Variation of soil seed bank composition, diversity and richness during the growing season (Case study: grasslands of SorkhAbad SvadKoh, Mazandaran)

A major part of species diversity in grassland ecosystem is in the soil seed bank. This source of species may change within and between years. These changes can be reflected in above-ground vegetation. The aim of this study is to study the variation of soil seed bank composition, diversity and richness during the growing season. This was carried out in a part of mountain grassland in Sorkhabad, Savadkoh in Mazandaran province. Soil seed bank was sampled in 1 m2 plot along eight transects with length of 200m in March, May, August, and October 2010. Seed bank composition and size were determined by germination of soil samples in glasshouse. A total of 76 species were identified in seed bank, of which 42, 58, 52 and 55 species were found in the seed bank in March, May, August and October, respectively. Species diversity and richness of soil seed bank increased significantly during the growing season. Also, these indices at 0-5 cm depth were significantly greater than that in lower depth. The evenness index significantly decreased during growing season while it increased significantly in lower soil depth. A multivariate analysis showed that seed bank in August and October was more similar according to species composition and seed density.