The use of variability diagrams to improve the interpretation of digital soil maps in a GIS

Abstract

A critical layer in geographic information systems (GIS), particularly when utilized in land management decisions, is soil survey information. The spatial component of this information is generally input from digitized survey maps, usually in the form of polygons representing different soil map units. It is a fact that the homogeneity of soils within soil map units varies. Conveying this variability to users is essential to ensure proper use of soil survey information. Using the transect method, four forested soil map units were examined to assess their homogeneity with respect to the variability of field determined soil taxonomy and physiography and the interpretive variability of selected soil properties for forest land management. The degree of interpretive variability was determined using Shannon's measure of entropy. Variability diagrams and interpretive maps were generated within a GIS. These diagrams and maps, coupled with the digitized soil maps, inform users of the degree of soil map unit variability and the variability of limiting soil properties. 26 refs.