Biogeography : Natural Vegetation

Q 1 / 4

UPSC CSE Prelims 2021

The vegetation of savannah consists of grassland with scattered small trees, but extensive areas have no trees. The forest development in such areas is generally kept in check by one or more or a combination of some conditions. Which of the following are such conditions?

  1. Burrowing animals and termites
  2. Fire
  3. Grazing herbivores
  4. Seasonal rainfall
  5. Soil properties
Select the correct answer using the code given below.

EXPLANATION

The correct option is (c).

Explanation

The Savannah landscape is characterized as a "parkland" topography, featuring tall grasses and scattered, fire-resistant trees. It represents a transitional biome between the equatorial rainforests and hot deserts. The suppression of dense forest growth in these regions is primarily driven by climatic conditions and biotic interference.

Analysis of Conditions:

  • 1. Burrowing animals and termites (Incorrect): While termites and burrowing animals modify soil structure and aeration, they are not the primary ecological factors responsible for preventing forest development on a landscape scale.
  • 2. Fire (Correct): Frequent fires, often occurring in the dry season, are a critical determinant of Savannah vegetation. Fires burn dry grasses and kill young tree saplings, preventing them from maturing into a closed canopy forest. Mature Savannah trees often possess thick, corky bark to resist fire damage.
  • 3. Grazing herbivores (Correct): Savannahs support large populations of herbivorous animals. Intense grazing and browsing pressure prevent tree seedlings from establishing and growing, thereby maintaining the dominance of grasses.
  • 4. Seasonal rainfall (Correct): The Savannah climate is defined by a distinct wet and dry season. While the rainfall is sufficient to support grass and scattered trees, the prolonged dry season restricts the availability of moisture required for the development of a dense, continuous forest canopy.
  • 5. Soil properties (Incorrect): While soil conditions influence local vegetation patterns, they are not the overarching factor keeping forest development in check across the entire biome compared to the limiting effects of moisture, fire, and grazing.

Key Takeaway:

The ecological balance of the Savannah biome is maintained by a combination of seasonal rainfall (climatic factor) and disturbance factors such as fire and grazing, which arrest ecological succession towards a dense forest.

SOURCEEnvironment by Shankar IAS, Chapter 2: Ecosystem