Climate, Soils and Natural Vegetation of India
Climate, Soils and Natural Vegetation of India
This topic gives 3 questions and covers the monsoon in greater depth than the General Studies paper. Soil types with their crops, and the forest types with their regions, are the two tables that carry most of the marks.
The Monsoon Mechanism
The monsoon is a seasonal reversal of winds, caused by the differential heating of land and sea. In summer the land heats faster, low pressure forms over north-west India, and moist air is drawn in from the sea.
| Season | Months | Character |
|---|---|---|
| Cold weather | December to February | Dry; western disturbances bring rain to the north-west |
| Hot weather | March to May | The loo blows; Kalbaisakhi in Bengal and Bihar |
| Southwest monsoon | June to September | Most of India's rainfall |
| Retreating monsoon | October to November | Winds withdraw; Tamil Nadu receives rain |
- The southwest monsoon has two branches, the Arabian Sea branch and the Bay of Bengal branch.
- The Bay of Bengal branch turns west up the Ganga valley and waters Bihar.
- The monsoon bursts over Kerala around the first week of June and withdraws from the north-west first.
- Mawsynram and Cherrapunji in Meghalaya receive the heaviest rainfall in the world.
- Rainfall decreases westward along the Ganga plain, so east Bihar is wetter than west Bihar.
The Kalbaisakhi is the pre-monsoon thunderstorm of Bengal and Bihar, and it is a named local phenomenon a state paper can ask about. The westward decrease in rainfall is the reasoning question, and it explains why the drought risk differs across a single state.
✗ Rainfall in the Ganga plain increases as you move west | ✓ It decreases westward — east Bihar receives more rain than west Bihar
Soils of India
| Soil | Where | Suited to |
|---|---|---|
| Alluvial | Northern plains, deltas | Rice, wheat, sugarcane; the most widespread |
| Black or regur | Deccan lava region | Cotton; retains moisture |
| Red and yellow | Eastern and southern peninsula | Millets, pulses |
| Laterite | High rainfall hills | Tea, coffee, cashew |
| Arid | Rajasthan | Drought-resistant crops with irrigation |
| Forest and mountain | Hill slopes | Tea, orchards, spices |
Alluvial soil covers the largest area in India and is the soil of the whole of Bihar. Black soil is formed from lava, retains moisture well and is therefore associated with cotton — the soil-crop pair asked most often.
Soil erosion is checked by contour ploughing, terrace farming, strip cropping, shelter belts and afforestation. In Bihar the more pressing problem is not erosion but waterlogging and sand deposition after floods, which is a state-specific angle worth having.
Natural Vegetation
| Forest type | Rainfall | Trees |
|---|---|---|
| Tropical evergreen | Above 200 cm | Rosewood, ebony, mahogany |
| Tropical deciduous | 100 to 200 cm | Teak, sal, sandalwood; the monsoon forest |
| Thorn and scrub | Below 70 cm | Acacia, kikar, cactus |
| Montane | Hills, by altitude | Pine, deodar, silver fir |
| Mangrove | Deltas | Sundari, which names the Sundarbans |
Tropical deciduous forest is the most widespread in India and is called the monsoon forest. Sal is its characteristic tree in eastern India and is found in Bihar's forested tracts. The Sundarbans take their name from the sundari tree, which is a direct one-line question.
सबसे व्यापक वन — उष्णकटिबंधीय पतझड़, यानी मानसूनी वन।
TRE pointer: The soil-and-crop table and the forest-and-rainfall table between them carry most of this topic's marks and are pure matching. For Bihar, three items are state-specific: the Bay of Bengal branch waters the state, the Kalbaisakhi is its pre-monsoon storm, and rainfall decreases westward across it. The Sundari-Sundarbans link is a reliable one-line mark.
60-Second Recap
- The monsoon is a seasonal wind reversal caused by differential heating of land and sea.
- It bursts over Kerala in early June; the Bay of Bengal branch waters Bihar.
- Kalbaisakhi is the pre-monsoon thunderstorm of Bengal and Bihar.
- Rainfall decreases westward along the Ganga plain.
- Alluvial soil covers the largest area; black soil suits cotton.
- Tropical deciduous is the most widespread forest; the Sundarbans are named after the sundari tree.
Frequently Asked Questions
Which branch of the monsoon brings rain to Bihar?
The Bay of Bengal branch of the southwest monsoon, which enters from the east and turns west up the Ganga valley. The Arabian Sea branch strikes the western coast instead. Rainfall then decreases as the branch moves west, so east Bihar is wetter than west Bihar.
What is Kalbaisakhi?
A violent pre-monsoon thunderstorm that occurs in Bengal, Bihar and Assam during the hot weather season, usually in April and May. It brings sudden rain and strong winds, and it is named as a local phenomenon in state examination papers.
Which soil covers the largest area in India?
Alluvial soil, deposited by rivers across the northern plains and the deltas. It is also the most fertile and supports rice, wheat and sugarcane. Bihar lies entirely within this soil region, which is the basis of the state's agriculture.
Why are the Sundarbans so named?
After the sundari tree, a mangrove species that grows there in large numbers. The Sundarbans form the delta of the Ganga and Brahmaputra, shared between India and Bangladesh, and are the largest mangrove forest in the world.