Abstract: Seedling survival and seedling growth of two annual herbs(Eragrostics poaeoides,Bassia dasyphylla) in soil microbiotic crusts and sand were studied in greenhouse and field experiments.Both species seedling survival was highest in moss crust and lowest in sand.The two species seedling survival was positively correlated with the water content of the upper soil.Seedlings of Bassia dasyphylla had more longer root a week after germination,so Bassia dasyphylla showed lower seedling mortality than Eragrostics poaeoides in three soil types and in dry and moist treatment.Dry weight of two plants in pots with microbiotic crusts were about five times greater than in pots without microbiotic crust in dry treatment.Addition of water greatly reduced the seedling mortality and increased seedling growth of both species.Soil types resulted differences to seedling survival and seedling growth,but these differences were greatly reduced by the addition of water.It is likely that variation in rainfall causes yearly differences in survival and growth in the two species and affects their cover and distribution in the artificial sand-fixing vegetation district.

Key words: soil microbiotic crust, seedling establishment, seedling survival, seedling growth