Species diversity index is an important indicator of rangelands health. This index bears vital effect on determination of ecosystems in general as well as rangelands in specific for assesment conditions and sustainability. In this study three sites were selected as follows:good rangeland, degraded rangeland and abandoned dryland. Samples were taken in four replications in each site. Percent of vegetation cover and plant density were determined. Number of species was determined by minimal area method as well as some edaphic factores in all sites. Distance from roads, village and watering points were measured for each site. Non parametric indices such as species richness, evenness and diversity were calculated. From parametric methods, aboundance-ordinal models were applied to evaluate species diversity. Curves of areas vs. species were drawn using semi logarithmic regression equations and their correlation coefficients were determined.Ordination technique was rendered to investigate the relationships between presence of species and environmental factors.Based on the results of this study significant differences (?=1%) were observed between species richness of studied sites using (margalof, jacknife and rarefaction) indices. Nonetheless rarefaction method emerged to be the most determinant. Amongest the non-parametric indices for species diversity the Hill N 1 and Shanon-Wainer revealed significant differences between sites(?=5%). Aboundance-ordinal method showed that data follow log-normal trend. Minimal areas for species richness determination were about 128, 32 and 16 square meters for good and degraded rangelands as well as abandoned dryland sites respectively. Distance from village, roads and watering points were significantly (?=1%) effective on species richness and species diversity and farther a way from these locations these indices increased and distance from village was the most effective one.Species diversity had positive relationships with organic matter, moisture saturation, lime and clay percentages. Wherease this index had negative relationships with sand percentage and soil electrical conductivity. Keywords : species diversity, species richness, Fereydan, good rangeland, degraded rangeland, abandoned dryland, ordination.
