Effect of Scale and Type of Classification System on the Results of Soil Mapping Using Geopedologic Approach (A Case Study: Damavand Region, Tehran Province)

Geopedology is a systematic approach to analyze the geomorphic levels for soil mappingwhich organizes natural terrains in a hierarchical order in accordance with their scale. Hereon، the effect of mapping scale and kinds of soil classification system on the reliability of the geopedologic approach was investigated. In view of that، after air-photos interpretation (1:55،000 and 1:40،000 scales) of an area (1500 ha) on the east of Damavand، two similar delineations (named A and B) were selected on the geoform map. Then، some pedons were dug in the similargeoforms based on semi-detailed soil surveys. The pedons were classified up to the family level according to Soil Taxonomy and up to the subunit level (including suffix and prefix qualifiers) based on WRB soil classification systems. This was the conducted when description and sampling from all genetic horizons and physical and chemical analyses had been already done. The results showed that mapping scale affected the results of the geopedologic approach significantly، so that relative similarity in all taxonomic levels was lower in 1:40،000 scale than the 1:55،000 scale for all studied pedons. Besides، Soil Taxonomywas more adaptable than WRB in predicting the relative similarity among soils in the same geoforms. On the whole، the geopedologic approach is still not able to estimate and determine the complete variability of soils and define their chaotic nature precisely، and the performance of this approach is limited to semi-detailed surveys and smaller ones.