Journal of Rangeland

Species diversity differs in various spatial and temporal scales in response to different biotic and abiotic conditions. The aim of this study was to investigate the effects of grazing impact on species diversity components in local and regional scales in Ilam province. Vegetation sampling was carried out using 40 plots of 2×2 m² (20 plots in exclosure and 20 plots in grazed area) in local scale and 8 sites (4 sites within exclusion and 4 sites within grazed area) in regional scales. Plant species richness (γ_r) partitioned into additive component among plots (α₁), between plots (β₁) and between sites (β₂). We used the PARTITION software for analysis of species diversity components in different scales. According to the results, 72 plant species were observed in exclosure and 60 species in grazed area from a total of 89 recorded plant species. Additive partitioning of plant species diversity showed that, in two regions, observed plant species components (α₁ and β₁) was smaller than expected values in local scale, and in regional scale and observed plant species components (β₂) was greater than the expected value. Species diversity among plot (α₁) in exclosure area was significantly greater than the grazed area, but there was no significant trend for species diversity between plots (β₁) and sites (β₂), indicating non-random patterns of plant species. The beta diversity, with respect to more contribution to total species diversity, was more important diversity component in regional scale. This study showed that some components are more sensitive to grazing, so we suggest using these indices in vegetation management studies.