UPSC Prelims 2013 Q22: Environment & Ecology – Ecosystems & Ecology Concepts
In the grasslands, trees do not replace the grasses as a part of an ecological succession
because of
- (a) insects and fungi
- (b) limited sunlight and paucity of nutrients
- (c) water limits and fire
- (d) None of the above
Answer: (c) water limits and fire
Explanation
Why trees do not replace grasses in grasslands
In a grassland, succession stops before forest can form.
Two things hold it back: too little water and frequent fire.
| Factor | Effect |
|---|---|
| Water limits | Rain is enough for grass but too little for trees |
| Fire | Burns tree seedlings; grasses regrow from their roots |
| Grazing | Large herds eat and trample young trees |
The options checked:
| Option | Verdict |
|---|---|
| (a) Insects and fungi | Incorrect |
| (b) Limited sunlight and paucity of nutrients | Incorrect; grasslands get plenty of sun and have rich soils |
| (c) Water limits and fire | Correct |
| (d) None of the above | Incorrect |
Grasslands of the world: Prairies (North America), Steppes (Eurasia), Pampas (Argentina), Veld (South Africa), Savanna (tropics).
Answer: (c) water limits and fire.
Why each option is right or wrong
- (a) Incorrect. Insects and fungi do not stop trees from taking over.
- (b) Incorrect. Grasslands have ample sunlight and fertile soil.
- (c) CORRECT. Water limits and fire stop trees from replacing grasses.
- (d) Incorrect. Option (c) is right, so 'None' fails.
Key point
Grasslands stay grasslands because of low rainfall, fire and grazing; they are a climax stage, not a step towards forest.
Remember
Grasslands: too dry and too often burnt for trees.
Common mistakes
- Thinking grassland soils are poor; many are very fertile.
- Forgetting the role of fire in keeping trees out.
- Assuming every succession must end in forest.
Exam tip
Grass survives fire and drought; tree seedlings do not.
Sources
- NCERT Class XII — Biology (Ecosystem: ecological succession)
- G.C. Leong — Certificate Physical and Human Geography (The Savanna and Temperate Grassland climates)