Monsoons - 02
- Most of the forests yield valuable timber, and are prized for their durable hardwood.
- Lumbering is undertaken in the more accessible areas. This is particularly important in continental South-East Asia.
- Of the tropical deciduous trees, teak, of which Burma is the leading producer, is perhaps the most sought after. It is valuable on account of its great durability, strength, immunity to shrinkage, fungus attack and insects.
- Teak logs are so heavy that they will not float readily on water. It is therefore necessary to ‘poison’ the tree several years before actual felling, so that it is dry and light enough to be floated down the Chindwin and the Irrawaddy to reach the saw mills at Rangoon.
- Other kinds of timber include Neem, Banyan, Mango, Teak, Sal, Acacia, Eucalyptus
- Together with the forests are bamboo thickets, which often grow to great heights.
- Burma alone accounts for as much as three – quarters of the world’s production.
- It is such a durable timber that it is extensively used for ship building, furniture and other constructional purposes.
- This most primitive form of farming is widely practiced.
- Instead of rotating the crops in the same field to preserve fertility, the tribesmen move to a new clearing when their first field is exhausted.
- Maize, dry padi, sweet potatoes and some beans are the most common crops.
- Farming is entirely for subsistence, i.e. everything is consumed by the farmer’s family, it is not traded or sold.
- As tropical soils are rapidly leached and easily exhausted, the first crop may be bountiful but the subsequent harvests deteriorate.
- Shifting cultivation is so widely practiced amongst indigenous peoples that different local names are used in different countries
|Region||Name of Shifting Cultivation|
|Africa and Central America||Milpa|
The Savanna or Sudan climate
- This type of climate has alternate wet and dry seasons similar to monsoon climate but has considerably less annual rainfall.
- Also, there is no distinct rainy season like in monsoon climate.
[Only two seasons – winter and summer. Rains occur in summer].
- Floods and droughts are common.
- Vegetation, wildlife and human life are quite different from monsoon climate regions.
Distribution of Savanna Climate
- It is confined within the tropics and is best developed in Sudan, hence its name the Sudan Climate.
- It is a transitional type of climate found between the equatorial rainforests and hot deserts.
- The belt includes West African Sudan, and then curves southwards into East Africa and southern Africa north of the Tropic of Capricorn.
SOUTH AMERICAN SAVANNA
- There are two distinct regions namely the llanos of the Orinoco basin [north of equator] and the compos of the Brazilian Highlands [South of equator].
The Australian savanna is located south of the monsoon strip (northern Australia) running from west to east north of the Tropic of Capricorn\
- Certain parts across Northern Karnataka, Southern Maharashtra and Telangana exhibit characteristics of both semi-arid and savanna climate.
- Due to irrigation and cultivation, this region is different from other savanna regions.
- Mean annual rainfall ranges from 80 – 160 cm [Rainfall decreases with distance from equator].
- In the northern hemisphere, the rainy season begins in May and lasts till September.
- In the southern hemisphere, the rainy season is from October to March.
- Mean annual temperature is greater than 18° C.
- The monthly temperature hovers between 20° C and 32° C for lowland stations.
- Highest temperatures do not coincide with the period of the highest sun (e.g. June in the northern hemisphere) but occur just before the onset of the rainy season, i.e. April in Northern Hemisphere and October in Southern Hemisphere.
- Days are hot and nights are cold. This extreme diurnal range of temperature is another characteristic feature of the Sudan type of climate.
- The prevailing winds of the region are the Trade Winds, which bring rain to the coastal districts.
- They are strongest in the summer [favorable position of ITCZ] but are relatively dry by the time they reach the continental interiors or the western coasts [Trade winds are easterlies – flow from east to west. So rainfall decreases from east to west here].
- In West Africa, the North-East Trades, in fact, blow off-shore [continent to sea] from the Sahara Desert and reach the Guinea coast as a dry, dust-laden winds.
Natural Vegetation of Savanna Climate
- The savanna landscape is typified by tall grass and short trees.
- The grasslands are also called as ‘bush-veld’.
- The trees are deciduous, shedding their leaves in the cool, dry season to prevent excessive loss of water through transpiration, e.g. acacias.
- Trees usually have broad trunks, with water-storing devices to survive through the prolonged drought.
- Many trees are umbrella shaped, exposing only a narrow edge to the strong winds.
- In true savanna lands, the grass is tall and coarse, growing 6 to 12 feet high. The elephant grass may attain a height of even 15 feet.
- Grasses appear greenish and well-nourished in the rainy season but turns yellow and dies down in the dry season that follows.
- As the rainfall diminishes towards the deserts the savanna merges into thorny scrub.