ABSTRACT
A. Expanse Tropical forests, in general, play an important role in global energy, biomass and nutrient turnovers. Such tropical evergreen lush forests and woodland ecosystems are extensive. They occupy nearly 25 x 106 km2, which is equivalent to 17% of Earth's land surface, and contribute as much as 40% terrestrial net primary production (Keller and Matson, 1994). The humid forests account for approximately 50% total tropical forest belt, with a net primary productivity that ranges between 13 and 28 Mg ha-1 yr_1. Whereas, dry tropical forests and woodlands possess a relatively lower net primary productivity, ranging from 8 to 21 Mg ha-1 yr-1. Clearly, dynamics of tropical forests, that is their spread, perpetuation or shrinking, as well as variations in productivity levels are partly attributable to underlying nutrient dynamics in both soil and aboveground portions. Some of these aspects are highlighted within this chapter. Globally, three distinct types of humid tropical forests can be identified, namely the
American, African and Indo-Malaysian. The American neotropical forest formation covers predominantly the Amazonia, foothills of Andes and Guyanian plateau extending into nearly 40,000 km2. Destruction of such neo-tropical forest formation have been greatest in parts of Amazonia, in Costa Rica, Belize and the Caribbean. Peripheral areas include the southeast of Brazil, Central American locations in Equador, Panama and southern Mexico, and small tracts in the Caribbean Islands. The African tropical forests are confined to humid zone in the Congo basin, comprising locations in countries such as Zaire, Cameroon, Gabon, Equatorial Guinea etc. The West African tropical zones are located in Liberia, Eastern Sierra Leone, Cote de Ivore, South West Ghana etc. The African humid forests are also located in Mozambique, Mauritius and Madagascar. The IndoMalaysian forest formations spread into small areas in Peninsular India (Western Ghats), Northeastern India, and Sub-Himalayas. In Southeast Asia, tropical forests are profuse in the Indonesian archipelago, Malaysian highlands, Sri Lanka, Philippines, Thailand and Vietnam. They are also frequent in Australian locations in Fiji, Papua New Guinea, Queensland, New South Wales, Pacific Islands etc. (Reading et al. 1995). In Australasia, humid tropical forests cover over 25,000 km-2.
