Editing Floodplain (section)

=== Phosphorus cycling in floodplain soils ===
Floodplains have high buffering capacity for phosphorus to prevent nutrient loss to river outputs.<ref>{{Cite journal |last1=Arenberg |first1=Mary R. |last2=Liang |first2=Xinqiang |last3=Arai |first3=Yuji |date=2020-10-01 |title=Immobilization of agricultural phosphorus in temperate floodplain soils of Illinois, USA |url=https://doi.org/10.1007/s10533-020-00696-1 |journal=Biogeochemistry |volume=150 |issue=3 |pages=257–278 |doi=10.1007/s10533-020-00696-1 |bibcode=2020Biogc.150..257A |issn=1573-515X}}</ref> Phosphorus [[Eutrophication|nutrient loading]] is a problem in freshwater systems. Much of the phosphorus in freshwater systems comes from municipal wastewater treatment plants and agricultural runoff.<ref name="Schönbrunner 329–337">{{Cite journal |last1=Schönbrunner |first1=Iris M. |last2=Preiner |first2=Stefan |last3=Hein |first3=Thomas |date=August 2012 |title=Impact of drying and re-flooding of sediment on phosphorus dynamics of river-floodplain systems |url=https://doi.org/10.1016/j.scitotenv.2012.06.025 |journal=Science of the Total Environment |volume=432 |issue=10 |pages=329–337 |doi=10.1016/j.scitotenv.2012.06.025 |issn=0048-9697 |pmc=3422535 |pmid=22750178|bibcode=2012ScTEn.432..329S }}</ref> Stream connectivity controls whether phosphorus cycling is mediated by floodplain sediments or by external processes.<ref name="Schönbrunner 329–337"/> Under conditions of stream connectivity, phosphorus is better able to be cycled, and sediments and nutrients are more readily retained.<ref>{{Cite journal |last1=Noe |first1=Gregory B. |last2=Hupp |first2=Cliff R. |last3=Rybicki |first3=Nancy B. |date=2013-01-01 |title=Hydrogeomorphology Influences Soil Nitrogen and Phosphorus Mineralization in Floodplain Wetlands |url=https://doi.org/10.1007/s10021-012-9597-0 |journal=Ecosystems |volume=16 |issue=1 |pages=75–94 |doi=10.1007/s10021-012-9597-0 |bibcode=2013Ecosy..16...75N |issn=1435-0629}}</ref> Water in freshwater streams ends up in either short-term storage in plants or algae or long-term in sediments.<ref name="Schönbrunner 329–337"/> Wet/dry cycling within the floodplain greatly impacts phosphorus availability because it alters water level, redox state, pH, and physical properties of minerals.<ref name="Schönbrunner 329–337"/> Dry soils that were previously inundated have reduced availability of phosphorus and increased affinity for obtaining phosphorus.<ref>{{Cite journal |last1=Baldwin |first1=D.S. |last2=Mitchell |first2=A.M. |date=September 2000 |title=The effects of drying and re-flooding on the sediment and soil nutrient dynamics of lowland river-floodplain systems: a synthesis |url=https://onlinelibrary.wiley.com/doi/10.1002/1099-1646(200009/10)16:53.0.CO;2-B |journal=Regulated Rivers: Research & Management |language=en |volume=16 |issue=5 |pages=457–467 |doi=10.1002/1099-1646(200009/10)16:5<457::AID-RRR597>3.0.CO;2-B |issn=0886-9375}}</ref> Human floodplain alterations also impact the phosphorus cycle.<ref>{{Cite journal |last1=Baldwin |first1=D.S. |last2=Mitchell |first2=A.M. |date=September 2000 |title=The effects of drying and re-flooding on the sediment and soil nutrient dynamics of lowland river-floodplain systems: a synthesis |url=https://onlinelibrary.wiley.com/doi/10.1002/1099-1646(200009/10)16:53.0.CO;2-B |journal=Regulated Rivers: Research & Management |volume=16 |issue=5 |pages=457–467 |doi=10.1002/1099-1646(200009/10)16:5<457::AID-RRR597>3.0.CO;2-B |issn=0886-9375}}</ref> Particulate phosphorus and soluble reactive phosphorus (SRP) can contribute to algal blooms and toxicity in waterways when the nitrogen-to-phosphorus ratios are altered farther upstream.<ref name="Jarvie 123–132">{{Cite journal |last1=Jarvie |first1=Helen P. |last2=Johnson |first2=Laura T. |last3=Sharpley |first3=Andrew N. |last4=Smith |first4=Douglas R. |last5=Baker |first5=David B. |last6=Bruulsema |first6=Tom W. |last7=Confesor |first7=Remegio |date=January 2017 |title=Increased Soluble Phosphorus Loads to Lake Erie: Unintended Consequences of Conservation Practices? |url=https://acsess.onlinelibrary.wiley.com/doi/10.2134/jeq2016.07.0248 |journal=Journal of Environmental Quality |volume=46 |issue=1 |pages=123–132 |doi=10.2134/jeq2016.07.0248 |pmid=28177409 |bibcode=2017JEnvQ..46..123J |issn=0047-2425}}</ref> In areas where the phosphorus load is primarily particulate phosphorus, like the Mississippi River, the most effective ways of removing phosphorus upstream are sedimentation, soil accretion, and burial.<ref>{{Cite book |last=Knighton |first=David |date=2014-04-08 |title=Fluvial Forms and Processes |url=http://dx.doi.org/10.4324/9780203784662 |doi=10.4324/9780203784662|isbn=978-1-4441-6575-3 }}</ref> In basins where SRP is the primary form of phosphorus, biological uptake in floodplain forests is the best way of removing nutrients.<ref name="Jarvie 123–132"/> Phosphorus can transform between SRP and particulate phosphorus depending on ambient conditions or processes like decomposition, biological uptake, redoximorphic release, and sedimentation and accretion.<ref>{{Cite journal |last1=Hoffmann |first1=Carl Christian |last2=Kjaergaard |first2=Charlotte |last3=Uusi-Kämppä |first3=Jaana |last4=Hansen |first4=Hans Christian Bruun |last5=Kronvang |first5=Brian |date=September 2009 |title=Phosphorus Retention in Riparian Buffers: Review of Their Efficiency |url=http://dx.doi.org/10.2134/jeq2008.0087 |journal=Journal of Environmental Quality |volume=38 |issue=5 |pages=1942–1955 |doi=10.2134/jeq2008.0087 |pmid=19704138 |bibcode=2009JEnvQ..38.1942H |issn=0047-2425}}</ref> In either phosphorus form, floodplain forests are beneficial as phosphorus sinks, and the human-caused disconnect between floodplains and rivers exacerbates the phosphorus overload.<ref>{{Cite journal |last=Pagano |first=T. C. |date=2014-07-17 |title=Evaluation of Mekong River commission operational flood forecasts, 2000–2012 |journal=Hydrology and Earth System Sciences |volume=18 |issue=7 |pages=2645–2656 |doi=10.5194/hess-18-2645-2014 |doi-access=free |bibcode=2014HESS...18.2645P |issn=1607-7938}}</ref>