Effects of Rangeland Ecosystem Simplification on Species Biodiversity and Functional Traits Changes in the Soil Seed Bank

The conversion of natural ecosystems into artificial or man-made ecosystems due to land use change can alter both ecosystem structure and function. The soil seed bank contains a source of viable and germinable seeds which can germinate under suitable environmental conditions. This can produce a new population or renew the present plant community. Information about the soil seed bank for Iranian flora is scarce and this study aimed to study the soil seed bank in rangeland which has been excluded from livestock grazing and the nearby area with a history of rangeland conversion into arable lands. We measured the seed bank in soils taken from two depths (0-5 and 5-10 cm) and how soil seed diversity and richness changes with land use changes. The results of this study showed that land use change significantly influenced soil seed bank diversity, species richness indices and functional group. The exclosure area showed the highest species richness, diversity and functional group while these indices significantly declined as rangeland became converted into arable lands. However, the abandoned area did not show significant differences from other two sites. Moreover, some functional groups such as annuals, therophytes, Gramineae and forb significantly reduced from the exclosure to the dryland area. This may show that abandoned areas have a potential according to their diversity and richness for returning into rangelands.