Question 90 from UPSC CSE 2021 - Geography

Question

â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.â This is the most likely description of

Accepted Answer

Correct Option: D. tropical rain forest

Strategy: Focus on unique ecological features described: rapid leaf litter decomposition, almost bare soil surface, and the abundance of climbing plants and epiphytes. These clues clearly point towards a biome with intense nutrient cycling, prolific canopy vegetation, and conditions favoring specialized plant adaptations — features characteristic only of tropical rain forests. This allows for confident elimination of biomes like coniferous, dry deciduous, or mangrove forests, none of which display all these traits.

Key Info: ## Tropical Rainforest Characteristics

Tropical rainforests are characterized by high temperatures, heavy rainfall, and consistently high humidity throughout the year. These conditions foster exceptional rates of organic matter decomposition, primarily due to active bacteria, fungi, and other microorganisms that thrive in warm, moist environments. As a result, leaf litter on the forest floor decomposes rapidly, often leaving the soil surface almost bare of organic debris. This ongoing nutrient cycling means most minerals and nutrients are stored within living vegetation, not in the soil, causing rainforest soils to be relatively infertile and acidic.

Vegetation in rainforests is multilayered, with a dense canopy of tall trees, and is further augmented by climbing plants (lianas) and a wide array of epiphytes — plants such as orchids, ferns, and bromeliads that grow on tree branches, drawing moisture and nutrients from the air. This adaptive strategy allows plants to access light in the crowded, shaded forest environment. Epiphytes are key to the ecology of tropical rainforests and are far less common or absent in other forest types.

## Comparison with Other Biomes

*   **Coniferous forests (taiga):** Found in cooler climates, have slow decomposition due to low temperatures, and soils often accumulate organic litter.
*   **Dry deciduous forests:** Lose leaves seasonally, and decomposition is slower.
*   **Mangrove forests:** Are coastal, dominated by salt-tolerant trees, and do not feature the described canopy or decomposition dynamics.

Thus, only tropical rainforests fit the pattern described in the passage.

Answer

Option A: coniferous forest

Answer

Option B: dry deciduous forest

Answer

Option C: mangrove forest