Wetness conditions and redoximorphic features in a microtoposequence on the Texas Coast Prairie

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Quantifying Soil Hydromorphology


The purpose of this study was to investigate the relationship between wetness conditions and redoximorphic features in three soils that occur on adjacent microtopographic landform positions. The landform positions included a closed, seasonally ponded depression, and intermound, and a pimple mound. Aquic conditions as defined by the Keys to Soil Taxonomy (Soil Surv. Staff, 1996) were assessed by: (i) redoximorphic features, and (ii) measurement of saturation and reduction to verify morphological features used to infer aquic conditions. Taxonomic classification of the three pedons representing the toposequence were: (i) mound (fine-loamy, siliceous, thermic Oxyaquic Paleudalfs), (ii) intermound (coarse-loamy, siliceous, thermic Typic Natraqualfs, and (iii) depression (fine-loamy, siliceous, thermic Typic Endoaqualfs). The soil sites were located northwest of Houston near the city of Cypress in Harris County on the Katy Prairie portion of the central Texas Gulf Coast Prairie. The three sites represent the upper, middle, and lower topographic positions on this landscape. During a 19-mo period, each of the different landform positions exhibited different perched and groundwater piezometric surfaces within the upper 200 cm. During periods of saturation, low oxidation-reduction potentials (≤ 120 mV in the intermound and <240 mV in the depression) suggested that Fe reduction occurred in the soils. The intermound was saturated at the surface and below 100 cm that corresponded closely with decreased water movement within the portion of the soil profile where a natric horizon occurred between 26 and 136 cm. The depression site exhibited saturation during the fall to spring and Fe reduction in the profile, so redox features were associated with current and possibly with relict aquic conditions.

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