Any major community (*
biome ) in which the dominant plants are trees. There are three main types of forest; cold forests, temperate forests, and tropical forests. The cold forests include the northern coniferous forest (boreal forest or taiga), where there are relatively few types of tree, mainly fir, pine, and spruce with some deciduous birches and larches. The latter are found mainly on the borders of the tundra where it is too cold and exposed for the conifers to grow. However conifers are well adapted to survive long cold winters and can take advantage of the short growing season as they retain their leaves. Boreal forest is found in North America and northern Eurasia. The mountain coniferous forest and pine forest of the southeast United States are also boreal forests.
Temperate forests have abundant and fairly evenly distributed rainfall with moderate temperatures, but there is a marked seasonal change. The vegetation consists of broad-leaved deciduous trees, an adaptation to the lack of available water during winter (see
physiological drought ). There are usually several different species of trees and the term mixed deciduous forest is often used. Warm temperate and cool temperate rain forests also exist, e.g. in south China and New Zealand respectively. Broad-leaved evergreen forest is characteristic of a Mediterranean-type climate with hot dry summers and mild wet winters. Tropical forests include tropical rain forest, monsoon forest, and thorn forest. Rain forests have regular heavy rain, constantly high temperatures, and therefore prolific plant growth. Rain forest regions, such as the Amazon basin and the Malay-Indonesian region, contain thousands of different species. Essentially similar forests, known as riverine forests, occur along river banks in drier regions. Monsoon forests have a period of drought, which may last for several months. They do not have such a great variety of species as tropical rain forest and have a more open canopy and very dense undergrowth. Many of the trees shed their leaves in the dry season. They are found in India, Burma, and Indo-China. Thorn forest is a transitional type of vegetation with some similarities to *
savanna and semidesert vegetation. It grades into tropical forests and is found in Central and South America, Australia, and Africa.
Generally trees need more light and moisture than other plant forms, although some trees are adapted to survive long periods of drought and cold.
