RAS question
Consider the following statements about temperate grasslands: 1. Temperate grasslands receive between 25–75 cm of annual rainfall, insufficient to support forests but sufficient to prevent desertification. 2. The absence of trees in temperate grasslands is solely due to periodic fires ignited by lightning. 3. Temperate grasslands typically have a thick, humus-rich topsoil that makes them among the world's most fertile agricultural lands. 4. Steppes of Central Asia are characterised by a continental climate with extreme temperature variations between summer and winter. Which of the statements given above are CORRECT?
Correct answer: (A) 1, 3 and 4 only.
For temperate grasslands, statements 1, 3 and 4 are correct: they receive about 25-75 cm of annual rainfall, have fertile humus-rich soils, and the Central Asian steppes show a strongly continental seasonal temperature range.
Explanation
Temperate grasslands occupy the moisture middle ground between deserts and forests. Their annual rainfall is 25-75 cm: enough to avoid desert conditions, but too low for closed-canopy forests. Biology LibreTexts notes that temperate grasslands have relatively low annual precipitation and therefore few trees, with grasses as the dominant vegetation. Statement 3 is right because dense grass roots and rhizomes add organic material, or humus, to the soil as they die and decay, making these soils highly fertile; this is why chernozem or mollisol soils and grain belts such as the Prairies and Steppes are associated with temperate grasslands. Statement 4 is also right: steppes are Eurasian temperate grasslands, and the climate has hot summers, cold winters, and pronounced annual temperature fluctuations.
Why the other options are wrong
- (B) Option B includes statement 2, but tree absence in temperate grasslands is not caused solely by lightning fires; low or seasonal rainfall, drought and grazing also matter, while Biology LibreTexts links few trees to low precipitation and treats fire as one natural disturbance.
- (C) Option C omits statement 1 even though temperate grasslands receive 25-75 cm of annual rainfall, enough to prevent desert formation but insufficient for closed-canopy forests.
- (D) Option D treats all four statements as correct, but statement 2 is over-absolute because fire is only one factor in maintaining treeless grassland, not the sole cause of tree absence.
Concept
This tests the world-geography concept of temperate grassland biomes: rainfall limits, soil fertility and continental climate. It recurs in RAS because grasslands connect physical geography with agriculture, soils and regional names such as prairie and steppe.