A fen is one of the main types of wetland, the others being grassy marshes, forested swamps, and peaty bogs. Along with bogs, fens are a kind of mire. Fens are minerotrophic peatlands,[1] usually fed by mineral-rich surface water or groundwater.[2] They are characterised by their distinct water chemistry, which is pH neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients. They are usually dominated by grasses and sedges, and typically have brown mosses in general including Scorpidium or Drepanocladus.[3] Fens frequently have a high diversity of other plant species including carnivorous plants such as Pinguicula.[4][5] They may also occur along large lakes and rivers where seasonal changes in water level maintain wet soils with few woody plants.[6] The distribution of individual species of fen plants is often closely connected to water regimes and nutrient concentrations.[7][8]

Fens have a characteristic set of plant species, which sometimes provide the best indicators of environmental conditions. For example, fen indicator species in New York State include Carex flava, Cladium mariscoides, Potentilla fruticosa, Pogonia ophioglossoides and Parnassia glauca.[9]

Fens are distinguished from bogs, which are acidic, low in minerals, and usually dominated by sedges and shrubs, along with abundant mosses in the genus Sphagnum.[3] Bogs also tend to exist on dome-shaped landmasses where they receive almost all of their usually-abundant moisture from rainfall, whereas fens appear on slopes, flats, or depressions and are fed by surface and underground water in addition to rain.

Fens have been damaged in the past by land drainage, and also by peat cutting.[10] Some are now being carefully restored with modern management methods.[11] The principal challenges are to restore natural water flow regimes, to maintain the quality of water, and to prevent invasion by woody plants.

Avaste soo ääreala (5)
Outer Avaste Fen, western Estonia
Illustrated diagram of a fen


Carr is the northern European equivalent of the wooded swamp of the southeastern United States,[12] also known in the United Kingdom as wet woodland. It is a fen overgrown with generally small trees of species such as willow (Salix spp.) or alder (Alnus spp.). In general, fens may change in composition as peat accumulates. A list of species found in a fen can therefore cover a range of species from those remaining from the earlier stage in the successional development to the pioneers of the succeeding stage.

Where streams of base-rich water run through bog, these are often lined by strips of fen, separating "islands" of rain-fed bog.

Temporary flooding by beavers can have negative effects on fens.[13]

Use of term in literature

Shakespeare used the term "fen-sucked" to describe the fog (literally: rising from marshes) in King Lear, when Lear says "Infect her beauty, You fen-sucked fogs drawn by the powerful sun, To fall and blister."[14]


Avaste soo põhjaosa vaated (5)

Avaste Fen is one of the biggest fens in Estonia and has a territory of 88 km2


View of Wicken Fen showing vegetation typical of a fen in the foreground and carr vegetation featuring trees and bushes in the background

See also

Specific fens


  1. ^ Rydin, Hakan and John K. Jeglum. The Biology of Peatlands, 2nd edn. Oxford: OUP, 2013. p. 11. ISBN 978-0-19-960299-5.
  2. ^ Godwin et al. (2002).
  3. ^ a b Keddy (2010), p. 8.
  4. ^ Wheeler & Giller (1982)
  5. ^ Keddy (2010), Chapter 9.
  6. ^ Charlton & Hilts (1989)
  7. ^ Slack et al. (1980)
  8. ^ Schröder et al. (2005)
  9. ^ Godwin et al. (2002), Table 3.
  10. ^ Sheail & Wells (1983)
  11. ^ Keddy (2010), Chapter 13.
  12. ^ Bug Life Archived 2010-03-04 at the Wayback Machine
  13. ^ Reddoch & Reddoch (2005)
  14. ^ William Shakespeare (2008). "King Lear, Act II, Scene IV, line 162". Penguin Books. Retrieved 5 September 2015. You nimble lightnings, dart your blinding flames, Into her scornful eyes! Infect her beauty, You fen-sucked fogs drawn by the powerful sun, To fall and blister.


  • Charlton, D. L.; S. Hilts (1989). "Quantitative evaluation of fen ecosystems on the Bruce Peninsula". In M. J. Bardecki; N. Patterson (eds.). Ontario Wetlands: Inertia or Momentum. Toronto, ON: Federation of Ontario Naturalists. pp. 339–354. Proceedings of Conference, Ryerson Polytechnical Institute, Toronto, Oct 21–22, 1988.
  • Godwin, Kevin S., James P. Shallenberger, Donald J. Leopold & Barbara L. Bedford (2002). "Linking landscape properties to local hydrogeologic gradients and plant species occurrence in New York fens: a hydrogeologic setting (HGS) framework". Wetlands. 22 (4): 722–737. doi:10.1672/0277-5212(2002)022[0722:LLPTLH]2.0.CO;2.CS1 maint: Uses authors parameter (link)
  • Keddy, P. A. (2010). Wetland Ecology: Principles and Conservation (2nd ed.). Cambridge, UK: Cambridge University Press.
  • Reddoch, Joyce M.; Allan H. Reddoch (2005). "Consequences of Beaver, Castor canadensis, flooding on a small shore fen in southwestern Quebec". Canadian Field-Naturalist. 119 (3): 385–394.
  • Schröder, Henning K., Hans Estrup Andersen & Kathrin Kiehl (2005). "Rejecting the mean: estimating the response of fen plant species to environmental factors by non-linear quantile regression". Journal of Vegetation Science. 16 (4): 373–382. doi:10.1111/j.1654-1103.2005.tb02376.x. JSTOR 4096617.CS1 maint: Uses authors parameter (link)
  • Sheail, J.; T. C. E. Wells (1983). "The Fenlands of Huntingdonshire, England: a case study in catastrophic change". In A. J. P. Gore (ed.). Mires: Swamp, Bog, Fen and Moor – Regional Studies. Ecosystems of the World. 4B. Amsterdam, the Netherlands: Elsevier. pp. 375–393. ISBN 9780444420046.
  • Slack, Nancy G., Dale H. Vitt & Diana G. Horton (1980). "Vegetation gradients of minerotrophically rich fens in western Alberta". Canadian Journal of Botany. 58 (3): 330–350. doi:10.1139/b80-034.CS1 maint: Uses authors parameter (link)
  • Wheeler, B. D.; K. E. Giller (1982). "Species richness of herbaceous fen vegetation in Broadland, Norfolk in relation to the quantity of above-ground plant material". Journal of Ecology. 70 (i): 179–200. JSTOR 2259872.

External links

  • Media related to Fens at Wikimedia Commons
Arger Fen

Arger Fen is a 49.7 hectare biological Site of Special Scientific Interest (SSSI) south-east of Sudbury in Suffolk, England. The site occupies two separate areas. The 17.6-hectare (43-acre) Arger Fen Local Nature Reserve is part of the larger eastern block, and contains part of the 21-hectare (52-acre) Tiger Hill Local Nature Reserve, along with part of the 110-hectare (270-acre) Arger Fen and Spouse's Vale, a nature reserve managed by the Suffolk Wildlife Trust. The site lies in the Dedham Vale Area of Outstanding Natural Beauty,The site is made up of a mix of woodland and meadow habitats with much of the woodland believed to be ancient in origin. The underlying geology is a mixture of sand and gravel banks and clay soils, producing a mix of habitat types, including wet fen type habitats at lower levels and dry grasslands on acidic soils on hill tops. It is one of only two known areas of ancient woodland in Eastern England which feature wild cherry (Prunus avium).Badgers are found on the reserve in a number of active setts. Other rare fauna include the hazel dormouse and barbastelle bat. In 2012 the reserve, which has ash trees at least 300 years old, was identified as a site of ash dieback and in 2013 it became a research site for Forestry Commission scientists studying genetic resistance to the Chalara fungus which causes the disease.There are onsite car parking facilities as well as two-way marked trails, including areas of board walk. The trust has attempted to encourage the growth of the dormouse population, partly by expanding the area of land it owns at Arger Fen.

Blo' Norton and Thelnetham Fens

Blo' Norton and Thelnetham Fens are a 21.3 hectare biological Site of Special Scientific Interest (SSSI) on the Norfolk/Suffolk border. Blo' Norton Fen is in the parish of Blo' Norton in Norfolk and Thelnetham Fen is in Thelnetham parish in Suffolk. It is a Nature Conservation Review site, Grade 2, and part of the Waveney and Little Ouse Valley Fens Special Area of Conservation, Thelnetham Fen is managed by the Suffolk Wildlife Trust and Blo' Norton Fen by the Little Ouse Headwaters Project (LOHP).

Carr (landform)

A carr is a type of waterlogged wooded terrain that, typically, represents a succession stage between the original reedy swamp and the likely eventual formation of forest in a sub-maritime climate. The name derives from the Old Norse kjarr, meaning a swamp. The carr is one stage in a hydrosere: the progression of vegetation beginning from a terrain submerged by fresh water along a river or lake margin. In sub-maritime regions, it begins with reed-swamp. As the reeds decay, the soil surface eventually rises above the water, creating fens that allow vegetation such as sedge to grow. As this progression continues, riparian trees and bushes appear and a carr landscape is created – in effect a wooded fen in a waterlogged terrain. At this stage, overall, unlike the overwhelming acidity of decaying reeds, the pH is not too acidic and the soil is not too deficient in minerals, making a habitat for endemic and other wildlife. Characteristic trees include alder, willow and sallow.

Cellophane noodles

Cellophane noodles, or Fensi (simplified Chinese: 粉丝; traditional Chinese: 粉絲; pinyin: fěnsī; literally: 'flour thread'), sometimes called glass noodles, are a type of transparent noodle made from starch (such as mung bean starch, potato starch, sweet potato starch, tapioca, or canna starch) and water.

They are generally sold in dried form, soaked to reconstitute, then used in soups, stir fried dishes, or spring rolls. They are called "cellophane noodles" or "glass noodles" because of their appearance when cooked, resembling cellophane, a clear material of a translucent light gray or brownish-gray color.

Cellophane noodles should not be confused with rice vermicelli, which are made from rice and are white in color rather than clear (after cooking in water).

Fen River

The Fen River drains the center of Shanxi Province, China. It rises in the Guancen Mountains of Ningwu County in northeast Shanxi, flows southeast into the basin of Taiyuan, and then south through the central valley of Shanxi before turning west to join the Yellow River west of Hejin. The Fen and the Wei Rivers are the two largest tributaries of the Yellow River. The river is 694 kilometers (431 mi) long and drains an area of 39,417 km2 (15,219 sq mi), 25.3% of Shanxi's area. The Fen River is the longest in Shanxi. It is also the second-longest tributary of the Yellow River. Within Taiyuan, the Fen runs from north to south; the prefecture includes one-seventh of the river's course.

Fen line

The Fen Line is a railway line in the east of England that links Cambridge in the south to King's Lynn in the north. The line runs through Cambridgeshire and Norfolk and is so called because it passes through the Fens. It is 41 miles 47 chains (66.9 km) in length and has eight stations.

The line is part of the Network Rail Strategic Route 5 and comprises SRS 05.06 and part of 05.05. It is classified as a secondary line except between Cambridge and Ely where it is classified as a London and South East commuter line.


The drug combination fenfluramine/phentermine, usually called fen-phen, was an anti-obesity treatment that utilized two anorectics. Fenfluramine was marketed by American Home Products (later known as Wyeth) as Pondimin, but was shown to cause potentially fatal pulmonary hypertension and heart valve problems, which eventually led to its withdrawal and legal damages of over $13 billion. Phentermine was not shown to have harmful effects.Fenfluramine acts as a serotonin releasing agent, phentermine as primarily a norepinephrine releasing agent. Phentermine also induces the release of serotonin and dopamine, although to a far lesser extent than it induces the release of norepinephrine.

Five-spice powder

Five-spice powder (Chinese: 五香粉; pinyin: wǔxiāng fěn) is a spice mixture of five or more spices used predominantly in almost all branches of Chinese cuisines and also used less commonly in other Asian and Arabic cuisines.

Five-spice powder can be used in cocktails.

Mareham le Fen

Mareham le Fen (otherwise Mareham-le-Fen) is a village and civil parish about 6 miles (10 km) south from the town of Horncastle, Lincolnshire, England. The hamlet of Mareham Gate lies about 0.5 miles (0.8 km) south from the village, and it is believed that the deserted medieval village (DMV) of Birkwood is situated nearby.Mareham le Fen is listed in the 1086 Domesday Book as "Marun", with 33 households, 60 acres (0.24 km2) of meadow, 300 acres (1.2 km2) of woodland, and a church. The Lord of the Manor was William I.The parish church is dedicated to St Helen, and is a Grade II* listed building of greenstone and dating from the 13th century. It was partially rebuilt in 1879, and in 1974 the vestry was extended using stone from the demolished church of St Margaret at Woodhall. In the north aisle is a tomb to James Roberts who died 1826, and sailed in the Endeavour with Captain Cook and Sir Joseph Banks. In the churchyard is a medieval stone cross, which is both Grade II listed and a scheduled monument. Dating from the 14th century, it was restored in 1904.The Grade II listed Royal Oak public house has a datestone of 1473, but is believed to date from the 17th century, with 18th- and 20th-century additions.Also in the village is a Grade II listed tower windmill dating from 1820, although it ceased working as a windmill in 1910.but continued to mill with an engine until mid 1940sMareham le Fen Church of England Primary School was built in 1840 as a National School and was enlarged in 1880.Mareham le Fen Victory Silver Band, established in 1919, plays in the local area at events and services.

Mutton Hunk Fen Natural Area Preserve

Mutton Hunk Fen Natural Area Preserve is a 516-acre (2.09 km2) Natural Area Preserve located in Accomack County, Virginia. Fronting on the Atlantic Ocean's Gargathy Bay to the east, it is also bounded by Whites Creek and Mutton Hunk Branch to its north. The property contains a rare "sea level fen" community, one of only four in Virginia. Despite the proximity to the ocean's saltwater, freshwater wetland plants are able to survive in this environment due to the influence of freshwater springs. Acidic conditions also encourage the growth of plants normally found in bogs, in addition to tidal freshwater wetland plants; five of the species found at the preserve are regionally rare.Mutton Hunk Fen Natural Area Preserve is owned and maintained by the Virginia Department of Conservation and Recreation, and is open to the public. Improvements at the preserve include a parking areas and trails to view the marsh and Whites Creek.

Poor fen

A poor fen (also known as transitional bog, transitional mire or sedge mire) is a natural wetland habitat, supporting a dense carpet of mosses and sedges. It develops where the water is fairly acidic and has very few plant nutrients.

Poor fen is intermediate between the taller vegetation of fen, which occurs where the water is much less acidic, and the short, mossy vegetation of bog, which is even more acidic.

Redgrave and Lopham Fens

Redgrave and Lopham Fens is a 127 hectare biological Site of Special Scientific Interest between Thelnetham in Suffolk and Diss in Norfolk. It is a National Nature Reserve, a Ramsar internationally important wetland site, a Nature Conservation Review site, Grade I, and part of the Waveney and Little Ouse Valley Fens Special Area of Conservation. It is managed by the Suffolk Wildlife Trust.It is the largest remaining area of river valley fen in England and consists of a number of different fen types, including saw-sedge beds, as well as having areas of open water, heathland, scrub and woodland. It is also one of only three sites in the UK where the fen raft spider Dolomedes plantarius is known to be found.

Rice vermicelli

Rice vermicelli are a thin form of rice noodles. They are sometimes referred to as rice noodles, rice sticks, or bee hoon, but they should not be confused with cellophane noodles, a different Asian type of vermicelli made from mung bean starch or rice starch rather than rice grains itself.

Shahe fen

Shahe fen or he fen is a type of wide Chinese noodle made from rice.Shahe fen is often stir fried with meat and/or vegetables in a dish called chao fen (炒粉; pinyin: chǎo fěn). While chao fen is a transliteration of Mandarin, chow fun from Cantonese is the name to which this dish is most often referred in Chinese restaurants in North America.

Silicon Fen

Silicon Fen (sometimes known as the Cambridge Cluster) is the name given to the region around Cambridge, England, which is home to a large cluster of high-tech businesses focusing on software, electronics and biotechnology. Many of these businesses have connections with the University of Cambridge, and the area is now one of the most important technology centres in Europe.

It is called "Silicon Fen" by analogy with Silicon Valley in California, because it lies at the southern tip of the English Fenland. The interest in technology in the area started with Acorn Computers.

Silver needle noodles

Silver needle noodle (simplified Chinese: 银针粉; traditional Chinese: 銀針粉; pinyin: yín zhēn fěn), rat noodle (Chinese: 老鼠粉; pinyin: lǎo shǔ fěn), bee tai bak (simplified Chinese: 米筛目; traditional Chinese: 米篩目; Pe̍h-ōe-jī: bí-thai-ba̍k) or lot (Khmer: លត) is a variety of Chinese noodles. It is short, about 5 cm long and 5 mm in diameter. It has a white semi-transparent colour. The noodle is available in many Chinese markets in Chinese populated areas such as Hong Kong, Taiwan, Indonesia, Malaysia and Singapore.

The Fens

The Fens, also known as the Fenlands, are a coastal plain in eastern England. This natural marshy region supported a rich ecology and numerous species, as well as absorbing storms. Most of the fens were drained several centuries ago, resulting in a flat, dry, low-lying agricultural region supported by a system of drainage channels and man-made rivers (dykes and drains) and automated pumping stations. There have been unintended consequences to this reclamation, as the land level has continued to sink and the dykes must be built higher to protect it from flooding.

A fen is the local term for an individual area of marshland or former marshland. It also designates the type of marsh typical of the area, which has neutral or alkaline water chemistry and relatively large quantities of dissolved minerals, but few other plant nutrients.

Fenland primarily lies around the coast of the Wash, occupying an area of nearly 1,500 sq mi (3,900 km2) in Lincolnshire, Cambridgeshire, and Norfolk.Most of the Fenland lies within a few metres of sea level. As with similar areas in the Netherlands, much of the Fenland originally consisted of fresh- or salt-water wetlands. These have been artificially drained and continue to be protected from floods by drainage banks and pumps. With the support of this drainage system, the Fenland has become a major arable agricultural region in Britain for grains and vegetables. The Fens are particularly fertile, containing around half of the grade 1 agricultural land in England.

The Fens have been referred to as the "Holy Land of the English" because of the former monasteries, now churches and cathedrals, of Crowland, Ely, Peterborough, Ramsey and Thorney. Other significant settlements in the Fens include Boston, Cambridge, Spalding, and Wisbech.

Thornton le Fen

Thornton Le Fen is a small civil parish in the East Lindsey district of Lincolnshire, England. It is situated approximately 4 miles (6 km) north from the town of Boston.

Thornton Le Fen lies in Wildmore Fen, created in 1812 after the fen was drained in 1802. It is mostly farmland with a population of 345, and contains the hamlets of Bunkers Hill and Gipsey Bridge. The Census of 2011 showed a reduced population of 322.Gipsey Bridge School was built in 1859 and was taken over by the Wildmore Fen United District School Board in 1879, when it was renamed the Gipsey Bridge Board School, until the Board was abolished in 1903. Following this it was known as Thornton Le Fen Council School, Thornton Le Fen County School, and Gipsey Bridge County Primary School, before it took its present name, Gipsey Bridge Primary School, in 1999.

Weston Fen

Weston Fen is a 49.7 hectare biological Site of Special Scientific Interest in Hopton in Suffolk. It is part of the Waveney and Little Ouse Valley Fens Special Areas of Conservation, and an area of 37 hectares is managed as a nature reserve called Market Weston Fen by the Suffolk Wildlife Trust.This spring-fed valley fen has a high and stable water table, and as a result it has a rich and varied flora. The dominant plants in the central fen area are saw sedge, the reed Phragmites australis and blunt-flowered rush. Other habitats include tall fen grassland, heath and a stream. There are many dragonflies and damselflies.There is access from Fen Street. Parking for 3-4 cars on verge immediately after the signposted public footpath and entrance to fen.

Classification systems

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