Micromorphology of Sandy Epipedons along an Upland-Wetland Transect
- M. C. Rabenhorst and
- D. L. Lindbo
Possible benefits of soil morphological features that might serve as indicators of hydric soil conditions have generated interest in organic features of hydric soils. It has been suggested that in soils with dark colors (value/chroma of 3/1 or less) significant coating or covering of the primary soil particles (>70%) with organic fine material may indicate hydric soil conditions. The objective of this project was to study the hydropedological significance of organic matter coatings in sandy epipedons along an upland-wetland transect using micromorphology. A transect was selected for study in sandy soils formed from late Pleistocene dunal deposits on the Delmarva Peninsula of Maryland, where upland soils graded into hydric soils. Hydrological measurements were recorded for approximately 7 yr at biweekly intervals. Macro- and micromorphological features were described in the sandy epipedons that were analyzed for C content. Soils in which the seasonal water tables occur within 30 cm of the surface for >10% of the year appear to have levels of organic materials in the A horizons >35 g/kg, and Munsell colors that are 3/1 or darker. Fine organic materials do not form true coatings around the mineral grains in A horizons, but there is an increase in the association of dark fine organic material (DFOM) with mineral grain surfaces as the soils become wetter, and there also is an increase in the proportion of DFOM to mineral grains in wetter soils. Soils that have water tables at or above 30 cm for approximately 30 d /yr or within 45 cm for approximately 90 d/yr have DFOM/grain ratios greater than 0.4 to 0.5, and have more than 25 to 30% of mineral grain surfaces associated (“coated”) with DFOM.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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