in India, also called monsoon forests.

Two commercially important trees:

1. Teak (Sagwan) — used for furniture, shipbuilding, railway sleepers.
2. Sal — used for railway sleepers, heavy construction.

Social forestry aims to reduce pressure on traditional natural forests by planting trees on unused and fallow lands near human settlements. Its three main objectives are:

1. Fuelwood Supply: Provide fuelwood and charcoal to rural communities, reducing their dependence on natural forests.
2. Fodder Supply: Grow fodder trees and shrubs for livestock.
3. Environmental Protection: Increase green cover, prevent soil erosion, regulate local climate, and promote ecological balance.

Major Types of Forests:

1. Tropical Evergreen & Semi-Evergreen Forests: High rainfall areas; no defined dry season; multi-layered canopy; Ebony, Mahogany, Rosewood.
2. Tropical Deciduous Forests (Monsoon Forests): Most widespread; shed leaves in dry season; Teak, Sal, Sandalwood.
3. Tropical Thorn Forests: Arid and semi-arid regions; sparse, thorny vegetation; Acacia, Cactus, Euphorbias.
4. Montane Forests: Himalayan mountains; clear altitudinal zonation from deciduous to temperate to alpine.
5. Littoral and Swamp Forests (Mangroves): Coastal areas and river deltas; roots adapted to waterlogged saline soil; Sundari tree.

Factors for Variation:

• Climate: Rainfall (most crucial): >200 cm → evergreen, 70–200 cm → deciduous, <75 cm → thorn forests. Temperature: high → tropical forests, low → Himalayan temperate. Photoperiod also affects growth rate.
• Relief: Altitude causes altitudinal zonation; steep slopes have thinner soil and less dense vegetation.
• Soil: Sandy soils support cacti; wet marshy delta soils support mangroves; rich loamy soils support deciduous forests.

Forest cover is the actual land area occupied by forests, measured by the India State of Forest Report (ISFR).

Current Status: Total forest and tree cover ≈ 24.62% of geographical area — below the National Forest Policy (1988) target of 33%.

State-wise distribution:

• High (>75%): Mizoram, Arunachal Pradesh, Meghalaya, Manipur, Andaman & Nicobar Islands.
• Low (<10%): Punjab, Haryana, Rajasthan, Gujarat, UP — due to extensive agriculture and high population density.

Reasons for being below target: Rapid agricultural expansion, urbanization, large-scale commercial exploitation of timber, and high population pressure.

Ecological Significance:

1. Climate Regulation: Forests are carbon sinks; they absorb CO2 and mitigate climate change. They influence local and regional rainfall patterns.
2. Biodiversity: Home to millions of species of flora and fauna; rich gene pool of biological diversity — India is one of 17 'mega-diverse' countries.
3. Soil Conservation: Root systems bind soil; forests prevent erosion by wind and water, preventing silting of rivers.
4. Water Cycle: Regulate stream flow, reduce runoff, recharge groundwater, and moderate floods and droughts.

Economic Significance:

1. Timber: Valuable hardwood for construction, furniture, and industry (Teak, Sal, Deodar).
2. Minor Forest Products: Bamboo, gums, resins, medicinal herbs, tendu leaves (beedi making) — multibillion rupee industry.
3. Livelihoods: Over 100 million tribal and forest-dwelling communities depend on forests for food, fodder, fuel, and medicine.
4. Eco-tourism: National Parks and Sanctuaries generate significant revenue and employment through eco-tourism.

The Himalayan region shows a classic example of altitudinal zonation where vegetation types change with increasing altitude — similar to vegetation change from the tropics to the poles.

1. Foothills (up to 1,000 m): Tropical moist deciduous forests; Sal is the most prominent tree.
2. Wet Temperate Forests (1,000–2,000 m): Broad-leaved evergreen trees; Oak, Chestnut. Famous hill stations like Shimla, Darjeeling are here.
3. Temperate Coniferous Forests (1,500–3,000 m): Pine, Deodar (State tree of Himachal Pradesh), Silver Fir, Spruce. Used extensively for timber.
4. Alpine Vegetation (3,000–4,000 m): Above the treeline. Temperature grasslands (bugyals/margs). Stunted shrubs — Junipers, Rhododendrons.
5. Tundra Vegetation (above 4,000 m): Mosses and lichens; these grade into permanent snowfields and glaciers above.

1. Pneumatophores: Specialized aerial roots that grow vertically upward from waterlogged soil. Help the plant obtain oxygen, which is scarce in anaerobic muddy delta soil.
2. Most characteristic tree: Sundari tree (Heritiera fomes) — the entire Sundarban delta is named after it.
3. Ecological Significance: Acts as a natural barrier against cyclones and tsunamis; protects the coastline from erosion; critical habitat for diverse fauna, including the endangered Royal Bengal Tiger.
4. Location: Sundarbans (Ganga-Brahmaputra delta, West Bengal) is the largest mangrove delta in the world — a UNESCO World Heritage Site.