Forest Zones, Tropical

natural zones of continents in the northern and southern hemispheres, situated in natural landscapes dominated by tropical forests. Tropical forest zones are found in the eastern sectors of the tropical regions—in southern Florida, the West Indies, Central and South America, East Africa (primarily on Madagascar), and eastern Australia, as well as on some islands of Oceania. They are characterized by a humid or seasonally humid tropical climate, forest vegetation, and lateritic soils. The radiation balance is 290–335 kilojoules per cm² (70–80 kilocalories per cm²) a year. There are comparatively minor variations in the average monthly atmospheric temperatures (from 18° to 28°C).

Because the temperature is always high and there are no frosts, the rate of plant growth throughout the year is determined primarily by the amount of moisture available. Under favorable moisture conditions (usually on windward slopes), a subzone of constantly humid tropical forests is formed. The total annual precipitation is usually more than 2,000 mm, the rainfall is uniform, and the climatic differences between the seasons are slight. Dense evergreen forests (myrtle, laurel, legumes, and palms, for example) with an abundance of lianas and epiphytes are found on red-yellow lateritic soils. Thick weathering crusts (up to 80 m) and heavy slope runoff, washout, and soil erosion are characteristic of tropical forest zones.

The subzone of seasonally humid tropical forests is more common than the subzone of constantly humid tropical forests. It develops in regions that have a distinct three-month dry season during which precipitation amounts to only 60–100 mm. In addition to evergreens, during the drought season there are deciduous trees on red ferralite and ferrite soils.

Red earth and yellow earth and coniferous and deciduous trees (during winter) are found in the mountains in the higher wooded areas of the tropical forest zones.

Because they were near the oceans and accumulative coastal plains, the tropical forest zones were developed early by man. Most of the large animals have been exterminated. The forests have been extensively cut, and cocoa, coffee, sugarcane, and cotton are grown in many places.