SHIFTING CULTIVATION OR SLASH AND BURN CULTIVATION
- This type of cultivation is followed in many parts of the world where dense forests are common [In India, North-East is known for this type of cultivation].
- Tribes cut the trees in a plot, burn them and cultivate the plot till the fertility is exhausted.
- Once the fertility is exhausted, the clearing is abandoned and they move on to a new plot. Such farming practices are becoming more and more widespread even among backward tribes.
- In the clearings for shifting cultivation, crops like manioc (tapioca), maize, bananas and groundnuts are grown.
- With the coming of the Europeans, many large plantations have been established, especially in Java, Sumatra, Malaysia, West Africa and Central America.
- The climate is very Favourable for the cultivation of certain crops that are highly valued in the industrial West. The most important is natural rubber.
- Malaysia and Indonesia are the leading producers. The home country, Brazil exports practically no natural rubber.
- Cocoa is another important crop which is cultivated in West Africa, bordering the Gulf of Guinea. The two most important producers are Ghana and Nigeria. All the cocoa here goes into American and European chocolate industry.
- From the same area another crop, oil palm, has done equally well and many countries like Indonesia have now taken to its cultivation.
- Other important crops include Coconuts, Sugar, Coffee (Brazil), Tea, Tobacco, Spices, Etc.
- The plantations resulted in the destruction of nearly half of equatorial forests.
- Occur within 5° to 30° N and S of the equator.
- On-shore [sea to land] tropical monsoons occur in the summer and off-shore [land to sea] dry monsoons in the winter.
- They are best developed in the Indian sub-continent, Burma, Thailand, Laos, Cambodia, parts of Vietnam and south China and northern Australia.
- The basic cause of monsoon climates is the difference in the rate of heating and cooling of land and sea (This is old theory.
- In the summer, when the sun is overhead at the Tropic of Cancer, a low pressure is created in Central Asia.
- The seas, which warm up much slower, remain comparatively at high pressure. At the same time, the southern hemisphere experiences winter, and a region of high pressure is set up in the continental interior of Australia.
- Winds blow outwards as the South-East Monsoon, to Java, and after crossing the equator are drawn towards the continental low pressure area reaching the Indian sub-continent as the South-West Monsoon (Coriolis force).
- In the winter, conditions are reversed.
- Monthly mean temperatures above 18 °C.
- Temperatures range from 30-45° C in summer. Mean summer temperature is about 30°C.
- In winters, temperature range is 15-30° C with mean temperature around 20-25° C.
- Annual mean rainfall ranges from 200-250 cm. In some regions it is around 350 cm.
- Places like Cherrapunji & Mawsynram receive an annual rainfall of about 1000 cm. [They lie on the windward side of the Meghalaya hills, so the resulting orographic lift (orographic rainfall) enhances precipitation. Also, they are located between mountains which enhances cloud concentration due to funneling effect]
- Seasons are chief characteristics of monsoon climate.
- Out blowing dry winds, the North-East Monsoon, bring little or no rain to the Indian sub-continent.
- However, a small amount of rain falls in Punjab from cyclonic sources (Western Disturbances: Frontal precipitation brought by jet streams) and this is vital for the survival of winter cereals.
- North-East Monsoons blowing over the Bay of Bengal acquires moisture and bring rains to the south-eastern tip of the peninsula at this time of the year (Nov-Dec).
- The temperature rises sharply with the sun’s northward shift to the Tropic of Cancer.
- Day temperatures of 35° C are usual in central India and the mean temperature in Sind and south India may be as high as 44° C.
- Coastal districts are a little relieved by sea breezes. There is practically little rain. [Hailstorms (thunderstorms with hail) occurs here and there]
- With the ‘burst’ of the South-West Monsoon in mid-June, torrential downpours sweep across the country. Almost all the rain for the year falls within this rainy season.
- This pattern of concentrated heavy rainfall in summer is a characteristic feature of the Tropical Monsoon Climate.
- The amount and frequency of rain decreases towards the end of the rainy season. It retreats gradually southwards after mid-September until it leaves the continent altogether.
- The skies are clear again and the cool, dry season returns in October, with the out blowing North-East Monsoon.