THE WORLD FORESTS

Trees have existed on the earth for around 275 million years, and for 90 million years they they dominated the earth’s vegetation During this period – known as the Carboniferous Era – millions of tones of plant material were laid down and later compressed under sediments over very long periods of time, to form the fossil fuels such as coal, oil and gas that we depend on today.

       During their long history many types of tree and forest have evolved. Today there are thousands of different tree species growing in a great variety of forest types- from tropical rain forests and coastal mangrove forests to the pine forests of the sub Arctic.

HUMAN

INFLUENCE:- Forests through out the world have been changed by people. Where a forest has been relatively Undisturbed by human activity it is called primary forest. Where people have had a significant effect and the original forest has been greatly altered this is known as secondary forest. A plantation is an artificial forest where tree species have been planted to provide a particular product, such as timber.

Trees can be divided into two broad types: conifers and broadleaved trees.

Conifer means literally ‘cone bearing’ and these trees are typically evergreen and often have needle shaped leaves. Broadleaved trees are often deciduous (losing their leaves seasonally) and have a wide variety of leaf shapes.

     The world’s forests are generally divided into three main types. These are boreal or northern forests, temperate forests and tropical forests. However, there is not usually any clear line to show where one forest type ends and another begins. The situation is also complicated by altitude, since highland areas in temperate or tropical forests can contain trees that are usually only found in much cooler locations.

BOREAL FORESTS:- The boreal forests stretch across Russia, Norway, Finland, Sweden, USA and Canada, forming an almost continuous belt around the earth. Although they are generally found between the latitudes 45-60 degrees north, some Siberian forests are situated as far north as 70 degree. Together, these forests make up one of

the world’s last great wildernesses which until recently, had been little altered by human activity.

Boreal forest are characterized by hot summers, extremely cold winters and

 low rainfall. The result of this harsh climate is a growing season of only three months each year, which is too short for most types of trees. Only hardy conifers such as spruce, larch, fir and pine trees thrive in these conditions, although it can take a tree 150-200 years to reach maturity.
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