Technical ArticleStabilization of Organic Carbon via Chemical Interactions with Fe and Al Oxides in Gley SoilsCloy, Joanna M.1; Wilson, Clare A.2; Graham, Margaret C.1Author Information 1School of GeoSciences, University of Edinburgh, West Mains Road, Edinburgh, UK. 2Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, UK. Address for correspondence: Dr. Joanna M. Cloy, Scotland’s Rural College, West Mains Rd, Edinburgh, UK. E-mail: [email protected] Financial Disclosures/Conflicts of Interest: This work was supported by the Natural Environment Research Council (Grant No. NE/G010102/1) and SAGES. The authors report no conflicts of interest. Received July 21, 2014. Accepted for publication December 24, 2014. Supplemental digital content is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (www.soilsci.com). Soil Science: December 2014 - Volume 179 - Issue 12 - p 547-560 doi: 10.1097/SS.0000000000000096 Buy SDC Metrics AbstractIn Brief The importance of soil organic carbon (SOC) stabilization via chemical interactions with Fe and Al oxide minerals within gley soils remains unclear. Changes in the proportions of Fe/Al oxides and SOC and N contents associated with Fe/Al oxides within the profiles of gley soils under contrasting hydrological regimes and freely draining control soils from Harwood Forest (northeast England) were investigated. Sequential selective dissolution techniques were used to measure Fe/Al oxide crystallinity and explore whether crystallinity differed between gleyed and freely draining soils. Extracts were analyzed using Fourier transform infrared spectroscopy to investigate the chemical characteristics of organic matter (OM) associated with Fe/Al oxides. Strongly crystalline Fe oxides were the dominant (∼50%–80% of total Fe oxides present) mineral phase in gley mineral soils. Contrasting gley soil hydrological regimes influenced total subsoil Fe and total and weakly crystalline Al oxide concentrations. Also, within-profile changes in strongly crystalline Fe oxide concentrations were linked to differences in hydrological and redox conditions. A large proportion of SOC (generally 70%–90% of total) seemed to be associated with Fe/Al oxides. Correlation plots, however, indicated that SOC contents were not linearly related to amounts of total Fe and Al oxides, weakly crystalline Fe and Al oxides, or strongly crystalline Fe oxides. The lack of linear correlations observed for these acidic soils may be caused by contributions from other extractable soil components and factors such as high organic loadings and insufficient amounts of Fe/Al oxides for interaction with SOC in topsoils and variable surface loadings of different organic inputs at different soil depths. Subsoil C/N ratios (∼18–21) were higher than those in extracted subsoil residues (∼9–17), suggesting that minerals other than Fe/Al oxides preferentially adsorbed N-rich microbially processed compounds. The OM associated with weakly and strongly crystalline Fe/Al oxides was chemically different, the latter generally having greater hydroxyl, aliphatic, carboxylate, and /or phenolic character and less carbohydrate character than the former. This research shows that interactions between Fe/Al oxides and SOM in redox-dynamic gley soils under different hydrological regimes are complex, and further investigations of SOC stabilization in these systems using selective dissolution and other complementary techniques are required. Supplemental digital content is available in the text. Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.