Previous Year 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:
Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(A) is false, but (R) is true.
(A) is true, but (R) is false.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Correct Answer: D
Detailed Solution
Assertion (A) is correct. Vegetation does not remain uniform from the Himalayan foothills to extremely high-altitude regions. There is a gradual transition from tropical/deciduous vegetation to temperate, coniferous, alpine and finally tundra vegetation.
Reason (R) is also correct. With increasing altitude, temperature generally decreases, while conditions of rainfall, snowfall, moisture and the growing season also change. Therefore, different altitudes create different climatic conditions for plants.
This produces the altitudinal zonation of vegetation. Deciduous forests occur in the Himalayan foothills, while wet temperate forests develop at about 1,000–2,000 metres.
At about 1,500–1,750 metres, Chir Pine forests may develop. At higher elevations, conifers such as blue pine and spruce occur, while at about 3,000–4,000 metres, vegetation such as silver fir, juniper, birch and rhododendron becomes prominent.
At very high elevations, the tree line begins to disappear and alpine grasslands and tundra vegetation develop; at still higher and harsher elevations, mosses and lichens occur.
Thus, the relationship is direct—change in altitude → change in climate → change in vegetation.