Investigating relationships of vegetation composition and soil seed bank (case study: Vaz watershed)

This study aimed to investigate the similarity between above ground vegetation and soil seed bank in order to evaluate the possible potential of seed bank for recovering eroded communities in Vaz watershed located in northern part of Iran. Soil samples were collected from two depths 0-5 and 5-10 cm in 40 plots established along four 100 m transects (two of which parallel to the slope gradient and two of which perpendicular to the slope gradient) in winter of 2010. Above ground vegetation was also studied and recorded in the next growth season, (2011) in each plot. Sorenson index was used to measure the relationship between soil seed bank and above ground vegetation. Paired t-test was applied to compare the similarities of above ground vegetation with upper- layer and deeper-layer soil seed banks. Relative abundance of each plant species in each plot was calculated and the relative abundances were recalculated into life form and life-span for each plot for both seed bank and above ground vegetation. Paired t-test was also used to compare each life form and each life-span between soil seed bank and above ground vegetation. The results showed that the similarity between soil seed bank and above ground vegetation was generally low and the similarity was lower for deeper soil seed bank (27% vs. 10%). Perennials were higher in the above ground vegetation than soil seed bank. Therophytes were higher in soil seed bank while hemicryptophytes were higher in the above ground vegetation. We also concluded that it was impossible to predict soil seed bank using above ground vegetation and vice versa.