Analysis of uncertainty of a soil map using taxonomic adjacency and pedodiversity indices

Soil classes are usually separated by arbitrary threshold values for soil properties. Based on the concepts of taxonomic adjacency and pedodiversity, this paper compares the potential variability and uncertainty associated with arbitrary boundaries or defined thresholds for soil classification criteria in both Soil Taxonomy and WRB systems. After preparing the geopedologic soil map (1:50,000 scale) for part of the Lalehzar region (Kerman province), based on the separated soil classes in both the mentioned classification systems, the taxonomic adjacency matrix of studied soils is prepared using algebraic graph theory. Then, the largest eigenvalue of the matrix (the spectral radius) was used for calculating taxonomic adjacency index of soil map of the region. Besides, the diversity of the soils of the area was calculated using Shannon diversity index and is compared with the taxonomic adjacency index. Results showed that the Soil Taxonomy criteria have greater degree of uncertainty in the classification of the soils of the studied area compared to the WRB system. Comparison of the taxonomic adjacency index results with those of the Shannon diversity index in showing the diversity of the soils indicated that the WRB system has acted more accurately than the Soil Taxonomy system.