Human influences on soils are very complex, with many interactions occurring between human, or
anthropedogenic, processes and natural pedogenic processes of soil formation. The spread of urban centers into forested landscapes and the increasing level of chemical inputs into forest ecosystems necessitate the inclusion of anthropogenic factors of soil formation in our concept of soil genesis. Rapid changes in the nature and intensity of human influences on forest soils occur along urban-rural land use gradients and provide an excellent opportunity to study human modifications of soils.
The spatial variability of soil characteristics and morphological features along the urban-rural land use gradient should be examined at various scales of observation. Historically, soil mapping for agricultural lands depended on intensity of land use with mapping typically at scales ranging from 1:15 840 to 1:24 000. Current technological advances (i.e. Global Positioning Systems, Ground Penetrating Radar, satellite imagery) and intensive urban land use require modern soil surveys at large map scales such as the 1:6000 scale used for engineering and site assessment by the recently closed Fairfax County, Virginia Soil Science Office or the 1:12 000 scale applied for modern soil survey revisions of various Maryland counties. Arnold (1983) proposes that current soil science theory has not yet agreed on a unified fundamental concept of soil as a ‘‘geographic body’’; however, map scales of 1:6000 to 1:12 000 may
offer a level of cartographic detail with ‘‘reasonable agreement of such units among field-soil mappers.’’ High-intensity (i.e. large scale) soil characterization and mapping in selected benchmark anthroposequences is proposed as a reference data source to effectively study the urban-rural land use gradient. A more comprehensive soil classification system that considers soils significantly influenced by nonagronomic human activity should be developed as a component of this project. Recently, an international committee addressing the classification of anthropogenic soils (ICOMANTH), chaired by R. B. Bryant,Cornell University, initiated activities to develop proposals revising Soil Taxonomy with respect to human effects on soils. Testing of the modified or new soil classes would be examined in other urban areas. Coincident with the study of benchmark anthroposequences in selected urban-rural landscapes,models of soil formation should be modified to include nonagronomic human activities that influence soil