Mossivand et al.: Effects of some ecological factors on distribution of Prangos uloptera and Prangos pabularia in rangelands ofArdabil province, Abstract. The aim of this study is to assess the effects of some environmental factors on the distribution of Prangos uloptera DC. and Prangos pabularia Lindl. In the rangelands of Ardabil province, in the north-west of Iran. Six sites with the distribution of the genus Prangos (presence) and six sites without Prangos (absence) were identified. Three 100m transects were established. On each transect, ten 4m 2 plots were located, and the total canopy cover and density of plants were recorded. Soil samples were collected from a depth of 0-30cm on each transect. Elevation, slope and aspect were extracted from the Digital Elevation Model (DEM), and rainfall, temperature were also extracted from the derived gradient equation and DEM for each plot. Soil parameters such as organic matter (OM), nitrogen (N), phosphate (P), potassium (K), pH, electric conductivity (EC) and texture were determined at the Soil Lab. Normality of data was tested. To compare the related parameters for the sites with the presence and absence of species, the one-way ANOVA was conducted. Cluster analysis was used to classify the collected samples.To determine the variables that were significant in the distinction of each groups and mean comparison, ANOVA and Tukey tests were conducted. To determine the importance of ecological factors for the presence and absence of the selected species, discriminant analysis was conducted. The results of the analysis of variance between presence and absence of P. uloptera and P. pabularia in habitats demonstrated significant differences for the parameters of elevation, slope, aspect, temperature, EC, pH, OM, nitrogen, phosphorus, clay, silt and sand and total canopy cover, P<0.01. The result of grouping sampling plots using cluster analysis showed that plots in three groups were separated by significant differences (P<0.05) in the multivariate analysis of variance. The results showed that P. uloptera was adapted in habitats with OM of 1.402%, N 0.126%, P 2.627 ppm , K 258 ppm , 1992m a.s.l., with average slope of 83.40%, clay 10.90%, silt 37.90%, sand 51.20%, and average precipitation of 353mm. However, P. pabularia was adapted in habitats with OM of 0.915%, N 0.088%, P 2.339 ppm , K 236 ppm , 1672m a.s.l., and with average slope of 84.80%, clay 13.60%, silt 29.70%, sand 56.70% and average precipitation of 370mm. With regard to the results from discriminant analysis, the percentages of slope, clay, sand, silt, OM, P and pH, aspect, precipitation and temperature play an effective role in the separation and distribution of the species studied. These results can be used to suggest suitable species in management and restoration of rangelands with the same ecological characteristics.