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UPSC Prelims 2011 · Environment · Nature’s Machinery
If a tropical rainforest is removed, it does not regenerate quickly as compared to a tropical deciduous forest. This is because
- (a) the soil of rain forest is deficient in nutrients
- (b) propagules of the trees in a rainforest have poor viability
- (c) the rain forest species are slow growing
- (d) exotic species invade the fertile soil of the rainforest
Show the answer and explanation
Answer: (a) the soil of rain forest is deficient in nutrients
Almost all nutrients are in the plants. Clear them and what is left is leached soil — regrowth is slow.
The idea
When a rainforest is cut, the nutrients leave with the logs or go up in smoke. The bare soil is then beaten by heavy rain, which washes away what little remains. Exposed laterite can even bake hard in the sun. New trees have almost nothing to grow on.
Forest cleared → Nutrient store (the trees) is removed → Rain washes the bare soil → Soil hardens in the sun → Regrowth is very slow
Why the others are wrong
(b) Rainforest seeds are short-lived, but that is not the main reason regeneration is slow.
(c) Many rainforest pioneer trees grow very fast.
(d) The soil is not fertile, so this premise itself is wrong.
The trap
(d) contains a false idea hidden inside — “fertile soil of the rainforest”.
Also know
A tropical deciduous forest is different. Its trees drop all their leaves in the dry season, when decay is slow, so humus builds up in the soil. Cut such a forest and the soil still holds a reserve.
🔒 Rainforest nutrients are in the biomass. Remove it → poor, leached soil → slow regrowth.