Factors Affecting Vegetation Development, Extent and Classification
Geography › Biogeography: Soils and Vegetation · Topic 7.6
Natural vegetation is the plant cover that grows without human help, and its development depends on climate, soil, relief and living and human factors. Temperature and moisture are the dominant controls, with sunlight, soil nutrients and drainage, altitude, slope and fire also important. Vegetation changes with latitude from the equator to the poles and with altitude up a mountain, in belts that match climate. It is classified into forests, grasslands, scrub, desert vegetation and tundra, and by plant adaptation into hydrophytes, xerophytes, mesophytes, halophytes and tropophytes.
5 min read · UPSC Prelims · Geography · Biogeography: Soils and Vegetation
At a Glance
- Main controls Temperature and moisture
- Other factors Light, soil, relief, fire, humans
- Latitude Forests to tundra
- Altitude Falls about 6.5 °C per km
- Adaptation groups Hydrophytes, xerophytes, mesophytes
- Exam link UPSC Prelims, Geography: Biogeography: Soils and Vegetation
Where Does It Fit?
This topic follows the account of forests and explains why vegetation differs from place to place. The factors set out here underlie the topics on grasslands, desert vegetation and tundra, and the vegetation of India. Previous topic: Vegetation Resources: Types of Forests and Their Economic, Ecological and Cultural Significance. Next topic: Grasslands, Desert Vegetation and Tundra Vegetation.
What Factors Affect the Development of Vegetation?
| Factor | Effect |
|---|---|
| Temperature | Controls growing season, rate of growth and types of plant. Too cold or too hot stops growth. Tropical plants need warmth, while tundra plants survive freezing |
| Moisture (rainfall and humidity) | Decides whether an area is forest, grassland or desert. Above about 200 cm of rain gives rainforest; below about 25 cm gives desert |
| Sunlight | Needed for photosynthesis; length of day and intensity matter. In forests, plants compete for light |
| Soil | Depth, texture, nutrients, acidity and drainage control the species; dealt with in Soil: Characteristics and Factors Responsible for Soil Formation |
| Relief and altitude | Temperature falls about 6.5 °C for every 1,000 m of height, so vegetation zones are stacked on a mountain. Slope aspect and steepness change moisture and soil depth |
| Winds | Dry winds raise transpiration; strong winds stunt trees; wind carries seeds and pollen |
| Biotic factors | Grazing animals, insects, pollinators, competition between plants and microbes |
| Fire | Maintains grasslands and savannas by killing tree seedlings |
| Human activity | Clearance, farming, grazing, plantations, pollution and introduction of species |
How Does Vegetation Change with Latitude and Altitude?
The vegetation of the world follows the climate belts. From the equator towards the poles, the sequence is tropical rainforest, savanna, desert and Mediterranean scrub in the dry subtropics, temperate forest or grassland, coniferous forest, and tundra. The same sequence is seen, in compressed form, going up a mountain, as in the Himalaya.
| Altitude zone in the Himalaya | Vegetation |
|---|---|
| Foothills (below about 1,000 m) | Tropical and subtropical forests, sal, bamboo |
| 1,000 to 2,000 m | Subtropical and moist temperate forests, pine, oak, rhododendron |
| 2,000 to 3,500 m | Temperate coniferous forests, deodar, spruce, fir |
| 3,500 to 4,500 m | Alpine meadows and scrub (bugyals), juniper, birch |
| Above the snowline | Mosses, lichens and bare rock |
The tree line, the highest altitude at which trees grow, is lower in cold, windy places and higher near the equator. The vegetation of India is covered in Categories of Forests in India and Extent of Forest Cover.
How Is Vegetation Classified?
- By form: forests (trees), grasslands (grasses), shrublands or scrub, desert vegetation and tundra (mosses, lichens). These are described in Vegetation Resources: Types of Forests and Their Economic, Ecological and Cultural Significance and Grasslands, Desert Vegetation and Tundra Vegetation.
- By water relation (plant adaptation): hydrophytes live in water, as with lotus and water hyacinth; xerophytes survive drought, with deep roots, thick leaves or spines, as cactus and acacia do; mesophytes need moderate moisture and include most crop and forest plants; halophytes tolerate salt, as mangroves do; tropophytes change with seasons, shedding leaves in the dry season.
- By origin: natural vegetation grows without human help; cultivated vegetation is planted. Virgin vegetation is untouched and endemic species are native to one place.
- By biome: a biome is a large community of plants and animals shaped by climate, such as the tropical rainforest biome and the desert biome.
As an analytical point, vegetation is the most visible product of climate and is a sensitive indicator of climate change: species shift north or uphill as temperatures rise.
Vegetation is also mapped and monitored from space. Satellites measure the greenness of plant cover through an index called the Normalised Difference Vegetation Index, which rises with leaf cover and falls with drought, and it is used to follow crops, forest loss and desert spread. In India, the Forest Survey of India uses such data in its two-yearly assessment. Because vegetation responds slowly, a change seen on the map often reflects climate or land use of decades before. Planners use vegetation maps to decide where to site protected areas, how to manage grazing and fire, and which species to plant in restoration, since a plant community in balance with local climate and soil is the most likely to survive.
Why Is This Topic Important?
- Concept Climate decides vegetation
- Terms Plant adaptation names
- Altitude Himalayan zones
What Came Next?
The next topic describes grasslands, desert vegetation and tundra vegetation. Next topic: Grasslands, Desert Vegetation and Tundra Vegetation.
Key People and Terms
- Xerophyte Plant adapted to dryness
- Hydrophyte Water plant
- Halophyte Salt-tolerant plant
- Tree line Highest altitude with trees
- Biome Large climate-defined community
- Endemic Native to one region only
Exam Corner
Points to Remember
- Temperature and moisture are the main controls.
- Temperature falls about 6.5 °C per 1,000 m.
- Xerophytes survive dry conditions.
- Halophytes tolerate salt, such as mangroves.
- Above the tree line, only alpine plants grow.
Do Not Confuse With
- Xerophyte and halophyte Dry-adapted versus salt-adapted
- Biome and habitat Large climate region versus local home
- Tree line and snowline Highest trees versus permanent snow
Memory Hook
Heat and wet decide the cover; up the hill, the zones recover.
Mains Angle
Questions ask for the relation between climate and vegetation. These points add depth.
- Controls Climate first
- Zonation Latitude and altitude
- Change Shift with warming
A Question You May Face
An original practice question, not a past paper question.
“Discuss the factors that affect the development and distribution of natural vegetation, with reference to altitudinal zonation in the Himalaya.”
How to Answer
- Factors Climate, soil, relief.
- Latitude Belts of vegetation.
- Altitude Himalayan zones.
- Humans Modification.
GS Relevance
Frequently Asked Questions
What factors affect natural vegetation?
Natural vegetation is affected mainly by temperature and moisture, and also by sunlight, soil, relief and altitude, winds, fire, biotic factors such as grazing, and human activity. Climate sets the broad type of vegetation, while local factors such as soil and slope decide the detail.
How does vegetation change with altitude?
Because temperature falls by about 6.5 degrees Celsius for every 1,000 metres, vegetation changes in zones up a mountain, like the changes with latitude. In the Himalaya the sequence runs from tropical forests in the foothills to temperate forests, conifers, alpine meadows and finally mosses and lichens near the snowline.
What are xerophytes?
Xerophytes are plants adapted to survive in dry conditions, with features such as deep or wide-spreading roots, thick fleshy stems, small or spiny leaves, and waxy coatings that reduce water loss. Cactus, acacia and date palm are examples, found in deserts and other dry regions.
What are halophytes?
Halophytes are plants that can tolerate high salt levels in the soil or water. They have special ways of removing or storing salt. Mangroves, which grow in the salty water of tropical coasts and estuaries, are the best-known halophytes, and their breathing roots help them grow in waterlogged soil.
How is natural vegetation classified?
Natural vegetation is classified by form into forests, grasslands, scrub, desert vegetation and tundra. It can also be classified by adaptation to water into hydrophytes, xerophytes, mesophytes, halophytes and tropophytes, or by biome, each being a large climate-defined community of plants and animals.
PYQ Practice — Statement Analysis
1 Temperature falls with altitude at about 6.5 degrees per 1,000 metres.
So vegetation zones are stacked on mountains.
2 Hydrophytes are adapted to dry conditions.
They live in water; xerophytes suit dry conditions.
3 Mangroves are halophytes.
They tolerate salt.
4 Rainfall has no effect on natural vegetation.
Moisture is a main control.
Past Mains Questions on This Topic
This topic comes under Biogeography: Soils and Vegetation. UPSC Mains questions asked on the matching syllabus topic, year-wise with marks:
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