In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

Q: What is UPSC Prelims?

UPSC Prelims is a competitive examination conducted in India. This question is from the 2013 UPSC Prelims Environment & Ecology paper.

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To prepare for UPSC Prelims Environment & Ecology, practice previous year questions (PYQs), understand concepts thoroughly, and solve mock tests regularly. This 2013 question covers Basics of Ecology – Ecosystem, Food Chain & Energy Flow topic.

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This UPSC Prelims 2013 Environment & Ecology question has a medium difficulty level and is marked as an important question.

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Question

In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

Accepted Answer

Correct Answer: C — Water limits and fireStep-by-step Solution:In normal ecological succession (without human interference), grasslands would theoretically transition to shrublands and eventually forest (if climatic conditions permit). The reason trees do NOT replace grasses in most natural grasslands is a combination of two key factors:Water limits: Grasslands (temperate grasslands/steppes, savannahs) typically occur in regions where rainfall is insufficient to support the growth of trees. Trees require more water than grasses — they have larger biomass, higher transpiration rates, and require sustained soil moisture to establish. In grassland regions (typically receiving 250-700 mm rainfall annually), the precipitation is adequate for grasses (which are drought-adapted) but insufficient or too seasonal for tree establishment and survival. When tree seedlings do germinate in grasslands, they often die during dry seasons because they cannot access water deep enough. Grasses with deep fibrous root systems are better at intercepting and using the limited rainfall. ✓Fire: Grassland fires — whether naturally ignited (lightning) or set by animals or humans — are a key mechanism maintaining the grassland ecosystem. Grasses are fire-adapted: after a fire, they quickly regenerate from their underground root systems (which are protected from fire). Tree seedlings and saplings, in contrast, are killed by fire — their thin bark and young tissue are vulnerable. Regular fire thus prevents tree seedlings from maturing into adults and maintains the open grassland structure. The grass-fire cycle is a self-reinforcing ecosystem dynamic: grasses fuel fires, fires kill trees, trees can't grow, grasses dominate. ✓Key Concept: Grassland maintenance mechanisms: (1) Insufficient rainfall (semi-arid conditions — below forest threshold); (2) Fire (natural lightning fires + human/animal burning); (3) Grazing (large herbivores prevent tree seedling establishment by eating saplings); (4) Soil (shallow soils with limited water-holding capacity in some grasslands). Ecological succession: primary succession (bare rock/sand → pioneer species → intermediate stages → climax community); secondary succession (after disturbance of existing community). Grassland climax: in appropriate rainfall zones (250-700 mm), grassland IS the climax community — it doesn't necessarily succeed to forest. Savannah: tropical grassland with scattered trees (fire-adapted trees like Acacia); maintained by seasonal rainfall + fire + elephant grazing. India's grasslands: Terai-Duar grasslands (tiger + rhino habitat); Banni grasslands (Gujarat); Deccan plateau grasslands; important for grassland species like Indian Bustard, Blackbuck, Chinkara.

In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

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In the grasslands, trees do not replace the grasses as a part of an ecological succession because of

Master UPSC Prelims with Our Test Series

More Questions from Basics of Ecology – Ecosystem, Food Chain & Energy Flow

Frequently Asked Questions