the effect of grazing on density, diversity and richness of soil seed bank in mountainous rangelands (case study: waz watershed, mazanderan province)

this study aimed to investigate the effect of animal grazing on soil seed bank characteristics in the northern slopes of alborz. for this purpose, soil seed bank characteristics were compared between grazed and ungrazed areas. therefore, four transects perpendicular to the sides of exclosure inside and outside of it were established. then soil samples were collected within 28 plots inside and 28 plots outside of exclosure along the transects from two different depth: 0-5 and 5-10 cm. soil samples were then spread in the greenhouse and the plant species germinated in the greenhouse were identified and removed one time per 12 days. general linear model and factorial was used to study on the effect of grazing, depth and interaction between grazing and depth on soil seed bank characteristics. in case that the interactions became significant, unpaired t-test was used to compared seed bank characteristics between grazed and ungrazed in each depth, separately. in addition, paired t-test was applied to compare seed bank characteristics between two depths in grazed and ungrazed areas, separately. the results showed that all seed bank characteristics were significantly higher in ungrazed than grazed area particularly in upper layer of soil. all seed bank characteristics were also significantly higher in upper layer than the deeper layer of soil. the results implied that soil seed bank is a reliable source to recover the over grazed degraded points in the study area.