Geography Form 2 Notes : VEGETATION

VEGETATION

Plant cover on the earth’s surface.

Types of Vegetation

1. Natural Vegetation

Grows by natural means of seed dispersal without interference or modification by humans.

1. Semi-Natural/Derived Vegetation

Natural vegetation in the process of recovering from human interference.

1. Planted/Cultivated Vegetation

Vegetation planted by people, e.g., forests of exotic trees, trees in agroforestry, and plants used as hedges such as cypress.

Factors Influencing Types and Distribution of Vegetation

Topographical Factors

1. Altitude

• Coniferous trees are found at high altitudes because they are adapted to cool conditions.
• There is no vegetation on mountain tops due to very low temperatures inhibiting plant growth.

1. Terrain

• Gentle slopes with deep, well-drained soils are better suited for plant growth than steep slopes with thin soils caused by severe erosion and high runoff.
• Flat areas have poor drainage, making them swampy and supporting only swamp plants.

1. Aspect

Slopes facing the sun and rain-bearing winds have a wide range of plants due to warmth and moisture. Grasslands dominate the leeward side because it is drier.

1. Drainage

Well-drained soils support a large variety of plants, while waterlogged soils have swamp plants such as reeds and papyrus.

Climatic Factors

• Temperature
• Plants in warm areas are numerous and grow faster, e.g., in tropical lands. Deciduous trees shed leaves to reduce transpiration.
• Low temperatures cause slow plant growth; coniferous forests are found in such areas.
• Precipitation
• Areas with high precipitation have many plants and are dominated by broad-leaved forests to increase transpiration.
• Moderate rainfall areas are dominated by grasslands; low rainfall areas have scanty scrub and desert vegetation.
• Sunlight
• Areas with long sunshine duration have many plants.
• Tropical rainforests have little undergrowth because the canopy blocks sunlight from reaching the ground.
• Wind
• Warm moist winds bring heavy rainfall, supporting many broad-leaved plants that increase transpiration surface area.

Edaphic/Soil Factors

• Fertile soils support more plants; infertile soils have scanty vegetation.
• Soil pollution, such as oil spillage, causes plant drying.
• Deep soils support deep-rooted plants like trees; shallow soils support shallow-rooted plants like grasses and shrubs.

Biotic/Biological Factors

• Living Organisms

• Bacteria, earthworms, and burrowing animals improve soil fertility, promoting vegetation growth.
• Insects and birds pollinate plants, enhancing propagation.
• Bacteria and insects cause plant diseases, leading to death of some plants, e.g., aphids affected cypress in the late 1980s.
• Large herds of wild animals can destroy vegetation through overgrazing, turning grasslands into deserts.
• Human Activities
• Clearing natural vegetation for settlement and agriculture can lead to desertification.
• Bush fires, such as burning grasslands to promote new growth, can cause extinction of some plant species.
• Overstocking leads to overgrazing, turning grasslands into deserts.
• Rehabilitation of deforested areas can stop desert spread.

Vegetation in Kenya

• Forests

Forest area is less than 7%, mostly found in the Central Highlands.

1. Plateau Forests

Once extensive around Lake Victoria, now limited to patches in Maragoli, Kakamega, Kaimosi, Malava, Turbo, and Tinderet forests.

These are tropical rainforests with tall trees among shorter trees intertwined with creepers.

1. Lowland Forests

Found along the Kenyan coast.

Main types include:

• Mangrove forests growing in shallow waters.
• Tropical rainforests in Shimba Hills (Kwale District) and Arabuko Sokoke (Kilifi).

1. Highland/Mountain Forests

Located on slopes of Mt. Kenya, Aberdare forests, Iveti, Mbooni, Kilala, and Marsabit forests.

Indigenous hardwoods include olive, Meru oak, mvule, Elgon teak, and camphor; indigenous softwoods include podocarpus, African pencil cedar, and bamboo.

Exotic hardwoods such as eucalyptus and silver oak, and exotic softwoods like pines, cypress, fir, and wattle have been planted.

2. Savanna

Most widespread vegetation, covering about 65% of the total area.

1. Wooded/Tree Grassland

Found along the coastal strip and plateau bordering highlands east of the Rift Valley.

Consists of 1m tall grass mixed with thorny acacias.

With decreasing rainfall, trees become fewer and shorter, and grassland becomes more open.

Large trees grow along watercourses due to abundant moisture (riverine or gallery forests).

Trees shed leaves during the dry season to reduce water loss by transpiration.

(b) Bushland and Thicket

Covers about 48% of savanna.

Found between coastal land and Machakos, extending into Kitui, Mwingi, Garissa, Wajir, and Mandera districts.

Consists of thorny acacias and shorter thorny shrubs forming thorn bush with gaps that are bare or covered by scattered grasses.

Plant adaptations include:

• Thin leaves and hard cuticle to reduce transpiration.
• Baobab’s large trunk stores water for dry periods.
• Shedding leaves to conserve water.

(c) Highland Grassland

Found on undulating slopes.

Grasses such as red oat, wire, Manyatta, and Kikuyu grass grow where forests have been cleared.

Clover grows alongside Kikuyu grass where rainfall exceeds 1000mm.

3. Semi-Desert and Desert Vegetation

Covers about 21% of Kenya.

Found in parts of northeastern and northern Kenya, including Marsabit and Turkana districts.

Receives less than 380mm of annual rainfall.

Vegetation mainly consists of scrub—underdeveloped trees or shrubs. Shrubs grow up to 1m; grasses up to 3m, with bare ground in between.

Tree species include acacia and commiphora.

True deserts have almost no vegetation.

Adaptations of Plants (Xerophytes)

• Thick leaves to store water.
• Long tap roots to access deep water.
• Needle-like leaves to conserve water.
• Shedding leaves to conserve water (deciduous).

4. Heath and Moorland

Vegetation found near mountain tops.

• Lower altitudes have groundsel, lobelia, and heather.
• Poor drainage areas have mountain swamp vegetation called bogs.
• High altitudes have tussock grasses, flowering plants, and alchemilla shrubs, adapted to cold, windy summit conditions.

5. Swamp Vegetation

Found in flat, wet areas along rivers and flood-prone regions, e.g., River Tana, Lorian swamp in Isiolo, Wajir, Garissa, and mangrove belts along the coast.

Vegetation includes marshes, grasses with smooth surfaces and long blades, and dominant papyrus.

Vegetation Zones of the World

A. Forests

A forest is a continuous growth of trees and undergrowth covering large land areas.

1. Tropical Rain Forests

Known as Selvas in South America.

Found in:

• Congo Basin
• Amazon Basin
• Western India, Burma, and Vietnam
• Coastal Queensland, Australia

Characteristics

• Closely set trees with three distinct canopies.
• Less undergrowth due to canopy light obstruction.
• Trees take a long time to grow.
• Large trunks with buttress roots.
• Broad leaves increase transpiration surface area due to high precipitation.
• Varied plant species over small areas.
• Tall trees with smooth stems and straight trunks.
• Some evergreen trees shed few leaves at a time; others shed all leaves.
• Some trees are very heavy and do not float on water.
• Mature between 70-100 years.

Tree species include mahogany, ebony, ironwood, rosewood, camphor, and Sapele.

Tree creepers and parasites grow around tall trees.

Uses of Tropical Rain Forests

1. Timber for furniture, building, and construction.
2. Oil palms for palm oil production.
3. Cacao crops for cocoa beans used in chocolates and beverages.
4. Chicle from Zabote tree bark for chewing gum.
5. Ivory nuts for making buttons.
6. Fibres from torquilla palm for hats, mats, baskets, and thatching.
7. Cinchona bark contains quinine for malaria treatment.

2. Mangrove Forests

Found in low-lying muddy coasts of tropical seas with shallow salty waters.

Areas

• East coast of Africa
• Estuary of Amazon River, South America

Characteristics

• Dominated by mangrove trees and about 30 other tree species.
• Mangrove roots are partly aerial to aid breathing: some grow horizontally then vertically into mud; others grow horizontally and bend upwards; some have stilt-like root networks.

Uses of Mangrove Forests

1. Tannin for leather tanning.
2. Strong poles for building and construction.
3. Firewood.
4. Habitats for marine life attracting tourists.

3. Tropical Monsoon Forests

Location

• Southwest and south coast of Mexico
• Parts of India, Bangladesh, Burma, Vietnam, Indonesia
• Monsoon regions of Australia

Characteristics

• Most trees shed leaves during dry season and grow during wet season.
• Fewer tree species than tropical rainforests.
• Tall trees up to 30m.
• Trees grow spaced apart.
• More branches due to light penetration at lower levels.
• Denser undergrowth than tropical rainforests.
• Some species dominate areas (pure stands), e.g., Leak in Burma, Sal in India, Eucalyptus in Queensland, Bamboo in Southeast Asia.
• Dominant species include leak, bamboo, acacia, camphor, ebony, Sapele, and Pyinkaido.

Uses of Tropical Monsoon Forests

1. Teak for building houses and boats; hard and termite-resistant.
2. Bamboo and rattan for furniture, baskets, and weaving.
3. Young bamboo shoots consumed as vegetables.

4. Mediterranean Forests

Areas

• Southern Europe and North Africa bordering the Mediterranean Sea
• Around Cape Town, South Africa
• Central coast of California
• Around Perth, Southwest Australia

Characteristics

• Open woodlands.
• Many deciduous trees.
• Some evergreen trees, e.g., oak.
• Woody scrub vegetation in dry, poor soil areas called marquis (France), chaparral (California), and macchia (Italy).
• Many aromatic plants, e.g., rosemary, lavender, oleander, broom, myrtle.
• Many xerophytic trees with adaptations:

• Long tap roots reaching deep water during dry spells.
• Waxy leaves to reduce transpiration.
• Water storage in thick leaves or stems.
• Small spiny leaves.

• Tree types include olive, sweet chestnut, beech, cedar, cypress, sequoia, eucalyptus.

Uses

1. Cork oak for wine bottle corks.
2. Olive fruits for cooking and olive oil extraction.
3. Timber from sweet chestnut, beech, cedar, cypress, and pine for building and furniture.
4. Shrubs and grasses as pasture for goats.

5. Temperate Evergreen Forests

Found in warm temperate eastern margin or China climate regions.

Areas

• Natal coast, South Africa
• South China and South Japan
• Southeast Australia
• Southeast and southern United States

Characteristics

• Evergreen due to abundant year-round rainfall.
• Most trees have broad leaves for efficient transpiration.
• Many evergreen trees are hardwoods.

Uses

1. Hardwoods like oak and ironwood for furniture and building materials.
2. Softwoods like cypress and pines for furniture.
3. Wattle trunks used in Natal coal mines.
4. Bamboo used for furniture and building in China and Japan.
5. Walnuts provide nuts for chocolate making.
6. Ivory nuts used for buttons.
7. Young bamboo shoots eaten as vegetables in China and Japan.

6. Temperate Deciduous Forests

Found in cool temperate western marginal climate regions.

Location

• Central and Western Europe
• Most Eastern United States
• Chile, South America

Characteristics

• Deciduous trees shed leaves in autumn and regrow in summer.
• Tree species are scattered with low density.
• Trees are smaller and broad-leaved.
• Most trees are hardwoods.
• Rich undergrowth due to openness.
• Trees grow in pure or mixed stands.
• Easier to exploit than tropical hardwoods.

Uses

1. Hardwoods like oak and birch for timber, wood fuel, and charcoal.
2. Chestnut and walnut nuts are edible.
3. Oak fruits used for pig feed.
4. Tung tree yields oil for paint and furniture.
5. Maple sap used for maple syrup.

Trees include eucalyptus (blue gum), olive, birch, walnut, elm, and ash.

Coniferous Forests

Dominant in cool climates; known as Taiga or Boreal forests in Russia.

Location

• West coast of Canada
• Scandinavia across Russia to the Pacific coast

Characteristics of Softwoods in Canada

• Seeds are cone-shaped.
• Most trees are softwoods and light in weight.
• Trees mature faster than tropical hardwoods.
• Large stem-to-leaf ratio.
• Most species are evergreen; few shed leaves (e.g., larch, fir).
• Grow in large pure stands.
• Little undergrowth due to acidic humus from leaf fall.
• Straight trunks.
• Mature in 50-70 years due to cold winters.

Species include pines, fir, spruce, larch, and hemlock.

Adaptations

• Needle-like leaves reduce transpiration.
• Tough waxy leaf skin protects from winter cold.
• Cone-shaped, flexible crowns allow snow to slide off branches.
• Evergreen to maximize sunlight use during short summers.
• Flexible trunks sway to avoid breakage in strong winds.
• Wide root systems maximize moisture uptake from topsoil; subsoil is permanently frozen.

Uses

Softwoods like spruce, fir, pine, and larch are used for construction and wood pulp for paper manufacture.

7. Mixed Forests

Found in transition zones between temperate deciduous and coniferous forests.

Location

• Saskatchewan and Alberta provinces, Canada
• Scottish regions, Europe
• Low-lying Mediterranean regions

Characteristics

A mixture of broadleaved deciduous and coniferous trees.

Uses

Cedar and hazel used for fencing posts.

Grazing occurs where forests are open.

Softwoods like spruce, fir, and pine used for wood pulp in paper manufacture.

Hardwoods like oak and birch are valuable for timber, wood fuel, and charcoal.

Maple trees provide sap for maple syrup.

B. Grasslands

Found in climatic regions with a seasonal pattern including a prolonged drought of about 5-7 months.

Tropical Grasslands/Savanna

Found in areas with tropical continental climate.

Areas

1. North and South of Congo Basin
2. Between Sahel and equatorial forests in East African plateau
3. Northeast of Australian Desert
4. Brazilian highlands

Divided into:

• Open grasslands dominated by grass
• Woodlands in higher rainfall areas

Characteristics

• Grasslands with widely spaced trees such as acacias.
• Grasses die in dry season and sprout quickly when it rains.
• Grasses are tall (up to 3m); elephant grass reaches 4m.
• Trees are medium-sized, up to 13m.
• Tree crowns are umbrella-shaped, shading roots to reduce evaporation.
• Most trees are deciduous, shedding leaves during dry season.
• Trees have small leaves and thick bark to reduce transpiration.
• Long tap roots reach deep water during dry spells.

Uses

1. Grass for grazing and commercial ranching, though low in phosphorus.
2. Cereal farming (e.g., wheat) due to humus-rich soil from grass cover.
3. Vegetation reduces soil erosion.
4. Habitat for wild animals attracting tourists, e.g., East and Central African savannas.
5. Trees provide habitat for bees producing honey.
6. Some shrubs and herbs used for medicine.
7. Acacia trees provide fuel wood and charcoal.

Temperate Grasslands

Found in continental interiors where rainfall is insufficient for forests.

Location

The Prairies

Areas

Canadian provinces of Alberta, Saskatchewan, Manitoba, and neighboring U.S. states.

Characteristics

Continuous tuft grass, nutritious and short, mixed with bulbons and leguminous plants.

Some areas have tall grasses with rainfall over 500mm.

The Steppes

Found in Eurasia—temperate interiors of Europe and Asia.

Characteristics

True steppes have rich grass carpets and flowering plants.

Desert steppes have coarse grass growing in tufts, with short grass growing close to the ground and no continuous cover.

The Pampas

Found in Argentina.

Characteristics

Feather-like grass forming tussocks with patches of bare soil.

Forests present in some moist areas.

Xerophytic or drought-resistant plants occur in some areas.

The Veldt

Found in South Africa.

Characteristics

• Extensive grass cover.
• Little or no trees or shrubs.
• Uniform grass cover on high plateaus.

The Downs

Found in Australia and New Zealand.

Characteristics

• Tall grass mixed with trees.
• Semi-desert areas with dominant grass patches.
• Mixture of temperate and tropical grass species.
• Grass is nutritious for livestock.
• Natural grasses replaced by alfalfa in Argentina and British meadow grasses in New Zealand.

Uses of Temperate Grasslands

1. Grain cultivation, e.g., wheat requiring as low as 325mm rainfall.
2. Cultivation of oil seeds, soybeans, vegetables, millet, and sorghum (widely grown in the Veldt).
3. Livestock farming (cattle, sheep, goats, horses) with scientifically managed ranches called Estancias in Argentina.

Desert Vegetation

Tropical Desert Vegetation

Found in tropical deserts.

Characteristics

• Vegetation present except in bare rock and sand-covered areas.
• More plants on oases, e.g., date palms and various shrubs.
• Some plants are succulent with high water storage.
• Spines protect plants from animals.
• Thorn-like leaves reduce transpiration.
• Long roots tap water from deep rocks.
• Some shed leaves during dry season and regrow during wet periods.
• Salt-tolerant (halophytic) plants have many water-storing cells to counter soil salinity or alkalinity.

Temperate and Arctic Desert Vegetation

Found in warm temperate deserts and arctic climates.

Characteristics

• Grasses and woody plants.
• Woody plants are xerophytic and halophytic.
• Shrubs have shallow roots due to permafrost.
• Plants flower and produce fruits within short wet season.
• Scarce vegetation in tundra.
• Arctic desert plants include lichens, mosses, and flowering plants such as anemones and marsh marigold.

Uses of Desert Vegetation

1. Bilberries in temperate deserts bear edible fruits.
2. Small trees provide fuel for Eskimos in the Arctic.
3. Tropical desert vegetation helps arrest sand dunes, protecting oases and settlements.
4. Fringe vegetation in tropical deserts is valuable food for animals.
5. Date palm is cultivated for its fruit.

Mountain Vegetation

Vegetation found near mountain tops.

Uses of Mountain Vegetation

1. Grasslands used for grazing.
2. Alpine meadows in temperate regions provide summer grazing pastures.
3. Mountain forests provide timber, building materials, fuel wood, and charcoal.
4. Mountain forests are habitats for wild animals, e.g., elephants.
5. Mountain vegetation makes mountains important water catchment areas.
6. Mountain forests help purify air by absorbing carbon dioxide and providing oxygen.
7. Mountain vegetation is used for research.

Significance of Vegetation

1. Forests add beauty to the country’s landscape.
2. Vegetation protects soil from erosion by wind and rainwater.
3. Decaying vegetation forms humus, making soil fertile.
4. Roots, barks, and leaves of some plants are used for medicine.
5. Forests modify local climate by increasing rainfall and reducing temperatures.
6. Some plants, such as bamboo shoots and wild fruits, are consumed as food.
7. Fibrous plants like sisal and jute are used for making ropes, sacks, and mats.
8. Latex from rubber trees is used to manufacture rubber for tires.