In arid and semi-arid ecosystems, shrubs may act as fertility islands but theireffect may vary depending on their morphology and ecological impacts. This research wasaimed to study effect of three shrubs Scariola orientalis, Astragalus heratensis, and Rosapersica on soil properties and on the microclimate conditions (temperature, luminance, andsoil moisture) of their understory in the steppe rangelands of Kakhek Gonabad, Iran. Along50-m transects, flexible plot sizes were selected to measure the microclimate factors ofunderstory species and the open spaces next to the shrubs based on the canopy diameters ofeach intercepted shrubs. Soil samples were taken from understory of shrubs. Themicroclimatic factors of understory and open spaces were compared using paired-t test.The soil properties were analyzed under 3 shrubs and open spaces and then comparisonwere made using Duncan‟s test. The results showed that temperature and luminanceintensity were significantly lower in understory than the open spaces (p<0.05). Soil depthmoistures (15-55 cm) were higher in understory than the open space while soil surfacemoistures (0-10 cm) did not vary. Among the investigated shrubs, Astragalus heratensishad the greatest facilitation effect on microclimatic factors. The soil criteria of EC (0.32mS/cm), organic matter (1.6%), and nitrogen (0.08%) were significantly higher inunderstory of Astragalus heratensis than in the open space (0.15 mS/cm, 0.39%, and0.028%), respectively. These effects can be related to the wider canopy cover, greaterstature, and possibly nitrogen fixation for Astragalus heratensis. تفاصيل المقالة