The Missing Geographic Dimension to Soil Taxonomy

Abstract

The establishment of Soil Taxonomy as the official United States system of soil classification introduced a number of innovative concepts of significance to soil classification, soil survey, and soil geography. These concepts include the pedon, the polypedon, the taxadjunct, consociation, and redefinitions of existing concepts such as the soil complex and the soil association. However, examination of the application of Soil Taxonomy in a geographic context reveals fundamental deficiencies in its ability to portray landscape pattern in a manner that concisely and effectively conveys to map users the soil surveyor's knowledge of soil distributions. Some of these problems can be illustrated by examining soils formed on the interbedded shales, sandstones, and dolomites of the Rome formation in the Central Valley of Virginia. These soils fall within four separate soil orders, arranged in such intimate landscape patterns that Soil Taxonomy seems inadequate as a vehicle for describing their geographic character. Alternative concepts for mapping units, including the génon, the pedotop, and the “elementary soil areal,'’proposed by pedologists with a concern for geographic properties of soils, may form the basis for developing mapping units more suitable for the description of complex spatial variation.

Key Words:

• soil patterns
• soil survey
• soil classification
• landscape mapping
• Virginia
• soils
• soil geography