Prelims 2021

Q. “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

a) coniferous forest
b) dry deciduous forest
c) mangrove forest
d) tropical rainforest

Correct Answer: d) tropical rainforest

Question from UPSC Prelims 2021 GS Paper

Explanation : 

Tropical Rainforest Characteristics

This description most accurately depicts a tropical rainforest. Here’s why:

Fast Decomposition

In tropical rainforests, the warm and humid climate promotes rapid decomposition of leaf litter. This is because the warm temperatures and high moisture levels are ideal conditions for decomposers like bacteria, fungi, and insects to thrive. These organisms break down dead organic material quickly, returning nutrients to the soil.

Bare Soil Surface

Due to the rapid decomposition, the soil surface can often appear almost bare. This is because the leaf litter that falls to the ground doesn’t accumulate in thick layers as it decomposes so quickly.

Diverse Vegetation

Tropical rainforests are known for their incredible biodiversity, including a variety of plant forms. Many plants grow as epiphytes, which are plants that live on other plants (usually trees) non-parasitically. They obtain moisture and nutrients from the air and rain, and sometimes from debris accumulating around them. This allows them to reach up into the canopy where they can access sunlight without having to grow a tall trunk of their own.

Climbing Plants

In addition to epiphytes, tropical rainforests are home to many lianas and other climbing plants that use trees as support to reach the sunlight in the upper canopy. This is a common adaptation in the dense, competitive environment of the rainforest where light is a valuable resource.

In contrast, the other biomes listed do not fit the description:

  • Coniferous forests (also known as boreal forests or taiga) are characterized by cold climates and evergreen coniferous trees. Decomposition is slower here due to the cold temperatures.
  • Dry deciduous forests have a seasonally dry climate and the trees shed their leaves during the dry season. The rate of decomposition can be slower than in rainforests, and the forest floor often has a layer of dry leaves.
  • Mangrove forests are found in coastal areas where salt-tolerant trees grow in brackish water. The soil is often anaerobic (lacking oxygen) and decomposition can be slow; the forest floor is typically muddy and covered with a layer of fallen leaves and detritus.

Given these distinctions, the tropical rainforest is the correct answer to the description provided.

More Questions:
UPSC Factory App
Get everything you need for upsc preparation with just one click! Install now!