Outcomes of applying a geopedologic approach to soil survey in Iran

The paper reviews a set of soil surveys carried out in Iran using a geopedologic approach for different surveying aims in different scales. Most of these studies have implemented a similar survey method including the following steps: delineation of landforms from air photos using geomorphic and soil-landscape relationships, field check of the delineations, sample areas inventory with soils classified at the family level (USDA Soil Taxonomy), and extrapolation of the soil patterns from sample areas to the whole survey perimeter. The objectives of the paper was first to assess the accuracy and precision of this method via comparing the pedodiversity and similarity indices. Second, to find out at what level of detail or scale the geopedologic survey provides reliable information for extrapolation from visited to unvisited landscape units. The results in all types of analyses showed that differences between distribution of soil types and variables in training and extrapolation units of any landform increases with increasing scale and descending taxonomic and geomorphic categories. Therefore, it is proposed that the geopedologic soil surveys to be used not more intensive than semi-detail scales. It is concluded that the geopedologic approach is a suitable method for preparing proper foundation for pedometrics methods in all scales to study the basic and applied aspects of pedology.