Forest and its importance on environment
Introduction:
A forest is an area with a high density of trees. There are many definitions of a forest, based on the various criteria.<href=”#cite_note-0″>[1] These plant communities presently cover approximately 9.4% of the Earth’s surface 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
Rainforest in Tasmania‘s Hellyer Gorge is considered a Gondwanan relic.
Mixed deciduous forest in Stara Planina, Bulgaria.
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 The word was introduced by the Norman rulers of England as a legal term denoting an uncultivated area legally set aside for hunting by feudal .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.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.<href=”#cite_note-oed-2″>[
Distribution:
A conifer forest in the Swiss Alps (National Park).
Description:
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.
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.
Among the major forested biomes are:
Classification:
Biogradska forest in Montenegro
Spiny forest at Ifaty, Madagascar, featuring various Adansonia species,
Alluaudia procera 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.
A number of global forest classification systems have been proposed, but none has gained universal acceptance. UNEP-WCMC’s forest category classification system is a simplification of other more complex systems. 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.
Temperate needle leaf:
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.
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.
Tropical moist
Tropical moist forests include many different forest types. The best known and most extensive are the lowland evergreen broadleaf rainforests include, for example: the seasonally inundated várzea and igapó forests and the terra firma forests of the Amazon Basin; the peat swamp forests and moist dipterocarp forests of Southeast Asia; and the high forests of the Congo Basin. The forests of tropical mountains are also included in this broad category, generally divided into upper and lower montane formations on the basis of their physiognomy, which varies with altitude. The montane forests include cloud forest, those forests at middle to high altitude, which derive a significant part of their water budget from cloud, and support a rich abundance of vascular and nonvascular epiphytes. Mangrove forests also fall within this broad category, as do most of the tropical coniferous forests of Central America.
Tropical dry
Tropical dry forests are characteristic of areas in the tropics affected by seasonal drought. The seasonality of rainfall is usually reflected in the deciduousness of the forest canopy, with most trees being leafless for several months of the year. However, under some conditions, e.g. less fertile soils or less predictable drought regimes, the proportion of evergreen species increases and the forests are characterised as “sclerophyllous“. Thorn forest, a dense forest of low stature with a high frequency of thorny or spiny species, is found where drought is prolonged, and especially where grazing animals are plentiful. On very poor soils, and especially where fire is a recurrent phenomenon, woody savannas develop.
Sparse trees and parkland:
Taiga forest near Saranpaul in the northeast Ural mountains, Khanty-Mansiysk Autonomous Okrug, Russia. Trees include Picea obovata, Larix sibirica, Pinus sibirica, and Betula pendula.
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:
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.
Forest categories:
A temperate deciduous broadleaf forest, the Hasenholz, southeast of Kirchheim unter Teck, Swabia, Germany.
Redwoods in old growth forest in Muir Woods National Monument, Marin County, California.
28 forest categories are used to enable the translation of forest types from national and regional classification systems to a harmonised global one:
Coastal Douglas fir woodland in northwest Oregon.
Redwood tree in northern California redwood forest, where many redwood trees are managed for preservation and longevity, rather than being harvested for wood production.
The scientific study of forest species and their interaction with the environment is referred to as forest ecology, while the management of forests is often referred to as forestry. Forest management has changed considerably over the last few centuries, with rapid changes from the 1980s onwards culminating in a practice now referred to as sustainable forest management. Forest ecologists concentrate on forest patterns and processes, usually with the aim of elucidating cause and effect relationships.
Anthropogenic factors that can affect forests include logging, urban sprawl, human-caused forest fires, acid rain, invasive species. The loss and re-growth of forest leads to a distinction between two broad types of forest, primary or old-growth forest and secondary forest. There are also many natural factors that can cause changes in forests over time including forest fires, insects, diseases, weather, competition between species, etc. In 1997, the World Resources Institute recorded that only 20% of the world’s original forests remained in large intact tracts of undisturbed forest. More than 75% of these intact forests lie in three countries – the Boreal forests of Russia and Canada and the rainforest of Brazil.
Canada has about 4,020,000 square kilometres of forest land. More than 90% of forest land is publicly owned and about 50% of the total forest area is allocated for harvesting. These allocated areas are managed using the principles of sustainable forest management, which includes extensive consultation with local stakeholders. About eight percent of Canada’s forest is legally protected from resource development. Much more forest land — about 40 percent of the total forest land base — is subject to varying degrees of protection through processes such as integrated land-use planning or defined management areas such as certified forests
In the United States, most forests have historically been affected by humans to some degree, though in recent years improved forestry practices has helped regulate or moderate large scale or severe impacts. However, the United States Forest Service estimates a net loss of about 2 million hectares this estimate includes conversion of forest land to other uses, including urban and suburban development, as well as afforestation and natural reversion of abandoned crop and pasture land to forest.
Old-growth forest contains mainly natural patterns of biodiversity in established seral patterns, and they contain mainly species native to the region and habitat. The natural formations and processes have not been affected by humans with a frequency or intensity to change the natural structure and components of the habitat. Secondary forest contains significant elements of species which were originally from other regions or habitats.
Some others photos of the Forest:
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A deciduous broadleaf (Beech) forest in Slovenia. |
A forest on San Juan Island in Washington. |
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Maple and Oak (broadleaf, deciduous) forest in Wisconsin during winter.