Understanding the responses of vegetation to grazing exclusion along a salinity gradient is useful for the management of grasslands. We studied the responses of vegetation to grazing removal (ungrazed areas) in three semiarid regions with different soil salinity levels: non-saline, moderately saline and hyper-saline. The results showed that Bray-Curtis dissimilarity between grazed and ungrazed areas were highest in the non-saline region. In the hyper-saline region, the grazing removal had no significant effect on any of the diversity indices, while in the non-saline regions, vegetation changes were occurred by grazing exclusion at the highest magnitude. Generally, the magnitude of vegetation changes by livestock grazing exclusion was decreased along the soil salinity gradient. This research could help to understand how disturbances and stresses interactively influence grasslands dynamics in semiarid regions and to understand the effects of grazing on grassland dynamics and sustainability in deserts in the context of salinization.

Shrub encroachment (SE) has been occurring and studied worldwide over the last century. What remains to be investigated is how soil and vegetation characteristics vary under canopy of different species of shrubs for restoration goals. Thus, this study aimed to compare the effect of three shrub species (Amygdalus scoparia, Ebenus stellata, and Daphne mezereum) on soil and vegetation characteristics under their canopies in semiarid rangelands in Iran for restoration purposes of degraded areas. Fifteen sites were randomly selected in such three shrub species which were found close to each other in each site. Soil and vegetation characteristics were measured under the three shrubs, comparing with outside the shrub canopies (control). One-way ANOVA and non-metric dimensional scaling were used to clarify the differences of the effects of different shrub species on sub-canopy soil and plants. The results indicated that the effect of different species of shrubs on soil properties was not equal, more pronounced by A. scoparia. Similarly, the highest value of herbaceous Shannon-Wiener diversity index was recorded under A. scoparia (2.07) as compared with D. mezerum (1.76), E. stellata (1.41). The highest and lowest values of Menhinick richness index were observed under A. scoparia (3.43) and E. stellata (1.46), respectively. Compared with two other shrubs, a taller canopy in A. scoparia (3.50m vs. 2.60m and 1.83m) probably led to greater litter input by the shrub. Different effects of different species of shrubs on sub-canopy soil and vegetation should be considered in the restoration projects of degraded semiarid rangelands.

Little information is available about the effects of different species of shrubs on the composition of the soil seed bank (SSB) in semiarid regions. We determined the role of three dominant shrub species on SSB characteristics and evaluated their potential for their possible use in rangeland restoration projects. Fifteen sites, each containing three shrub species (Amygdalus scoparia, Daphne mezereum and Ebenus stellata) and a herbaceous patch (control) in close proximity, were sampled and their SSB density, species richness and diversity at 0-10 cm depth were determined. The results showed that the density of the SSB was highest under A. scoparia (1133 seeds per m2) and lowest in herbaceous vegetation (110 seeds per m2). Species richness and diversity of the SSB was significantly greater under E. stellata than under the other shrubs and control. This study revealed that the extent to which vegetation affected SSB characteristics did not only depend on the presence of shrubs, but also on the species of shrub. These different roles of different species of shrubs on SSB are advised to be considered in the restoration of degraded areas through planting of shrubs in semiarid regions. Planting and the extension of E. stellata cover in degraded sites could be of priority due to its prominent role in herbaceous SSB reservoir and species diversity and richness.

Little information is available about the effects of different species of shrubs on the composition of the soil seed bank (SSB) and how the SSB could contribute to the restoration of degraded area in semiarid regions. We determined the role of three dominant shrub species on SSB characteristics and evaluated their potential for their possible use in rangeland restoration projects. Fifteen sites, each containing three shrub species (Amygdalus scoparia, Daphne mezereum and Ebenus stellata) and a herbaceous patch (control) in close proximity, were sampled and their SSB density, species richness and diversity at 0-10 cm depth were determined. The results showed that density of the SSB was highest under A. scoparia (1133 seeds per m2) and lowest in herbaceous vegetation (110 seeds per m2). Species richness and diversity of the SSB was significantly greater under E. stellata than under the other shrubs and control. This study revealed that the extent to which vegetation affected SSB characteristics did not only depend on the presence of shrubs, but also on the species of shrub. These different roles of different species of shrubs on SSB are advised to be considered in restoration of degraded areas through conservation of shrubs in semiarid regions.