Effects of topographic variables on plant species diversity in rangelands of Hir County, Ardabil Province, Iran

Aims: This study was conducted to investigate the association between plant species diversity indices with topographic variables in the rangelands of Hir county, Ardabil Province, Iran. Materials Methods: Random-systematic sampling was performed in three elevation profiles at 11 sites. The elevation was divided into five classes, the slope into three classes, and the aspect into four classes. Indices of plant species richness, Margalef’s, Menhinick’s, Hill evenness, density, and dominance were calculated. Indices in different classes of topographic variables were analyzed using a one-way analysis of variance (ANOVA) and Duncan’s mean comparison. Findings: Results showed that the highest value of the Shannon-Wiener indices was observed in the elevation class of 1800-2000 meters above sea level (masl). The highest values of plant species evenness, richness, and diversity of Simpson’s and Shannon-Wiener were related to the slope of 0-20%. The values of species richness indices and dominance in the southwest direction, and Menhinick’s richness in the northwest direction, were higher than in the other directions. At the level of Plant Functional Types (PFTs), the highest amount of evenness is at the grasses PFT and elevation classes of 1800-2000 and 2400-2600 masl. The maximum amount of Hill evenness at the shrub PFT and slope of 40-60%. The highest amount of Margalef’s richness and Shannon-Wiener plant diversity was in the forbs PFT and the southwest direction. Conclusion: According to the results, elevation, and slope have the greatest effect and the aspects of the slope have the least effect on the diversity of plant species in the region.