Authentic Classroom Explanation by IAS Monk

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📍 The Question

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

Correct Answer: (d)

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🎯 Theme of the Question

Physical Geography | Biogeography | Soils | Tropical Rainforests

This is a classic assertion–reason question, testing understanding of nutrient cycling in tropical rainforest ecosystems.

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🧠 Classroom Explanation

Let us examine each statement carefully.

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🔹 Statement-I: The soil in tropical rain forests is rich in nutrients. ❌

• Contrary to popular belief, tropical rainforest soils are nutrient-poor
• Most nutrients are:
  • Locked in living biomass (trees, plants)
  • Present in leaf litter and dead wood
• Due to rapid recycling, very little organic matter accumulates in the soil
• Heavy rainfall also causes leaching, further reducing soil fertility

✘ Statement-I is incorrect

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🔹 Statement-II: High temperature and moisture cause rapid decomposition. ✅

• Tropical rainforests have:
  • High temperatures
  • High humidity
• These conditions promote:
  • Intense activity of decomposers (bacteria, fungi, termites)
• Organic matter decomposes very rapidly
• Nutrients are taken up almost immediately by plants, not stored in soil

✔️ Statement-II is correct

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🔗 Relationship Between the Statements

• Rapid decomposition explains why soil is NOT nutrient-rich
• Therefore:
  • Statement-II does not support Statement-I
  • It actually contradicts it

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📊 Final Assessment

Statement	Status
Soil is nutrient-rich	❌ Incorrect
Rapid decomposition due to heat & moisture	✅ Correct

👉 Correct option: (d)

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❌ UPSC Elimination Logic

• UPSC often traps aspirants with:
  • “Dense vegetation = fertile soil” assumption
• In rainforests:
  • Biomass is rich
  • Soil is poor

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🧩 Memory Hook

“Rainforests store nutrients in trees, not in soil.”

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🧠 Prelims Strategy Insight

For ecosystem questions:

• Always separate:
  • Biomass richness
  • Soil fertility
• Fast recycling ≠ nutrient accumulation

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🧭 IAS Monk Whisper

In rainforests, the ground stays poor because life above is too efficient.