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UPSC CSE Prelims 2021 · Question 60 · Ecology & ecosystems

"Leaf litter decomposes faster than in any other biome and as a result the soil surface is often…

Prelims 2021 · Q60

Ecology & ecosystems Easy

"Leaf litter decomposes faster than in any other biome and as a result the soil surface is often almost bare. Apart from trees, the vegetation is largely composed of plant forms that reach up into the canopy vicariously, by climbing the trees or growing as epiphytes, rooted on the upper branches of trees." This is the most likely description of

Answer & explanation

Answer: (d) tropical rain forest

The description fits a tropical rain forest, where constant heat and moisture make dead leaves rot very fast, leaving the ground almost bare, and where climbers and epiphytes reach the tall canopy by using tree trunks and branches.

  • ✓ (d) In a rain forest, NASA notes, leaf litter on the floor decomposes rapidly in wet, warm conditions, so the ground stays nearly bare. Woody vines climb the trees to reach the light, and epiphytes such as orchids and ferns grow on the branches. NCERT links tropical evergreen forests with a dense canopy.
  • ✗ (a) Coniferous forests grow in cold regions, where decay is slow, so they do not show the fastest leaf-litter breakdown of any biome.
  • ✗ (b) Dry deciduous forests have a long dry season, which slows decay, and they lack the dense layered canopy of climbers and epiphytes described here.
  • ✗ (c) Mangroves stand in tidal, salty waterlogged mud, so a description of bare forest soil with epiphytes in the canopy does not point to them.

Remember · Tropical rain forest: fast litter decay, thin humus, dense canopy, and climbers and epiphytes reaching the light. Nutrients sit in living plants, not in the soil.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 11 (practise this chapter)

Sources

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·

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