AbstractSpecies diversity is an index for sustainability of rangeland ecosystems. We studied the effect of environmental factors (soil properties and aspects) on plant species diversity in Zagros mountainous rangelands (vegetation type: Festuca ovina-Astragalus parrowianus) in the west of Hamadan in March–July 2009. For this purpose, four aspects were defined in the study area. Vegetation types were studied by physiognomic-floristic method in the field. The factors of vegetation were measured by transects using a systematic-randomized method. Five transects (100 m) and five plots along each transect were used. One soil sample (composition, 0–40 cm) in each plot was collected by a randomized method and assessed the following factors: pH, OM, N, EC, P, K and texture in the laboratory. The multiple regression method was used to investigate the relationship between species diversity (dependent variables) and soil and topographical factors (independent variables). Results showed that soil characteristics and aspects had significant effects on diversity in which north, east and west aspects as well OM, N, EC and clay were the most prominent factors influencing diversity.
