History and Application of Micromorphological Techniques in Land Use Regulation.

Micromorphology is a branch of pedology that describes, interprets, and measures the components, features, and fabrics of soils and regolith materials. This historical review (1930 to present) will cover three main topics: terminology and concepts, techniques, and applications.  Descriptive systems developed during this period include contributions of Kubiena, Brewer, Bullock et al., and Stoops.  Focus will be placed on three principal areas: matrix, structure, and features.  Features will include redoximorphic features, clay coatings, and mineral transformations.  Major techniques developed during the time of interest include use of plastic resins for impregnation, water removal by solvent exchange, and quantification using image analysis.  To illustrate applications, we will focus on how redoximorphic features have been built into land use regulations that include wetland protection and on-site waste disposal.  Redox features form the basis for how wetland soils are identified for jurisdictional purposes across the U.S.  Types and amounts of redox depletions and concentrations have been defined for soil layers called “hydric soil field indicators”.  The boundaries of every wetland protected by state and federal laws are determined using field indicators that were defined in part using micromorphology.  Seasonal high water tables are also commonly identified using depth to specific types of redoximorphic features.  Numerous state laws include the concepts of redoximorphic regulations that specify requirements for home sites that are needed to allow disposal and treatment of household wastewater.