Measuring and Scaling Dynamic Soil Properties in Soil Survey.

Traditional soil survey products deliver information about soil properties without taking into account current land use or management systems.  Soil surveys vary in the scale of information they provide on spatial, taxonomic and property-specific scales.  The order (spatial scale) and purpose of a given soil survey impacts the design of soil mapping units.  Map unit design includes decisions about the types of map units (consociations, associations, or complexes) used, the arrangement and composition of those map units.  The individual map unit components have their own scales – how finely are taxonomic classes defined, or how many different slope classes can be recognized.  In the National Cooperative Soil Survey (NCSS), soil property information is then assigned to map unit components using available data and expert knowledge.   Decisions about the inclusion of data are made using expert opinion (e.g. is data part of the central concept) and rules-of-thumb about appropriate property classes which subsequently impact the values (Low – Representative Value (RV) – High) populated in available databases such as SSURGO.  Currently, the NCSS uses the Soil Change Guide to organize the collection of use-dependent properties under the name Dynamic Soil Properties (DSPs).  In this conception, additional decisions impact the spatial and conceptual scales of the data.   For current DSP projects, two or more conditions are selected that represent the ‘best’ and most common management systems in common land uses for an individual soil series component.  The range of data collected depends how tightly the selected soil components represent the central concept, and how the comparison of systems was constructed.  Critical questions remain about how this information is extrapolated across multiple scales and conditions.  Incorporating soil-landscape-ecosystem systems into NCSS hierarchies will allow us to apply information from DSP projects to similar soils.  Further work is needed to link and expand ecosystems, land use/cover types and management systems.