Forest
Forest, plant community, predominantly of trees or other woody vegetation, occupying an extensive area of land. In its natural state, a forest remains in a relatively fixed, self-regulated condition over a long period of time. Climate, soil, and the topography of the region determine the characteristic trees of a forest. In local environments, dominant species of trees are characteristically associated with certain shrubs and herbs. The type of vegetation on the forest floor is influenced by the larger and taller plants, but because low vegetation affects the organic composition of the soil, the influence is reciprocal. Disturbances such as a forest fire or timber harvesting may result in a shift to another forest type. Left undisturbed, ecological succession will eventually result in a climax forest community (see Ecology). Human intervention is practiced to maintain some desirable forest types.
CLASSIFICATION
Forests may be divided into the following eight general types on the basis of leaf characteristics and climate.
1. Deciduous forests of the temperate regions are the typical formation of the eastern United States. Two subtypes exist; forests of the same latitude in the northern and southern hemispheres are radically different, probably due to the continental climate of the northern hemisphere and the oceanic climate of the southern.
2. Deciduous monsoon forests are characteristic of Bengal and Myanmar (formerly known as Burma) and common throughout Southeast Asia and India; they are also found along the Pacific coastal regions of Mexico and Central America. The climate is characterized by heavy daily rainfall, seasonally relieved by dry periods during which the trees shed their leaves.
3. Tropical savanna forests are found in regions such as the campos of Brazil, where forest and grassland meet. Savannas, which occur widely in Africa and South America, are dominated by grasses and sedges, with open stands of widely spaced trees that are frequently thorny. Some savannas are created by fire or by grazing and browsing mammals. (See Savanna)
4. Northern coniferous forests form a worldwide belt in subarctic and alpine regions of the northern hemisphere. Gnarled scrub trees dominate at the northern tree line and on mountaintops. Spruce and fir trees are characteristic of the more northerly forests; pine, larch, and hemlock dominate farther south. These forests usually occupy formerly glaciated regions and occur in association with lakes, bogs, and rivers.
5. Tropical rain forests are characteristic of central Africa and the Amazon watershed. Plant growth is profuse, and because the fall and regrowth of leaves occur gradually throughout each year, the forest is always active. Tree species are highly diverse but usually have smooth, straight trunks and large, simple leaves. Large vines are common, but the tangled growth of a jungle occurs only where the normal forest area has been abused or at a river’s edge.
6. Temperate evergreen forests are found in the subtropical regions of North America and the Caribbean islands that have a warm maritime climate. The type is best developed along the Gulf Coast and in the Florida Everglades. The characteristic trees are live oak, magnolia, palms, and bromeliads.
7. Temperate rain forests, with broad-leaved evergreen trees, are common on Mediterranean coasts. Rainfall may be low, but the ocean-cooled air is moisture laden, and fogs are frequent.
8. Tropical scrub forests occur in regions of slight rainfall, bordering wetter forests (see Chaparral).
CLASSIFICATION
Forests may be divided into the following eight general types on the basis of leaf characteristics and climate.
1. Deciduous forests of the temperate regions are the typical formation of the eastern United States. Two subtypes exist; forests of the same latitude in the northern and southern hemispheres are radically different, probably due to the continental climate of the northern hemisphere and the oceanic climate of the southern.
2. Deciduous monsoon forests are characteristic of Bengal and Myanmar (formerly known as Burma) and common throughout Southeast Asia and India; they are also found along the Pacific coastal regions of Mexico and Central America. The climate is characterized by heavy daily rainfall, seasonally relieved by dry periods during which the trees shed their leaves.
3. Tropical savanna forests are found in regions such as the campos of Brazil, where forest and grassland meet. Savannas, which occur widely in Africa and South America, are dominated by grasses and sedges, with open stands of widely spaced trees that are frequently thorny. Some savannas are created by fire or by grazing and browsing mammals. (See Savanna)
4. Northern coniferous forests form a worldwide belt in subarctic and alpine regions of the northern hemisphere. Gnarled scrub trees dominate at the northern tree line and on mountaintops. Spruce and fir trees are characteristic of the more northerly forests; pine, larch, and hemlock dominate farther south. These forests usually occupy formerly glaciated regions and occur in association with lakes, bogs, and rivers.
5. Tropical rain forests are characteristic of central Africa and the Amazon watershed. Plant growth is profuse, and because the fall and regrowth of leaves occur gradually throughout each year, the forest is always active. Tree species are highly diverse but usually have smooth, straight trunks and large, simple leaves. Large vines are common, but the tangled growth of a jungle occurs only where the normal forest area has been abused or at a river’s edge.
6. Temperate evergreen forests are found in the subtropical regions of North America and the Caribbean islands that have a warm maritime climate. The type is best developed along the Gulf Coast and in the Florida Everglades. The characteristic trees are live oak, magnolia, palms, and bromeliads.
7. Temperate rain forests, with broad-leaved evergreen trees, are common on Mediterranean coasts. Rainfall may be low, but the ocean-cooled air is moisture laden, and fogs are frequent.
8. Tropical scrub forests occur in regions of slight rainfall, bordering wetter forests (see Chaparral).
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