| Sphagnum | |
|---|---|
 | |
| Sphagnum flesum | |
Scientific classification | |
| Kingdom: | Plantae |
| Division: | Bryophyta |
| Class: | Sphagnopsida |
| Order: | Sphagnales |
| Family: | Sphagnaceae |
| Genus: | Sphagnum L. |
| Species | |
| Synonyms[1] | |
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Sphagnum is agenus of approximately 380 acceptedspecies[2][3] ofmosses, commonly known assphagnum moss, alsobog moss andquacker moss (although that term is also sometimes used forpeat). Accumulations ofSphagnum can store water, since both living and dead plants can hold large quantities of water inside their cells; plants may hold 16 to 26 times as much water as their dry weight, depending on the species.[4] The empty cells help retain water in drier conditions.
AsSphagnum moss grows, it can slowly spread into drier conditions, forming largermires, both raisedbogs andblanket bogs.[5] Thus,Sphagnum can influence the composition of such habitats, with some describingSphagnum as 'habitat manipulators' or 'autogenic ecosystem engineers'.[6] Thesepeat accumulations then provide habitat for a wide array of peatland plants, including sedges andericaceous shrubs, as well as orchids and carnivorous plants.[7][8]
Sphagnum and the peat formed from it do not decay readily because of thephenolic compounds embedded in the moss'scell walls. In addition, bogs, like all wetlands, develop anaerobic soil conditions, which produces sloweranaerobic decay rather than aerobic microbial action. Peat moss can also acidify its surroundings by taking upcations, such ascalcium andmagnesium, and releasinghydrogen ions.
Under the right conditions, peat can accumulate to a depth of many meters. Different species ofSphagnum have different tolerance limits for flooding and pH, and any one peatland may have a number of differentSphagnum species.[9][7]
An individualSphagnum plant consists of a mainstem, with tightly arranged clusters of branchfascicles usually consisting of two or three spreading branches and two to four hanging branches. The top of the plant (capitulum) has compact clusters of young branches that give the plant its characteristic tuft-like appearance. Along the stem are scattered leaves of various shapes, named stem leaves; the shape varies according to species.
Sphagnum has a distinctive cellular structure. The stem portion consists of two important sections. Thepith which is the site of food production and storage, and thecortical layer which serves to absorb water and protect the pith. Mosses have novascular system to move water and nutrients around the plant. Thus tissues are thin and usually one cell thick to allow them to diffuse easily.Sphagnum mosses have two distinct cell types. There are small, green, living cells withchlorophyll (chlorophyllose cells) that produce food for the plant. Additionally, there are largerhyaline or retort cells that are barrel shaped and have a pore at one end to allow for water absorption and improved water-holding capacity. These unique cells helpSphagnum to retain water during prolonged UV exposure.[10]
Sphagnum, like all other land plants, has analternation of generations; like otherbryophytes, the haploid gametophyte generation is dominant and persistent. Unlike other mosses, the long-lived gametophytes do not rely upon rhizoids to assist in water uptake.[4]
Sphagnum species can be unisexual (male or female, dioecious) or bisexual (male and female gametes produced from the same plant;monoecious); In North America, 80% ofSphagnum species are unisexual.[11]
Gametophytes have substantial asexual reproduction byfragmentation, producing much of the living material in sphagnum peatlands.[12]
Swimmingsperm fertilize eggs contained inarchegonia that remain attached to the femalegametophyte. Thesporophyte is relatively short-lived, and consists almost entirely of a shiny green, spherical spore capsule that becomes black with spores. Sporophytes are raised on stalks to facilitate spore dispersal, but unlike other mosses,Sphagnum stalks are produced by the maternal gametophyte. Tetrahedral haploid spores are produced in the sporophyte by meiosis, which are then dispersed when the capsule explosively discharges its cap, called anoperculum, and shoots the spores some distance. The spores germinate to produce minuteprotonemae, which start as filaments, can become thalloid, and can produce a few rhizoids. Soon afterwards, the protonema develops buds and these differentiate into its characteristic, erect, leafy, branched gametophyte with chlorophyllose cells and hyaline cells.[13]
Carpets of livingSphagnum may be attacked by variousfungi, and one fungus that is also amushroom,Sphagnurus paluster, produces conspicuous dead patches. When this fungus and otheragarics attack theprotonema,Sphagnum is induced to produce nonphotosyntheticgemmae that can survive the fungal attack and months later germinate to produce new protonema and leafy gametophytes.[14]
As with many othermosses,Sphagnum species disperse spores through the wind. The tops of spore capsules are only about 1 cm (1⁄2") above ground, and where wind is weak. As the spherical spore capsule dries, theoperculum is forced off, followed by a cloud of spores. The exact mechanism has traditionally attributed to a "pop gun" method using air compressed in the capsule, reaching a maximum velocity of 3.6 meters (12 feet) per second,[15] but alternative mechanisms have been recently proposed.[16] High-speed photography has shownvortex rings are created during the discharge, which enable the spores to reach a height of 10 to 20 cm (4 to 8 in), further than would be expected by ballistics alone. The acceleration of the spores is about 36,000g.[17][18] Spores are extremely important in establishment of new populations in disturbed habitats and on islands.[19]
Human activities likeslash-and-burn and cattle grazing are believed to promote the growth and expansion of Sphagnum moss. Oceanic islands such as theFaroe Islands, theGalápagos or theAzores have recorded a significant increase in their Sphagnum populations after human settlement.[20][21]
Peat moss can be distinguished from other moss species by its unique branch clusters. The plant and stem color, the shape of the branch and stem leaves, and the shape of the green cells are all characteristics used to identify peat moss to species.Sphagnum taxonomy has been very contentious since the early 1900s; most species require microscopic dissection to be identified. In the field, mostSphagnum species can be identified to one of four major sections of the genus—classification and descriptions follow Andrus 2007 (Flora North America):[11]
The reciprocalmonophyly of these sections and two other minor ones (Rigida andSquarrosa) has been clarified using molecularphylogenetics.[22] All but two species normally identified asSphagnum reside in one clade; two other species have recently been separated into new families within theSphagnales reflecting an ancestral relationship with theTasmanian endemicAmbuchanania and long phylogenetic distance to the rest ofSphagnum.[23] Within main clade ofSphagnum, phylogenetic distance is relatively short, and molecular dating methods suggest nearly all currentSphagnum species are descended from a radiation that occurred just 14 million years ago.[24]
Sphagnum mosses occur mainly in theNorthern Hemisphere in peat bogs, conifer forests, and moisttundra areas. Their northernmost populations lie in the archipelago ofSvalbard, ArcticNorway, at 81° N.[25]
In theSouthern Hemisphere, the largest peat areas are in southernChile andArgentina, part of the vastMagellanic moorland (circa 44,000 square km; 17,000 sq. mi).[26] Peat areas are also found inNew Zealand andTasmania. In the Southern Hemisphere, however, peat landscapes may contain many moss species other thanSphagnum.Sphagnum species are also reported from "dripping rocks" in mountainous, subtropicalBrazil.[27]
Several of the world's largest wetlands are sphagnum-dominatedbogs, including the West Siberian Lowland, the Hudson Bay Lowland and the Mackenzie River Valley. These areas provide habitat for common and rare species. They also store large amounts of carbon, which helps reduce global warming.[28]
According to an article written in 2013, the U.S. got up to 80% of sphagnum peat moss it uses from Canada. At that time, in Canada, the peat bog mass harvested each year was roughly 1/60th of the peat mass that annually accumulated. About 0.02% of the 1.1 million km2 (420,000 sq mi) of Canadian peat bog are used for peat moss mining.[29] Some efforts are being made to restore peat bogs after peat mining, and some debate exists as to whether the peat bogs can be restored to their premining condition and how long the process takes. "The North American Wetlands Conservation Council estimates that harvested peatlands can be restored to 'ecologically balanced systems' within five to 20 years after peat harvesting." Some wetlands scientists assert that "a managed bog bears little resemblance to a natural one. Like tree farms, these peatlands tend toward monoculture, lacking the biodiversity of an unharvested bog."[30]
PittMoss, a peat moss alternative made from recycled newspaper, has emerged as a sustainable substitute in growing media.[31]Coir has also been touted as a sustainable alternative to peat moss in growing media.[32] Another peat moss alternative is manufactured in California from sustainably harvestedredwood fiber. Semi-open cell polyurethane materials available in flaked and sheet stock are also finding application as sphagnum replacements with typical usage in green wall and roof garden substrates.[33]
In the 2010s,Sphagnum peat inChile began to be harvested at a large scale for export to countries like Japan, South Korea, Taiwan and the United States.Sphagnum’s ability to absorb excess water and release it during dry months means thatoverexploitation may threaten the water supply in thefjords and channels of Chile.[34] Extraction ofSphagnum in Chile has been regulated by law since 2 August 2018.[35] Between 2018 and 2024, Chilean law allowed for the manual extraction ofSphagnum using only pitchforks or similar tools as an aid.[36] In a given designated harvesting area (polygon) at least 30% ofSphagnum coverage had to be left unharvested.[36] HarvestedSphagnum fibers were not allowed to exceed 15 cm (5.9 in) in length and the remainingSphagnum after harvest was not to be left with a length of less than 5 cm (2.0 in) over the water table.[36] In the regions ofLos Ríos (40°S) andLos Lagos (41–43°S) the same plots could be harvested after 12 years, while further south inAysén (44–48°S) andMagallanes (49–56°S) 85 years had to pass before the same area can be harvested again.[36]
According to a 2024 law harvesting ofSphagnum can only be done with land-management plans approved byServicio Agrícola y Ganadero.[37][38] Some environmental organisations expressed regret as the original law project presented in 2018 sought the extablish a definitive ban on the harvest.[38] AlongRubens River inMagallanes Region there are some historically important harvesting fields of peat inSphagnum peatlands.[39]Sphagnum peatlands in Chile disturbed by peat extraction have been found to host variousinvasive plant species includingRumex acetosella,Carex canescens,Holcus lanatus andHieracium pilosella.[39] Harvesting of peat inSphagnum mosses or any where else is forbidden in Chile since April 2024.[37]
Harvesting aside, bogs whereSphagnum grows have also come under threat by the development ofwind farms in cool humid areas such as theCordillera del Piuchén where theSan Pedro Wind Farm was constructed in the 2010s.[40] The construction of eachwind turbine usually implies the removal of vegetation and the alteration of the soil, changing the localhydrology.[40]
Europe has a long history of the exploitation of peatlands. TheNetherlands, for example, once had large areas of peatland, both fen and bog. Between 100 AD and the present, they were drained and converted to agricultural land.[8]: Fig. 14.2 The English broadlands have small lakes that originated as peat mines.[41]More than 90% of the bogs in England have been damaged or destroyed.[42][43] A handful of bogs has been preserved through government buyouts of peat-mining interests.[44] Over longer time scales, however, some parts of England, Ireland, Scotland, and Wales have seen expansion of bogs, particularly blanket bogs, in response to deforestation and abandonment of agricultural land.[8]: Fig. 11.8
New Zealand has, like other parts of the world, lost large areas ofpeatland. The latest estimates for wetland loss in New Zealand are 90% over 150 years.[45] In some cases, better care is taken during the harvesting ofSphagnum to ensure enough moss is remaining to allow regrowth. An 8-year cycle is suggested, but some sites require a longer cycle of 11 to 32 years for full recovery of biomass, depending on factors including whether reseeding is done, the light intensity, and the water table.[46]
Decayed, dried sphagnum moss has the name of peat or peat moss. This is used as asoil conditioner which increases the soil's capacity to hold water and nutrients by increasingcapillary forces andcation exchange capacity – uses that are particularly useful in gardening. This is often desired when dealing with verysandy soil, or plants that need increased or steady moisture content to flourish. A distinction is sometimes made between sphagnum moss, the live moss growing on top of a peat bog, and 'sphagnum peat moss' (North American usage) or 'sphagnum peat' (British usage), the latter being the slowly decaying matter underneath.[47]
Anaerobic acidic sphagnum bogs have low rates of decay, and hence preserve plant fragments and pollen to allow reconstruction of past environments.[8] They even preserve human bodies for millennia; examples of these preserved specimens areTollund Man,Haraldskær Woman,Clonycavan Man andLindow Man. Such bogs can also preserve human hair and clothing, one of the most noteworthy examples beingEgtved Girl,Denmark. Because of the acidity of peat, however, bones are dissolved rather than preserved. These bogs have also been used to preserve food.[48] Up to 2000-year-old containers ofbutter orlard have been found.[49]
Sphagnum moss has been used for centuries as a dressing for wounds, including throughWorld War I.[4][50] BotanistJohn William Hotson's paper, "Sphagnum as a surgical dressing", published inScience in 1918, was instrumental in the acceptance ofSphagnum moss use as a medical dressing in place of cotton.[51][52] Preparations usingSphagnum such as Sphagnol soap have been used for various skin conditions includingacne,ringworm, andeczema. The soap was used by theBritish Red Cross during both World Wars to treat facial wounds and trench sores.[53]
Sphagnum moss is used as a substrate in reptile terrariums because it supports humidity and provides a soft base for burrowing or nesting.[54]
Peat moss is used to dispose of the clarified liquid output (effluent) fromseptic tanks in areas that lack the proper conditions for ordinary disposal means. It is also used as an environmentally friendly alternative tochlorine inswimming pool sanitation.[55] The moss inhibits the growth ofmicrobes and reduces the need for chlorine in swimming pools.[56]
InFinland, peat mosses have been used to make bread duringfamines.[57]
InChina,Japan andKorea, long strand dried sphagnum moss is traditionally used as a potting medium for cultivatingVanda falcata orchids.[58]
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| National | |
| Other | |
