Abstract: The effect of intensive livestock grazing is the most important factor in reducing biodiversity, especially in arid climates, despite many studies, is still not fully understood. In order to study the effect of plant-plant interaction and livestock grazing in one of the arid rangelands of South Khorasan province, 6 pairs of sampling area were selected in low and high grazing intensities and in each sampling area, 15 pairs of plots under the canopy of Artemisia and in Adjacent open ground were examined. Species richness and Shannon diversity were used to calculate alpha diversity. Also, Anosim analysis was performed to calculate beta diversity between the under a canopy of Artemisia and adjacent open areas, as well as the beta diversity between low and high grazing intensities. Linear mixed-effect models were used to study the effect of plant-plant interaction, livestock grazing, and their interaction on alpha and beta diversity. The results showed that in intensive grazing, the canopy of Artemisia increased alpha diversity in its under-canopy compared to the adjacent open area. But the effect of Artemisia on low grazing intensity is less. Conversely, intensive grazing intensity increased the beta diversity of open areas compared to Artemisia under-canopy. Therefore, plant diversity depends on both plant-plant interaction and intensive livestock grazing.

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