Effects of Grazing Gradients on Diversity of Vegetation in Arid Rangelands (Case Study: Haji Abad Rangelands, Southern Khorasan)

the effects of grazing on the rangeland quality and quantity changes are inevitable. One of the rangeland ecological characteristics that are affected by grazing is the richness and diversity. The main objective of this study was to evaluate changes of species richness, diversity and evenness in the grazing gradient (distance from watering point). Sampling of vegetation was performed along two main vectors at 500 m, 1000 m, 3000 m and 5000 m from each watering point. Numerical indices richness, diversity, dominance and evenness were calculated and comparison of different indices among the intervals was performed. The data of vegetation in grazing gradient were then subjected to ordination by Detrended Correspondence Analysis (DCA) using the Bray–Curtis distance coefficient. In general, 37 species were identified from 15 families. The results showed that livestock grazing in addition to changes in vegetation cover and density, also richness and diversity will be affected. So that with increasing distance from watering point, the numerical value of the richness and diversity indices were increased significantly. Detrended Correspondence Analysis ordination results showed that a clear distinction between plant species within 500m and 5000m from of watering point.