|A forest is an area with a high density of trees (or, historically,
an area set aside for hunting). Forests can be found in all regions capable
of sustaining tree growth, at altitudes up to the tree-line, except where
rainfall is too low, or natural fire frequency too high. Forests generally
contain a large number of different tree species growing to different heights,
combined with an understory, which makes efficient use of sunlight. A forest
in its natural form is home to many animal and plant species, and biomass
per unit area is high compared to most other biomes.
In ecological terms, a forest may be differentiated from a woodland: a forest is considered to have a more or less closed canopy, where the branches and foliage of trees meet or interlock; a woodland is considered to have an open canopy, where some sunlight penetrates between the trees (see also: savanna).
Numerous types of forests exist. Among the ecological types are:
* rain forest (tropical and temperate)
The science of studying and managing forests, with a goal of sustainable extraction, is called forestry. Ecologists study forests