Evidence for Contemporary and Relict Redoximorphic Features of an Alfisol in East-Central Texas
Interpretation of redoximorphic features is sometimes complicated by the presence of relict features, particularly in areas where soils have experienced paleoenvironments with wetter moisture regimes. The Rader series (fine-loamy, mixed, thermic Aquic Paleustalfs) is one of many soils in Texas that exhibit redoximorphic features that appear to be unrelated to their current moisture regime. The primary purpose of this study was to calibrate hydrologic data with redoximorphic features in order to assess which features are likely associated with contemporary conditions and which may be relict features. Saturation, matric potential, and redox potential were measured with piezometers, tensiometers, and permanently installed Eh electrodes for 3 yr. Redoximorphic features were described in the field and from thin sections. There was a perched water table at a depth of 1 m for several months each year (episaturation) and on top of the Bt horizon for shorter periods following rainfall events. The Eh readings indicated that the studied soil has sufficient periods of reduction in some microsites in the saturated zones to mobilize Fe. There are Fe pore linings in the Bt2 and BC1 horizons, suggesting contemporary mobilization and reoxidation of Fe. Nodules throughout the profile have sharp boundaries and either coatings or evidence of dissolution, indicating that they are probably relict features. Therefore, redoximorphic features below the perched water table at the BC horizon are considered relicts, while redoximorphic features within the perched water tables appear to reflect current as well as previous saturation and reducing conditions. The redoximorphic features best correlated with contemporary saturation and reduction are Fe pore linings and soft concentrations with diffuse boundaries.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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