Agriculture Reference
In-Depth Information
soil properties existed previously in the system (mainly as Anthrepts), but were not represented in
all orders. Andisols have some similarity of occurrence in areas of geologically recent volcanism,
and are not found across all continents. The Gelisols were separated because of their current or
former permafrost content, which gives them similar behavior and interpretation. These frozen soils
were found in a few soil orders, mainly Histosols, Inceptisols, and Spodsols. Gelisols have a
predictable zone of occurrence and are not ubiquitous (Soil Survey Staff, 1999).
In accordance with the logic used to classify aquic conditions, Andisols and Gelisols, we should
Ýrst consider whether anthropogenic soils have more in common with each other than they do with
the soils from which they originated (their parents). As noted earlier, there is a wide variety of
distinct processes that control formation of anthropogenic soils. Although they formed under
anthropogenic processes, they may or may not share common, unique properties or behaviors that
are distinct from existing natural soils. Those anthropogenic soils that have had signiÝcant additions
of artifacts potentially have unique properties that govern their behavior and interpretation, and
cause them to be distinctly different from any existing soil classes. Conversely, other anthropogenic
soils do not have a unique set of characteristics that are distinctly different from existing soils. For
example, reclamation practices can result in soil proÝles that have the morphological characteristics
of Mollisols, and mechanically disturbed Oxisols, Vertisols, and Gelisols might very well still meet
the criteria for classiÝcation within the order of their respective parent soils. If classiÝed with their
natural soil counterparts, it can be assumed that anthropogenic soils would be represented in most,
if not all, soil orders, because they occur in all climates and land areas.
The categorical structure of Soil Taxonomy and existing class structure poses additional
challenges for incorporating anthropogenic soil processes in an efÝcient and logical manner. The
most efÝcient method of incorporation would be to add a new soil order at the very beginning
of the Keys, to avoid proliferation of classes throughout Soil Taxonomy and disruption of existing
classes. All other classiÝcation systems that recognize anthropogenic soil processes do include
a separate order of Anthrosols. Suborders and great groups could be structured to group soils
according to dominant anthropogenic process, anthropogenic materials, and properties important
to interpretation.
Alternatively, the formation of new suborders of Entisols based on anthropogenic materials, as
proposed by Fanning and Fanning (1989), would be an expedient approach if classes of soils were
added only after proof of their existence. This would temporarily capture most of the soils with
drastic physical or hydrologic alteration, and would keep the number of new classes at a minimum.
However, there would eventually be similar suborders (or exclusion statements) added to all other
orders, or the addition of a great number of suborders to Entisols. Logic would demand that aquic
characteristics of Entisols be recognized after anthropogenic characteristics, thereby disrupting
existing classes and leading to constraints in recognizing other characteristics, because of a limited
number of categories within the system.
Given the problems of classifying soils formed by anthropogenic processes within Soil Taxon-
omy and other systems that use morphology-based criteria for deÝning classes, the challenge
becomes one of modifying the system, but with minimal impact on existing classes, procedures of
identiÝcation, and underlying concepts and principles that guided the original development of the
system. Addition of a new soil order at the beginning of the Keys appears to be the most efÝcient
means of incorporating anthropogenic processes in the long run.
DIAGNOSTIC CRITERIA FOR ANTHROPOGENIC SOILS
There are two major approaches to developing diagnostic criteria for anthropogenic processes
in Soil Taxonomy and like systems that rely on morphological criteria for deÝning classes. The
Ýrst approach would involve working within existing Soil Taxonomy procedures and protocols by
deÝning new anthropogenic soil diagnostic horizons and materials, along with new rules and classes.
