Soil seed bank of the Atriplex canescens cultivated area under different grazing intensities (Case study: Shahryar, Iran)

The aim of this study was to investigate the changes in soil seed bank of Atriplex canescens cultivated area under different grazing intensities, in Shahryar. From a 18 years old Atriplex cultivated area four sites including two sites with low and moderate grazing intensity, one ungrazed site and one site in non-planted area as control were selected. In each site, four line transects of 200m were established, and sampling was done in five 1m2 plots along each transect. Soil samples were collected from 0-5 and 5-10 cm depth using an auger with 2.5 cm diameter. After transporting the soil samples to the lab, they were cultivated in the greenhouse and the plant species germinated were identified. The experiments were continued for a period of 6 months in the greenhouse. GLM test was used to assess the effects of grazing, soil depth and their interactions on soil seed bank. When the interaction was significant, a one- way ANOVA was used. Paired t-test was also applied to compare soil seed bank characteristics in each soil depth. The highest seed density at 0-5 cm depth was recorded in ungrazed site, sites with low and moderate grazing intensity, and control site, respectively (mean: 3535, 2641, 1759, 908 seed/m2). However for the depth of 5-10 cm, the highest seed density was recorded in ungrazed site, site with moderate grazing intensity, control site, and site with low grazingintensity, respectively (mean: 945, 607, 262, 122 seed/m2). The highest species diversity of seed bank in the depth of 0-5 cm was observed in site with moderate grazing intensity (Shannon diversity index=3.12). A significant difference in seed bank species diversity was only observed between site with low grazing intensity (Shannon diversity index=0.65) and other sites. In all sites, seed bank diversity and density decreased with soil depth