UPSC Prelims 2023 Q63: Geography – Biogeography & Natural Vegetation
Consider the following statements :
Statement - I :
The soil in tropical rain forests is rich in nutrients.
Statement - II :
The high temperature and moisture of tropical rain forests cause dead organic matter in the soil
to decompose quickly.
Which one of the following is correct in respect of the above statements?
- (a) Both Statement - I and Statement - II are correct and Statement - II is the correct explanation for Statement - I
- (b) Both Statement - I and Statement - II are correct and Statement - II is not the correct explanation for Statement - I
- (c) Statement - I is correct but Statement - II is incorrect
- (d) Statement - I is incorrect but Statement - II is correct
Answer: (d) Statement - I is incorrect but Statement - II is correct
Explanation
Tropical rainforest soils — rich forest, poor soil
| Feature | Fact |
|---|---|
| Soil type | Mainly laterite-type, highly weathered soils |
| Nutrients | Poor — heavy rain leaches minerals deep below the root zone |
| Decomposition | Very fast because of heat and moisture |
| Nutrient store | Mostly in the living plants, not in the soil |
| After clearing | Soil loses fertility within a few years |
Statement I — incorrect. Rainforest soils are nutrient-poor.
Statement II — correct. High temperature and moisture make dead matter decompose quickly.
The nutrients released are taken up at once by plants or washed away, so they do not build up in the soil.
Answer: (d) Statement - I is incorrect but Statement - II is correct.
Why each option is right or wrong
- (a) Incorrect. Statement I is false; rainforest soils are poor in nutrients.
- (b) Incorrect. Both are not correct; heavy leaching leaves the soil poor.
- (c) Incorrect. It is the reverse: Statement I is false and Statement II is true.
- (d) CORRECT. Fast decomposition is true, but nutrients are quickly absorbed or leached, so the soil is poor.
Key point
Rainforest: fast decomposition + heavy leaching = nutrient-poor soil; nutrients stay locked in living vegetation.
Remember
Tropical rainforest soils are nutrient-poor despite fast decomposition.
Common mistakes
- Assuming lush forest means fertile soil; the nutrients are in the plants, not the soil.
- Thinking fast decomposition enriches soil; the nutrients are recycled or leached at once.
- Forgetting why shifting cultivation moves on after a few years — the soil is exhausted.
Exam tip
Lush forest, poor soil. This contrast is a favourite trap in rainforest questions.
Sources
- NCERT Class XI — Fundamentals of Physical Geography (Soils and Biomes)
- NCERT Class XII — Fundamentals of Human Geography (Primitive subsistence farming)