Role of Different Shrubs in Soil Seed Bank Conservation in Different Climates of Iran

Shrubs often produce positive effects on understory soil seed bank (SSB) characteristics. However, the effect of shrubs on SSB could be variable in different habitats depending on the climate and the type of shrub. In this study, the effect of Crataegus pseudomelanicarpa (humid areas, northern Iran), Onobrychis cornuta, Berberis integerrima and Juniperus sabina (sub alpine areas, northern Iran) and, Astragalus myriacanthus and Acantholimon spinosum (semi-arid areas, central Iran) on SSB characteristics was studied. Soil samples were collected under the canopy of shrubs and the control (out of canopies) from 0-5 cm and 5-10 cm depths by auger and seed germination was monitored in the greenhouse. The results showed that generally all shrub species in different climates had a significant positive influence on SSB density and diversity in all climates. In comparison between subalpine shrubs, density of the SSB was lowest under J. sabina and highest in the control area, but did not differ between B. integerrima and O. cornuta. In comparison between semi-arid shrubs, the mean density of SSBs under A. myriacanthus (904 seeds/m2 ) was significantly higher than that of A. spinosum (361 seeds/m2 ). This study revealed that the extent to which vegetation affected SSB characteristics depends on the presence and species of shrubs in the area