Rain Forests

located in regions of the earth that have an annual rainfall of 2,000-7,000 mm or more.

Tropical rain forests (wet tropical rain forests are sometimes called tropical forests), located on plains and foothills in the equatorial zone and as far as 25°N lat. and 30°S lat., at elevations of 800-1,000 m. Tropical rain forests are found in America (the Amazon Basin and Central America), Southeast Asia (Indonesia, the Peninsula of Malacca, the Philippines, and New Guinea), West Africa (the Congo Basin and Uganda), and Australia (Queensland). Smaller, badly depleted tropical rain forests are located in India, Bangladesh, Sri Lanka, northern Indochina, southern China, New Caledonia, Oceania, and Madagascar. Remnants of them are also found in Florida (USA).

In general form and ecology all tropical forests are similar. The leaves of most trees are middle-sized (cherry laurel type). Flowers are usually opaque. The forest consists of three or four strata or layers of trees, the highest of which is usually no more than 35 m, although some trees may reach 60 and even 80 m. The tree trunks are straight, smooth, relatively slender, with diameters of 60-70 cm, and the trees often have flat roots. The undergrowth is sparse and consists primarily of small trees rather than shrubs. There is little grass, and there is almost no forest humus layer. Epiphytes (including woody types) and lianas are widespread, and evergreens prevail, except in monsoonal forests, where deciduous trees are more common. The flora is very rich—up to 70 species of trees may be found on one hectare. Most of the trees are dicotyledonous and are pollinated by insects, birds, and bats. There are almost no conifers. In America there are many palms, but there are few in Asia, where they are usually part of the undergrowth. Common monocotyledons include Pandanus, bamboo, and wild bananas. Characteristic of rain forests is the concentration of entire plant families, including almost all the genera and species, in one growth area (for example, Dipterocarpaceae in Asia). This phenomenon indicates undisturbed phylogenetic bonds and confirms the theory of the primacy of the tropical rain forests as a plant community, as well as theories of the origins of many plant families in the wet tropics.

Subtropical and temperate rain forests, found north and south of the tropical zones and in the mountains in the tropics. In the structure of their plant community and in their outer appearance, subtropical and temperate rain forests are similar to tropical rain forests. However, they differ sharply in their flora. Trees from the families Fagaceae and Lauraceae are found in subtropical and temperate rain forests, and conifers have begun to prevail (yews and several species of Araucaria). Treelike ferns are characteristic. An example of a subtropical rain forest is the Tjibadag forest on Java, where there are many giant rasamalas (60 m high and more) from the family Hamamelidaceae. Among the temperate rain forests are the evergreen beech forests (Nothofagus) in the mountains of New Guinea, Tasmania, and New Zealand, in Patogonia and Tierra del Fuego in South America. The forests of giant conifers in the northwestern USA are classified as rain forests.

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