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

Aim 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 ۱۱ sites. The elevation was divided into five classes, slope into three classes, and 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 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 ۱۸۰۰-۲۰۰۰ 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 ۰-۲۰%. The values of species richness indices and dominance in the southwest direction, and Menhinick’s richness in the northwest direction, were higher than 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 ۱۸۰۰-۲۰۰۰ and ۲۴۰۰-۲۶۰۰ masl. The maximum amount of Hill evenness at the shrub PFT and slope of ۴۰-۶۰%. The highest amount of Margalef’s richness and Shannon-Wiener plant diversity was in the forbs PFT and in 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.

کلیدواژه ها:

Elevation gradient ، Physiographic factors ، Plant functional types ، Richness ، Uniformity.