Editing Fen (section)

==== Phosphorus ====
Almost all of the phosphorus that arrives in a wetland does so through sediments or plant litter from other ecosystems.<ref name=":23" /> Along with nitrogen, phosphorus limits wetland fertility.<ref name=":23" /> Under basic conditions like those found in extremely rich fens, calcium will bind to [[phosphate]] anions to make [[calcium phosphate]]s, which are unavailable for uptake by plants.<ref name=":23" /> 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 the moss cover.<ref name=":5">{{Cite journal|last1=Crowley|first1=Katherine F.|last2=Bedford|first2=Barbara L.|date=September 2011|title=Mosses influence phosphorus cycling in rich fens by driving redox conditions in shallow soils|url=http://link.springer.com/10.1007/s00442-011-1970-8|journal=Oecologia|language=en|volume=167|issue=1|pages=253–264|doi=10.1007/s00442-011-1970-8|pmid=21445686|bibcode=2011Oecol.167..253C|s2cid=24302679|issn=0029-8549|access-date=2021-04-14|archive-date=2022-01-12|archive-url=https://web.archive.org/web/20220112234330/https://link.springer.com/article/10.1007%2Fs00442-011-1970-8|url-status=live}}</ref> 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.<ref>{{Cite journal|last1=Zak|first1=Dominik|last2=Gelbrecht|first2=Jörg|last3=Zerbe|first3=Stefan|last4=Shatwell|first4=Tom|last5=Barth|first5=Martin|last6=Cabezas|first6=Alvaro|last7=Steffenhagen|first7=Peggy|date=May 2014|title=How helophytes influence the phosphorus cycle in degraded inundated peat soils – Implications for fen restoration|url=https://linkinghub.elsevier.com/retrieve/pii/S0925857413004187|journal=Ecological Engineering|language=en|volume=66|pages=82–90|doi=10.1016/j.ecoleng.2013.10.003|bibcode=2014EcEng..66...82Z |access-date=2021-04-14|archive-date=2018-07-01|archive-url=https://web.archive.org/web/20180701165754/https://linkinghub.elsevier.com/retrieve/pii/S0925857413004187|url-status=live}}</ref> Under normal conditions, phosphorus is held within soil as dissolved inorganic phosphorus, or [[phosphate]], which leaves trace amounts of phosphorus in the rest of the ecosystem.<ref>{{Cite journal|last1=Richardson|first1=Curtis J.|last2=Marshall|first2=Paul E.|date=December 1986|title=Processes Controlling Movement, Storage, and Export of Phosphorus in a Fen Peatland|url=https://onlinelibrary.wiley.com/doi/10.2307/1942548|journal=Ecological Monographs|language=en|volume=56|issue=4|pages=279–302|doi=10.2307/1942548|jstor=1942548|bibcode=1986EcoM...56..279R |issn=0012-9615}}</ref>

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.<ref name=":5" /> In iron-rich fens, the area can become vulnerable to acidification, excess nitrogen and potassium, and low water levels.<ref name=":8">{{Cite journal|last1=Kooijman|first1=A. M.|last2=Cusell|first2=C.|last3=Hedenäs|first3=L.|last4=Lamers|first4=L. P. M.|last5=Mettrop|first5=I. S.|last6=Neijmeijer|first6=T.|date=February 2020|title=Re-assessment of phosphorus availability in fens with varying contents of iron and calcium|journal=Plant and Soil|language=en|volume=447|issue=1–2|pages=219–239|doi=10.1007/s11104-019-04241-4|s2cid=208649335|issn=0032-079X|doi-access=free|bibcode=2020PlSoi.447..219K |hdl=2066/214408|hdl-access=free}}</ref> 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.<ref name=":8" />