Sphagnum
| Peat moss | ||||||||||||||
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 a clump of Sphagnum, peat moss | ||||||||||||||
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| Sphagnum affine Sphagnum apiculatum |
Sphagnum is genus of between 150-350 species of mosses commonly called peat moss, due to its prevalence in peat bogs. Members of this genus can hold large quantities of water inside their cells; some species can hold up to 20 times their dry weight in water, which is why peat moss is commonly sold as a soil amendment. Sphagnum and the peat formed from it do not decay readily because of the phenolic compounds embedded in the moss's cell walls. Peat moss can also acidify its surroundings by taking up cations such as calcium and magnesium and releasing hydrogen ions.
Individual peat moss plants consist of a main stem, with tightly arranged clusters of branch fascicles usually consisting of two or three spreading branches and two to four hanging branches. The branches are covered by ovate to lanceolate leaves called branch leaves. The top of the plant, or capitulum, has compact clusters of young branches. Along the stem are scattered leaves of various shape, named stem leaves; the shape varies according to species. The leaves consist of two kinds of cell; small, green, living cells (chlorophyllose cells), and large, clear, structural, dead cells (hyaline cells). The latter have the large water-holding capacity.
Spores are released from specialized black, shiny capsules located at the tips of thin stalks. Sphagnum species also reproduce by fragmentation.
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.
Geographic distribution
Peat mosses occur mainly in the Northern Hemisphere where different species dominate the bottom layer of peat bogs and moist tundra areas. The northernmost populations of peat moss lie in the archipelago of Svalbard, arctic Norway at 81° N.
In the Southern Hemisphere, the largest peat moss areas are in New Zealand, Tasmania, southernmost Chile and Argentina, but contain comparatively few species. Many species are reported from mountainous, subtropical Brazil, but uncertainty exists regarding the specific status of many of them.
Uses
Decayed, compacted Sphagnum moss has the name of peat moss. Peat moss can be used as a soil additive which increases the soil's capacity to hold water. This is often necessary when dealing with very sandy soil, or plants that need an increased moisture content to flourish. One such group of plants are the carnivorous plants, often found in wetlands (bogs for example). Dried Sphagnum moss is also used in northern Arctic regions as an insulating material. Peat moss is also a critical element for growing mushrooms; mycelium grows in compost with a layer of peat moss on top, through which the mushrooms come out, a process called pinning.
Anaerobic acidic Sphagnum bogs (mosses, Scottish) are known to preserve mammalian bodies extremely well for millennia. Examples of these preserved specimens are Tollund Man, Haraldskær Woman, Clonycavan Man and Lindow Man. Such Sphagnum bogs can also preserve human hair and clothing, one of the most noteworthy examples being Egtved Girl, Denmark.
It is also used at horse stables as a bedding in horse stalls. It is not a very common bedding, but some farm owners choose peat moss as a great compost with horse manure.
Conservation
There is some question about the sustainability of large-scale Sphagnum harvesting. In particular, the extraction of large quantities of moss is a threat to raised bogs [1].
Health dangers
Although rare, exposure to Sphagnum moss can potentially cause the chronic fungal disease, sporotrichosis. Sporothrix schenckii spores enter the skin via abrasions, scratches, and small puncure wounds as a result of unprotected contact exposure to Sphagnum moss. Sphagnum moss has also been used for centuries as a dressing for wounds. This works because of the moss's ability to evenly soak up blood.
