Soil taxonomic distance, a tool for correlation: As exemplified by the Hungarian Brown Forest Soils and related WRB Reference Soil Groups

This paper discusses the application of taxonomic distance calculations for the correlation of soil units from different soil classification systems.Conceptual and centroid-based methods were tested on the brown forest soil types of the Hungarian Soil Classification System, correlated with the Reference Soil Groups of the World Reference Base for Soil Resources. The results of the distance calculations were compared and evaluated with previous expert based correlation studies.Earlier studies to derive taxonomic distances between soil taxa based on their dominant identifiers were further developed with the introduction of finer coding, and the application for correlation purposes. For the centroid-based approach, values were calculated from legacy laboratory data of different soil properties of the studied soil classes to derive the taxonomic distances.The results of the three different approaches are concordant, but as each method studied has its own limitations, we recommend their joint application. Therefore the methods complement each other and provide a good tool to assist correlation tasks. We found this study very helpful in identifying the shortcomings of certain definitions and the conceptual conflicts within and between systems. The numerical approaches should be applied in the evaluation of current systems in the efforts toward a Universal Soil Classification System.

► Taxonomic distance calculations applied successfully for correlation purposes.
► Distance metrics is suggested for the evaluation of current and future systems.
► Strengths and limits of concept- and centroid-based approaches were revealed.
► The studied methods complement each other, combined usage is recommended.