Abstract: Biological soil crusts are widely distributed on the surface soil in the Gurbantunggut Desert. Studies on soil seed bank with the coverage of biological soil crusts can facilitate our understanding of the ecological functioning of biological soil crusts and vegetation renewal and succession. In this study, we focused on three types of biological soil crusts (cyanobacterialalgal crusts, lichen crusts and moss crusts) regarding the dominant functional group in crusts and investigated soil seed bank diversity and distribution in the Gurbantunggut Desert. In the horizontal distribution of soil seed bank, soil seed bank density was significantly higher in biological soil crusts than in bare sand, and it differed among the three types of crusts. Soil seed band density was highest in lichen crusts (5905±778 seeds·m^-3), suggesting lichen crusts has the largest potential to entrap seeds. Seed bank density in moss crusted soil was 1138±380 seeds·m^-3; cyanobacterialalgal crusts showed no difference in seed bank density with bare sand. The degree of biological soil crust development, the seed morphology, the spatial distribution difference of different biological soil crusts were the reasons for the difference of the horizontal distribution of soil seed bank. Seeds were primarily distributed in the shallow soil layer of 0-2 cm in biologically crusted soil, consistent with that in bare sand. This demonstrates that biological soil crusts exert no impacts on the vertical distribution of seeds. The similarity index of soil seed bank with vegetation was very low, ranging from 0.14 in bare sand to 0.29 in moss crusted soil. The species diversity and abundance in seed bank were lower than those of the plant community. This result, to some extent, suggests a limited role of soil seed bank in vegetation restoration in this region. However, the inhabitation of biological soil crusts facilitates the reservoir of soil seed bank and is important to sustain species diversity and ecosystem stability in the deserts.

Key words: seedling emergence, morphological plasticity, shade, Chinese fir, biomass allocation, natural regeneration