Through the Decades: Taxonomic Proposals for Human-Altered and Human-Transported Soil Classification

Abstract

For decades, pedologists all over the world have been debating about anthropogenic (human-altered and human-transported, or HAHT) soil classification. The result has been several taxonomic proposals, based on varying rationale, each aiming to ensure a more correct assignment of HAHT soils to the different U.S. Soil Taxonomy class levels. Starting from such innovative ideas, this study aimed to assess whether or not such proposals may actually be adequate and appropriate when applied to HAHT soils representing conditions that differ from those for which the relevant changes were proposed and tested. More specifically, reference is made to the soil of an important industrial district of Italy, where human manipulation of earthy materials has given rise to soil entisolization processes, with a consequent taxonomic shift from natural Alfisols to anthropogenic Entisols (HAHT soils). These HAHT soils currently meet the requirements for a “mantle” classifiable as Alfic Xerarents, although this classification gives no information about its having been formed from human transported materials (HTM). On the premise that the intention is not to introduce changes to U.S. Soil Taxonomy, the study presents and discusses an overview of possible new taxonomic accommodations of the investigated HAHT soils by comparing a top-down approach (introduction of a new soil order) to a bottom-up approach (introduction of taxa at subgroup levels). In the first case Alfic Geofragmexerant may be the most suitable designation, while the bottom-up approach results in the more informative Anthroportic Xerorthents Subgroup.