[Soil seed banks of different grassland types of Alashan arid desert region, Inner Mongolia].

Investigations on the soil seed banks of different grassland types of Alashan arid desert region in Inner Mongolia showed that when the altitudes of sampling plots increased from 1,370 m to 1,750 m, the soil seed densities of natural grasslands decreased from 326 grain.m-2 to 76 grain.m-2. At the altitude of 1,100 m, the soil seed density was 56 grain.m-2 in typical desert plot, but only 8 grain.m-2 in the sand dune plot. After the vegetation was restored with Artemisa sphaerocephala on sand dune, its soil seed density increased obviously, almost as 17-29 times as sand dune's. In this study, 31 seeds m-2 were sampled, which belonged to 11 families. Among them, annual plants accounted for 77%, 100% and 70%, perennial plants accounted for 21%, 0 and 16%, and semi-shrubs accounted for 2%, 0 and 14%, respectively for natural grassland, sand dune and sown grassland. Shrub seeds were not found in all the soil seed bank plots. When the altitudes of sampling plots increased from 1,100 m to 1,750 m, the species richness (Margalet index) of soil seed banks of natural grasslands increased from 1.49 to 2.77, and the species diversity (Shannon-Winner index) increased from 0.697 to 0.917.