Forest

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 the Earth's biosphere.

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 environment has been impaired by natural processes or by human activities. As a general rule, forests dominated by angiosperms (broadleaf forests) are more species-rich than those dominated by gymnosperms (conifer or needleleaf forests), although exceptions exist (for example, species-poor aspen and birch stands in northern latitudes). Forests sometimes contain many tree species within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid montane coniferous forests). Forests are often home to many animal and plant species, and biomass per unit area is high compared to other vegetation communities. Much of this biomass occurs below-ground in the root systems and as partially decomposed plant detritus. The woody component of a forest contains lignin, which is relatively slow to decompose compared with other organic materials such as cellulose or carbohydrate.

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).

Among the major forested biomes are:

• rain forest (tropical and temperate)
• taiga
• temperate hardwood forest
• tropical dry forest

Classification

Forests can be classified in different ways and to different degrees of specificity. One such way is in terms of the biome in which they exist combined with leaf longevity of the dominant species (whether they are evergreen or deciduous). Another distinction is whether the forests composed predominantly of broadleaf trees, coniferous (needle-leaved) trees, or mixed.

• Boreal forests occupy the subarctic zone and are generally evergreen and coniferous.
• Temperate zones support both broadleaf deciduous forests (e.g., temperate deciduous forest) and evergreen coniferous forests (e.g., Temperate coniferous forests and Temperate rainforests). Warm temperate zones support broadleaf evergreen forests, including laurel forests.

• Tropical and subtropical forests include tropical rainforests, tropical and subtropical moist forests, tropical and subtropical dry forests, and tropical and subtropical coniferous forests.

• Physiognomy classifies forests based on their overall physical structure or developmental stage (e.g. old growth vs. second growth).

• Forests can also be classified more specifically based on the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).

Forest management

The scientific study of forests is referred to as forest ecology, while the management of forests is often referred to as forestry, often with the goal of sustainable resource extraction. Forest ecologists concentrate on forest patterns and processes, usually with the aim of elucidating cause and effect relationships. Foresters often focus on wood extraction and silviculture, including tree regeneration and growth processes.

Forests can be altered when logging, forest fires, acid rain, herbivores, or diseases, among other things, cause damage to trees. In the United States, most forests have historically been affected by humans to some degree, though in recent years environmental protection has helped regulate or moderate large scale or severe impacts.

For more comprehensive information on this sub-topic visit the Indian Institute of Forest Management in India.