Editing Floodplain (section)

== Floodplain soils ==

=== Oxygen in floodplain soils ===
Floodplain soil composition is unique and varies widely based on microtopography. Floodplain forests have high topographic heterogeneity which creates variation in localized hydrologic conditions.<ref>{{Cite journal |last1=De Jager |first1=Nathan R. |last2=Thomsen |first2=Meredith |last3=Yin |first3=Yao |date=April 2012 |title=Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA |url=https://doi.org/10.1016/j.foreco.2012.01.023 |journal=Forest Ecology and Management |volume=270 |pages=135–146 |doi=10.1016/j.foreco.2012.01.023 |issn=0378-1127|url-access=subscription }}</ref> Soil moisture within the upper 30 cm of the soil profile also varies widely based on microtopography, which affects oxygen availability.<ref>{{Cite journal |last=Krumbach |first=A. W. |date=October 1959 |title=Effects of microrelief on distribution of soil moisture and bulk density |url=http://doi.wiley.com/10.1029/JZ064i010p01587 |journal=Journal of Geophysical Research |volume=64 |issue=10 |pages=1587–1590 |doi=10.1029/JZ064i010p01587|bibcode=1959JGR....64.1587K |url-access=subscription }}</ref><ref>{{Cite journal |last1=Hupp |first1=Cliff R. |last2=Osterkamp |first2=W. R. |date=June 1985 |title=Bottomland Vegetation Distribution along Passage Creek, Virginia, in Relation to Fluvial Landforms |url=https://esajournals.onlinelibrary.wiley.com/doi/10.2307/1940528 |journal=Ecology |volume=66 |issue=3 |pages=670–681 |doi=10.2307/1940528 |jstor=1940528 |bibcode=1985Ecol...66..670H |issn=0012-9658|url-access=subscription }}</ref> Floodplain soil stays aerated for long periods in between flooding events, but during flooding, saturated soil can become oxygen-depleted if it stands stagnant for long enough. More soil oxygen is available at higher elevations farther from the river. Floodplain forests generally experience alternating periods of aerobic and anaerobic soil microbe activity, affecting fine root development and desiccation.<ref>{{Cite journal |last=Keeley |first=Jon E. |date=March 1979 |title=Population Differentiation along a Flood Frequency Gradient: Physiological Adaptations to Flooding in Nyssa sylvatica |url=https://esajournals.onlinelibrary.wiley.com/doi/10.2307/1942574 |journal=Ecological Monographs |volume=49 |issue=1 |pages=89–108 |doi=10.2307/1942574 |jstor=1942574 |bibcode=1979EcoM...49...89K |issn=0012-9615|url-access=subscription }}</ref><ref>{{Citation |last=Kozlowski  |first=T.T. |title=Extent, Causes, and Impacts of Flooding |date=1984 |work=Flooding and Plant Growth |pages=1–7 |url=https://doi.org/10.1016/b978-0-12-424120-6.50006-7 |access-date=2024-04-20 |publisher=Elsevier |doi=10.1016/b978-0-12-424120-6.50006-7|isbn=978-0-12-424120-6 |url-access=subscription }}</ref><ref>{{Cite journal |last1=Jones |first1=Robert H. |last2=Lockaby |first2=B. Graeme |last3=Somers |first3=Greg L. |date=1996 |title=Effects of Microtopography and Disturbance on Fine-Root Dynamics in Wetland Forests of Low-Order Stream Floodplains |url=https://www.jstor.org/stable/2426631 |journal=The American Midland Naturalist |volume=136 |issue=1 |pages=57–71 |doi=10.2307/2426631 |jstor=2426631 |issn=0003-0031|url-access=subscription }}</ref>

=== 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|url-access=subscription }}</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|url-access=subscription }}</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|url-access=subscription }}</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|url-access=subscription }}</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|url-access=subscription }}</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>

=== Environmental pollutants in floodplain soils ===
Floodplain soils tend to be high in eco-pollutants, especially [[persistent organic pollutant]] (POP) deposition.<ref>{{Cite journal |last1=Skála |first1=Jan |last2=Vácha |first2=Radim |last3=Čupr |first3=Pavel |date=June 2018 |title=Which Compounds Contribute Most to Elevated Soil Pollution and the Corresponding Health Risks in Floodplains in the Headwater Areas of the Central European Watershed? |journal=International Journal of Environmental Research and Public Health |volume=15 |issue=6 |pages=1146 |doi=10.3390/ijerph15061146 |doi-access=free |pmid=29865159 |pmc=6025328 |issn=1660-4601}}</ref> Proper understanding of the distribution of soil contaminants is complex because of high variation in microtopography and soil texture within floodplains.<ref>{{Cite journal |last1=Rinklebe |first1=Jörg |last2=Franke |first2=Christa |last3=Neue |first3=Heinz-Ulrich |date=October 2007 |title=Aggregation of floodplain soils based on classification principles to predict concentrations of nutrients and pollutants |url=https://doi.org/10.1016/j.geoderma.2007.06.001 |journal=Geoderma |volume=141 |issue=3–4 |pages=210–223 |doi=10.1016/j.geoderma.2007.06.001 |bibcode=2007Geode.141..210R |issn=0016-7061|url-access=subscription }}</ref>