, Volume 51, Issue 1, pp 1–32

Al and Fe Biogeochemistry in a floodplain forest: Implications for P retention

  • Arlene K. Darke
  • Mark R. Walbridge

DOI: 10.1023/A:1006302600347

Cite this article as:
Darke, A.K. & Walbridge, M.R. Biogeochemistry (2000) 51: 1. doi:10.1023/A:1006302600347


We examined spatial and temporal variationsin soil chemistry in a floodplain forest landscape todetermine the effects of flooding on aluminum (Al) andiron (Fe) oxide biogeochemistry and inorganicphosphorus (Pi) sorption capacity. Whenpreviously sorbed Pi was considered, the sorptioncapacities of floodplain and adjacent upland soilswere comparable, suggesting that floodplain soilsrepresent a second line of defense protectingdownstream aquatic ecosystems from agriculturalrun-off. Pi sorption capacity was highlycorrelated with oxalate-extractable Al (Alo)(rs = 0.78); Alo and percent organic matter(OM) were also highly correlated (rs = 0.72),suggesting the importance of OM-Al complexes in thesesoils. The correlation of oxalate-extractable Fe(Feo) with OM (rs = 0.64) was improved(rs = 0.80) by removing lower elevation (swale)soils, suggesting that flooding inhibits theassociation of Feo with OM. Fe oxidecrystallinity decreased during seasonal flooding, buttotal extractable Fe did not change significantly. Fesolubilized during flooding was either replaced bysediment deposition (252 ± 3 mmol kg−1yr−1), and/or reprecipitated locally. Al oxidecrystallinity also decreased during flooding due to asignificant decline in NaOH-extractable Al (AlN). AlN concentrations subsequently returned topre-flooding levels, but sediment Al inputs (57 ±3 mmol kg−1 yr−1), were insufficient to account for this recovery. Observed Fetransformations suggest the importance offlooding-induced declines in soil redox potential toFe biogeochemistry; observed Al transformationssuggest the importance of complexation reactions withsoil OM to Al biogeochemistry in this floodplainforest.

aluminumfloodplain forestsironorganic matterP sorption capacityphosphorussoilwetlands

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Arlene K. Darke
    • 1
  • Mark R. Walbridge
    • 1
  1. 1.Department of BiologyGeorge Mason UniversityFairfaxU.S.A.