The soil seed bank has a large influence on the potential for grassland restoration. This study aimed to characterise the composition, density, richness, and evenness of seedlings emerging from the soil seed bank under different sheep stocking rates, in a summer grazing system, in semi-arid China. Soil was sampled in 2015, a year with extreme drought conditions and in 2016, a normal rainfall year. The soil seed bank was assessed by measuring seedling emergence under laboratory conditions. Comprising 16 species, 85.4% of the seedlings were concentrated within a depth of 0–5cm. Drought significantly reduced the density and richness of the seedlings. Grazing increased the richness of seedlings by increasing the richness of aboveground species, and grazing significantly reduced the evenness of the seedlings by reducing the evenness of aboveground species. Drought significantly reduced the similarities between the seedlings and the aboveground species, whereas grazing increased similarities in both years. This study revealed that the density and richness of seedlings were higher in higher stocking rate in drought year. We conclude that negative effects on density, richness and evenness of the seedlings caused by drought can be overcome by rotational grazing especially at higher stocking rate.
Responses of Soil Seed Bank and Vegetation to the Increasing Intensity of Human Disturbance in a Semi-Arid Region of Northern China