Plant Species Diversity Response to Animal Grazing Intensity in Semi-Steppe Rangelands

Knowledge of the relationships between biotic components of rangeland ecosystem i.e. herbivores and plants is important for range managers. In order to study herbivorse grazing intensity on plant species diversity, an experiment was conductef using fuor grazing treatments in darrehshar rangelands, Ilam province in 2015. Plant species data were taken based on a randomized-systematic sampling method. Numerical values of diversity, richness and evenness indices were calculated using PAST as well as Ecological Methodology softwares. Significant differences were observed between grazing treatments for all diversity indices, except Camargo evenness index (P ≤ 0.05).The highest values of Simpson and Shannon diversity indices as 0.916 and 3.96 respectively were obtained in the ungrazed site and the lowest values of those indices as 0.87 and 3.36 were obtained in the heavy grazing treatment. Ungrazed site had 6.4٪ and 12.2٪ higher diversity than the heavily grazed site. The highest values of Margalef and Menhinick richness as 4.66 and 0.91 were obtaned in the moderately grazed site. The lowest values of those indices as 2.71 and 0.598 were occurred in the heavy grazing site. Margalef and Menhinick indices values in the moderately grazed site were 36.8٪ and 46% higher than those in the heavy grazing treatment, respectively. The highest modified and Smith & Wilson evenness indices with average values of 0.163 and 0.272 were obtained in the heavy grazing site and the lowest values with the average of 0.101 and 0.178 were in the ungrazed area. This study concludes that heavy grazing intensity can adversely affect plant species diversity in semi-steppe rangelands.