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|~ ~ A forest is an area
with a high density of trees.The forests can e classified based on various
criteria. These plant communities cover approximately 9.4% of the Earth's
surface (or 30% of total land area) and function as habitats for organisms,
hydrologic flow modulators, and soil conservers, constituting one of the
most important aspects of the Earth's biosphere. Historically, "forest"
meant an uncultivated area legally set aside for hunting by feudal nobility,
and 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. A woodland
is ecologically distinct from a forest.
~ ~ The latitudes 10 degrees north and south of the Equator are mostly covered in tropical rainforest and the latitudes between 53N and 67N with boreal forest.
~ ~ Forests can be found in all regions capable of sustaining tree growth, at altitudes up to three line, except where natural fire frequency or other disturbance is too high, or where the environment has been altered by human activity. 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.
|Sparse trees and parkland|
|~ ~ Sparse trees and parkland are forests with open canopies of 10-30% crown cover. They occur principally in areas of transition from forested to non-forested landscapes. The two major zones in which these ecosystems occur are in the boreal region and in the seasonally dry tropics. At high latitudes, north of the main zone of boreal forest or taiga, growing conditions are not adequate to maintain a continuous closed forest cover, so tree cover is both sparse and discontinuous. This vegetation is variously called open taiga, open lichen woodland, and forest tundra. It is species-poor, has high bryophyte cover, and is frequently affected by fire.|
|~ ~ Forest plantations, generally intended for the production of timber and pulpwood increase the total area of forest worldwide. Commonly mono-specific and/or composed of introduced tree species, these ecosystems are not generally important as habitat for native biodiversity. However, they can be managed in ways that enhance their biodiversity protection functions and they are important providers of ecosystem services such as maintaining nutrient capital, protecting watersheds and soil structure as well as storing carbon. They may also play an important role in alleviating pressure on natural forests for timber and fuelwood production.|