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| − | {{redirect|Pteridium|the Ediacaran organism|Pteridinium}}
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| | | name = Bracken | | | name = Bracken |
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| − | '''Bracken''' (''Pteridium'') is a [[genus]] of large, coarse [[fern]]s in the [[family (biology)|family]] [[Dennstaedtiaceae]]. Ferns (Pteridophyta) are [[vascular]] plants that have alternating generations, large plants that produce spores and small plants that produce [[gamete|sex cells]] (eggs and sperm). Brackens are noted for their large, highly divided leaves. They are found on all continents except Antarctica and in all environments except deserts, though their typical habitat is [[moorland]]. The genus probably has the widest distribution of any fern in the world.
| + | See also [[Pteridium aquilinum]]. |
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| − | In the past, the genus was commonly treated as having only one species, ''Pteridium aquilinum'', but the recent trend is to subdivide it into about ten species.
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| − | Like other ferns, brackens do not have seeds or fruits, but the immature fronds, known as ''[[fiddlehead]]s'', are sometimes eaten, although some are thought to be carcinogenic. (see [[Bracken#Poisoning|Poisoning]])
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| − | The word bracken is of [[Old Norse]] origin, related to Swedish ''bräken'' and Danish ''bregne'', both meaning fern.
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| − | ==Description and biology==
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| − | Evolutionarily, bracken may be considered one of the most successful ferns. Bracken, like heather, is typically found in moorland environments, and is commonly referred to by local populations in the north of England as 'Moorland Scrub'. It is also one of the oldest ferns, with fossil records over 55 million years old having been found. The plant sends up large, triangular fronds from a wide-creeping underground rootstock, and may form dense thickets. This rootstock may travel a metre or more underground between fronds. The fronds may grow up to {{convert|2.5|m|ft|abbr=on}} long or longer with support, but typically are in the range of {{convert|0.6|–|2|m|ft|abbr=on}} high. In cold environments, bracken is [[deciduous]] and, as it requires well-drained soil, is generally found growing on the sides of hills.
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| − | [[Image:Pteridium leaf kz1.jpg|thumb|left|Sori on outer edge under the leaves]]
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| − | The [[spores]] are contained in structures found on the underside of the leaf called [[Sorus|sori]]. The linear pattern of these is different from other ferns which are circular and towards the centre.
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| − | ==Distribution==
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| − | ''[[Pteridium aquilinum]]'' (bracken or common bracken) is the most common species with a [[cosmopolitan distribution]], occurring in [[temperateness|temperate]] and [[subtropical]] regions throughout much of the world. It is a prolific and abundant plant in the moorlands of Great Britain, where it is limited to altitudes of below 600 metres. It does not like poorly drained marshes or fen. It has been observed growing in soils from [[pH]] 2.8 to 8.6. Exposure to cold or high pH inhibits its growth. It causes such a problem of invading pastureland that at one time the British government had an eradication programme. Special filters have even been used on some British water supplies to filter out the bracken spores.<ref>{{cite web|url=https://www.independent.co.uk/arts-entertainment/spores-for-thought-1364558.html|title=SPORES FOR THOUGHT|author=|date=22 September 1996|website=independent.co.uk|accessdate=6 April 2018}}</ref> [https://species.nbnatlas.org/species/NBNSYS0000002031 NBN distribution map for the United Kingdom]
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| − | Bracken is a characteristic moorland plant in the UK which over the last decades has increasingly out-competed characteristic ground-cover plants such as [[Molinia|moor grasses]], [[cowberry]], [[bilberry]] and [[Ericaceae|heathers]] and now covers a considerable part of upland moorland.
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| − | Once valued and gathered for use as animal bedding, tanning, soap and glass making and as a fertiliser, bracken is now seen as a pernicious, invasive and opportunistic plant, taking over from the plants traditionally associated with open moorland and reducing easy access by humans. It is toxic to cattle, dogs, sheep, pigs and horses and is linked to cancers in humans.<ref name=Potter>{{cite journal|last1=Potter|first1=D.M.|title=Carcinogenic effects of ptaquiloside in bracken fern and related compounds|journal=British Journal of Cancer|date=4 September 2000|volume=83|issue=7|pages=914–920|doi=10.1054/bjoc.2000.1368|pmid=10970694|pmc=2374682}}</ref> It can harbour high levels of sheep ticks, which can pass on Lyme Disease. Grazing provided some control by stock trampling but this has almost ceased since the [[2007 United Kingdom foot-and-mouth outbreak|2007 foot-and-mouth disease outbreak]] reduced commercial livestock production. Global climatic changes have also suited bracken well and contributed to its rapid increase in land coverage.
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| − | Bracken is a well-adapted pioneer plant which can colonise land quickly, with the potential to extend its area by as much as 1–3% per year. This ability to expand rapidly is at the expense of other plants and wildlife, can cause major problems for land users and managers. It colonises ground with an open vegetation structure but is slow to colonise healthy, well managed heather stands.
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| − | The biodiversity that depends on these uplands is very special and very rich. Many of the species only occur on upland moorland, tied to features unique to the habitat. The loss and degradation of such areas due to the dominance of bracken has caused many species to become rare and isolated.{{Citation needed|date=April 2014}}
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| − | ;species<ref>[http://www.theplantlist.org/tpl1.1/search?q=Pteridium The Plant List, search for ''Pteridium'']</ref>
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| − | {{columns-list|colwidth=30em|
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| − | # ''[[Pteridium aquilinum]]'' - nearly cosmopolitan
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| − | # ''[[Pteridium arachnoideum]]'' - Mexico, Central + South America, [[Galápagos]]
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| − | # ''[[Pteridium caudatum]]'' - Mexico, Central + South America, Florida, West Indies
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| − | # ''[[Pteridium centrali-africanum]]'' - Zaire, Zambia, Tanzania, Burundi
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| − | # ''[[Pteridium esculentum]]'' - China, SE Asia, Australia
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| − | # ''[[Pteridium falcatum]]'' - [[Guangxi]]
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| − | # ''[[Pteridium feei]]'' - Mexico, Central America
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| − | # ''[[Pteridium lineare]]'' - [[Yunnan]]
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| − | # ''[[Pteridium revolutum]]'' - China
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| − | # ''[[Pteridium tauricum]]'' - [[Caucasus]]
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| − | # ''[[Pteridium yunnanense]]'' - [[Yunnan]]
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| − | }}
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| − | ==Fungi associations==
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| − | Woodland [[fungi]] can be found growing under the bracken canopy, for example ''[[Mycena epipterygia]]''. Both ''[[Camarographium stephensii]]'' and ''[[Typhula quisquiliaris]]'' grow primarily from dead bracken stems.
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| − | ==Other plant associations==
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| − | [[Allelopathy]]: Bracken fern is known to produce and release allelopathic chemicals, which is an important factor in its ability to dominate other vegetation, particularly in regrowth after fire. Its chemical diffusions, shady canopy and its thick litter inhibit other plant species from establishing themselves – with the occasional exception of plants which support rare butterflies. Herb and tree seedling growth may be inhibited even after bracken fern is removed, apparently because active plant toxins remain in the soil.
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| − | Brackens substitute the characteristics of a woodland [[Canopy (forest)|canopy]], and are important for giving shade to European plants such as [[common bluebell]] and [[Anemone nemorosa|wood anemone]], where the woodland does not exist. These plants are intolerant to stock trampling. Dead bracken provides a warm microclimate for development of the immature stages. [[Climbing corydalis weevil|Climbing corydalis]], [[Gladiolus|wild gladiolus]] and [[chickweed wintergreen]] also seem to benefit from the conditions found under bracken stands.
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| − | The high humidity helps mosses survive underneath including ''Campylopus flexuosus'', ''[[Hypnum cupressiforme]]'', ''[[Polytrichum commune]]'', ''Pseudoscelopodium purum'' and ''Rhytidiadelphus squarrosus''.
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| − | ==Animal species that use bracken==
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| − | {{Refimprove section|date=October 2011}}
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| − | Brackens of the Northern Hemisphere are used as food plants by the [[larva]]e of some [[Lepidoptera]] species including [[dark green fritillary]], [[dot moth]], [[high brown fritillary]], [[Phymatopus|gold swift]], [[Pharmacis|map-winged swift]], [[pearl-bordered fritillary]], [[orange swift]], [[small angle shades]], [[small pearl-bordered fritillary]]. They also form an important ecological partnership with plants such as [[Viola (plant)|violet]] and [[cow-wheat]] (''[[Melampyrum pratense]]'') for various ''[[Boloria]]'' fritillary species.
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| − | It is also a favoured haunt of the sheep tick ''[[Ixodes ricinus]]'' which can carry [[lyme disease]].
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| − | Between 27 and 40{{vague|date=October 2011}} invertebrates (including nine moths) in the UK feed on bracken. These include the [[sawfly]], a [[planthopper]] (''Dytroptis pteridis''), the [[map-winged swift]] moth caterpillar, brown silver-line moth caterpillar (''[[Petrophora chlorosata]]'') and ''[[Paltodora]] cytisella''. The numbers feeding on the bracken increase as the season progresses due to the decreasing levels of toxin, and the production of nectaries in the spring, food for ants which in turn may kill any [[herbivorous]] insects in the vicinity.
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| − | Where bracken is dominant it excludes most specialist heathland/moorland bird species of conservation concern, although there are a few species that may benefit from a certain proportion of bracken. Deeper bracken stands provide a good food site for many resident or breeding birds, such as threatened ground-nesting species [[Eurasian skylark|skylark]], [[yellowhammer]], [[Eurasian curlew|curlew]] and [[northern lapwing|lapwing]]. Some British birds such as the [[whinchat]] and the [[European nightjar|nightjar]] use bracken as their preferred habitats. The nightjar may lay its eggs on the bare ground under the bracken. The [[skylark]] often nests in bracken and uses it for cover. Small stands of bracken provide nesting, feeding and roosting habitat for a variety of smaller birds, including the [[willow warbler]] (which will also use bracken to construct its nest), the [[tree pipit]], the [[yellowhammer]], the [[ring ouzel]], the [[Eurasian woodcock|woodcock]] and the [[twite]].
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| − | These stands also give cover, especially during the nesting season, from predators such as birds of prey and crows; and from free-ranging dogs and users straying off the paths which, usually unintentionally, disrupts nesting and can identify the nest site to predators. On heavily used spaces, this may be an important protection.
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| − | The [[Vipera berus|European adder]] can be found basking on bracken, the colour of their skin concealing them.
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| − | ==Uses==
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| − | {{Refimprove section|date=July 2010}}
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| − | [[Image:Curled bracken fronds.JPG|thumb|Young bracken fronds curled]]
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| − | Bracken [[fiddlehead]]s (the immature, tightly curled emerging fronds) have been eaten by many cultures throughout history, and are still commonly used today as a foodstuff. Bracken fiddleheads are either consumed fresh (and cooked) or preserved by salting, pickling, or sun drying. In Korea,<ref>{{cite web|title=Dol Sot Bibimbap|url=http://korean-cuisine.blogspot.com/2010/06/dol-sot-bibimbap.html|work=Korean cuisine}}</ref> where they are called ''gosari'' (고사리), they are a typical ingredient in the mixed rice dish called ''[[bibimbap]]''.
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| − | The British Royal Horticultural Society recommends against consumption of bracken either by humans or livestock, since it contains carcinogens linked with oesophageal and stomach cancer.<ref>{{cite web|title=Dol Sot Bibimbap|url=http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=445}}</ref> However, the poison found in bracken, [[ptaquiloside]], is both water-soluble and is destroyed in heat and alkaline conditions.<ref>{{cite web|url=http://www.fs.fed.us/database/feis/plants/fern/pteaqu/all.html|title=Pteridium aquilinum|author=|date=|website=www.fs.fed.us|accessdate=6 April 2018}}</ref><ref name="atlantic">{{cite web|url=https://www.theatlantic.com/health/archive/2011/06/the-bracken-fern-a-natural-born-killer/241271/|title=The Bracken Fern: A Natural Born Killer?|first=Hank|last=Shaw|date=|website=theatlantic.com|accessdate=6 April 2018}}</ref> Despite this, moderation of consumption is still recommended to mitigate chance of throat and stomach cancers.<ref name="atlantic"/>
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| − | Both [[frond]]s and [[rhizome]]s have been used to brew [[beer]],<ref>{{cite book|last1=Jones|first1=David L.|title=Encyclopaedia of ferns : an introduction to ferns, their structure, biology, economic importance, cultivation and propagation|date=1987|publisher=Timber Press|location=Portland, Ore.|isbn=0881920541|page=13}}</ref> and the rhizome [[starch]] has been used as a substitute for [[arrowroot]].{{Citation needed|date =December 2014}} Bread can be made out of dried and powdered rhizomes alone or with other [[flour]]. [[Indigenous peoples of the Americas]]{{Which|date=December 2014}} cooked the rhizomes, then peeled and ate them or pounded the starchy fiber into flour.{{Citation needed|date =December 2014}} In [[Japan]], where it is known as {{Nihongo||蕨|warabi}}, starch from the rhizomes is used to make confections, most significantly [[warabimochi]].
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| − | Bracken is called ''wiwnunmí útpas'' ‘[[huckleberry]]’s blanket’ by the Umatilla Indians of the Columbia River in the United States Northwest. The fronds were used to cover a basket full of huckleberries in order to keep them fresh.{{Citation needed|date=July 2010}}
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| − | The [[Māori people|Māori]] of New Zealand used the rhizomes of ''P. esculentum'' (''aruhe'') as a staple food, especially for exploring or hunting groups away from permanent settlements; much of the widespread distribution of this species in present-day New Zealand is in fact a consequence of prehistoric deforestation and subsequent tending of ''aruhe'' stands on rich soils (which produced the best rhizomes). The rhizomes were air-dried so that they could be stored and became lighter; for consumption, they were briefly heated and then softened with a ''patu aruhe'' (rhizome pounder); the starch could then be sucked from the fibers by each diner, or collected if it were to be prepared for a larger feast. ''Patu aruhe'' were significant items and several distinct styles were developed.<ref>{{cite journal |author1=McGlone, Matt S. |author2=Wilmshurst, Janet M. |author3=Leach, Helen M. |title=An ecological and historical review of bracken (''Pteridium esculentum'') in New Zealand, and its cultural significance |journal=[[New Zealand Journal of Ecology]] |volume=28 |pages=165–184 |year=2005 |url=http://www.newzealandecology.org/nzje/free_issues/NZJEcol29_2_165.pdf<!-- You might want to periodically check the link, because it has been announced that the fulltext will soon be closed except for subscribers. Change to abstract when this becomes the case. --> |format=PDF}}</ref>
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| − | In East Asia, ''Pteridium aquilinum'' (bracken [[fiddlehead]]s) is eaten as a vegetable, called ''warabi'' (蕨 / わらび) in Japan, ''gosari'' (고사리) in Korea, and ''juécài'' (蕨菜) in China and Taiwan. In Korea, a typical ''[[banchan]]'' (small side dish) is ''gosari-namul'' (고사리나물) that consists of prepared bracken [[Fiddlehead fern|fiddleheads]] that has been sauteed. It is a component of the popular dish ''[[bibimbap]]''.
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| − | Bracken has been shown to be [[carcinogen]]ic in some animals<ref name=Evans71>{{cite journal |vauthors=Evans IA, Widdop B, Jones RS |title=The possible human hazard of the naturally occurring bracken carcinogen |journal=Biochem. J. |volume=124 |issue=2 |pages=29P–30P |date=September 1971 |pmid=5158492 |pmc=1177200 |display-authors=etal}}</ref> and some have suggested it could have some part in causing the high incidence of [[stomach cancer]] in Japan.<ref name=Evans71/> It is currently under investigation as a possible source of new [[insecticide]]s.<ref>{{cite journal |vauthors=Jbilou R, Amri H, Bouayad N, Ghailani N, Ennabili A, Sayah F |title=Insecticidal effects of extracts of seven plant species on larval development, α-amylase activity and offspring production of ''Tribolium castaneum'' (Herbst) (Insecta: Coleoptera: Tenebrionidae) |journal=Bioresour. Technol. |volume=99 |issue=5 |pages=959–64 |date=March 2008 |pmid=17493805 |doi=10.1016/j.biortech.2007.03.017 |url=http://linkinghub.elsevier.com/retrieve/pii/S0960-8524(07)00247-7}}</ref>
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| − | Uncooked bracken contains the [[enzyme]] [[thiaminase]], which breaks down [[thiamine]]. Eating excessive quantities of bracken can cause [[beriberi]], especially in creatures with simple stomachs. [[Ruminant]]s are less vulnerable because they synthesize thiamine.{{Citation needed|date=July 2010}}
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| − | It was traditionally used (and still is in certain areas like mid-Wales) for animal bedding, which later broke down to a rich mulch which could be used as fertilizer.<ref name="abdn.ac.uk">{{cite web |url=http://www.abdn.ac.uk/organic/organic_24.php |title=Archived copy |accessdate=2009-07-08 |deadurl=yes |archiveurl=https://web.archive.org/web/20091212233858/http://www.abdn.ac.uk/organic/organic_24.php |archivedate=2009-12-12 |df= }}</ref>
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| − | When used by gardeners as a winter [[mulch]] it has been shown to reduce the loss of [[potassium]] and [[nitrogen]] and to lower soil [[pH]].<ref name="abdn.ac.uk"/>
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| − | Other uses were as packing material for products such as earthenware, as a fuel, as a form of thatch. The ash was used for degreasing woolen cloth.{{Citation needed|date =December 2014}}
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| − | The ash of bracken fern was used in making [[forest glass]] in Central Europe from about 1000 to 1700.{{Citation needed|date =December 2014}}
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| − | Bracken is currently harvested in the Lake District, Cumbria, United Kingdom to make commercial composts.{{Citation needed|date =December 2014}}
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| − | A quick and easy [[Urtica dioica#Nettle sting treatment|remedy for nettle stings]] is to rub bracken on the affected area. The juice it releases alleviates the sting, and bracken often grows near stinging nettle.{{Citation needed|date=September 2014}}
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| − | ==Poisoning==
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| − | The plant is [[carcinogenic]] to animals such as mice, rats, horses and cattle when ingested, although they will usually avoid it unless nothing else is available. Young stems are quite commonly used as a vegetable in China, Japan and Korea. However, some researchers suspect a link between consumption and higher stomach cancer rates.<ref name=Evans71/> The spores have also been implicated as a carcinogen. Danish scientist Lars Holm Rasmussen released a study in 2004 showing that the carcinogenic compound in bracken, [[ptaquiloside]] or PTA, can leach from the plant into the water supply, which may explain an increase in the incidence of gastric and esophageal cancers in bracken-rich areas.<ref>{{cite web|url=https://www.theguardian.com/society/2004/sep/09/research.science|title=The fatal fern|first=Kate|last=Ravilious|date=9 September 2004|website=the Guardian|accessdate=6 April 2018}}</ref>
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| − | In cattle, bracken poisoning can occur in both an acute and chronic form, acute poisoning being the most common. In pigs and horses bracken poisoning induces vitamin B deficiency.<ref>{{cite book |author1=Auld, RA |author2=Medd, RW |title=Weeds |publisher=Inkata Press |location=Sydney |year=1992 }}</ref> Poisoning usually occurs when there is a shortage of available grasses such as in drought or snowfalls.
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| − | Along with the DNA damage caused by [[ptaquiloside]] it is shown that chemicals in the fern can damage blood cells and can destroy [[thiamine|Vitamin B1]]. This in turn causes [[beriberi]], a disease normally linked to nutritional deficiency.
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| − | [[Hydrogen cyanide]] is released by the young fronds of bracken when eaten by mammals or insects.<ref>{{cite journal|last=Amelot ME|first=Alonso|date=February 2005|title=Kinetics of the natural evolution of hydrogen cyanide in plants in neotropical Pteridium arachnoideum and its ecological significance|journal=Journal of Chemical Ecology|volume=31 | issue = 2|pages=315–31|doi=10.1007/s10886-005-1343-z|pmid=15856786}}</ref> Two major insect [[moulting]] hormones, alpha [[ecdysone]] and 20-hydroxyecdysone, are found in bracken. These cause uncontrollable, repeated moulting in insects ingesting the fronds, leading to rapid death.<ref>{{cite journal | title= Insect Hormones: Alpha Ecdysone and 20-Hydroxyecdysone in Bracken Fern|journal= Science Classic |volume=157 |pages=1436–1438|date=22 September 1967 |doi= 10.1126/science.157.3795.1436 |issue=3795}}</ref>
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| − | ==Archaeology==
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| − | [[File:Bleak hillside with bracken - geograph.org.uk - 1618991.jpg|thumb|200px|Bracken in Ireland with a linear pattern running across the hillside, a possible indication of past cultivation.]]
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| − | Many sites have many archaeological remains dating from the Neolithic and Bronze Ages through to the Industrial Revolution. The root systems of established bracken stands degrade archaeological sites by disrupting the strata and other physical evidence. These rhizomes may travel a metre or more underground between fronds and form 90% of the plant, with only the remainder being visible.
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| − | ==Control==
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| − | Some small level of scattered cover can provide beneficial habitats for some wildlife, at least in the UK (as given above). However, on balance, removing bracken encourages primary habitats to re-establish, which are of greater importance for wildlife. Control is a complex question with complex answers, which need to form part of a wider approach. Management can be difficult and expensive; plans may need to be about cost-effective, practical limitation and control rather than give an expectation for eradication.
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| − | All methods need follow-up over time, starting with the advancing areas first. Given the decades elapsed to arrive at the current levels of coverage on many sites, slowing or reversing the process will be also of necessity long-term, with consistency and persistence from all parties being key.
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| − | Various techniques are recommended by [[Natural England]] and the [[RSPB]] to control bracken either individually or in combination [https://web.archive.org/web/20140815035945/http://www.rspb.org.uk/ourwork/farming/advice/details.aspx?id=204253 RSPB Bracken management in the uplands].
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| − | * Cutting — once or twice a year, repeatedly cutting back the fronds for at least 3 years
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| − | * Crushing/rolling — using rollers, again for at least 3 years
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| − | * Livestock treading — during winter, encouraging livestock to bracken areas with food. They trample the developing plants and allow frost to penetrate the [[rhizomes]]. In May and June, temporary close grazing or mob stocking on small areas away from nests, particularly using cattle, horses, pigs or ponies may crush emerging bracken fronds resulting in reduced bracken cover. Sufficient fodder will be required to prevent livestock eating the bracken. This may suit steep areas where human access is difficult and herbicide undesirable.
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| − | * Herbicide — [[Asulam]] (also known as Asulox) is selective for ferns; [[glyphosate]] is not; but the latter has the advantage that the effects can be seen soon after application. They are applied when the fronds are fully unfurled to ensure that the chemical is fully absorbed. Rare ferns such as adder’s tongue (''[[Ophioglossum vulgatum]]''), killarney (''[[Trichomanes speciosum]]'') and lemon-scented ferns can also be found in similar habitats and it is important that these are not destroyed in the process of bracken control.
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| − | [[Natural England]] recommends that only [[Asulam]] can be sprayed aerially, Glyphosate requires spot treatment, e.g. using a weedwiper or knapsack spray. The toxicity of [[Asulam]] is low and has been generally highly cost-effective but its use is now restricted by the EU after 2012, at least until specific registered uses can be defined.
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| − | Selective sprays like Starane, Access, Metsulfuron 600WG, etc. work well but only if sprayed in late autumn so the rhizomes store food for winter and hence absorb the poison.
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| − | On archaeological sites, chemical control is usually required as mechanical methods may cause damage.
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| − | * Allowing plants to grow in its place, e.g., the establishment of woodland, causes shade that inhibits bracken growth. In the UK, trees, notably rowan, have done well since grazing reduced greatly after the foot-and-mouth epidemic in 2000 but young saplings struggle in high bracken. In decades to come, tree shade cover may increase, if permitted, and so may reduce bracken growth, but this is both long-term and in some cases is contentious in the change it would bring to traditionally open heath or moorland, both aesthetically and as a valuable habitat.
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| − | * Burning — useful for removing the litter, but may be counter-productive as bracken is considered to be a fire-adapted species
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| − | * Ploughing — late in the season followed by sowing seed
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| − | Any bracken control programme must be completed, or bracken will re-establish.
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| − | A Bracken Control Group was established in 2012 to provide best-practice guidance for all bracken control techniques. The Group has also been responsible for submitting an application for an Emergency Authorisation to secure the continued availability of Asulam for bracken control, following the decision not to register the product under new regulations in the EU. Registration has been re-applied for but this will not be available until 2017 at the earliest. Until re-registration is approved the Group will aim to keep Asulam available under the emergency provisions. [http://www.brackencontrol.co.uk Bracken Control Group website]
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| − | <gallery>
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| − | Image:Adelaarsvaren planten Pteridium aquilinum.jpg|''Pteridium aquilinum''
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| − | Image:Tylerfinvold023 bracken ferns.jpg|Fronds of the bracken fern
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| − | </gallery>
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| − | ==See also==
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| − | * [[Bibimbap]]
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| − | * [[List of plants poisonous to equines]]
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| | == References == | | == References == |
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| | {{Reflist|2}} | | {{Reflist|2}} |
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| − | == External links ==
| + | [[Category:Ferns]] |
| − | {{Commons|Pteridium aquilinum}}
| + | [[Category:Plants for Keenan to eat]] |
| − | * [http://homepages.caverock.net.nz/~bj/fern/pteridium.htm World fern species list — ''Pteridium'']
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| − | * [https://web.archive.org/web/20020808100202/http://www.rook.org/earl/bwca/nature/ferns/pteridiumaqui.html Independent page devoted to bracken (uses older classification scheme)]
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| − | *{{cite journal |vauthors=Alonso-Amelot ME, Avendaño M |title=Human carcinogenesis and bracken fern: a review of the evidence |journal=Curr. Med. Chem. |volume=9 |issue=6 |pages=675–86 |date=March 2002 |pmid=11945131 |url=http://www.benthamdirect.org/pages/content.php?CMC/2002/00000009/00000006/0004C.SGM |doi=10.2174/0929867023370743 |deadurl=yes |archiveurl=https://web.archive.org/web/20111006102621/http://www.benthamdirect.org/pages/content.php?CMC%2F2002%2F00000009%2F00000006%2F0004C.SGM |archivedate=2011-10-06 |df= }}
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| − | * [http://naturalengland.communisis.com/NaturalEnglandShop/product.aspx?ProductID=30f3211f-bc91-4e19-9d74-77b49cc0ba29 Natural England — Bracken control, vegetation restoration and land management]{{dead link|date=November 2016 |bot=InternetArchiveBot |fix-attempted=yes }}
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| − | * [https://web.archive.org/web/20140815035945/http://www.rspb.org.uk/ourwork/farming/advice/details.aspx?id=204253 RSPB: Bracken management in the uplands]
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| − | * [http://www.butterfly-conservation.org/downloads/47/habitat_advice.html Bracken for Butterflies] by [[Butterfly Conservation]]
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| − | *[http://www.northernbushcraft.com/plants/bracken/notes.htm Edibility of Bracken]: Identification and edible parts of bracken
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| − | {{Taxonbar|from=Q258034}}
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| − | [[Category:Dennstaedtiaceae]] | |
| − | [[Category:Japanese vegetables]] | |
| − | [[Category:IARC Group 2B carcinogens]]
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