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Something about Climate and Natural Vegetation

 

Something about Climate and Natural Vegetation

Something about Climate and Natural Vegetation




How does climate affect natural vegetation?


The climate of a place has a lot to do with the way people live in that place. If it is hot and wet they may grow and eat rice ; if it is cool they may depend for their food on wheat . If there is a hot dry summer and a warm wet winter ( what is called a Mediterranean Climate ) grapes and other juicy fruits will be an important crop. The modern textile industry ( the spinning and weaving of cotton ) started in places like Bombay , and Lancashire in England , where humi dity was high and the cotton thread was less particularly liable to snap . The way people build their houses , and the clothes they wear , are largely con trolled by the climate of the place they live in . 



Tradee and exploration across the oceans were first largely controlled by the regular or planetary winds. In the past people tended to emigrate to places with climates similar to those they were used to - Indians Malaysia , Guyana and South Africa , northern Europeans to Canada and southern Europeans to Brazil and the Argentine and the Chinese to Man churia and southern Chinese Malaysia . 



Thee humidity and tiring heat of tropical and equatorial climates make it more difficult for people with to these climates to work harder than it is for people who live in cooler climates




these climates to work harder than it is for people who live in cooler climates .


 Man , of course , is learning to exercise some control over the effects of climate : for example , crops are being bred by crossing different strains or breeds that are resistant to heat and cold and more or less of rainfall . Air conditioning of houses and offices makes it possible for those fortunate enough to be able to use it , to work in greater comfort and for longer hours. Cotton can be spun in dry climates in factories with artificial humidity . 


Climate , however , still largely controls the way we live , the plants , trees and grasses that grow around us , the food we can buy in the village market , the animals we use for agriculture and transport , and climate is the result of temperature , rain or snowfall , winds , height above the sea , ocean currents and distance from the sea . 


What climate is natural vegetation under? 


There are four main climatic regions dependent on latitude : tropical , sub and tropical , temperate and polar these can be further split up ; For example , a tropical climate may have equatorial forests or hot grasslands known as savannah , or hot desert . A sub - tropical climate , again according to the rain it gets , may have what is 


Something about Climate and Natural Vegetation


called a Mediterranean climate when the Horse Latitudes stretch across it in summer time and it is hot and dry , and the westerly wind belt moves over it in winter bringing winter rain ( see Fig. 38 ) ; or it may have rain through out the year and be known as a China type or Cotton Belt climate. The temperate regions ( roughly latitudes 40 ° to 60 ° ) may have their climate warmed by ocean currents and so be what is called temperate oceanic , the climate of north - western Europe ; or they may be far inland and have a small rainfall and steppe climate whose natural vegetation is grass , and here wheat is the great crop ; or they may have very little rain and be a desert like the Gobi Desert. In the polar region there is the Tundra where the ice melts in the summer and flowers, mosses and lichens flourish for a few months, and also the ice cap which never melts. In any part of the world the climate may be changed by mountains which will have a mountain climate .  


Different climates have their different natural vegetation . Where there is good rainfall there will be trees - ever green where it is hot , deciduous where it is cooler . Deciduous trees are trees that shed their leaves ; and those with which you are most familiar , I expect , are the trees of the monsoon forests of India which shed their leaves during the hot season , possibly to protect themselves against losing too much moisture by evaporation from their leaves . Where it is cooler still , round some hill stations and in warm tempe rate climates , the trees shed their leaves on the approach of winter to protect themselves against the cold and frosts . The Americans call the time they do this ' the fall ' . Where it is cooler still we find coniferous trees with needle like leaves , and these you will have seen if you have ever been to the Himalayas or other high hills .  


How do climate and vegetation differ? 


Where there is less rainfall there will be fewer or no trees and grasslands . Savannah takes the place of equatorial forest as the rainfall grows less with distance from the sea, and here there are scattered trees and tall grass that flourishes when the rain falls in the hot season. This is the region of herds of antelope and the animals that feed on them, and where man often keeps many cattle. Where there is less rain still there is desert ; and where it is cooler the savannah changes to temperate grasslands: the steppes of Europe and Asia, the prairies of North America, the pampas of South America, the veld of South Africa, and the pastures of New South Wales in Australia. 


 Let us look for a moment at the climate of India . But before we do this let me tell you how I drew India's rough outline for the figures below. I made a templet by tracing the outline of a map of India on to a piece of card and then cutting round the outline .


Such a templet is a useful thing to make and keep as you will need to draw lots of maps of India , and it will save you much time. Fig. 46 shows the rough position of three isotherms , those of 15 , 20 and 25 degrees Centigrade , over India and the In December it gets warmer as you go southwards to lower latitudes, as we would expect, and the land tends to be cooler than the sea in the same latitude - look how the isotherm of 25 °C bulges southward over the land. In June , however , it gets hotter as we go northwards and the land is warmer than the sea in the same latitude , and the hottest part of India is in the north - west over Rajasthan and the Punjab .


 It is this great heating of the land mass of India during the dry sunny months from April to June that causes its monsoon climate. The heated air rises over the hot land , the pressure is lowered and moisture - laden winds blow in from the sea from the S.W. from the Arabian sea , and from the S.E. deflected eastwards by the Hima layas, from the Bay of Bengal. 


Thee heaviest rain brought by these winds will be where they have to rise over mountains , along the Western Ghats and on the southern slopes of the Himalayas . That is why the rivers flowing from the Himalayas are so liable to floods . 


Rainn over the plains of India is more the result of local currents of rising air than of hills. 



Thesee currents , known as convection currents , and often associated with thunderstorms , you must learn about later . Where a moisture - laden wind has shed much of its moisture blowing over a range of hills , and descends and gets warmer the far side of the range ,


it will shed little more rain , and the far side of the hills is said to be in a ' rain shadow ' That is why Poona gets so much less rainfall than Bombay. Perhaps the easiest way to appreciate climate is to look at graphs showing the rainfall and temperature of places with different climates. The daily temperature of any place is normally found by adding the maximum and minimum and dividing by two . 


Thee mean monthly temperature is the average temperature of all the days of the month, often for a period of years. The monthly rainfall , unless given for any particular year , is the average monthly rainfall for a period of years .   



 scale being one small square a month , and the vertical scales as marked . This is a typical graph of a monsoon climate in central northern India. Note the rapid rise of temperature from January to May , the sharp fall of the maximum during the rains and the more gradual fall of the minimum , and then the slight rise in the maximum in October while the minimum begins to fall fast , and finally the fall of both maximum and minimum .



 The rise of the maximum in October is because the rains and clouds have almost gone and the sun shines hot again, while the minimum falls during clear nights. During the rains the range of tempe rate is smaller because clouds shade the sun during daytime and act as a blanket at night, preventing the more rapid loss of heat there is on a clear night. You will find statistics for some other typical climates in the exercises at the end of this article.



Finallyy, I want you to see how the natural vegetation regions of the world, fertile or desert according to climatic regions, can be shown on an imaginary continent stretching from pole to pole. From this diagram you can work out what the vegetation is likely to be in any actual continent ; but remember the effect of mountains , and remember too that this is only a diagram on a very small scale , and so can give you only a general idea of ​​basic principles that , in any actual place , may be altered by local conditions .  and I will explain it a little.


 Starting from the equator we find the belt of equatorial and tropical forest wider on the east side of the continent because that side gets rain from the Trade Winds when they have blown over the ocean. 


Onn the east side of the continent the tropical forest changes to temperate forest as we go to higher latitudes because it gets cooler , while on the west side of the forest turns into tropical grasslands as it gets drier and then into desert ; By the time the Trade Winds have crossed the continent they have lost any moisture they were carrying, and the convectional rainfall from the belt of rising air in the doldrums grows less and less with distance from the equator. 


Onn the west side of the continent , between the deserts and the regular rainfall brought all the year by the westerly winds , are areas which get winter rain from the southward shift of the south westerlies as the sun comes over the Tropic of Capricorn , and the northward movement of the north westerlies as the sun comes over the Tropic of Cancer. These areas have a Mediterranean climate .


 In the centers of each half - continent , far from the rain - bearing winds from the oceans , are areas with temperate grasslands , while , as rainfall increases towards the oceans , there is temperate forest . Then , as we go towards the poles , first there are the belts of coni ferous forest , and then the Tundra and permanent ice . The ice caps stretch into lower latitudes on the east side of the continent because the westerly winds, which will have been blowing over ' warm ' currents, make the west side of the continent warmer than the east.



Also read

Earthquake in India 

Measuring the earth 

Volcano on other planate




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