- Rich Pouyat, United States Forest Services
- Ian Yesilonis, University of Maryland
- Carl Robinette, Natural Resources Conservation Service
- Jim Brewer, Natural Resources Conservation Service
The Soil Taxonomy and other soil classification systems organize soil variability into useful groupings that are identifiable by field investigation and documented in soil survey activities to promote effective resource management and technology transfer. Processes of soil formation that are altered by human activity are considered to be deviations from the normal, and as a consequence, changes in soil characteristics resulting from human intervention are not applicable to the current Soil Taxonomy. To incorporate human modifications of soil in Soil Taxonomy, we propose that human activities should be considered as a factor of soil formation. Specifically, we present a conceptual model of soil genesis that incorporates humans as a soil forming factor and details the "anthroposequence," which we suggest may be applied to studying soil systems along urban-rural land use gradients. We are applying this concept to investigate human modifications of soil and to conduct a high resolution soil survey of the Baltimore City metropolitan area. Specifically, we are working to 1) describe the characterization of soils in an urbanized watershed (Gwynns Falls, Maryland) being monitored and investigated in the Baltimore Ecosystem Study (BES); 2) identify key soil properties (chemical, physical, biological) and their spatial distribution and relationship with other factors such as, socio-economic and hydrologic factors, being characterized for the watershed; 3) propose various soil properties as descriptors and diagnostic properties for the development of a disturbed soil classification system; and 4) describe a high resolution field survey and associated map unit composition for the watershed.
General soils pattern
Baltimore City lies within two physiographic provinces, the Piedmont Plateau and the Atlantic Coastal Plain. The north-northeast trending Fall Line separates the two provinces, dividing the city in half. Most of the city is characterized by nearly level to gently rolling uplands, dissected by narrow stream valleys. The Piedmont Plateau in the City of Baltimore is underlain by old igneous and metamorphic rocks. The Coastal Plain in the city is underlain by much younger, poorly consolidated sediments. Four soil Associations make up most of the City's area. These include 1) Urban Land-Legore Association, which are very deep, nearly level to moderately sloping, well drained upland soils that are underlain by semibasic or mixed basic and acidic rocks (34% of the land area, of which 43% is urban land); 2) Urban Land-Joppa-Sassafras Association, which are very deep, somewhat excessively drained and well drained upland soils that are underlain by sandy or gravelly sediments (18% of the land area, of which 40% is urban land); 3) Urban Land-Sunnyside Association, which are very deep, nearly level to moderately sloping, well drained upland soils that are underlain by unstable clayey sediment (24% of land area, of which 54% is urban land); and 4) highly disturbed soils that vary in slope position, drainage, and origin that make up 24% of the land area. Based on the percentage of cover of these soil associations, the total land cover of the city that is made up of highly disturbed soils (urban land and Udorthents) is approximately 60%, though the coverage of relatively undisturbed soils by impervious surfaces, such as roads, is not included in this estimation.
