Comparisons between USDA Soil Taxonomy and the Australian Soil Classification System I: Data harmonization, calculation of taxonomic distance and inter-taxa variation

Soil classification as a world exercise consists of predominantly individual organizations, creating locally meaningful categories for regional soils. This process has inevitably created a recognized disconnect between classification systems, and a push for a universal classification has been proposed. In this paper, as a way of standardization between systems, soil taxa at the great group level from two separate regions and soil classification systems, Australia and the United States of America were represented by separate databases of soil profile descriptions (SPDs) comprising the same 23 properties at 18 depth intervals. Taxa centroids from Soil Taxonomy (ST) and the Australian Soil Classification System (ASC) were calculated via principal component analysis. Convex hulls of each soil order of both systems were created and the associations each taxon had with other individuals in the same taxon discussed, as well as the variance. We determined that ASC orders have smaller overall dispersion compared with the ST. The influence of each property to the overall taxonomic distances was also explored. It was concluded that this analysis opened the way for the possibility of comparing differing taxonomies and could pave the way for a more comprehensive classification method.