Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R).
Assertion (A) : In the Himalayan mountains different types of vegetation are found.
Reason (R) : In Himala

Question

Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R).
Assertion (A) : In the Himalayan mountains different types of vegetation are found.
Reason (R) : In Himalayas, there are variations in climate with change in altitude.
Select the correct answer from the code given below :
Code :

UnlockIAS · Accepted Answer

Correct — D, both (A) and (R) are true and (R) is the correct explanation of (A). The Assertion is true: no other Indian region packs so many vegetation types into so small a horizontal distance. Walking up from the Terai you pass tropical moist deciduous sal forest, then subtropical chir pine, then temperate oak, deodar, fir and spruce, then sub-alpine birch and rhododendron, then alpine meadows, and finally bare rock and permanent snow. The Reason is also true: air temperature falls with height at roughly 6.5 degrees Celsius for every 1,000 metres, so climate changes continuously up a Himalayan slope. And the Reason is precisely why the Assertion holds. Vegetation is controlled above everything else by temperature and moisture, so where climate changes with altitude the plant community must change with it — a climb of three or four thousand metres reproduces the temperature gradient that would otherwise require a journey of thousands of kilometres towards the pole. That is altitudinal zonation, a causal link and not a coincidence, so the answer is not merely 'both true' but 'both true AND R explains A'.

Why the other options are wrong — (a) This is the real trap of the question, and it catches two kinds of candidate: the one who assumes by reflex that two true statements must be unconnected, and the one who reads the code in its usual UPSC order and thinks option (a) is the 'R explains A' choice. Both statements are true, but the altitudinal change in climate is not an incidental fact standing beside the variety of vegetation — it is the mechanism that produces it. Remove the temperature and moisture gradient and there is no reason for the vegetation to change at all.  (b) The Reason is a plain fact of physical geography. In the troposphere temperature falls with height at the normal lapse rate of about 6.5 degrees Celsius per kilometre, and Himalayan slopes also show sharp changes in precipitation, humidity and length of the growing season with height. There is nothing false in R.  (c) The Assertion is not false. Champion and Seth's Revised Survey of the Forest Types of India recognises several forest type groups that occur only in the Himalaya — Himalayan moist temperate, Himalayan dry temperate, sub-alpine, moist alpine scrub and dry alpine scrub — on top of the tropical and subtropical types found at the foot of the range. The diversity of Himalayan vegetation is exactly what the classification records.

Concept: Altitudinal zonation is the arrangement of plant communities in horizontal belts up a mountainside, produced because temperature falls and moisture, wind exposure and growing-season length change with height. In the Himalaya the sequence from the foothills upward is broadly: tropical moist deciduous sal forest in the Bhabar, Terai and Shivalik; subtropical pine forest dominated by chir pine at roughly 1,000 to 2,000 metres; Himalayan moist and dry temperate forest of oak, deodar, blue pine, silver fir and spruce from about 1,500 to 3,000 metres; sub-alpine birch, juniper and rhododendron up to the tree line; alpine meadows above it; and finally lichens, mosses and permanent snow. Altitude is the leading control, but rainfall and slope aspect matter too, which is why the wetter eastern Himalaya carries evergreen forest at heights where the drier western Himalaya carries chir pine and deodar.

State PCS 2025 Q103 — Geography PYQ with Answer

State PCS 2025 Q103 — Geography PYQ with Answer