Studying the Effect of Index Species Astragalus ammodendron on Associated Plants Agropyron tauri and Bromus tomentellus from Different Aspects (Case Study: Arak Province-Shazand, Iran)

The aim of this research was to investigate the effect of index species, Astragalusammodendron on the associated plants of Agropyron tauri and Bromus tomentellus fromdifferent aspects in Shazand rangeland in southwest of Markazi province. The effects ofspecies density and distribution pattern and then index species on the soil properties werestudied. Based on the randomized – systematic method, 4 transects with a length of 50 m wereestablished. To find the relationships between index and associated plants, 30 points wererandomly chosen along the transects and the number of species was counted from these pointsto a 50 cm distance in different aspects. Along the transects, the distribution pattern of indexplants and their presence and absence were determined. To find the effects of index species onsoil properties, soil samples were taken and soil properties were determined in laboratory.Data were analyzed using SPSS software. The results showed that Astragalus ammodendrondensity with Agropyron tauri and Bromus tomentellus were similar to the east and westaspects and near distances. Astragalus ammodendron distribution pattern was randomizedwith a tendency toward the clumped pattern. The effect of Astragalus ammodendron on thesoil characteristics was not significant except for the north aspect. Generally, it is concludedthat the effect of Astragalus ammodendron (index species) on Agropyron tauri and Bromustomentellus densities was not significant.