UPSC Prelims 2021 Q60: Environment & Ecology – Ecosystems & Ecology Concepts
- (a) coniferous forest
- (b) dry deciduous forest
- (c) mangrove forest
- (d) tropical rain forest
Answer: (d) tropical rain forest
Explanation
Biome Identification: Tropical Rainforest
| Feature in the description | Which biome? |
|---|---|
| Leaf litter decomposes faster than any other biome | Tropical rainforest (year-round warm/humid, high microbial activity) |
| Soil surface almost bare (rapid nutrient cycling) | Tropical rainforest (most nutrients in biomass, thin soils) |
| Vegetation with plants reaching canopy via climbers and epiphytes | Tropical rainforest (lianas, orchids, ferns as epiphytes) |
| Roots on upper branches (epiphytes) | Tropical rainforest signature |
All features describe tropical rainforest - warm, humid, year-round decomposition, thin nutrient-poor soils, vertically-stratified vegetation with lianas and epiphytes.
Answer: (d) tropical rain forest.
Why each option is right or wrong
- (a) Incorrect. Coniferous (taiga) forests have SLOW decomposition (cold), thick litter layer, no epiphytes.
- (b) Incorrect. Dry deciduous forests have moderate decomposition, soil-anchored plants, few epiphytes.
- (c) Incorrect. Mangrove forests have salt-tolerant halophytes with prop roots and pneumatophores - not epiphyte-dominated.
- (d) CORRECT. Tropical rainforest matches all features: fastest leaf litter decomposition (warm/humid microbial activity), bare soil (rapid nutrient cycling into biomass), lianas and epiphytes reaching canopy on tree branches.
Key point
Tropical rainforest = fastest litter decomposition + bare thin soil + lianas + epiphytes on tree branches. Nutrients stored in biomass, not soil. Warm-humid year-round = high microbial activity. Amazon, Congo, SE Asia rainforests + India's Western Ghats/NE.
Remember
The description of fastest leaf litter decomposition, almost bare soil surface, and vegetation dominated by climbers (lianas) and epiphytes rooted on tree branches is a signature of tropical RAIN FOREST. This is because year-round warm/humid conditions drive rapid nutrient cycling. Correct answer: (d).
Common mistakes
- Assuming rainforest soil is rich. It is actually POOR - nutrients are locked in biomass, not soil.
- Confusing epiphytes (plants growing ON other plants) with parasites (plants deriving nutrients from hosts). Epiphytes use host only for support.
- Not knowing India has tropical rainforests in Western Ghats (evergreen forests) and Northeast (Assam, Meghalaya, Arunachal).
Exam tip
Biome features quick ID: Rainforest = epiphytes, lianas, bare soil; Taiga/coniferous = thick litter, slow decomposition; Deciduous = seasonal leaf drop; Savannah = grass + scattered trees; Mangrove = prop roots + salt tolerance; Tundra = permafrost, mosses/lichens.
Sources
- NCERT Class XI Physical Geography - Chapter on Biomes
- NCERT Class XII Biology - Chapter 14: Ecosystem