Harmonization of a large-scale national soil database with the World Reference Base for Soil Resources 2014

Abstract

Legacy soil data currently represents an irreplaceable source of data for many national and international applications. Their full use at the international level largely depends on adequate harmonization. In this study, we adopted different methods of taxonomic distance and reclassification of soil properties to convert a large-scale database originating from an extensive national mapping campaign of agricultural soils in Czechoslovakia (1961–1971), according to the criteria of the World Reference Base for Soil Resources (WRB), version 2014. The harmonization was effectuated at two levels of detail represented by two different types of soil mapping units [soil type and general soil representative (GSR)] and resulted in the conversion of original soil units into their counterparts in the WRB (Reference Soil Groups). The results showed a good potential of the adopted methods for soil data harmonization. The conceptual differences of the two harmonised classifications decreased the applicability of the taxonomic distance in the case of broadly defined and less developed soil classes lacking specific diagnostic features. The replacement of a simple conversion by soil association was a relevant approach, especially at the soil type level, where the simple one-to-one conversion showed only poor accuracy (39.5%). The accuracy at the GSR level was satisfactory (reaching ca 60%) and increased with soil association (72%). The conversion accuracy of different soil classes significantly differed from very high (e.g. 92% in Luvisols) to completely mismatched (Technosols and Histosols). The latter can be attributed to a questionable determination of soil classes in legacy maps. The study showed the potential of taxonomic distance methods in soil data harmonization and the limits of historical databases resulting from the way data were collected and recorded.