Agriculture Reference
In-Depth Information
The Categories of the System
The categories of the hierarchical system are designed to serve speciÝc functions, and the use
of any categoric level has restrictions imposed by its information content. Conceptually, categories
follow these rules:
A category has completeness, because it permits all members of the population with similar attributes
to be included.
A category is deÝned by an abstract concept that characterizes the population.
The deÝnition is the only basis by which the individuals of the population can be separated;
different properties or marks may be used to recognize or satisfy that basis.
The usefulness of a category is judged in terms of its deÝnition, its function(s), and its potential
uses. In Soil Taxonomy, the categories are Ýxed, but other evolving classiÝcation systems usually
rely on their previous system to determine the number of categories. Determining or developing a
rationale for each of the categories in the three terms could augment this approach. Table 4.3
summarizes the rationale for each of the categories in the Soil Taxonomy.
The
is a statement of the conceptual framework that permits the construction of
classes in that category providing the boundary conditions for lower categories within each class.
It provides the Ñraison dÔetreÒ for that category.
The
deÝnition
determines the need for the category and is a statement of the purpose for which
it was constructed. If a category does not perform its function, or if it is believed that the designated
functions could be achieved by other means, then the role of the category must be examined.
function
provide examples of the application of the categoric level. It also suggests
appropriate scale and the smallest land area where the information content of the category is
applicable.
Table 4.1 provides a basis for reÝning current systems or developing new national systems.
Potential uses
ACCOMPLISHING THE OBJECTIVE
The questions we set out with were these: Why soils, what is soil, why classiÝcation, and what
objectives? Herein lies the foundation of systems and the biases that they promulgate.
Purpose
Purpose is the driving force of any classiÝcation, and it is the only real basis for judging the
adequacy of the system. Does the system satisfy its own purpose and objectives?
1.
Soil survey is a complex process because it is designed to allow predictions of behavior of soils
(applied objectives) and to support the recognition and mapping of soils (scientiÝc objectives).
The geography of factors and processes implies that soils are pieces of landscapes, and that
genesis based on static property correlations will be needed. Interpreting behavior implies current
interactions of properties and environments (dynamics), including manipulations by humans. Its
purpose is to do both, mainly by identifying bodies and kinds of soils. Some have argued that
because of the contrasting (though interrelated) nature of objectives, one system will not accom-
plish both objectives.
2.
Genesis is less of a mixed bag, as genetic relationships can be separated into facets that emphasize
special factors, features, or concepts. Particular attention can be given to what, where, and why
parent materials are the initial stage of evolution. Deciphering pathways of processes that seem
to result in speciÝc kinds of soils may be a main purpose. Development of morphology has always
been important, and so the static-historical properties are given more emphasis. Geographic dis-
tributions of kinds of soils as a consequence of evolution and pedogenetic development are valued
purposes as well.
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