RAS question
The Sewan grass (Lasiurus sindicus) is characteristic of which region of Rajasthan?
Correct answer: (D) Western Thar Desert.
Sewan grass, or Lasiurus sindicus, is characteristic of the Western Thar Desert region of Rajasthan.
Explanation
Sewan grass is linked with Rajasthan's Western Thar Desert because it is described as the primary grass of the extremely arid parts of western Rajasthan in the Indian Thar desert. Dairy Knowledge Portal places it in Jaisalmer, Barmer and Bikaner districts. Its habitat also explains the exam answer: it thrives under moisture stress on sandy plains, low dunes and hummocks, and is suitable for arid and semi-arid zones. That is why Sewan is not just any grass species in Rajasthan geography; it is a marker of the dry western desert landscape and an important fodder resource for livestock in that arid zone.
Why the other options are wrong
- (A) The eastern humid zone does not fit Sewan's arid-zone ecology, because it thrives under moisture stress in western Rajasthan's Thar desert.
- (B) The southern hilly region is associated in the question's explanation with deciduous forests, while Sewan is identified with sandy, extremely arid western Rajasthan.
- (C) Hadoti Plateau has black soil and different vegetation, unlike the sandy plains, low dunes and hummocks where Dairy Knowledge Portal places Sewan grass.
Concept
This tests Rajasthan's natural vegetation and region-specific grasslands. RAS repeatedly asks such questions because grasses like Sewan connect climate, desert landforms and livestock-based livelihoods in western Rajasthan.