Forest

:This article is about forests as communities of trees. For other uses of the word, see Forest (disambiguation).

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A forest is an area with a high density of trees (or, historically, a wooded area set aside for hunting). These plant communities cover large areas of the globe and function as carbon dioxide sinks, animal habitats, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of our biosphere.

Related Topics:
Trees - Hunting - Carbon dioxide sink - Habitat - Biosphere

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Forests can be found in all regions capable of sustaining tree growth, at altitudes up to the tree-line, except where natural fire frequency is too high, or where the tree growing environment has been impaired by natural processes or humans. Forests sometimes contain many tree species in a small area (e.g. tropical rain and temperate deciduous forests), but other forest types have relatively few species over large areas (e.g. taiga and arid montane coniferous forests). As a general rule, forests dominated by angiosperms are species-rich, while those dominated by gymnosperms are not so rich, although exceptions do exist (e.g., species-poor aspen and birch stands in northern latitudes). Forests are often home to many animal and plant species, and biomass per unit area is high compared to other vegetation types. Much of this biomass occurs below-ground in the root systems and as partially decomposed plant detritus. The woody component of forests contains lignin, which is relatively slow to decompose compared with other organic materials such as cellulose or carbohydrate.

Related Topics:
Tree-line - Angiosperms - Gymnosperms - Biomass - Detritus - Lignin - Decompose - Cellulose

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Forests are differentiated from woodlands by the extent of canopy coverage: in a forest the branches and foliage of separate trees often meet or interlock, although there can be gaps of varying sizes within an area referred to as forest. A woodland has a more continuously open canopy, with trees spaced further apart, which allows more sunlight to penetrate to the ground between them (see also: savanna).

Related Topics:
Woodlands - Canopy - Savanna

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Among the major forested biomes are:

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• rain forest (tropical and temperate)
• taiga
• temperate hardwood forest
• tropical dry forest
 
Forest: Classification ►