Soils of the Mall in Washington, DC: II. Genesis, Classification, and Mapping

Abstract

Abstract The soils on the Mall in Washington, DC have formed in about 6 m of miscellaneous fill deposited in repeated applications to the site during filling operations. Some limited pedogenesis has occurred; cambic, or cambic‐like B horizons were recognized in 26% of the profiles examined. Buried A horizons were found in 42% of the profiles. Classification of these soils using Soil Taxonomy alone was not satisfactory, as variations in organic matter with depth caused many of the soils to be placed in Fluv‐classes that connoted deposition of the parent material as alluvium and did not show unique accessory characteristics such as high bulk density. Proposed Urbic and Spolic subgroups of Udorthents and Ochrepts, with criteria to exclude them from Fluv‐classes, were utilized to classify these soils in a manner more consistent with their genesis and characteristics. A detailed soil map was prepared for the Mall using the proposed classification, and recommendations are made for mapping such highly manipulated areas.