The Potential of Species Richness and Diversity in Soil Seed Bank under Exclosure and Grazing

Conservation and restoration of biodiversity is very important for degraded rangeland ecosystems. It is necessary to assess the potential of soil seed bank as a major source of species. In this study, the soil seed bank size and composition were compared between exclosure and grazed areas. This was done in Chahar-Bagh rangelands in Golestan province. Soil was sampled in Exclosure and Grazing from 0-5 and 5-10 cm depths in 90 quadrates of 1 m2. Then seed bank composition was identified after seed germination in glasshouse. A total of 28 species from 15 families were found in soil seed bank flora of both exclosure and grazed areas. Compositae, Gramineae, and Rosaceae were dominant in soil seed bank. Also, hemicryptophyte, Forbs and perennials were abundant in the seed bank of both areas. Exclosure significantly increased the seed density of Digitaria sanguinalis, Potentilla canescens, Stellaria media, Sonchus oleraceusand Galium verum in the seed bank. The species richness and diversity indices were not significantly different between two areas. These indices significantly increased in upper soil layer in exclosure while these indices were not significantly different between two soil depths in grazed area. The result of this study showed that exclosure influenced the soil seed banks, however, there was no evidence of positive changes in species richness and diversity indices and also an increase of grasses in soil seed bank.