Sri Lanka is a tropical island of continental origin and shares tectonic plates with Peninsular India. The island lies between 50 54 and 90 52 North latitude and 790 41and 810 54 East longitude. The island has two main climatic zones, namely the Dry Zone and the Wet Zone with an Intermediate Zone in between. Nearly two thirds of the island constitutes of the Dry Zone, which consists mainly of flat and undulating land receiving less than 2000 mm annual rainfall. The Wet Zone is located in the south and southwest of the island and consists of coastal plains and very rugged mountainous terrain (Montane Zone) rising up to an elevation of 2750 m asl. The Wet Zone receives 2500 mm to 5000 mm of annual rainfall. Sri Lanka receives rainfall from two monsoons; the northeast monsoon between October and January and the southwest monsoon from May to July and these monsoons affect the three climatic zones differently.
Soils in the Dry Zone are reddish-brown and yellowish-brown, varying from medium/heavy to light and are generally well drained. In the Wet and Intermediate Zones, soils are prevalently red-yellow podzolic and are shallow and well drained in the highlands, but deep and poorly drained in the lowlands. The diverse climate, soil types and altitude have contributed to the high variation in natural vegetation in Sri Lanka. The flora includes 192 families of flowering plants with 1290 genera and 3268 species of which 25% are endemic to the country (Sumithraarachchi 1990).
