WALLPAPER OF FOREST

A forest is an area with a high density of trees. There are many definitions of a forest, based on the various criteria.[1] These plant communities presently cover approximately 9.4% of the Earth's surface (or 30% of total land area) in many different regions and function as habitats for organisms, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the Earth's biosphere. Although a forest is classified primarily by trees a forest ecosystem is defined intrinsically with additional species such as fungi.[2] A woodland, with more open space between trees, is ecologically distinct from a forest.
Contents
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* 1 Etymology
* 2 Distribution
* 3 Classification
o 3.1 Temperate needleleaf
o 3.2 Temperate broadleaf and mixed
o 3.3 Tropical moist
o 3.4 Tropical dry
o 3.5 Sparse trees and parkland
o 3.6 Forest plantations
o 3.7 Forest categories
+ 3.7.1 Temperate and boreal forest types
+ 3.7.2 Tropical forest types
* 4 Forest loss and management
* 5 Gallery
* 6 See also
* 7 References
* 8 Further reading
* 9 External links

[edit] Etymology

The word "forest" was borrowed by Middle English from Old French and Medieval Latin forestis, literally meaning "outside". Uses of the word "forest" in English to denote any uninhabited area of non-enclosure are now considered archaic.[3] The word was introduced by the Norman rulers of England as a legal term (appearing in Latin texts like the Magna Carta) denoting an uncultivated area legally set aside for hunting by feudal nobility (see Royal Forest).[3][4] These hunting forests were not necessarily wooded much, if at all. However, as hunting forests did often include considerable areas of woodland, the word "forest" eventually came to mean wooded land more generally.[citation needed] By the start of the fourteenth century the word appeared in English texts, indicating all three senses: the most common one, the legal term and the archaic usage.[3]

[edit] Distribution
A conifer forest in the Swiss Alps (National Park).
Amazon Rainforest in Brazil.

Forests can be found in all regions capable of sustaining tree growth, at altitudes up to the tree line, except where natural fire frequency or other disturbance is too high, or where the environment has been altered by human activity.

The latitudes 10° north and south of the Equator are mostly covered in tropical rainforest, and the latitudes between 53°N and 67°N have boreal forest. As a general rule, forests dominated by angiosperms (broadleaf forests) are more species-rich than those dominated by gymnosperms (conifer, montane, or needleleaf forests), although exceptions exist.

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 the 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 (also see: savanna).

Among the major forested biomes are:

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

[edit] Classification
Biogradska forest in Montenegro
Spiny forest at Ifaty, Madagascar, featuring various Adansonia (baobab) species, Alluaudia procera (Madagascar ocotillo) and other vegetation.
Even, dense old-growth stand of beech trees (Fagus sylvatica) prepared to be regenerated by their saplings in the understory, in the Brussels part of the Sonian Forest.

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 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 climate and the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).

A number of global forest classification systems have been proposed, but none has gained universal acceptance.[5] UNEP-WCMC's forest category classification system is a simplification of other more complex systems (e.g. UNESCO's forest and woodland 'subformations'). This system divides the world's forests into 26 major types, which reflect climatic zones as well as the principal types of trees. These 26 major types can be reclassified into 6 broader categories: temperate needleleaf; temperate broadleaf and mixed; tropical moist; tropical dry; sparse trees and parkland; and forest plantations. Each category is described as a separate section below.

[edit] Temperate needleleaf

Temperate needleleaf forests mostly occupy the higher latitude regions of the northern hemisphere, as well as high altitude zones and some warm temperate areas, especially on nutrient-poor or otherwise unfavourable soils. These forests are composed entirely, or nearly so, of coniferous species (Coniferophyta). In the Northern Hemisphere pines Pinus, spruces Picea, larches Larix, silver firs Abies, Douglas firs Pseudotsuga and hemlocks Tsuga, make up the canopy, but other taxa are also important. In the Southern Hemisphere most coniferous trees, members of the Araucariaceae and Podocarpaceae, occur in mixtures with broadleaf species that are classed as broadleaf and mixed forests.

[edit] Temperate broadleaf and mixed

Temperate broadleaf and mixed forests include a substantial component of trees in the Anthophyta. They are generally characteristic of the warmer temperate latitudes, but extend to cool temperate ones, particularly in the southern hemisphere. They include such forest types as the mixed deciduous forests of the USA and their counterparts in China and Japan, the broadleaf evergreen rain forests of Japan, Chile and Tasmania, the sclerophyllous forests of Australia, Central Chile, the Mediterranean and California, and the southern beech Nothofagus forests of Chile and New Zealand.Source URL: http://worldofcelebrityz.blogspot.com/2009/08/wallpaper-of-forest.html
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