UPSC Prelims 2021 question on Savannah Vegetation

Analysis

Savanna ecosystems are heterogeneous environments characterized by the presence of trees, bushes, and grasses.

Nutrient and soil moisture availability are usually the limiting factors affecting the biomass growth in savannas, and overall biomass is impacted by competition, fire, grazing, and harvesting.

Savanna grassland soils are not very fertile. The nutrients in the soil are found near the surface as they come from decayed organic matter (vegetation) from the previous growing season. This organic matter decays rapidly due to the high temperatures.

In the parched grasslands and savannas, or drylands, of Africa, South America and Asia, termite mounds store nutrients and moisture and via internal tunnels, allow water to better penetrate the soil. Dirt mounds the insects build sustain significantly more shrubs, fruit-bearing trees, bugs, and animals, such as elephants, cheetahs, and zebras, than do surrounding areas.

Herbivory and burrowing activities can reduce overall plant biomass associated with burrowing mammal colonies, but the higher levels of soil nutrients and greater degree of water infiltration that occurs around their mounds can result in elevated foliar nutrient concentrations and greater plant biomass surrounding their burrows.

In general, savannas grow in tropical regions 8° to 20° from the Equator. Conditions are warm to hot in all seasons, but significant rainfall occurs for only a few months each year—about October to March in the Southern Hemisphere and April to September in the Northern Hemisphere. Due to limited rainfall, it is characterized by an open tree canopy.