The thick surface accumulations of organic matter in Mollisols confound the possibility of recognizing soil morphological features such as redoximorphic features that indicate seasonally saturated and reduced soils. The most obvious morphological change in the soil across Mollisol hydrosequences in Minnesota is the thickening and darkening of the A horizon(s). Our purpose is to quantify this trend across the landscape and examine its correlation with duration of saturated and/or reducing conditions for distinguishing between hydric and nonhydric Mollisols. We examined trends in soil morphology and soil organic C in conjunction with hydrologic monitoring data across three Mollisol hydrosequences. We define a new color index that is a function of the thickness and color of the A horizon(s) of Mollisols of three hillslopes in Minnesota. Coefficients of correlation (r) between this index and duration of saturated and reducing conditions at various depths in these Mollisols are as high as 0.69. This index is also linearly related to organic C content of the A horizon(s) of a single hillslope with a coefficient of correlation of 0.98. This index may be useful for identifying and delineating hydric soils and may be employed to examine soil C storage at a landscape scale; however, specific relationships will vary considerably with soil parent material and climate.
|Original language||English (US)|
|Number of pages||10|
|Journal||Soil Science Society of America Journal|
|State||Published - Jan 1 1996|