Meijel ( Dutch: [ˈmɛi.əl] ; Limburgish : Méél ) is a former municipality and a village in south-eastern Netherlands .
75-518: The village was first mentioned in 1303 as "Iohannes et Henricus fratres dicti van der Vloet de Meyele". The etymology is uncertain. It might mean "middle of the forest". Meijel developed on a sandy ridge in the raised bog of the Peel . It became a free heerlijkheid (no fief). In 1716, it became part of the Austrian Upper Guelders . The Catholic St Nicolaas Church is a three-aisled church with
150-447: A distinct type of wetland, shares many biogeochemical characteristics with other wetlands. Like all wetlands, they play an important role in nutrient cycling because they are located at the interface of aerobic (oxic) and anaerobic (anoxic) environments. Most wetlands have a thin top layer of oxygenated soil in contact with the atmosphere or oxygenated surface waters. Nutrients and minerals may cycle between this oxidized top layer and
225-415: A distinction is made between lake mires or 'siltation-formed raised bogs' ( Verlandungshochmoore ) and 'mire-formed raised bogs' ( wurzelechte Hochmoore ). The former emerged in a secondary process after the silting up of lakes or oxbows (see illustration on the right in the sequence). At first, fens emerged under the influence of groundwater ( minerotrophy ). Oxygen deficiencies and high acidity in
300-458: A fen directly is particularly damaging because it lowers the water table. A lower water table can increase aeration and dry out peat, allowing for aerobic decomposition or burning of the organic matter in peat. Draining a fen indirectly by 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
375-592: 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." Rich fens tend to be highly biodiverse and harbor a number of rare or endangered species, and biodiversity tends to decrease as the richness of fen decreases. Fens tend to be found above rocks that are rich in calcium, such as limestone . When groundwater flows past calcareous (calcium-rich) rocks like limestone ( calcium carbonate ),
450-459: A fuel. Pollutants can alter the chemistry of fens and facilitate invasion by invasive species . Common pollutants of fens include road salts, nutrients from septic tanks , and runoff of agricultural fertilizers and pesticides. 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
525-671: A gradient from poor to rich, with bogs at the poor end, extremely rich fens at the rich end, and poor fens in between. In this context, "rich" and "poor" refer to the species richness, or how biodiverse a fen or bog is. The richness of these species is strongly influenced by pH and concentrations of calcium and bicarbonate. These factors assist in identifying where along the gradient a particular fen falls. In general, rich fens are minerotrophic , or dependent on mineral-rich groundwater, while bogs are ombrotrophic , or dependent on precipitation for water and nutrients. Poor fens fall between these two. Rich fens are strongly minerotrophic; that is,
600-412: A large proportion of their water comes from mineral-rich ground or surface water. Fens that are more distant from surface waters such as rivers and lakes, however, are more rich than fens that are connected. This water is dominated by calcium and bicarbonate, resulting in a slightly acidic to slightly basic pH characteristic of rich fens. These conditions promote high biodiversity. Within rich fens, there
675-536: A major determinant of fen biota and biogeochemistry . Fen soils are constantly inundated because the water table is at or near the surface. The result is anaerobic (oxygen-free) soils due to the slow rate at which oxygen diffuses into waterlogged soil. Anaerobic soils are ecologically unique because Earth's atmosphere is oxygenated, while most terrestrial ecosystems and surface waters are aerobic. The anaerobic conditions found in wetland soils result in reduced , rather than oxidized , soil chemistry. A hallmark of fens
750-515: A moist, balanced climate in which to grow. The quantity of precipitation has to be greater than the water losses through discharge and evaporation. In addition, the precipitation must be evenly spread through the year. Raised bogs in Europe have been developing for about 11,000 years, since the beginning of the Holocene and after the retreat of the last ice sheet . As far as their origins are concerned,
825-418: A pH of approximately 5.5 to 4. Peat in poor fens tends to be thicker than that of rich fens, which cuts off vegetation access to the mineral-rich soil underneath. In addition, the thicker peat reduces the influence of mineral-rich groundwater that buffers the pH. This makes the fen more ombrotrophic, or dependent on nutrient-poor precipitation for its water and nutrients. Poor fens may also form in areas where
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#1732859202040900-457: A raised bog on neighbouring mineral soil. The formation of a typical raised bog is a very slow process, which lasts from centuries to a thousand years even in favourable, undisturbed conditions. Furthermore, there are a number of transitional and intermediate bogs , which in different ways combine characteristics of both raised bogs and fens. (See bog .) The main constituents of the peat are rootless peat mosses that grow slowly in height whilst at
975-538: A result of freeze-thaw processes of the surrounding water. The low temperatures prevent full decomposition of the organic material. Polygonal bogs ( Polygonmoore ) are widespread on the Arctic and sub-Arctic plains of Siberia and North America and cover vast areas. They are associated with patterned peatland and ice wedges . A scanty layer of peat-forming vegetation can occur in the inner honeycomb-shaped areas of this frost pattern terrain ( cryoturbation ) and are fed during
1050-601: A small amount dissolves and is carried to the fen supplied by the groundwater. When calcium carbonate dissolves, it produces bicarbonate and a calcium cation according to the following equilibrium: CaCO 3 + H 2 CO 3 ↽ − − ⇀ Ca 2 + + 2 HCO 3 − {\displaystyle {\ce {CaCO3 + H2CO3 <=> Ca^2+ + 2HCO3^-}}} where carbonic acid (H 2 CO 3 )
1125-684: A type of wetland, but its use is generally limited to the southern United States. 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. The result is a large number of wetland classification systems that each define wetlands and wetland types in their own way. However, many classification systems include four broad categories that most wetlands fall into: marsh , swamp, bog , and fen. While classification systems differ on
1200-551: A wetland is. Almost all of the phosphorus that arrives in a wetland does so through sediments or plant litter from other ecosystems. Along with nitrogen, phosphorus limits wetland fertility. Under basic conditions like those found in extremely rich fens, calcium will bind to phosphate anions to make calcium phosphates , which are unavailable for uptake by plants. Mosses also play a considerable role in aiding plants in phosphorus uptake by decreasing soil phosphorus stress and stimulating phosphatase activity in organisms found below
1275-709: A wide tower which was constructed from 1953 to 1955 to replace the church which was destroyed in 1944. Meijel was home to 996 inhabitants in 1840. It was severely damaged during World War II . Meijel was an independent municipality until 2010 when it was merged into Peel en Maas . This Dutch Limburg location article is a stub . You can help Misplaced Pages by expanding it . Raised bog Raised bogs , also called ombrotrophic bogs , are acidic, wet habitats that are poor in mineral salts and are home to flora and fauna that can cope with such extreme conditions. Raised bogs, unlike fens , are exclusively fed by precipitation ( ombrotrophy ) and from mineral salts introduced from
1350-519: Is a large amount of variability. The richest fens are the extreme rich (marl) fens, where marl deposits are often build up. These are often pH 7 or greater. 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 phosphorus and decreasing primary production. Rich bogs with limited primary production can stabilize with
1425-470: Is a more potent greenhouse gas than carbon dioxide. Methanogenic archaea that reside in the anaerobic layers of peat combine carbon dioxide and hydrogen gas to form methane and water. This methane can then escape into the atmosphere and exert its warming effects. Peatlands dominated by brown mosses and sedges such as fens have been found to emit a greater amount of methane than Sphagnum -dominated peatlands such as bogs. Fens play an important role in
1500-408: Is a result of the ground or surface water input. Typically, this input results in higher mineral concentrations and a more basic pH than found in bogs. As peat accumulates in a fen, groundwater input can be reduced or cut off, making the fen ombrotrophic rather than minerotrophic . In this way, fens can become more acidic and transition to bogs over time. Fens can be found around the world, but
1575-457: Is a succession of raised bog types along the line of descent towards the ocean, from northwest to southeast. As a result of peat use, raised bogs have been harvested for peat and cultivated, apart from a few remnants (less than 10% of the original area). The largest contiguous raised bog in central Europe was the Bourtange Moor , which originally covered an area of about 2,300 km including
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#17328592020401650-419: Is abundant in peat. When the organic matter in peat is decomposed in the absence of oxygen, ammonium is produced via ammonification . In the oxidized surface layer of the wetland, this ammonium is oxidized to nitrite and nitrate by nitrification . The production of ammonium in the reduced layer and its consumption in the top oxidized layer drives upward diffusion of ammonium. Likewise, nitrate production in
1725-458: Is difficult for a number of reasons. First, wetlands are diverse and varied ecosystems that are not easily categorized according to inflexible definitions. They are often described as a transition between terrestrial and aquatic ecosystems with characteristics of both. This makes it difficult to delineate the exact extent of a wetland. Second, terms used to describe wetland types vary greatly by region. The term bayou , for example, describes
1800-478: Is estimated that there are approximately 1.1 million square kilometers of fens worldwide, but quantifying the extent of fens is difficult. Because wetland definitions vary regionally, not all countries define fens the same way. In addition, wetland data is not always available or of high quality. Fens are also difficult to rigidly delineate and measure, as they are located between terrestrial and aquatic ecosystems. Rigidly defining types of wetlands, including fens,
1875-420: Is greater than decomposition, which results in the accumulation of organic matter as peat. Resident mosses usually carry out decomposition within the fen, and temperate fens are often driven by plant roots' decomposition. These peat stores sequester an enormous amount of carbon. Nevertheless, it is difficult to determine whether fens net take up or emit greenhouse gases . This is because fens emit methane, which
1950-411: Is low in salt. By contrast, mire-formed raised bogs are created directly on the mineral substrate of low-salt areas without having been initially formed as fens (see figure on the left in the sequence). They are formed either as a primary bog due to the erosion of previously dry mineral soils, for example due to clearing, climate change or infiltration, or as a secondary process as a result of the growth of
2025-459: Is not yet clear how these bogs have emerged as mosses are entirely absent here. Coastal bogs ( Planregenmoore ) or Atlantic bogs, as their names suggest, tend to form close to the sea. In addition, in regions covered by blanket bog, there are also lightly convex coastal bogs with low energy surface relief in level locations. The distribution of coastal bogs in Europe extends from Ireland to the east via South Norway to Southwest Sweden and north to
2100-576: Is produced by the dissolution of carbon dioxide in water. In fens, the bicarbonate anion produced in this equilibrium acts as a pH buffer, which keeps the pH of the fen relatively stable. Fens supplied by groundwater that doesn't flow through minerals and act as a buffer when dissolved tend to be more acidic. The same effect is observed when groundwater flows through minerals with low solubility, such as sand. In extreme rich fens, calcium carbonate can precipitate out of solution to form marl deposits. Calcium carbonate precipitates out of solution when
2175-428: Is strongly decomposed, and an overlying white peat layer which is less decomposed. This difference is a result of changes in the hydrology of the bog. The white peat grew more rapidly under humid conditions than the black peat. This is attributed to a climate change with high precipitation and low evaporation around 1000 to 500 BC. As a result, the peat moss growth grew locally and the black peat/white peat boundary layer
2250-404: Is that a significant portion of their water supply is derived from groundwater (minerotrophy). 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. Groundwater chemistry, in turn, is largely determined by the geology of the rocks that the groundwater flows through. Thus, the characteristics of
2325-613: The Amazon Basin . In these regions, bogs of all kinds and peat deposits of four million square kilometres have been formed, covering three percent of the Earth's surface. In the southern hemisphere low-mineral-rich bogs are rarely formed from peat mosses. Only in the Tierra del Fuego do peat moss raised bogs exist. The most peaty countries in the tropics are found in Southeast Asia. In many cases it
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2400-586: The Annex 1 habitats : active raised bog, turlough (both priority habitats), degraded raised bog (capable of regeneration) and vegetation of depressions (rhynchosporion). These habitats are considered to be among the best examples in Ireland due to their relatively large size and the generally low levels of disturbance. In the Natura form compiled for the site active raised bog was given a rating of A (Excellent value) which emphasises
2475-618: The Black Forest the Wildseemoor has been protected and, in the Vosges on le Tanet , north of the Col de la Schlucht a large area has been protected. The Alpine Foreland , which was formed by ice-age glaciation, is also rich in peatland. The Wurzacher Ried (Haidgauer Regenmoorschild) is considered the largest and best preserved raised bog in central Europe. Other raised bogs and peatland areas include
2550-704: The Federsee , the High Fens on the Germano-Belgian border, the Ewiges Meer near Aurich and the Lengener Meer near Wiesmoor. In 2003, Estonia exported 3.6 million m³ of peat for west European garden use, more than 60% of the state production. In Lithuania 60% of the usable peat area has been prepared for extraction or is already exhausted. Lough Lurgeen Bog and Glenamaddy Turlough Bog contains very good examples of
2625-574: The Lofoten . In North America there are coastal bogs in the area of the Great Lakes (especially in Minnesota and Ontario ). Coastal bogs are also fed exclusively by rain. In the less oceanically influenced climatic regions of North-West Europe (lower precipitation), raised bogs take on the classical lens shape and are called plateau bogs or plateau raised bogs ( Plateauregenmoore ). They grow more strongly in
2700-687: The Okavango Delta in Botswana and the highland slopes in Lesotho . Fens can also be found at the colder latitudes of the Southern Hemisphere. They are found in New Zealand and southwest Argentina, but the extent is much less than that of the northern latitudes. Locally, fens are most often found at the intersection of terrestrial and aquatic ecosystems, such as the headwaters of streams and rivers. It
2775-430: The cycling of nutrients such as carbon, nitrogen, and phosphorus due to the lack of oxygen (anaerobic conditions) in waterlogged organic fen soils. Fens have historically been converted to agricultural land. Aside from such conversion, fens face a number of other threats, including peat cutting, pollution, invasive species, and nearby disturbances that lower the water table in the fen, such as quarrying. Interrupting
2850-432: The partial pressure of carbon dioxide in the solution falls. The decrease in carbon dioxide partial pressure is caused by uptake by plants for photosynthesis or direct loss to the atmosphere. 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. Fen, being
2925-924: The Dutch portion, but only small sections remain. The largest remaining raised bog in northern Europe is the 76 km Lille Vildmose . Other large raised bogs are the Teufelsmoor northeast of Bremen, the Vehnemoor (exhausted) and the Esterweger Dose (formerly about 80 km , exhausted) between Oldenburg and Papenburg. The raised bogs of the Central Uplands of the Harz , Solling , Thuringian Forest ( Großer Beerberg , Schneekopf - Teufelsbad, Fichtenkopf, Saukopf), Giant Mountains , Ore Mountains , Fichtel and Rhön ( Black Moor , Red Moor ) are, by contrast, comparatively small. In
3000-468: The Scandinavian hills, central Finland, Karelia and north Siberia. In North America, Alaska is the main location for string bogs, thanks to its cold continental climate. Frost action plays an important role in these bogs. On the ridges or hummocks, ground ice is found until early summer. Palsa bogs ( Palsamoore or Palsenmoore ) are found on the margins of the Arctic permafrost soils ( tundra ). Here
3075-811: The accumulation of mosses and mycorrhiza , which promote phosphorus cycling and can support the growth of new vegetation and bacteria. Brown mosses (family Amblystegiaceae ) and sedges (genus Carex ) are the dominant vegetation. However, an accumulation of mosses such as Sphagnum can lead to the acidification of the rich fen, potentially converting it into a poor fen. Compared to poor fens, rich fens have higher concentrations of bicarbonate, base cations (Na , Ca , K , Mg ), and sulfate . Poor fens are, in many ways, an intermediate between rich fens and bogs. Hydrologically, they are more similar to rich fens than to bogs, but regarding vegetation composition and chemistry, they are more similar to bogs than rich fens. They are much more acidic than their rich counterparts, with
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3150-425: The air. They thus represent a special type of bog , hydrologically , ecologically and in terms of their development history, in which the growth of peat mosses over centuries or millennia plays a decisive role. They also differ in character from blanket bogs which are much thinner and occur in wetter, cloudier climatic zones. Raised bogs are very threatened by peat cutting and pollution by mineral salts from
3225-434: The bog 'floor'. Here fresh organic substances (peat formation horizon) are created by the growth and dying of plant elements. The "catotelm" (Greek: kato = below) is the underlying water-saturated part with less biological activity. This layer is counted as a geological subsoil due to the small earth-forming processes that are still going on and is known as the peat preservation horizon ( Torferhaltungshorizont ). In raised bogs,
3300-471: The central area of these bogs, there are always large kolks. In northern Russia and western Siberia, kermis frequently occur in giant complexes where the bogs have grown into one another. Kermis are also found in Finland in the central and northern boreal forest zone. String bogs or aapa fens ( Aapamoore or Strangmoore ) are typically found on the northern fringes of the distribution area for raised bogs, in
3375-433: The centre than at the margins. This results in the centre of the bog bulging, hence the name "raised bog". This bulging can be several metres high. As a result, the perimeter of the bog is more or less inclined, and is known as the rand . The sloping bog sides of larger bogs are traversed by drainage channels or soaks ( Rüllen ) through which excess water is discharged. Other characteristic structures of these raised bogs are
3450-509: The classical, lens-shaped bogs of northwest Germany . The bogs are not influenced by mineral-rich groundwater or surface water, but are fed exclusively by precipitation — mainly rainwater, hence their alternative German designation of Regenmoor or "rain-fed bog". Thus the latter refers to all bogs, not just those that are arched or only slightly arched, but which nevertheless are characterized by an extreme mineral salt deficiency and other resulting ecological properties. A living raised bog needs
3525-433: The constantly moist substrate inhibited the decomposition of dead plant parts and led to peat formation. Thus the raised bog rises very slowly above the groundwater level, hence its name. As the resulting peat slowly rises above the influence of mineral salts in the groundwater, it reaches a point where the development of the raised bog begins to change in nature; that is, the bog now becomes fed solely by rainwater, which
3600-556: The continuous input of groundwater stimulates production. Bogs , which lack this input of groundwater , have much lower primary production. Carbon from all types of wetlands, including fens, arrives mostly as organic carbon from either adjacent upland ecosystems or by photosynthesis in the wetland itself. Once in the wetland, organic carbon generally has three main fates: oxidation to CO 2 by aerobic respiration , burial as organic matter in peat, or decomposition to methane . In peatlands, including fens, primary production by plants
3675-480: The entire system is very important from both a hydrological and ecological perspective. A region of peatland extends from Alaska in the west to the coast of the Atlantic in the east, and is comparable in size to that of West Siberia. A zone of domed raised bogs adjoins the zones of palsa bogs and string fens. In the direction of descent towards the ocean, blanket bogs occur east of Hudson Bay. These are superseded towards
3750-406: 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." Three examples are presented below to illustrate more specific definitions for
3825-756: The fen. This can make the fen more ombrotrophic (dependent on precipitation), which results in acidification and a change in water chemistry. This directly impacts the habitat of these species, and many signature fen species disappear. Fens are also threatened by invasive species , fragmentation , peat cutting, and pollution. Non-native invasive species, such as the common buckthorn in North America, can invade fens and outcompete rare fen species, reducing biodiversity. Habitat fragmentation threatens fen species, especially rare or endangered species that are unable to move to nearby fens due to fragmentation. Peat cutting, while much more common in bogs, does happen in fens. Peat cut from fens has many uses, including burning as
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#17328592020403900-563: The flat, treeless raised bog core with its characteristic microrelief of shallow wet depressions or flarks ( Schlenken ) alternating with hummocks ( Bülten ) of drier peat moss. Larger accumulations of water in the middle of the bogs are called kolks or bog ponds (of humic acid -rich water); the wet area on the outer margins is known as a moat or lagg . Genuine ombrotrophic bogs on the North German Plain are usually sharply divided into two layers: an underlying black peat layer, which
3975-540: The flow of mineral-rich water into a fen changes the water chemistry, which can alter species richness and dry out the peat. Drier peat is more easily decomposed and can even burn. Fens are distributed around the world, but are most frequently found at the mid-high latitudes of the Northern Hemisphere. 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
4050-459: The global nitrogen cycle due to the anaerobic conditions found in their soils, which facilitate the oxidation or reduction of one form of nitrogen to another. Most nitrogen arrives in wetlands as nitrate from runoff , in organic matter from other areas, or by nitrogen fixation in the wetland. There are three main forms of nitrogen found in wetlands: nitrogen in organic matter, oxidized nitrogen ( nitrate or nitrite ), and ammonium . Nitrogen
4125-554: The groundwater supplying the fen flows through sediments that don't dissolve well or have low buffering capacity when dissolved. Species richness tends to be lower than that of rich fens but higher than that of bogs. Poor fens, like bogs, are dominated by Sphagnum mosses, which acidify the fen and decrease nutrient availability. One of the many threats that fens face is conversion to agricultural lands. Where climates are suitable, fens have been drained for agricultural use alongside crop production, grazing , and hay making . Draining
4200-453: The importance of the site. Raised bog habitats are now very rare in Europe and it has recently been estimated that the Republic of Ireland contains 50% of the relatively intact oceanic raised bog systems in Europe. The site contains the second largest area of intact raised bog surface in Ireland. The combination of raised bog, oligotrophic lake and turlough habitats is unique in Ireland and thus
4275-494: The kermi bog type. They represent probably the most important type of raised bog on earth. The Vasyugan Swamp in this region, is the largest bog system on earth and covers more than 50,000 km (19,000 sq mi). It is estimated to contain over 14 billion tonnes of peat deposits. The largest central European raised bog areas are the southern North Sea coastal area and the Alpine Foreland . As in North America there
4350-477: The margins of lowland bogs i.e. fens , or transition into them. Kermi bogs ( Kermimoore, Schildhochmoore, Strangmoore or Blankenmoore ) or kermi raised bogs have only a slightly domed shape. The surface of the bog rises steadily from the broad lagg zone. Kermis have ridge-shaped hummocks of peat moss, that are aligned with the contours of the bog. The flarks or elongated depressions are generally tub-shaped and hardly distinguishable externally from kolks . In
4425-410: The moss cover. Helophytes have been shown to bolster phosphorus cycling within fens, especially in fen reestablishment, due to their ability to act as a phosphorus sink, which prevents residual phosphorus in the fen from being transferred away from the it. Under normal conditions, phosphorus is held within soil as dissolved inorganic phosphorus, or phosphate , which leaves trace amounts of phosphorus in
4500-429: The oxidized layer and nitrate consumption in the reduced layer by denitrification drives downward diffusion of nitrate. Denitrification in the reduced layer produces nitrogen gas and some nitrous oxide , which then exit the wetland to the atmosphere. Nitrous oxide is a potent greenhouse gas whose production is limited by nitrate and nitrite concentrations in fens. Nitrogen, along with phosphorus, controls how fertile
4575-442: The presence of peat. In The Biology of Peatlands fens are defined by the following 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. Hydrological conditions, as seen in other wetlands, are
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#17328592020404650-520: The reduced layer below, undergoing oxidation and reduction reactions by the microbial communities adapted to each layer. Many important reactions take place in the reduced layer, including denitrification , manganese reduction, iron reduction, sulfate reduction, and methanogenesis . Because wetlands are hotspots for nutrient transformations and often serve as nutrient sinks, they may be constructed to treat nutrient-rich waters created by human activities. Fens are also hotspots for primary production , as
4725-573: The rest of the ecosystem. Iron is important in phosphorus cycling within fens. Iron can bind to high levels of inorganic phosphate within the fen, leading to a toxic environment and inhibition of plant growth. In iron-rich fens, the area can become vulnerable to acidification, excess nitrogen and potassium, and low water levels. Peat soils play a role in preventing the bonding of irons to phosphate by providing high levels of organic anions for iron to bind to instead of inorganic anions such as phosphate. Bogs and fens can be thought of as two ecosystems on
4800-478: The ridges of the string bogs can grow into hummocks several metres high. Like string bogs, the so-called palsas frequently lie within peatlands fed by mineral soil water. Some are surrounded by water-filled, ditch-like hollows. Peat formation is limited; these bogs are peat deposits from warmer, interglacial periods and did not experience frost heaving of their inner core of ice until the climate became colder. These ice lenses increase in size from year to year as
4875-407: The same time the lower layer becomes peat as the air is excluded. Depending on the geographical location, various species of peat moss are involved in making a raised bog. The growth rate of the peat layer is only about a millimetre per year. Growing bogs can be divided into two layers. The ' acrotelm ' ( Greek : akros = highest; telma = bog) is the upper part and includes the vegetation layer and
4950-400: The short summers with sufficient moisture, because the meltwater is prevented from draining away by the raised polygonal margins. The peat layers can attain a thickness of 0.3 to 1 m (1.0–3.3 ft). The west Siberian raised bog area covers 700,000 km (270,000 sq mi). The large bogs have domes in the centre up to 10 m (33 ft) high. They are predominantly of
5025-498: The sub-polar zone, north of the 66th latitude in the northern hemisphere. Here, raised bogs only occur as islands within wetlands supplied by mineral soil water. On level ground these islands are irregularly distributed; on hillsides they form ridges parallel to the contours and at right angles to line of slope. The ridges separate boggy hollows of mineral soil known by the Finnish word, rimpis . The main distribution area for string bogs are
5100-465: The surrounding land (due to agriculture and industry ). The last great raised bog regions are found in western Siberia and Canada . The term raised bog derives from the fact that this type of bog rises in height over time as a result of peat formation. They are like sponges of peat moss, full of water, that form a more or less dome shape in the landscape. In Germany, the term Hochmoor ( lit. ' high bog ' ) strictly refers only to
5175-413: The temperature. In addition, the relief of the terrain has an influence on the water discharge behaviour and thus the shape of a raised bog. This results in geographical limitations to the formation of raised bogs. Favourable conditions for the development of raised bogs are found mainly in North America ( Canada and Alaska ), Northern Europe and Western Siberia , South America , Southeast Asia and in
5250-538: The term fen . In the Canadian Wetland Classification System, fens are defined by six characteristics: In the textbook Wetland Ecology: Principles and Conservation , Paul A. Keddy offers a somewhat simpler definition of a fen 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." This definition differentiates fens from swamps and marshes by
5325-412: The upper peat layer is called white peat, since it consists of largely undecomposed light brown peat mosses. The lower layer is black peat, which is already well humified and has a black-brown colour with still recognizable plant remains. The formation of raised bogs is dependent on the climate, that is to say the amount of precipitation and rate of evaporation, which in turn are decisively determined by
5400-430: The vast majority are located at the mid to high latitudes of the Northern Hemisphere. They are dominated by sedges and mosses , particularly graminoids that may be rarely found elsewhere, such as the sedge species Carex exilis . Fens are highly biodiverse ecosystems and often serve as habitats for endangered or rare species, with species composition changing with water chemistry. They also play important roles in
5475-412: The west by plateau bogs in the area of the large lakes and, eventually, by kermi bogs. Intermediate bog A fen is a type of peat -accumulating wetland fed by mineral-rich ground or surface water . It is one of the main types of wetland along with marshes , swamps , and bogs . Bogs and fens, both peat-forming ecosystems , are also known as mires . The unique water chemistry of fens
5550-636: The world. In the United States, fens are most common in the Midwest and Northeast, but can be found across the country. In Canada, fens are most frequent in the lowlands near Hudson Bay and James Bay , but can also be found across the country. Fens are also spread across the northern latitudes of Eurasia, including Britain and Ireland, as well as Japan, but east-central Europe is especially rich in fens. Further south, fens are much rarer, but do exist under specific conditions. In Africa, fens have been found in
5625-427: Was formed, although this did not develop simultaneously in all raised bogs. Raised bogs also occur in precipitation-rich upland regions at the montane and, more rarely, alpine levels (i.e. above the tree line ). As a result of the sloping terrain, they often have a characteristic, asymmetric or non-concentric appearance. Mountain or upland bogs may be topographically divided into: All these bog types may occur on
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