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A further distinction is made between open and wooded fens, where open fens have canopy cover less than 10% and wooded fens have 10-25% canopy cover. If tall shrubs or trees dominate, the wetland is instead classified as a wooded bog or swamp forest depending on other criteria.
A further distinction is made between open and wooded fens, where open fens have canopy cover less than 10% and wooded fens have 10-25% canopy cover. If tall shrubs or trees dominate, the wetland is instead classified as a wooded bog or swamp forest depending on other criteria.

== Biogeochemistry ==

=== Hydrology ===
The major determinant of fen biota and biogeochemistry in fens, like other wetlands, is hydrology.<ref name=":2">{{Cite book|last=Keddy|first=Paul A.|url=https://www.worldcat.org/oclc/801405617|title=Wetland ecology : principles and conservation|date=2010|publisher=Cambridge University Press|isbn=978-1-139-22365-2|edition=2nd ed|location=Cambridge|oclc=801405617}}</ref> Fen soils are constantly inundated because the water table is just below, just above, or at the surface.<ref name=":6">{{Cite book|last=Rydin|first=Håkan|url=https://www.worldcat.org/oclc/861559248|title=The biology of peatlands|date=2013|others=J. K. Jeglum|isbn=978-0-19-150828-8|edition=Second edition|location=Oxford, UK|oclc=861559248}}</ref> The result is anaerobic soils due to the slow rate at which oxygen diffuses into waterlogged soil.<ref name=":2" /> Anaerobic soils are ecologically unique; because Earth's atmosphere is oxygenated, most terrestrial ecosystems and surface waters are aerobic. The anaerobic conditions found in wetland soils result in reduced, rather than oxidized, soil chemistry.<ref name=":2" />

A hallmark of fens is that a significant portion of their water supply is derived from groundwater (minerotrophy).<ref name=":6" />Because hydrology is the dominant factor in wetlands, the chemistry of the groundwater has an enormous effect on the characteristics of the fen it supplies.<ref name=":3">{{Cite journal|last=Godwin|first=Kevin S.|last2=Shallenberger|first2=James P.|last3=Leopold|first3=Donald J.|last4=Bedford|first4=Barbara L.|date=2002-12|title=Linking landscape properties to local hydrogeologic gradients and plant species occurrence in minerotrophic fens of New York State, USA: A Hydrogeologic Setting (HGS) framework|url=http://dx.doi.org/10.1672/0277-5212(2002)022[0722:llptlh]2.0.co;2|journal=Wetlands|volume=22|issue=4|pages=722–737|doi=10.1672/0277-5212(2002)022[0722:llptlh]2.0.co;2|issn=0277-5212}}</ref> Groundwater chemistry, in turn, is largely determined by the geology of the rocks that the groundwater flows through.<ref>{{Citation|last=Fitts|first=Charles R.|title=10 - Groundwater Chemistry|date=2013-01-01|url=https://www.sciencedirect.com/science/article/pii/B9780123847058000108|work=Groundwater Science (Second Edition)|pages=421–497|editor-last=Fitts|editor-first=Charles R.|place=Boston|publisher=Academic Press|language=en|isbn=978-0-12-384705-8|access-date=2021-03-20}}</ref> Thus, the characteristics of a fen, especially its pH, are directly influenced by the type of rocks its groundwater supply contacts. pH is a major factor in determining fen species composition and richness, with more basic fens called "rich" and more acidic fens called "poor."<ref name=":6" /> Rich fens tend to be highly biodiverse and harbor a number of rare or endangered species, and biodiversity tends to decrease as fen richness decreases.<ref name=":3" /><ref name=":6" />

Fens tend to be found above rocks that are rich in calcium, such as limestone.<ref name=":2" /> When groundwater flows past calcareous (calcium-rich) rocks like limestone (CaCO<sub>3</sub>), a small amount dissolves and is carried to the fen supplied by the groundwater.<ref name=":12">{{Cite book|last=Clark|first=Ian|title=Environmental Geochemistry of Isotopes|publisher=Unpublished|year=2006|location=University of Ottawa|pages=1-7|chapter=Chapter 6: Weathering}}</ref> When calcium carbonate dissolves, it produces bicarbonate and a calcium cation according to the following equilibrium:<ref name=":12" />

<chem>CaCO3 + H2CO3 <=> Ca^2+ + 2HCO3^-</chem>

where carbonic acid (H<sub>2</sub>CO<sub>3</sub>) is produced by the dissolution of carbon dioxide in water.<ref name=":12" /> In fens, the bicarbonate anion produced in this equilibrium acts as a pH buffer, which keeps the pH of the fen relatively stable.<ref name=":11">{{Cite journal|last=Bourbonniere|first=Richard A.|date=2009-01|title=Review of Water Chemistry Research in Natural and Disturbed Peatlands|url=http://www.tandfonline.com/doi/abs/10.4296/cwrj3404393|journal=Canadian Water Resources Journal|language=en|volume=34|issue=4|pages=393–414|doi=10.4296/cwrj3404393|issn=0701-1784}}</ref> Fens supplied by groundwater that doesn't flow through minerals that act as a buffer when dissolved tend to be more acidic.<ref name=":10">{{Cite journal|last=Bedford|first=Barbara L.|last2=Godwin|first2=Kevin S.|date=2003-09|title=Fens of the United States: Distribution, characteristics, and scientific connection versus legal isolation|url=http://dx.doi.org/10.1672/0277-5212(2003)023[0608:fotusd]2.0.co;2|journal=Wetlands|volume=23|issue=3|pages=608–629|doi=10.1672/0277-5212(2003)023[0608:fotusd]2.0.co;2|issn=0277-5212}}</ref> The same effect is observed when groundwater flows through minerals with low solubility, such as sand.<ref name=":10" />

In extreme rich fens, calcium carbonate can precipitate out of solution to form marl deposits.<ref name=":10" /> Calcium carbonate precipitates out of solution when the partial pressure of carbon dioxide in the solution falls.<ref name=":13">{{Cite journal|last=Bartigs|first=Rodney|date=Mar. 1984|title=Marl Wetlands in Eastern West Virginia: Distribution, Rare Plant Species, and Recent History|journal=Castanea|volume=49|pages=17-25|via=JSTOR}}</ref> The decrease in carbon dioxide partial pressure is caused by uptake by plants for photosynthesis or direct loss to the atmosphere.<ref name=":13" /> This reduces the availability of carbonic acid in solution, shifting the above equilibrium back towards the formation of calcium carbonate. The result is the precipitation of calcium carbonate and the formation of marl.<ref name=":13" />

=== Bog-rich fen gradient ===
Bogs and fens can be thought of as two ecosystems on a gradient from poor to rich, with bogs at the poor end, extremely rich fens at the rich end, and poor fens in between.<ref>{{Cite journal|last=Szumigalski|first=Anthony R.|last2=Bayley|first2=Suzanne E.|date=1996-12|title=Net above-ground primary production along a bog-rich fen gradient in Central Alberta, Canada|url=http://dx.doi.org/10.1007/bf03161336|journal=Wetlands|volume=16|issue=4|pages=467–476|doi=10.1007/bf03161336|issn=0277-5212}}</ref> In this context, "rich" and "poor" refer to the species richness, or how biodiverse a fen or bog is.<ref name=":6" /> Species richness is strongly influenced by pH and concentrations of calcium and bicarbonate, so these factors together may be used to classify where along the gradient a particular fen falls.<ref>{{Cite journal|last=Bourbonniere|first=Richard A.|date=2009-01|title=Review of Water Chemistry Research in Natural and Disturbed Peatlands|url=http://www.tandfonline.com/doi/abs/10.4296/cwrj3404393|journal=Canadian Water Resources Journal|language=en|volume=34|issue=4|pages=393–414|doi=10.4296/cwrj3404393|issn=0701-1784}}</ref> In general, rich fens are minerotrophic, or dependent on mineral-rich groundwater, while bogs are ombrotrophic, or dependent on precipitation for water and nutrients.<ref name=":6" /> Poor fens fall between these two.

==== Rich fens ====
Rich fens are strongly minerotrophic; that is, a large proportion of their water comes from mineral-rich ground or surface water. This water is dominated by calcium and bicarbonate, resulting in a slightly acidic to slightly basic pH, which is characteristic of rich fens.<ref name=":6" /><ref name=":14">{{Citation|last=Zoltai|first=S. C.|title=Canadian wetlands: Environmental gradients and classification|date=1995|url=http://dx.doi.org/10.1007/978-94-011-0427-2_11|work=Classification and Inventory of the World’s Wetlands|pages=131–137|place=Dordrecht|publisher=Springer Netherlands|isbn=978-94-010-4190-4|access-date=2021-04-01|last2=Vitt|first2=D. H.}}</ref> These conditions promote high biodiversity. Within rich fens, there is a large amount of variability. The richest fens are the extreme rich (marl) fens, where marl deposits are often build up.<ref name=":10" /> These are often pH 7 or greater.<ref name=":6" /> Rich and intermediate rich fens are generally neutral to slightly acidic, with a pH of approximately 7 to 5. Rich fens are not always very productive; at high calcium concentrations, calcium ions bind to phosphate anions, reducing the availability of phosphorous and decreasing primary production.<ref name=":2" /><ref name=":6" /> Brown mosses (family ''Amblystegiaceae'') and sedges (genus ''Carex'') are the dominant vegetation.<ref name=":14" /> Compared to poor fens, rich fens have higher concentrations of bicarbonate, base cations (Na<sup>+</sup>, Ca<sup>2+</sup>, K<sup>+</sup>, Mg<sup>2+</sup>), and sulfate.<ref name=":11" />

==== Poor fens ====
Poor fens are in many ways an intermediate between rich fens and bogs. Hydrologically, they are more alike to rich fens than to bogs, but in terms of vegetation composition and chemistry, they are more similar to bogs than rich fens.<ref name=":14" /> They much more acidic than their rich counterparts, with a pH of approximately 5.5 to 4.<ref name=":6" /> Peat in poor fens tends to be thicker than that of rich fens, which cuts off vegetation access to the mineral-rich soil underneath.<ref name=":2" /> In addition, the thicker peat reduces the influence of mineral-rich groundwater that buffers the pH.<ref name=":2" /> This makes the fen more ombrotrophic, or dependent on nutrient-poor precipitation for its water and nutrients.<ref name=":2" /> Poor fens may also form in areas where the groundwater supplying the fen flows through sediments that don't dissolve well or have low buffering capacity when dissolved.<ref name=":10" /> Species richness tends to be lower than that of rich fens but higher than that of bogs.<ref name=":6" /> Poor fens, like bogs, are dominated by ''Sphagnum'' mosses, which acidify the fen and decrease nutrient availability.<ref name=":14" />

== Threats ==
Fens face many threats, but they are most commonly lost to conversion to agricultural lands.<ref name=":42">{{Cite journal|last=van Diggelen|first=Rudy|last2=Middleton|first2=Beth|last3=Bakker|first3=Jan|last4=Grootjans|first4=Ab|last5=Wassen|first5=Martin|date=2006-11|title=Fens and floodplains of the temperate zone: Present status, threats, conservation and restoration|url=http://dx.doi.org/10.1111/j.1654-109x.2006.tb00664.x|journal=Applied Vegetation Science|volume=9|issue=2|pages=157–162|doi=10.1111/j.1654-109x.2006.tb00664.x|issn=1402-2001}}</ref> In climates where agriculture is possible, fens have been drained for agricultural use, including crop production, grazing, and hay making.<ref name=":15">{{Cite web|title=Threats to Fens|url=https://www.canr.msu.edu/nativeplants/restoration/threats_to_fens|access-date=2021-04-01|website=Native Plants and Ecosystem Services|language=en}}</ref> Directly draining a fen is particularly damaging because it lowers the water table.<ref name=":6" /> A lower water table can improve aeration and dry out peat, allowing for aerobic decomposition or burning of the organic matter in peat.<ref name=":2" /><ref name=":6" /> Indirectly draining a fen or decreasing its water supply can be just as damaging. Disrupting groundwater flow into the fen with nearby human activities such as quarrying or residential development changes how much water and nutrients enter the fen.<ref name=":15" /> This can make the fen more ombrotrophic (dependent on precipitation), which results in acidification and a change in water chemistry.<ref name=":42" /> Species composition changes often follow, and many signature fen species disappear.<ref name=":42" />

Fens are also threatened by invasive species, fragmentation, peat cutting, and pollution.<ref name=":15" /> Non-native invasive species, such as the common buckthorn in North America, can invade fens and outcompete rare fen species, reducing biodiversity.<ref name=":15" /> Habitat fragmentation threatens fen species, especially rare or endangered species that are unable to move to nearby fens due to fragmentation.<ref name=":15" /> Peat cutting, while much more common in bogs, does happen in fens. Peat cut from fens has many uses, including burning as a fuel.<ref name=":15" /> Pollutants can alter the chemistry of fens and facilitate invasion of invasive species.<ref name=":15" /> Common pollutants of fens include road salts, nutrients from septic tanks, and runoff of agricultural fertilizers and pesticides.<ref name=":15" />


==Vegetation==
==Vegetation==

Revision as of 01:21, 5 April 2021

This article is about the type of wetland. For other uses, see Fen (disambiguation).
Not to be confused with Fenn.
Avaste Fen, Estonia
View of Wicken Fen showing vegetation typical of a fen in the foreground and carr vegetation featuring trees and bushes in the background

A fen is one of the main types of wetlands, 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 characterized by their distinct water chemistry, which is pH neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients. Continuous input of groundwater into fens maintains a stable water table throughout the course of a year.[3] The stable water table helps maintain multiple defining characteristics of fens, namely the neutral pH, high base (Mg, Fe, Ca) saturation, and low nutrient availability. They are usually dominated by grasses and sedges, and typically have brown mosses.[4] Fens frequently have a high diversity of other plant species including carnivorous plants such as Pinguicula.[5][6] They may also occur along large lakes and rivers where seasonal changes in water level maintain wet soils with few woody plants.[7] The distribution of individual species of fen plants is often closely connected to water regimes and nutrient concentrations.[8][9]

Fens have a characteristic set of plant species, which sometimes provide the best indicators of environmental conditions. For example, fen indicator species in the State of New York include the flora Carex flava, Cladium mariscoides, Potentilla fruticosa, Pogonia ophioglossoides and Parnassia glauca.[10]

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.[4] 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.[11] Some are now being carefully restored with modern management methods.[12] The principal challenges are to restore natural water flow regimes, to maintain the quality of water, and to prevent invasion by woody plants.

Distribution and extent

Fens are distributed around the world, but are most frequently found at the mid-high latitudes of the Northern Hemisphere.[13] They are found throughout the temperate zone and boreal regions, but are also present in tundra and in specific environmental conditions in other regions around the world.[14][15] In the United States, fens are most common in the Midwest and Northeast, but can be found across the country.[16] In Canada, fens are most frequent in the lowlands near the Hudson Bay and James Bay, but can also be found across the country.[15] Fens are also spread across the northern latitudes of Eurasia, including the British Isles and Japan, but east-central Europe is especially rich in fens.[15][16] Further south, fens are much rarer, but do exist under specific conditions. In Africa, fens have been found in the Okavango Delta in Botswana and the highland slopes in Lesotho.[15] Fens can also be found at the colder latitudes of the Southern Hemisphere. They are found in New Zealand and southern Chile and Argentina, but the extent is much less than that of the northern latitudes.[15][13] Locally, fens are most often found at the intersection of terrestrial and aquatic ecosystems, such as the headwaters of streams and rivers.[15][17]

It is estimated that there are approximately 1.1 million square kilometers of fens worldwide, but quantifying the extent of fens is difficult.[13] Because wetland definitions vary regionally, not all countries define fens the same way.[15] In addition, wetland data isn't always available or of high quality.[15] Fens are also difficult to rigidly delineate and measure, as they are located between terrestrial and aquatic ecosystems.[15]

Definition

Rigidly defining types of wetlands, including fens, is difficult for a number of reasons. First, wetlands are diverse and varied ecosystems that are not easily defined by inflexible definitions. They are often described as a transition between terrestrial and aquatic ecosystems with characteristics of both.[17] This makes it difficult to delineate the exact extent of a wetland. Second, terms used to describe wetland types vary greatly by region.[14] The term bayou, for example, describes a type of wetland, but its use is generally limited to the southern United States.[18] Third, different languages use different terms to describe types of wetlands. For instance, in Russian, there is no equivalent word for the term swamp as it is typically used in North America.[17] The result is a large number of wetland classification systems that each define wetlands and wetland types in their own way.[14] However, many classification systems include four broad categories that most wetlands fall into: marsh, swamp, bog, and fen.[14] While classification systems differ on the exact criteria that define a fen, there are common characteristics that describe fens generally and imprecisely. A general definition provided by the textbook Wetlands describes a fen as "a peat-accumulating wetland that receives some drainage from surrounding mineral soil and usually supports marsh like vegetation."[17]

Three examples are presented below to illustrate more specific definitions for the term fen.

Canadian Wetland Classification System definition

In the Canadian Wetland Classification System, fens are defined by six characteristics:[19]

  1. Peat is present.
  2. The surface of the wetland is level with the water table. Water flows on the surface and through the subsurface of the wetland.
  3. The water table fluctuates. It may be at the surface of the wetland or a few centimeters above or below it.
  4. The wetland receives a significant amount of its water from mineral-rich groundwater or surface water.
  5. Decomposed sedges or brown moss peat are present.
  6. The vegetation is predominantly graminoids and shrubs.

Wetland Ecology: Principles and Conservation (Keddy) definition

In the textbook Wetland Ecology: Principles and Conservation, Paul A. Keddy offers a somewhat simpler definition of fens as "A wetland that is usually dominated by sedges and grasses rooted in shallow peat, often with considerable groundwater movement, and with pH greater than 6."[14] This definition differentiates fens from swamps and marshes by the presence of peat.

The Biology of Peatlands (Rydin) definition

Fens are defined by the following criteria:[15]

  1. The wetland is not flooded by lake or stream water.
  2. Woody vegetation 2 meters or taller is absent or canopy cover is less than 25%.
  3. The wetland is minerotrophic (it receives its nutrients from mineral-rich groundwater).

A further distinction is made between open and wooded fens, where open fens have canopy cover less than 10% and wooded fens have 10-25% canopy cover. If tall shrubs or trees dominate, the wetland is instead classified as a wooded bog or swamp forest depending on other criteria.

Biogeochemistry

Hydrology

The major determinant of fen biota and biogeochemistry in fens, like other wetlands, is hydrology.[20] Fen soils are constantly inundated because the water table is just below, just above, or at the surface.[21] The result is anaerobic soils due to the slow rate at which oxygen diffuses into waterlogged soil.[20] Anaerobic soils are ecologically unique; because Earth's atmosphere is oxygenated, most terrestrial ecosystems and surface waters are aerobic. The anaerobic conditions found in wetland soils result in reduced, rather than oxidized, soil chemistry.[20]

A hallmark of fens is that a significant portion of their water supply is derived from groundwater (minerotrophy).[21]Because hydrology is the dominant factor in wetlands, the chemistry of the groundwater has an enormous effect on the characteristics of the fen it supplies.[22] Groundwater chemistry, in turn, is largely determined by the geology of the rocks that the groundwater flows through.[23] Thus, the characteristics of a fen, especially its pH, are directly influenced by the type of rocks its groundwater supply contacts. pH is a major factor in determining fen species composition and richness, with more basic fens called "rich" and more acidic fens called "poor."[21] Rich fens tend to be highly biodiverse and harbor a number of rare or endangered species, and biodiversity tends to decrease as fen richness decreases.[22][21]

Fens tend to be found above rocks that are rich in calcium, such as limestone.[20] When groundwater flows past calcareous (calcium-rich) rocks like limestone (CaCO3), a small amount dissolves and is carried to the fen supplied by the groundwater.[24] When calcium carbonate dissolves, it produces bicarbonate and a calcium cation according to the following equilibrium:[24]

where carbonic acid (H2CO3) is produced by the dissolution of carbon dioxide in water.[24] In fens, the bicarbonate anion produced in this equilibrium acts as a pH buffer, which keeps the pH of the fen relatively stable.[25] Fens supplied by groundwater that doesn't flow through minerals that act as a buffer when dissolved tend to be more acidic.[26] The same effect is observed when groundwater flows through minerals with low solubility, such as sand.[26]

In extreme rich fens, calcium carbonate can precipitate out of solution to form marl deposits.[26] Calcium carbonate precipitates out of solution when the partial pressure of carbon dioxide in the solution falls.[27] The decrease in carbon dioxide partial pressure is caused by uptake by plants for photosynthesis or direct loss to the atmosphere.[27] This reduces the availability of carbonic acid in solution, shifting the above equilibrium back towards the formation of calcium carbonate. The result is the precipitation of calcium carbonate and the formation of marl.[27]

Bog-rich fen gradient

Bogs and fens can be thought of as two ecosystems on a gradient from poor to rich, with bogs at the poor end, extremely rich fens at the rich end, and poor fens in between.[28] In this context, "rich" and "poor" refer to the species richness, or how biodiverse a fen or bog is.[21] Species richness is strongly influenced by pH and concentrations of calcium and bicarbonate, so these factors together may be used to classify where along the gradient a particular fen falls.[29] In general, rich fens are minerotrophic, or dependent on mineral-rich groundwater, while bogs are ombrotrophic, or dependent on precipitation for water and nutrients.[21] Poor fens fall between these two.

Rich fens

Rich fens are strongly minerotrophic; that is, a large proportion of their water comes from mineral-rich ground or surface water. This water is dominated by calcium and bicarbonate, resulting in a slightly acidic to slightly basic pH, which is characteristic of rich fens.[21][30] These conditions promote high biodiversity. Within rich fens, there is a large amount of variability. The richest fens are the extreme rich (marl) fens, where marl deposits are often build up.[26] These are often pH 7 or greater.[21] Rich and intermediate rich fens are generally neutral to slightly acidic, with a pH of approximately 7 to 5. Rich fens are not always very productive; at high calcium concentrations, calcium ions bind to phosphate anions, reducing the availability of phosphorous and decreasing primary production.[20][21] Brown mosses (family Amblystegiaceae) and sedges (genus Carex) are the dominant vegetation.[30] Compared to poor fens, rich fens have higher concentrations of bicarbonate, base cations (Na+, Ca2+, K+, Mg2+), and sulfate.[25]

Poor fens

Poor fens are in many ways an intermediate between rich fens and bogs. Hydrologically, they are more alike to rich fens than to bogs, but in terms of vegetation composition and chemistry, they are more similar to bogs than rich fens.[30] They much more acidic than their rich counterparts, with a pH of approximately 5.5 to 4.[21] Peat in poor fens tends to be thicker than that of rich fens, which cuts off vegetation access to the mineral-rich soil underneath.[20] In addition, the thicker peat reduces the influence of mineral-rich groundwater that buffers the pH.[20] This makes the fen more ombrotrophic, or dependent on nutrient-poor precipitation for its water and nutrients.[20] Poor fens may also form in areas where the groundwater supplying the fen flows through sediments that don't dissolve well or have low buffering capacity when dissolved.[26] Species richness tends to be lower than that of rich fens but higher than that of bogs.[21] Poor fens, like bogs, are dominated by Sphagnum mosses, which acidify the fen and decrease nutrient availability.[30]

Threats

Fens face many threats, but they are most commonly lost to conversion to agricultural lands.[31] In climates where agriculture is possible, fens have been drained for agricultural use, including crop production, grazing, and hay making.[32] Directly draining a fen is particularly damaging because it lowers the water table.[21] A lower water table can improve aeration and dry out peat, allowing for aerobic decomposition or burning of the organic matter in peat.[20][21] Indirectly draining a fen or decreasing its water supply can be just as damaging. Disrupting groundwater flow into the fen with nearby human activities such as quarrying or residential development changes how much water and nutrients enter the fen.[32] This can make the fen more ombrotrophic (dependent on precipitation), which results in acidification and a change in water chemistry.[31] Species composition changes often follow, and many signature fen species disappear.[31]

Fens are also threatened by invasive species, fragmentation, peat cutting, and pollution.[32] Non-native invasive species, such as the common buckthorn in North America, can invade fens and outcompete rare fen species, reducing biodiversity.[32] Habitat fragmentation threatens fen species, especially rare or endangered species that are unable to move to nearby fens due to fragmentation.[32] Peat cutting, while much more common in bogs, does happen in fens. Peat cut from fens has many uses, including burning as a fuel.[32] Pollutants can alter the chemistry of fens and facilitate invasion of invasive species.[32] Common pollutants of fens include road salts, nutrients from septic tanks, and runoff of agricultural fertilizers and pesticides.[32]

Vegetation

Carr is the northern European equivalent of the wooded swamp of the southeastern United States,[33] also known in the United Kingdom as wet woodland. It is a fens 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.[citation needed]

Temporary flooding by beavers can have negative effects on fens.[34]

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."[35]

Images

  • Kakerdaja fen in spring, Estonia
    Kakerdaja fen in spring, Estonia
  • Spaulding Fen in Wisconsin
    Spaulding Fen in Wisconsin
  • Dernford Fen in Cambridgeshire
    Dernford Fen in Cambridgeshire
  • Sugar Fen in Norfolk
    Sugar Fen in Norfolk

See also

Specific fens

References

  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. ^ Anderson, Dagmar (January 7, 2013). "Cost-effective assessment of conservation of fens". Applied Vegetation Science. 16 – via Wiley Online Library.
  4. ^ a b Keddy (2010), p. 8.
  5. ^ Wheeler & Giller (1982)
  6. ^ Keddy (2010), Chapter 9.
  7. ^ Charlton & Hilts (1989)
  8. ^ Slack et al. (1980)
  9. ^ Schröder et al. (2005)
  10. ^ Godwin et al. (2002), Table 3.
  11. ^ Sheail & Wells (1983)
  12. ^ Keddy (2010), Chapter 13.
  13. ^ a b c Loisel, Julie; Bunsen, Michael (2020). "Abrupt Fen-Bog Transition Across Southern Patagonia: Timing, Causes, and Impacts on Carbon Sequestration". Frontiers in Ecology and Evolution. 8. doi:10.3389/fevo.2020.00273. ISSN 2296-701X.
  14. ^ a b c d e Keddy, Paul A. (2010). Wetland ecology : principles and conservation (2nd ed.). Cambridge: Cambridge University Press. ISBN 978-1-139-22365-2. OCLC 801405617.
  15. ^ a b c d e f g h i j Rydin, Håkan (2013). The biology of peatlands. J. K. Jeglum (Second ed.). Oxford, UK. ISBN 978-0-19-150828-8. OCLC 861559248.{{cite book}}: CS1 maint: location missing publisher (link)
  16. ^ a b van Diggelen, Rudy; Middleton, Beth; Bakker, Jan; Grootjans, Ab; Wassen, Martin (November 2006). "Fens and floodplains of the temperate zone: Present status, threats, conservation and restoration". Applied Vegetation Science. 9 (2): 157–162. doi:10.1111/j.1654-109x.2006.tb00664.x. ISSN 1402-2001.
  17. ^ a b c d Mitsch, William J. (2007). Wetlands. James G. Gosselink (4th ed.). Hoboken, N.J.: Wiley. ISBN 978-0-471-69967-5. OCLC 78893363.
  18. ^ "bayou". dictionary.cambridge.org. Retrieved 2021-02-23.
  19. ^ Canada Committee on Ecological Land Classification. National Wetlands Working Group (1997). The Canadian wetland classification system. Barry G. Warner, C. D. A. Rubec (2nd ed.). Waterloo, Ont.: Wetlands Research Branch, University of Waterloo. ISBN 0-662-25857-6. OCLC 43464321.
  20. ^ a b c d e f g h i Keddy, Paul A. (2010). Wetland ecology : principles and conservation (2nd ed ed.). Cambridge: Cambridge University Press. ISBN 978-1-139-22365-2. OCLC 801405617. {{cite book}}: |edition= has extra text (help)
  21. ^ a b c d e f g h i j k l m Rydin, Håkan (2013). The biology of peatlands. J. K. Jeglum (Second edition ed.). Oxford, UK. ISBN 978-0-19-150828-8. OCLC 861559248. {{cite book}}: |edition= has extra text (help)CS1 maint: location missing publisher (link)
  22. ^ a b Godwin, Kevin S.; Shallenberger, James P.; Leopold, Donald J.; Bedford, Barbara L. (2002-12). "Linking landscape properties to local hydrogeologic gradients and plant species occurrence in minerotrophic fens of New York State, USA: A Hydrogeologic Setting (HGS) framework". Wetlands. 22 (4): 722–737. doi:10.1672/0277-5212(2002)022[0722:llptlh]2.0.co;2. ISSN 0277-5212. {{cite journal}}: Check date values in: |date= (help)
  23. ^ Fitts, Charles R. (2013-01-01), Fitts, Charles R. (ed.), "10 - Groundwater Chemistry", Groundwater Science (Second Edition), Boston: Academic Press, pp. 421–497, ISBN 978-0-12-384705-8, retrieved 2021-03-20
  24. ^ a b c Clark, Ian (2006). "Chapter 6: Weathering". Environmental Geochemistry of Isotopes. University of Ottawa: Unpublished. pp. 1–7.
  25. ^ a b Bourbonniere, Richard A. (2009-01). "Review of Water Chemistry Research in Natural and Disturbed Peatlands". Canadian Water Resources Journal. 34 (4): 393–414. doi:10.4296/cwrj3404393. ISSN 0701-1784. {{cite journal}}: Check date values in: |date= (help)
  26. ^ a b c d e Bedford, Barbara L.; Godwin, Kevin S. (2003-09). "Fens of the United States: Distribution, characteristics, and scientific connection versus legal isolation". Wetlands. 23 (3): 608–629. doi:10.1672/0277-5212(2003)023[0608:fotusd]2.0.co;2. ISSN 0277-5212. {{cite journal}}: Check date values in: |date= (help)
  27. ^ a b c Bartigs, Rodney (Mar. 1984). "Marl Wetlands in Eastern West Virginia: Distribution, Rare Plant Species, and Recent History". Castanea. 49: 17–25 – via JSTOR. {{cite journal}}: Check date values in: |date= (help)
  28. ^ Szumigalski, Anthony R.; Bayley, Suzanne E. (1996-12). "Net above-ground primary production along a bog-rich fen gradient in Central Alberta, Canada". Wetlands. 16 (4): 467–476. doi:10.1007/bf03161336. ISSN 0277-5212. {{cite journal}}: Check date values in: |date= (help)
  29. ^ Bourbonniere, Richard A. (2009-01). "Review of Water Chemistry Research in Natural and Disturbed Peatlands". Canadian Water Resources Journal. 34 (4): 393–414. doi:10.4296/cwrj3404393. ISSN 0701-1784. {{cite journal}}: Check date values in: |date= (help)
  30. ^ a b c d Zoltai, S. C.; Vitt, D. H. (1995), "Canadian wetlands: Environmental gradients and classification", Classification and Inventory of the World’s Wetlands, Dordrecht: Springer Netherlands, pp. 131–137, ISBN 978-94-010-4190-4, retrieved 2021-04-01
  31. ^ a b c van Diggelen, Rudy; Middleton, Beth; Bakker, Jan; Grootjans, Ab; Wassen, Martin (2006-11). "Fens and floodplains of the temperate zone: Present status, threats, conservation and restoration". Applied Vegetation Science. 9 (2): 157–162. doi:10.1111/j.1654-109x.2006.tb00664.x. ISSN 1402-2001. {{cite journal}}: Check date values in: |date= (help)
  32. ^ a b c d e f g h "Threats to Fens". Native Plants and Ecosystem Services. Retrieved 2021-04-01.
  33. ^ Bug Life Archived 2010-03-04 at the Wayback Machine
  34. ^ Reddoch & Reddoch (2005)
  35. ^ 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.

Bibliography

External links

  • Media related to Fens at Wikimedia Commons
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