Seasonal variation in soil seed bank of summer rangelands at Sorkh-Abad Savadkooh, Mazandaran province

Seasonal variation in seed bank impacts vegetation dynamic. The purpose of this study was to determine the changes of soil seed bank during the growing season. This study was carried out in a summer grassland in the northern slopes of Alborz Mountain, SorkhAbad, Savadkoh in Mazandaran province, Iran. Sampling was done in March, May, August and October 2010 from two soil depths (0-5 and 5-10 cm). Seed bank composition and size were determined by seed germination of soil samples in glasshouse for 11 months. In this study, 76 species were identified in the soil seed bank during the growing season. In all months, seed density was greater in the upper soil layer than that in lower soil depth. The seed bank in summer (August) and autumn (October) had the maximum seed density. Significant temporal changes were found in the seed bank of 21 species. The seed bank of Thlaspi sp. , Stellaria media, Fumaria sp., Poa bulbosa, Alyssum sp., Thlaspi hastulatum, Hieracium sp. and Myosotis silvatica significantly increased during growing season while a significant reduction was found in the seed bank of Sonchus oleraceus, Cynodon dactylon, Carex sp., Potentilla canescense, Digitaria sanguinalis, Taraxacum montanum, and Dactylis glomerata.For some species such as Medicago lupulina, Agropyron repens, Veronica persica, Stachys byzantine, Tragopogon sp., and Bromus sp. soil seed banks showed a peak and then significantly declined.