本研究在室温培养条件下研究了三种荒漠优势蓝藻¬¬¬¬¬―具鞘微鞘藻(Microcoleus vaginatus)、爪哇伪枝藻(Scytonema javanicum)、纤细席藻(Phormidium tenue)――的生长特性，不同温度(2, 5, 10, 15, 25, 35℃)、开放式载体培养状态下三种蓝藻的生长状况及形态观察，以及爪哇伪枝藻在不同温度（10, 15, 20, 25, 30℃）培养条件下的光合活性、光合色素含量和伪枝藻素含量的变化。实验结果表明：1) 在液体培养基中，纤细席藻生长速率最快，高于具鞘微鞘藻和爪哇伪枝藻；2) 开放式载体培养条件下，藻株的生长速率低于液体培养，因此荒漠优势藻类的培养优先选择液体培养，具鞘微鞘藻和爪哇伪枝藻不易被细菌污染，纤细席藻容易受到细菌污染，在培养该藻株时要考虑采取措施(如使用抗生素)抑制细菌过度繁殖；3) 爪哇伪枝藻短期培养(18天)宜选择相对较高的培养温度（25-30℃），而长期培养(30天)宜选择相对较低的培养温度（15-20℃）。
研究了温室条件下干燥沙子不同掩埋时间(0, 5, 10, 15, 20, 30天)和深度(0, 0.2, 0.5, 1, 2 cm)对人工藻结皮生物量、叶绿素荧光活性和胞外多糖的影响。结果表明: 大体上随着沙埋时间的延长和深度的增加人工藻结皮的Fv/Fm值和胞外多糖含量逐渐降低, 但是在20天和30天沙埋处理之间, 两者在不同沙埋深度均不存在显著性差异; 生物量的降低出现在沙埋处理20天和30天, 在不同的沙埋深度这2种处理时间之间差异亦不显著。Fv/Fm值和胞外多糖含量的协同降低说明两者之间或许存在着一定的关联。
|Other Abstract||Biological soil crusts occur in semiarid and arid regions throughout the world. They are formed by microorganisms and their by-products, creating a crust of soil particals bound together by organic materials. Crusts microorganisms may include cyanobacteria, green algae, lichens, mosses liverworts, microfungi, bacteria. Biological soil crusts have been proved to play an important role in maintaining or improving the state of the environment. However, due to their sensitivity to anthropogenic and natural disturbances, they are in a degraded state in many areas throughout their range. Many studies were conducted to estimate the recovery rates of the biological soil crusts under natural conditions. The results indicated that there existed a range of decades to millennia for full recovery of all components. To speed up recovery, inoculation of soils with biological crust components has been recommended in degraded arid and semiarid ecosystems.
Cyanobacteria, even though they have less ability to fix nitrogen and carbon compared with lichens and mosses respectively, grow faster and can be easily mass-cultured in liquid medium. They are generally the first photosynthetic species to appear on disturbed soils. Much interest has been focused on the effects of cyanobacterial inoculation on arid and semiarid soils.
Practical testing the feasibility of this method in the field was conducted in this study. Results showed that algal cover climbed up to 48.5% and total 14 algal species were identified at the termination of inoculation experiment; algal crusts' thickness, compressive strength and chlorophyll a content increased with inoculation time among three years; moss species occured in the second year which shortened colonization time by 100%; algal inoculation increased organic carbon (C) and total nitrogen (N) of the soil; total salt, calcium carbonate (CaCO3) and electrical conductivity (EC) in the soil also increased after inoculation; Diverse vascular plant communities composed of 10 and 9 species are established by algal inoculation in windward and leeward surface of the dunes respectively after 3 years. Simpson index for above two communities are 0.842 and 0.852, while Shannon-Weiner index are 2.097 and 2.053 respectively. In conclusion, we suggested that algal inoculation would be a suitable and effective technique to rehabilitation biological soil crusts, and may further restore ecological system.
Three experiments were conducted to measuring temperature tolerance of three cyanobacterial strains: The growth curves of Microcoleus vaginatus, Scytonema javanicum, Phormidium tenue were examined under room temperature; three strains were cultured in open conditions using carrier cluture method under 2, 5, 10, 15, 25, 35℃ respectively, and their growth and morphological observation were studied; S. javanicum was cultured under 10, 15, 20, 25, 30℃ respectively and its biomass, phycobiliprotein content, photosynthetic activity, carotenoids content and scytonemin content were investigated. The results are as follow: 1) P. tenue grows faster than M. vaginatus and S. javanicum in the liquid medium.2) Liquid medium should be preferred for mass culture of these cyanobaterial strains, because growth rate of these strains in liquid medium is faster than in carrier; P. tenue growing in carriers is easily contaminated with some bacteria and these bacteria should be inhibited by antibiotics. 3) Optimal cultivation temperature for S. javanicum is about 25-30℃ for short-term (18days) culture and about15-20℃ for long-term (30 days) culture.
A greenhouse experiment was conducted to determine the effects of sand burial on biomass, chlorophyll fluorescence and extracellular polysaccharides of man-made cyanobacterial crusts in six periods of time (0, 5, 10, 15, 20 and 30 days after burying) and at five depths (0, 0.2, 0.5, 1 and 2cm). The results indicated that with the increase of the burial time and burial depth extracellular polysaccharides content and Fv/Fm decreased correspondingly and there were no significant differences between 20 and 30 burial days under different burial depths. The degradation of chlorophyll a content appeared only at 20 and 30 burial days and there was also no significant difference between them under different burial depths. It was also observed a simultaneous decrease of the values of the Fv/Fm and the content of extracellular polysaccharides happened in the crusted cyanobacterium Microcoleus vaginatus Gom. It may suggest that there exists a relationship between extracellular polysaccharides and recovery of the activity of photosystem II (PS II) after rehydration.
Effects of mulching on forming of man – made algal crusts were studied. Four types of physical mulching materials and four different concentrations of chemical mulching materials were used in this experiment. The result found that only polythene film net might promote forming of man – made algal crusts, other physical mulching materials such as black polythene net, mat weaving(willow twig)，medical gauze had no effect on the forming of algal crusts, or even inhibited the formation of algal crusts. The reason for this was that inoculum rested on the soil surface and was usually killed by high light radiation when mulching materials removed. Four concentrations of alginate all inhibited growth of inoculum. However, alginate could stick sand particals together and formed chemical soil crusts.
In this study, an integrated conceptual process was designed for inoculating cyanobacteria to speed up the recovery of biological soil crusts. The process was as follows: After site analysis, disturbance is removed；proper soil pre-fixation activities are conducted; selected cyanobacterial species are mass-cultured, collected and inoculated to the soil; supplementary treatments such as irrigation, mulching and fertilization are used.|