6.8   Soils of Tamil Nadu · Part 2

the northeast monsoon winds. The apparent migration of the sun from Tropic of Cancer to the Tropic of Capricorn causes a change in receiving temperature and air pressure during this season. It makes the wind to blow towards Bay of Bengal from North India and get deflected by Coriolis force and takes the northeast direction. Hence, it is known as northeast monsoon. As the northeast monsoon is a part of returning of southwest monsoon wind, it is also called as the retreating monsoon. This is the main rainy season for Tamil Nadu, accounting for its % of annual rainfall. Coastal districts of the state get nearly % of their annual rainfall and the interior districts get about – % of the annual rainfall during this season. Tropical cyclones are common during this season. Cyclone originating from the Bay of Bengal bring heavy rainfall to the east coastal regions of Tamil Nadu. More than % of the  Physical Geography of Tamil Nadu Tropical Evergreen Forest This forest type is found in the regions that receive heavy rainfall. It is a dense, multi-layered forest. It is found in the upper slopes of Western Ghats of Tirunelveli, Tenkasi, Kanniyakumari, the Nilgiris and Coimbatore districts. The major tree species of this forest are cinnamon, Malabar ironwood, panasa, java plum/jamun, jack, kindal, ayani and crape myrtle. The semi- evergreen type of forest in the state is found over the regions of sub-tropical climate over the Eastern Ghats. The prominent regions are Servarayan, Kollimalai and Pachaimalai. Species of Indian mahogany, monkey teak, woolly cassia, jack and mango trees are common in this region. Montane Temperate Forest It is found in sheltered valleys of Anaimalai, the Nilgiris and Palani hills over a metres altitude. They are known as ‘ Sholas ’. The trees in this forest are evergreen and usually short. Nilgiri champa, wights litsea and rose apple are the common trees found in this forest. Tropical Deciduous Forest This type of forest lies in the margin of semi-evergreen and evergreen forests. The trees in