Old growth forest
Old growth forest, (also termed primary forest, ancient forest, virgin forest, primeval forest, frontier forest or in the
UK, Ancient Woodland), is a type of forest that has attained great age and so exhibits unique biological features. Old growth forests typically contain large live trees, large dead trees (sometimes called " snags"), and large logs, as well as many other common characteristics representative of forestsin general. Due to the great age and height of many trees within old growth forests, they are often more shaded than other types of forests. Old growth forests are unique, and usually have multiple horizontal layers of vegetationrepresenting a variety of tree speciesand age-classes. Many old growth forest stands are threatened by habitat destructiondue to excessive loggingand clear-cut logging, activity, which reduces biodiversity, both in terms of decreasing the amount of old growth forest and habitatthat remain on the planet, and in terms of the destruction, and therefore reduction in the level of remaining native, or indigenous speciesthat rely upon and thrive within old growth forest habitat. [ [http://ran.org/issues/forests/ Protect the World's Forests] from [http://ran.org/ Rainforest Action Network] ] [ [http://www.guardian.co.uk/environment/interactive/2007/dec/13/forests The world's remaining great forests] from [http://www.guardian.co.uk/ The Guardian newspaper] ]
Forest regenerated after severe disruptions, such as clear-cut or fire is often called second-growth or "regeneration" until enough time passes that the effects of the disturbance are no longer evident. Depending on the forest, this may take anywhere from a century to several millennia.
Hardwoodforests of the eastern United Statescan develop old-growth characteristics in one or two generations of trees, or 150-500 years.
Old growth forests are often home to
rare species, threatened speciesand endangered speciesof plants and animals, making them ecologically significant. One example of a rare species reliant upon old growth forest is the Northern Spotted Owl. Levels of biodiversity, the variation of life forms within unique old growth forest ecosystems, may be higher or lower in old growth forests compared to that in second-growth forests, depending on specific circumstances, environmental variables and geographic variables (where the forest is located). Logging in old growth forests is a contentious issue in many parts of the world.
Common cultural definitions and common denominators regarding what comprises old growth forest, and of the variables that define, constitute and embody old-growth forests include:
* The forest habitat possesses relatively mature, old trees;
* The old growth trees have long continuity on the same site;
* The forest itself has not been subjected to significant inhabitation by mankind that has altered the appearance of the landscape and its ecosystems, has not been subjected to
logging, and has inherently progressed per natural tendencies.
Ancient Woodland" is a term used in the United Kingdomto refer specifically to woodlanddating back to 1600or before (in Englandand Wales), or 1750(in Scotland). Before this, planting of new woodland was uncommon, so a wood present at these dates was likely to have developed naturally. By this definition Ancient Woodland may have been affected by human management, and may have no very ancient trees: the important characteristic is long continuity of woodland on the land.
United States, the term "old growth" is often, (but not always), used to characterize a forest that has experienced little direct disruption or disturbance by humans during contemporary historical epochs, although sometimes determining the long-term history of human land management can be difficult. Additionally, because landscapes are naturally dynamic and continue to change as time progresses, it is difficult to ascertain hypothetical old growth forest characteristics that may have come into fruition had humans not destroyed such a great deal of old growth forests.
The role of natural disturbances in defining old growth is more ambiguous. For example some definitions exclude recently burned forests, even where fire has been part of the natural forest dynamics for millennia. In other cases such natural disturbance is incorporated in the old-growth concept. However, it is sometimes difficult to distinguish the ecological effects of natural disruption from human-caused disruption. Furthermore, many forests that have never experienced direct manipulation by humans have been subjected to indirect effects in the form of
invasive species, removal of native species (including megafauna), climate change, and regional modifications of ecological disturbanceregimes (e.g., fire suppression).
Many botanists specifically define old growth in terms of meeting several criteria, under which system forests with sufficient age and minimal disturbance are considered old growth. Typical characteristics of old-growth forest include presence of older trees, minimal signs of human disturbance, mixed-age stands, presence of canopy openings due to tree falls, pit-and-mound
topography, fallen timber in various stages of decay, standing snags (dead trees), multi-layered canopies, intact soils, a healthy fungal ecosystem, and presence of indicator species.
The mixed age of the forest is an important criterion in ensuring that the forest is a relatively stable ecosystem in the long term. A climax stand that is uniformly-aged is a less stable ecosystem, because it becomes senescent and degrades within a relatively short time to result in a new cycle of forest succession.
Openings in the
forest canopyare essential in creating and maintaining mixed-age stands. Also, some herbaceous plants only become established in canopy openings but persist beneath an understory. Openings created by natural disturbance events such as wind, ice and mixed-severity fire retain much structural enrichment from dead trees, unlike openings created by logging.
The characteristic topography of much old growth forest consists of pits and mounds. Mounds are caused by decaying fallen trees, and pits (
tree throws) by the roots pulled out of the ground when trees fall due to natural causes, including being pushed over by animals. Pits expose humus-poor, mineral-rich soil and often collect moisture and fallen leaves soon form a thick organic layer and so able to nurture certain types of organisms, while mounds provide a place free of leaf inundation and saturation, where other types of organisms thrive.
Standing snags provide food sources and habitat for many types of organisms. In particular, many species of dead-wood predators such as
woodpeckers must have standing snags available for feeding. In North America the spotted owlis well-known for needing standing snags for nesting habitat.
Decaying ground layer
Fallen timber contributes
carbon-rich organic matterdirectly to the soil, thus providing a substrate for mosses, fungi and for seedlings, and in creating microhabitats by creating relief on the forest floor. In some ecosystems, such as the temperate rain forestof the North American Pacific coast, fallen timber may become "nurse logs", providing a substrate for seedling trees.
Intact soils harbor many life-forms and usually have well-defined
soil profiles. Different organisms may need different soil profiles, while many trees need well-structured soils free of disturbance. Some herbaceous plants in northern hardwood forests need thick duff Clarifyme|date=July 2008 layers (which are part of the soil profile).
Fungal ecosystems are essential for efficient "
in-situ" recycling of nutrients back into the entire ecosystem.
*Old growth forests often contain rich communities of
plants and animals that settle there thanks to the long period of forest stability. These varied and sometimes rare species may depend on the unique environmental conditions created by these forests.
*Old growth forest serves as a reservoir for species which cannot thrive or easily regenerate in younger forest, and so can be used as a baseline for research.
* Plant species that are native to old growth forests may someday prove to be invaluable towards curing various human ailments, as has been realized in numerous plants in
tropical rainforests. [ [http://www.mongabay.com/10drugs.htm Medicinal Drugs Derived from Rainforest Plants] from [http://www.mongabay.com/ Mongabay] ] [ [http://www.netsci.org/Science/Special/feature11.html The Rainforest as a Source For New Pharmaceuticals] August, 2008 from [http://www.netsci.org/ Network Science website] ]
*Old growth forests also store large amounts of
carbonabove and below the ground (either as humus, or in wet soils as peat). They collectively represent a very significant store of carbon. Destruction of these forests releases this carbon as greenhouse gases, and may increase the risk of global climate change. [http://www.grida.no/climate/ipcc_tar/wg1/235.htm IPCC Climate Change 2001:Working Group I: The Scientific Basis]
The large trees in old growth forests are often economically valuable, so these forests have been subjected to aggressive
loggingaround the world. This has led to much controversy between logging companies and environmental groups. An example of this was that over Spotted Owls in the 1980s and 1990s.
In Australia, the regional forest agreement (RFA) attempted to prevent the clearfelling of defined "Old Growth Forests". This led to struggles over what constitutes "Old Growth". For example in Western Australia, the
timberindustry tried to limit the area of Old Growth in the karriforests of the Southern Forests Region; this led to the creation of the Western Australian Forests Alliance, the splitting of the Liberal Government of Western Australia and the election of the Gallop Labor Government. Old Growth Forests in this region have now been placed inside National Parks. A small proportion of Old Growth Forest also exists in South-West Australia, and is protected by a Federal laws from logging, which hasn't occurred there for more than twenty years.
Locations of remaining intact forests
Greenpeaceidentified that the world's remaining intact old growth forest area was distributed among the continents as follows: [http://www.intactforests.org/ IntactForests.org]
* 35% in
Latin America. The Amazon rainforestis mainly located in Brazil, which clears a larger area of forest annually than any other country in the world. [http://www.greenpeace.org/international/campaigns/forests/our-disappearing-forests/intact-forest-landscapes Intact Forest Landscapes | Greenpeace International ] ]
* 28% in
North America. North America harvests 10,000 square kilometres of ancient forests every year. Many of the fragmented forests of southern Canadaand the USlack adequate animal travel corridors and functioning ecosystems for large mammals.
* 19% in Northern
Asia. Northern Asia is home to the second largest boreal forestin the world. The Siberian tigeronce roamed across huge areas of Northern Asia but today can only be found in a small area of intact forest near the Sea of Japan. Only about 400 remain in the wild and 800 in zoos.
* 8% in Africa. Africa has lost most of its intact forest landscapes in the last 30 years. The timber industry is responsible for destroying huge areas of intact forest landscapes and continues to be the single largest threat to these areas.
* 7% in South Asia Pacific. The
Paradise Forestsof Asia Pacificare being destroyed faster than any other forest on Earth. Much of the large intact forest landscapes have already been cut down, 72% in Indonesiaand 60% in Papua New Guinea.
* Less than 3% in Europe. In Europe, more than 150 square kilometres of intact forest landscapes are cleared every year and the last areas of the region’s intact forest landscapes in European Russia are shrinking rapidly.
Effect on climate change
Old growth forests store large amounts of carbon, which is stored in wood, soil humus and peat. When forests are cut, the trees' wood, soil humus and peat all decay, releasing the carbon as carbon dioxide or methane.cite web |url=http://query.nytimes.com/gst/fullpage.html?res=9A02E3DA113BF931A1575AC0A9669C8B63 |title= Planting New Forests Can't Match Saving Old Ones in Cutting Greenhouse Gases, Study Finds |accessdate=2008-06-04 |publisher=New York Times |date=September 22, 2000 ] Logging practices often include burning of the logged area, releasing further CO2.
While old growth forests are often perceived to be in equilibrium — releasing as much carbon dioxide as they capture; or even in a state of decay [ [http://www.wired.com/science/planetearth/magazine/16-06/ff_heresies_04forests Old-Growth Forests Can Actually Contribute to Global Warming] , Wired magazine, May 19, 2008] , studies of soils in undisturbed tropical rain forests, Siberian woods and in German national parks have found that soils contain enormous amounts of carbon derived from fallen leaves, twigs and buried roots that can bind to soil particles and remain for 1,000 years or more. Replacing old growth forests with plantations is counter-productive from a carbon-storage view, as the new forest may take centuries to recapture the carbon lost. Further, the loss of
biodiversityin a plantation monoculture lessens the performance of ecosystems regarding biomass production, nutrient retention and carbon dioxide absorption. [Shahid Naeem, Lindsey J. Thompson, Sharon P. Lawler, John H. Lawton & Richard M. Woodfin, "Declining biodiversity can alter the performance of ecosystems", Nature, 368:734-736, 21 April 1994.]
* [http://www.fs.fed.us/pnw/oldgrowth.htm Old-growth forest information] from [http://www.fs.fed.us/ U.S. Forest Service]
* [http://ran.org/issues/forests/ Rainforest Action Network] - forest protection organization
* [http://www.reo.gov/library/reports/old_growth_definitions.htm Old-Growth Forest Definitions] from [http://www.reo.gov U.S. Regional Ecosystem Office]
* [http://www.uoregon.edu/~arronfre/pmwiki/index.php?n=Main.GoogleMapFinds Collection of Google map links of clear cuts in or around old growth]
* [http://www.fsl.orst.edu/cfer/pdfs/mang_bio.pdf Managing for Biodiversity in Young Forests] - U.S. Geological Survey Biological Science Report (pdf)
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Look at other dictionaries:
Old-growth forest — Old growth redirects here. For the Dead Meadow album, see Old Growth (album). See also: Ancient woodland Old growth European Beech forest in Biogradska Gora National Park, Montenegro … Wikipedia
old-growth forest — OHLD GROHTH», a forest that has reached its final or stable stage of growth; climax forest: »If finalized, the designation [of the spotted owl as an endangered species] will protect 1.5 million acres…of old growth forest (Eugene J. Walter) … Useful english dictionary
old-growth forest — /oʊld groʊθ ˈfɒrəst/ (say ohld grohth foruhst) noun an ecologically and structurally mature community of trees, especially where the effect of past disturbances is negligible. Compare regenerated forest. Old growth forests are made up of trees of … Australian English dictionary
old growth forest — (Ecology) forest that contains large old trees and has not been disturbed by humans, forest that has grown naturally for centuries (subject to environmental protection) … English contemporary dictionary
old-growth forest — noun A forest which has never been logged … Wiktionary
Obabika Old-Growth Forest — is an Eastern White Pine and Red Pine dominated old growth forest at the north end of Obabika Lake, just west of the Temagami region of Ontario, Canada. At 2,400 hectares (5,900 acres) in size, is commonly considered to be the largest remaining… … Wikipedia
old-growth — [ōld′grōth′] adj. designating or of a forest characterized by very large, very old trees and great biodiversity * * * See old growth. * * * … Universalium
old-growth — [ōld′grōth′] adj. designating or of a forest characterized by very large, very old trees and great biodiversity … English World dictionary
old growth — old growth, adj. 1. forest growth consisting of mature or overmature trees. 2. virgin timber. [1880 85] * * * … Universalium
old'-growth — adjective (of forest or woodland) ancient • • • Main Entry: ↑old … Useful english dictionary