| Desertification has been recognized as one of the most serious environmental problem in the world. The consequences caused by desertification directly threaten the environment on which people live, bringing considerable economic, social and environmental problems to the local residents. Therefore, finding a viable approach to reverse desertification has become such an urgent problem for humanity. In this study, we choose a kind of lyophilic colloid, Artemisia sphaerocephala gum(ASG) which was extracted from seed coat of perennial semi-shrub of A. sphaerocephala, as the research object. We studied the sand-fixing property of ASG and its impacts on soil microbes and cultivation of biological soil crusts (BSCs). The results showed:(1) When the ASG was applied on the sand surface, the crust was formed in surface layer. The ASG could remarkably increase the crusts thickness and compressive strength. The ability of anti-erosion was improved greatly with increasing concentration of ASG. The sand specimens could withstand a strong wind of 20 m/s without wind erosion when the concentration was more than 0.10%. The mass fraction of micro-aggregates decreased and that of large aggregates increased because the sand specimens bonded together under the influence of ASG. The mean weight diameter of soil aggregates was strikingly enhanced, which suggested that the ASG can enhance the soil aggregate water stability. The ASG had excellent water absorption and retention, and could promote the seed germination and seedling growth of the two pioneer sand-fixing plants (Corispermum puberulum and A. sphaerocephala). Sand surface treated with 0.20% and 0.50% ASG have no obvious wind erosion in the field sand-fixing test.(2) In the soil bacterial community, the relative abundance of higher phyla included Proteobacteria, Firmicutes, Bacteroidetes and Actiobacteria. The ASG have significant effect on Proteobacteria and Firmicutes (P<0.05). A small amount of ASG are favorable to Firmicutes growth and reproduction, and Firmicutes gradually replaced Proteobacteria become the dominant groups, as well as Bacillus become the most dominant genera. The ASG has increased the soil bacterial a-diversity and it has significant effect on soil bacterial community structure. Bacillus and Klebsiella were the main contribution species resulting community structure differences between no ASG addition treatment and others treatment; Azotobacter was the main contribution species resulting community structure differences between high ASG addition treatment and others treatment.(3) The ASG have a significant effect on BSCs cultivation. The thickness and compressive strength of BSCs were significantly increased with increasing dosage of ASG. The ASG can notably raise the content of chlorophyll a in BSCs, while high dosage (15.0 g/m2) has no remarkable effect on it. The mass fraction of micro-aggregates decreased and that of large aggregates increased, and the ASG can strikingly enhance the mean weight diameter of soil aggregates, which showed that the ASG could notably enhance the water stability of BSCs.The results indicated that the ASG as a kind of sand-fixing agent has the characteristics of better sand-fixing, lower cost, and environment-friendly, and can be used to desertification control with vegetation. The ASG not only can promote the growth and reproduction of soil microbe, as well as improve soil microenvironment, but also improve the resistance of BSCs to wind erosion, as well as accelerate the formation and developmet of BSCs. From the perspective of the spraying amount, the optimum concentration was 0.20% for field sand-fixing, and the optimum additive amount was 6.0 g/m2 for BSCs cultivation. This study can provide the theoretical basis for ASG in the application of desertification control. |
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