Plant diversity and vegetation distribution in an area are related to the soil physical and chemical properties. The knowledge of relationships between species diversityand soil parameteris essential for sustainable ecosystem management. This study was conducted to investigate the relationships between soil factors and species diversity indices in the protected rangelands of Lashgardar, Malayer, Iran in 2013. The land units in the area were selected in terms of slope, aspect and elevation. Two 100 m length transects were established on the slopes perpendicular to each other with the ten 2 m2 plots on each transect. The diversity, richness and evenness indices were estimated in each plot based on canopy cover percent. Soil samples were taken from each plot in two depths (0-10 cm and 10-30 cm). Then, soil physico-chemical characteristics were measured in the soil laboratory for moisture, texture, Organic Carbon (OC), Organic Matter (OM), CaCo3, bulk density, pH, and EC. The relationships between species diversity, richness and evenness with soil parameters were estimated using correlations and the multiple regressions using SPSS18 software. Results showed linear relationships between soil factors, species diversity and richness. The relationships in upper layer were stronger than the lower one. Among soil parameters, silt, OC and OM had positive significant effects on species diversity and richness whereas CaCo3, clay and sand had an inverse relationship with plant diversity indices.
