The aim of this study was to assess the relationship between biodiversity and the richness of woody and ground vegetation species, soil physicochemical and physiographic characteristics of the Zagros forests. This study was conducted at Arghavan reservoir in the North of Ilam Province in Iran. For this study, plots with a systematic distribution across the northern (n =24), southern (n =20) and western (n =13) aspects were selected and vegetation, soil and physiographic data were measured. Results showed that, in the southern aspect, ground vegetation diversity had a negative relationship with clay and sand while it had positive correlation with silt. In the northern aspect, ground vegetation diversity had a negative correlation with elevation above sea level. In the western aspect, ground vegetation diversity had a positive correlation with CaCo3 while it had negative correlation with salinity and elevation above sea level. Results also showed that, in all the aspects, woody species only had a relationship with physical factors. These results suggest that in ecological studies for assessing the relationship between vegetation and environment, soil factors should be measured for the assessment of ground vegetation and, for woody species, physical and physiographic factors.