Agriculture Reference
In-Depth Information
classiÝcation system loses credibility as a tool of communication when members of a single group
have vastly different morphological characteristics, as is often the case with soils in urban envi-
ronments (Burghardt, 1994). For example, human-transported soils that contain garbage, coal ash,
or construction debris are currently grouped with naturally formed Entisols or Inceptisols at the
subgroup and family levels in Soil Taxonomy, even though their morphology and behavior are
easily recognized as being distinct (Hernandez and Galbraith, 1997).
A recognized purpose of many classiÝcation systems is to group like soils for purposes of
correlation and interpretation. Correlating and interpreting soils forming in mine spoil is a major
concern on large acreages in the U.S. and other countries (Sencindiver and Ammons, 2000). Soil
scientists working with these soils would prefer a taxonomic class that excludes soils that are not
derived from mine spoil, to focus on distinguishing characteristics that are important to the use
and management of these anthropogenic landscapes. At the very least, those anthropogenic soils
that have been modiÝed to the extent that they would be considered dissimilar to their parent soil
and have limiting interpretations should be placed into a separate class.
Some classiÝcation schemes, such as Soil Taxonomy, were purposely designed to provide a
framework for research on soil-forming processes. To meet that objective, classes were constructed
to imply processes of genesis, but criteria are based on observed morphology or measurable
properties. Although the major anthropogenic process responsible for the formation of an anthro-
pogenic soil may be a matter of historical record, the processes of future change and development
in response to the active factors of soil formation, climate, and organisms is of interest to researchers.
Incorporating anthropogenic processes into soil classiÝcation would provide a framework for these
research efforts.
FUNDAMENTAL APPROACHES TO SOIL CLASSIFICATION
Concepts valid during the development of a system necessarily prejudice the future modiÝca-
tions of the system, and may or may not complicate the incorporation of anthropogenic processes.
Fundamental concepts that affect the incorporation of anthropogenic processes can be discussed
in terms of three broad approaches to soil classiÝcation. The ecologically based soil classiÝcation
system, typiÝed by the 1938 U.S. Soil ClassiÝcation System and the Russian Soil ClassiÝcation
System contemporary to that time, used the ecological zone in which soils formed as criteria for
classiÝcation. For example, the
included those soils that formed in a
mountain meadow. In accordance with that concept, anthropogenic soils could easily be grouped
according to the anthropogenic environment in which they formed. Mine soils could be deÝned as
those formed on mined lands; urban soils could be deÝned as those formed in urban environments.
Two other more recent approaches to soil classiÝcation can be described as Ñprocess-based with
descriptive morphologyÒ and Ñmorphology-based with implied process of formation.Ò The Chinese
Soil Taxonomic ClassiÝcation (Chinese Soil Taxonomy Research Group, 1995; Zitong et al., 1999),
the Revised Legend of the Soil Map of the World (Food and Agriculture Organization, 1996), and
the World Reference Base for Soil Resources (International Soil Science Society Working Group
RB, 1998) are examples of systems that use processes of soil formation as criteria for identifying
soil class, and describe the central concept of the class in terms of morphological characteristics
that are typical of soils that belong in the class. For example, as deÝned in the World Reference
Base, a ÑLuvisolÒ is a soil in which clay has been washed out of the upper part of the soil and
accumulated in the lower part of the soil. Moderate to high activity clays and low aluminum
saturation further characterize Luvisols. These speciÝcally named systems and other systems of
this kind do include anthropogenic processes. In the World Reference Base, Anthrosols are deÝned
as those soils that have been transformed by anthropogenic processes to the extent that the original
soil is no longer recognizable or remains only as a buried soil. In these systems, the process of
formation is the essential criteria for classiÝcationÐthus including anthropogenic processes is not
Mountain Meadow soils
