关键词: 微生物结皮, 种子萌发, 出苗

Abstract: Experiments on seed germination and seedling emergence of two annual plants in microbiotic crusts and sand (as for contrast) were conducted in greenhouse. The experiment was arranged in four treatments: soil in moist and dry situations; crusts (moss and algae) in intact and disturbed situations. Overall, Bassia dasyphlla seedlings emerged better in intact moss crust and two disturbed microbiotic crusts, but intact algae crust acted as the physical barrier to Bassia dasyphylla seedling emergence by preventing its root from contacting soil. The small-seed specie, Eragrostics poaeoides, can overcome this barrier by having a greater soil contact area compared with larger seeds and having special structure such as fibre that penetrate intact algae crust into the soil. The emergence of Eragrostics poaeoides was reduced in disturbed microbiotic crusts. Moisture had a significant effect only on the emergence of Bassia dasyphylla seedlings, which emerged better in the moist treatment than in the dry. Hence, it is likely that variation in rainfall causes yearly differences in seedling emergence of the two species and affects their distribution on different habitats.

Key words: microbiotic crusts, seed germination, seedling emergence