Investigation of Pedological Criterion on Rangeland Desertification (Case Study: South of Rude-Shoor Watershed)

Investigation of desertification trend needs understanding of phenomena creating changes singly or action and reaction together in the manner that these changes were ended up in land degradation. In investigation of pedological criterion onland degradation in Quaternary rock units, first, a part of the Rude-Shoor watershed area was selected. After distinguishing target area, maps of slope classes, land use and geology were created, and then map of units was foundedby overlaying and crossing these maps. In this research three indices of erodibility, salinity and permeability of soil were considered that finally each of them was shown in the shape of classified map. Then by overlaying and cross of these three maps, a new map was created that is an expression of research area zonation from the viewpoint of indices that formerly,were explained. As determining and distinguishing of desertification intensity of potential of created units from crossing of indices was not possible with using of pure mathematical or statistical relations, so were exploited principles and concepts of fuzzy logic and statistics for achieving to main result and were used functions of fuzzy algebraic sum, fuzzy algebraic product and fuzzy gamma after determining weight or value fuzzy gamma after determining weight or value of factors. Obtained results from a comparison of gained maps from different operators with an evidence map expresses thisactual that the most appropriate of fuzzy function for zoning desertification intensity or potential in research area and similar area with that is function of 0.8 from fuzzy gamma model (gamma = 0.8). After classification of obtained mapfrom function of 0.8 from fuzzy gamma model, by overlaying the desertification potential zonation map with land use map, kinds of soil zones were characterized on the base of their desertification effect. This research determined twoclasses of desertification qualitative potential (high 43.08% and moderate 56.92%).