Within the context of EMRIS, the soil and substrate class is very similar to climate: it is not classified per se (although soil classifications do exist), but is generally used as a determinant or modifier for other components of the classification systems. The primary component affected by soils and substrate is vegetation; soils data can provide the user with a better understanding of what types of vegetation should grow where, and thus aid in the classification process. Data on soils are available through the USDA soil surveys; the status of these surveys, along with other potentially useful soils information, is provided by the http://www.statlab.iastate.edu/soils/nsdaf. Specific soils classification information can be found at http://www.statlab.iastate.edu/soils/sc.
Classification systems that consider soils information in developing the classification include: HGM Classification of Wetlands, Cowardin , Bailey's Ecoregions, Rosgen , and the NVCS.