Sphagnum
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Sphagnum is a 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. Peat moss can 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 to 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 Peru, 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).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 [link].
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