Agriculture Reference
In-Depth Information
not present a complete solution to the problem, but do provide a means of separating soils in which
anthropogenic processes are the primary process of formation.
INTRODUCTION
Anthropogenic (also appears as Anthrogenic in some publications) soil-forming processes are
deÝned as those actions by humans that modify and control soil-forming processes. Humans
themselves are not a process, but they act as a factor of soil formation (Pouyat and EfÞand, 1999).
These anthropogenic processes can be generally grouped into physical alterations, hydrologic
alterations, and geochemical alterations. Examples of speciÝc processes are excavation and depo-
sition of soil, sediment, and rock; deposition of artifacts (human-manufactured or modiÝed objects
and materials); mechanical mixing or compaction; long-term increase in phosphorous and organic
matter through agriculture and waste disposal; long-term protection from natural Þooding, artiÝcial
Þooding and drainage; accelerated erosion; alteration of soil reaction by chemical additions; and
contamination with pollutants. Some of these processes may lead to formation of anthropogenic
soils
deÝned as those soils that have been profoundly affected by anthropogenic soil processes
and have morphological characteristics and properties that are irreversible, or very slowly reversible
(Galbraith and Bryant, 1999).
Anthropogenic soils may fall into two distinct categories, based on their content of artifacts
(Galbraith et al., 1999). There is no set of morphological characteristics or properties that uniquely
typify anthropogenic soils that have few artifacts. In fact, most physically altered anthropogenic
soils exhibit soil proÝles that, in terms of morphology, are indistinguishable from stratiÝed or
weakly developed soils in natural landscapes. Although many processes related to long-term
agricultural use have profoundly affected soil properties over a time scale of a few thousand years,
these anthropogenic processes are relatively fast-acting, compared to natural processes of soil
formation, and are usually documented in historical records (Fanning and Fanning, 1989).
The morphological characteristics and properties of anthropogenic soils are usually not con-
gruent with neighboring soils that formed under natural soil-forming processes. For example, the
anthropic epipedon (Soil Survey Staff, 1999) that formed under long-term irrigation has high organic
matter content relative to the expected levels in nonirrigated soils, and in comparison to surrounding
non-irrigated soils. Soils forming in transported material, such as mine spoil, occupy landforms
that can usually be identiÝed as artiÝcial or out of sync with the surrounding naturally occurring
landforms. Although the soils that form on these artiÝcial landforms often have morphology that
can be explained by anthropogenic processes, their morphology ranges from strikingly dissimilar
to indistinguishable, in comparison to soils formed under natural processes. Identical classiÝcation
of anthropogenic soils and surrounding natural soils, in some systems, is the cause of much
frustration for those attempting to identify the major reason for their existence, behavior, properties,
and location (Sencindiver and Ammons, 2000).
This chapter considers the need for incorporating anthropogenic processes in soil classiÝcation
systems, describes fundamental approaches to soil classiÝcation and their underlying concepts that
affect the incorporation of anthropogenic processes, and proposes possible approaches to incorpo-
rating anthropogenic processes in Soil Taxonomy and similar systems.
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THE NEED FOR INCORPORATING ANTHROPOGENIC PROCESSES
Anthropogenic processes should be incorporated into existing soil classiÝcation systems because
they are widely found, impact large numbers of people and extensive land areas, and may produce
soils that are distinctly different from existing soils. Additionally, in some current systems such as
Soil Taxonomy, the lack of sufÝcient classes for anthropogenic soils and processes results in areas
