Ray B. Bryant, Chair
ICOMANTH
Dept. of Soil, Crop & Atm. Sciencesemail:RBB1@CORNELL.EDU
Cornell Universityphone: 607-255-1716
Ithaca, NY 14853-1901USAfax:607-255-2644

ICOMANTH is charged with defining appropriate classes in Soil Taxonomy for soils that have their major properties derived from human activities. The committee should establish which criteria significantly reflect human activities, or when a soil's properties are dominantly the result of human activities. If new classes are to be defined, they should serve a useful purpose.

As we begin the process of modifying Soil Taxonomy to better classify Anthropogenic soils, there are some issues related to the fundamental principles of Soil Taxonomy which must be addressed. Since Soil Taxonomy was designed primarily with naturally occurring soils in mind and with a strong agricultural bias, these underlying principles do not always seem consistent with the goals of classifying anthropogenic soils. However, any attempt to modify Soil Taxonomy must adhere as closely as possible to the existing principles in order to maintain the integrity of the system. Any departure must be carefully considered, and the logic for modifying the system must be carefully and completely documented. Discussion of the following issues is proposed as a prelude to constructing classes.

Some discussions about anthropogenic soils treat man as a natural part of the ecosystem (the biota factor) and man's activities as soil forming processes. However, many of man's activities are destructive with respect to the ordering of horizon's, i.e. - soil is drastically disturbed and horizonation is set back to (or near) time zero. In many cases the "parent material" is not earthy material that could be observed in landscapes not disturbed by human activity (landfills with garbage near the surface, urban fills containing construction debris, etc.). In one sense, the anthropogenic activity is constructive in that the "parent materials" could not derive from natural processes other than anthropogenic. It has been proposed that these processes are "anthropogeomorphic" processes, whereas human processes that modify existing soil characteristics (such as puddling paddy rice soils) are "anthropogenic" processes. Conceptually, it is helpful to keep this distinction in mind. However, I believe we are expected to address the classification of soils derived by either of these processes. In any case, the logic of Soil Taxonomy is that the dominant factors (and processes) of soil formation that explain the existing gross morphology are recognized at the highest levels of Soil Taxonomy. In the cases of Andisols and Vertisols, it is parent material that is the dominant factor explaining the gross morphology. There is much debate about whether or not we can adequately classify anthropogenic soils by modifying the existing soil orders or whether a new soil order is needed. The answer would seemingly need to be consistent with the existing logic of Soil Taxonomy, and also allow for an adequate degree of flexibility for showing differences and relationships among anthropogenic soils.

Questions:

The pedon and polypedon are defined in Chapter 1 of Soil Taxonomy, and all soil scientists have a working understanding of these concepts. The polypedon is the landscape unit to be classified and the pedon is the unit of sampling that supposedly is representative of the range of characteristics within the polypedon. Natural breaks in the landscape are the more desirable limits of the polypedon as we strive for a system that is most useful for soil survey, but class limits of soil series (including higher class limits, such as family particle size classes, which are also limits for series in a categorical system) may also determine a boundary of a polypedon. In spite of diligent efforts to tailor Soil Taxonomy to fit naturally occurring soil landscapes, we frequently encounter landscapes that cannot be mapped as simple consociations. The dominant characteristic of some anthropogenic soils may well be their variability. Can the concepts of pedons and polypedons be directly applied to anthropogenic soils or should we revisit the definitions in Soil Taxonomy to determine their applicability?

Case example:

Urban fill may or may not be extremely variable in terms of the nature and arrangement of materials. In some cases, layers of materials such as bricks, concrete and rebar, asphalt, coal ash, etc. may be very predictable and mappable. It is conceivable that we may wish to establish series with very limited ranges in characteristics. But we are also certain to find areas of urban fill which are characteristically unpredictable. Must we continue to handle these situations at the mapping level by treating them as complexes, or might higher classes be established specifically for these soils where the nature and arrangement of materials are virtually unpredictable? Such classes might then be further differentiated on the basis of other important properties such as wetness, presence or absence of certain types of materials, etc.

Questions:

•How do we deal with the variability of anthropogenic soils in our classification scheme? Is variability in and of itself a highly significant characteristic that can be used as criteria for a class?

•What is our unit of classification? Are we concerned in all cases with the mappability of our classes where accommodating variability is of major concern, or will the system also be used on a site-by-site basis where specificity of information is most desirable?

In some cases, the reason for wanting to differentiate among anthropogenic soils derives more from the nature of the substratum that it does from the nature of the material in the "soil zone", and we commonly have knowledge of the substratum that would allow classification based on the nature of those deeper materials. In recent years there has been a move to expand our lower depth of mapping (and classification?) of naturally occurring soils and geological deposits in response to the acknowledged need for more information. Our best chance for success in classifying to lower depths would seem to be in anthropogenic soils where we have historical knowledge of the nature of the substratum. Can we really form desired groupings of soils without taking into consideration the nature of the substratum?

Case example:

An unregulated landfill on Staten Island, New York has a thin cap of "soil" cover over urban garbage. Over most of the landfill, one can readily observe urban waste within the 2 meter zone. The major limitations to use and management are the evolution of methane gas and settling as a result of waste decomposition. The long range plan for use of the landfill is as a city park. In one area, an additional 2 meters or more thickness of clean fill has been added and a ball field was constructed. Assuming that we had classes designed to differentiate between landfills containing garbage and soils forming in clean fill (i.e. - fill derived from soil or geologic material not containing trash and which may be suitable for home construction), how would we handle this case?

Questions:

At the higher categories in Soil Taxonomy, classes are formed to group soils in order to reflect their genesis. Our theories of genesis govern the groupings and reflect our current state of knowledge about soils and the factors and processes of formation. Since our state of knowledge is never complete, we guard against biasing our classification by requiring that criteria for classification be based on morphological characteristics that can be observed or measured by laboratory or field techniques. In following the strict rules for classifying soils according to their morphology, we frequently discover that some soils make odd bedfellows. That may lead us to conclude that our current concepts of genesis may be flawed. Hence, Soil Taxonomy becomes a valuable research tool to assist us in improving our knowledge of soils and their genesis. It would not be so if we allowed our current bias with respect to mode of genesis to enter into the classification process. Grouping soils according to theories of genesis at the higher categories and using morphology-based criteria are fundamental principles that guided the construct of Soil Taxonomy.

In the vast majority of cases of anthropogenic soils, the anthropogenic processes resulting in the present expression of morphology are a matter of historical record. There may be absolutely no uncertainty with respect to the anthropogenic processes of development or modification which led to the current soil morphology. Why then should we constrain ourselves from using that knowledge to form groups of soils with similar genesis? What rationale would there be for ignoring historical record? This becomes especially relevant when there may be no reliable morphological indicators that can be consistently applied to identify the genetic processes. There are many soils for which this is the case.

Case example:

In China, there are soils that have formed by deposition of sediments as a result of long-term irrigation. The morphology (and in a sense the process of formation) of these soils is identical to that of a Fluvent. But these soils may occur on a terrace or upland position where their presence in clearly "not natural" (i.e. - anthropogenic). They do not conform to the ecology of the landscape. In natural landscapes, the presence of Entisols may be due to recent deposition by geologic processes indicating a geologically active environment, resistance of the parent material to weathering and soil development, etc., but they occur in predictable landscape positions. To the Chinese, this anthropogenic "Fluvent" is not the same as a naturally occurring Fluvent. Yet there are no morphological clues as to the difference.

Questions:

Any subdivisions of anthropogenic soils within Soil Taxonomy should be based on properties of greatest significance to their genesis in the higher categories and on properties of greatest significance to use and management in the lower categories. Most current and evolving systems differentiate on the basis of the nature of the "parent material" as one of the properties of highest significance. But what other properties of anthropogenic soils are highly significant? An aquic moisture regime (and its modifications, i.e. -- aeric, epi, endo, etc.) is a highly significant property to both genesis and use and management in existing soil orders, but how important is it in anthropogenic soils? How should anoxic conditions due to methane gas be treated? How important is bulk density (and/or porosity)? For all of these properties and others, are there morphological properties that can be used to consistently and reliably identify the condition, and can they be used in mapping?

Questions:

It is relatively easy to envision classes of anthropogenic soils forming in anthropogenic parent materials. Criteria can be based at least in part on morphology. But how do we address anthropogenic processes that result in the removal of soil material? By some of the logic above, what is not there due to the activities of man may be as important (at least conceptually) as what is put there by the activities of man. A borrow pit formed by the removal of gravel or caliche is as readily identified as a landfill and is as much "out of place" in the ecology of the landscape. If we allow the use of historical knowledge, it would not be difficult to construct classes for these situations. But the difficulty may lie in determining how much soil must be lost before we begin to recognize the effects of anthropogenic processes. A recent DRAFT of a revised definition of a buried soil is appended. Classification of anthropogenic soils may begin when the thickness of a surface mantle of new material (of anthropogenic origin) effectively buries the underlying soil. But how much soil must be lost before the rules of classifying anthropogenic soils are invoked? It has been proposed that this committee address the issue of eroded Mollisols. Is accelerated erosion an intergrade to soils where removal was affected by other anthropogenic processes? If so, how do we treat it within the context of Soil Taxonomy?

The previous discussion touched on the issue of defining intergrades between anthropogenic soils and other classes. There are other situations in which anthropogenic processes affect changes in classification within Soil Taxonomy. How do we address the agricultural liming of an Ultisol to the point that it classifies as an Alfisol? What about the Mollisol that no longer meets the color requirements of a Mollic epipedon due to the incorporation of carbonates by deep plowing? I believe we are expected to address soils in California that are drastically disturbed by "deep" plowing. How deep is deep? Are salinization and desalinization, due to irrigation, anthropogenic processes that should be addressed by this committee? The point here is that Soil Taxonomy was designed so that "normal agricultural practices" would not change the classification of a soil. But "normal agricultural practices" of the day have changed, and they do in fact cause changes in taxonomic classification. By expressly recognizing anthropogenic processes in Soil Taxonomy, we will be forced to define degrees of anthropogenic modification which are expected to grade into other classes of soils having insignificant anthropogenic modification.

Questions:

After reading and contemplating these comments, I invite you to comment on any or all of these issues. A good first step would be to compile case examples of soils modified by or derived from human processes, and I would appreciate brief descriptions of human activities that result in altered soils which you feel should be included in our deliberations. I would also like your suggestions or proposals for specific classes of anthropogenic soils complete with definitions of the classes similar to what appears in Soil Taxonomy in the introduction of every class at any categorical level.

• Draft definition of "buried soils"
• Summary report of Drastically Altered Soil Committee, Midwestern/Western Regional Cooperative Soil Survey Conference, 1994
• Summary report of Drastically Altered Soils Committee, Northeastern/Southern Regional Cooperative Soil Survey Conference, 1994